Visit: https://a2zcareers.viden.io
Knowledge in Biological Science
Cell Division
Notes on cell division which are mitosis and meiosis of the subject Biological Science
Hrithik Anand
Protein Structure and Function
Proteins• Make up about 15% of the cell• Have many functions in the cell– Enzymes, Structural, Transport, Motor, Storage, Signaling, Receptors, Gene regulation, Special functionsShape = Amino Acid Sequence• Proteins are made of 20 amino acids linked by peptide bonds• Polypeptide backbone is the repeating sequence of the N-C-C-N-C-C… in the peptide bond• The side chain or R group is not part of the backbone or the peptide bondProtein Folding• The peptide bond allows for rotation around it and therefore the protein can fold and orient the R groups in favorable positions• Weak non-covalent interactions will hold the protein in its functional shape – these are weak and will take many to hold the shapeNon-covalent Bonds in ProteinsGlobular Proteins• The side chains will help determine the conformation in an aqueous solutionHydrogen Bonds in ProteinsH-bonds form between 1) atoms involved in the peptide bond; 2) peptide bond atoms and R groups; 3) R groupsProtein Folding• Proteins shape is determined by the sequence of the amino acids• The final shape is called the conformation and has the lowest free energy possible• Denaturation is the process of unfolding the protein– Can be down with heat, pH or chemical compounds– In the chemical compound, can remove and have the protein renature or refoldRefolding• Molecular chaperones are small proteins that help guide the folding and can help keep the new protein from associating with the wrong partnerProtein Folding• 2 regular folding patterns have been identified – formed between the bonds of the peptide backbone• a-helix – protein turns like a spiral – fibrous proteins (hair, nails, horns)• b-sheet – protein folds back on itself as in a ribbon –globular proteinb Sheets• Core of many proteins is the b sheet• Form rigid structures with the H-bond• Can be of 2 types: Anti-parallel – run in an opposite direction of its neighbor (A)– Parallel – run in the same direction with longer looping sections between them (B)a Helix• Formed by a H-bond between every 4th peptide bond – C=O to N-H• Usually in proteins that span a membrane• The a helix can either coil to the right or the left• Can also coil around each other – coiled-coil shape – a framework for structural proteins such as nails and skinLevels of Organization• Primary structure : Amino acid sequence of the protein• Secondary structure: H bonds in the peptide chain backbone• a-helix and b-sheets• Tertiary structure : Non-covalent interactions between the R groups within the protein• Quaternary structure: Interaction between 2 polypeptide chainsProtein StructureDomains• A domain is a basic structural unit of a protein structure – distinct from those that make up the conformations• Part of protein that can fold into a stable structure independently• Different domains can impart different functions to proteins• Proteins can have one to many domains depending on protein sizeUseful Proteins• There are thousands and thousands of different combinations of amino acids that can make up proteins and that would increase if each one had multiple shapes• Proteins usually have only one useful conformation because otherwise it would not be efficient use of the energy available to the system• Natural selection has eliminated proteins that do not perform a specific function in the cellProtein Families• Have similarities in amino acid sequence and 3-D structure• Have similar functions such as breakdown proteins but do it differentlyProteins – Multiple Peptides• Non-covalent bonds can form interactions between individual polypeptide chains– Binding site – where proteins interact with one another– Subunit – each polypeptide chain of large protein– Dimer – protein made of 2 subunits• Can be same subunit or different subunitsSingle Subunit ProteinsDifferent Subunit Proteins• Hemoglobin : 2 a globin subunits & 2 b globin subunitsProtein Assemblies• Proteins can form very large assemblies• Can form long chains if the protein has 2 binding sites – link together as a helix or a ring• Actin fibers in muscles and cytoskeleton – is made from thousands of actin molecules as a helical fiberTypes of Proteins• Globular Proteins – most of what we have dealt with so far– Compact shape like a ball with irregular surfaces– Enzymes are globular• Fibrous Proteins – usually span a long distance in the cell– 3-D structure is usually long and rod shapedImportant Fibrous Proteins• Intermediate filaments of the cytoskeleton – Structural scaffold inside the cell• Keratin in hair, horns and nails• Extracellular matrix – Bind cells together to make tissues– Secreted from cells and assemble in long fibers • Collagen – fiber with a glycine every third amino acid in the protein• Elastin – unstructured fibers that gives tissue an elastic characteristicCollagen and ElastinStabilizing Cross-Links• Cross linkages can be between 2 parts of a protein or between 2 subunits• Disulfide bonds (S-S) form between adjacent -SH groups on the amino acid cysteineProteins at Work• The conformation of a protein gives it a unique function• To work proteins must interact with other molecules, usually 1 or a few molecules from the thousands to 1 protein • Ligand – the molecule that a protein can bind• Binding site – part of the protein that interacts with the ligand– Consists of a cavity formed by a specific arrangement of amino acids
Structure of Nucleic Acids
Structure of Nucleic AcidsThis guide will focus on the "central dogma" of molecular biology. We will review the processes responsible for replicating the nucleic acid DNA, transcribing DNA into RNA, and translating an RNA sequence into a functional protein. Knowledge of these topics is critical before a more complex understanding of advanced molecular biology topics is possible. Just as importantly, knowledge of these topics is fundamental to understanding what inside our bodies allowed us to grow as humans and why our growth is different from that of other organisms.Figure %: The Central Dogma of Molecular BiologyDNA is the nucleic acid that is responsible for "programming" many or our traits. As the material that composes our genes, DNA has become one of the most fundamental molecules in molecular biology. In Molecular Genetics, we will address some fundamentally important questions. We will learn how DNA, our genetic material, is copied and passed on from generation to generation. We will also address the issue of how the genetic information encoded into a DNA sequence is used in organisms to express certain proteins, the major constituents of cells. In addressing these major questions, we will also see how these processes are not perfect and look at how organisms protect against mutations that could potentially kill cells.In this topic section, Structure of Nucleic Acids, we will begin our discussion at a more elementary level, investigating the structure of the nucleic acids DNA and RNA. As DNA and RNA are the major molecules of molecular biology, understanding their structure is critical to understanding the mechanisms of gene replication and protein synthesis. The structural elements of each of these molecules play key roles in their performance of the various processes of the central dogma. Anti-parallel - Refers to the orientations of the two single strands that compose a double-stranded DNA helix. Strands are oriented such that one strand's 5' end is directly across from the other strand's 3' end. Complementary - Term used to refer to the natural pairing of the nitrogen bases within DNA and RNA. In DNA, cytosine pairs with guanine and adenine with thymine. In RNA, the thymine is replaced with uracil, which pairs with adenine. Each member of these pairs are said to be a "complements" of the other. Deoxyribose - A five-membered sugar ring that lacks a hydroxyl group at one position, and is the sugar group for DNA. Double-stranded helix - A common structural motif of DNA. Two linear strands of single-stranded DNA fold into a helical shape stabilized internally by hydrogen bonds between complementary base pairs. Ester bond - In DNA, refers to the oxygen-carbon linkage between the triphosphate group and the 5' carbon of the ribose sugar group in a single DNA or RNA nucleotide. Glycosidic Bond - In DNA, refers to the nitrogen-carbon linkage between the 9' nitrogen of purine bases or 1' nitrogen of pyrimidine bases and the 1' carbon of the sugar group. Helical Twist - The angular rotation needed to get from one nucleotide to another in helical structures. Hydrogen Bonding - Weak, noncovalent linkages between a donor and an acceptor which, when lined up next to each other, have favorable electrostatic interactions. Provide small amount of stability to DNA and RNA helices. Provide specificity of the interactions between polynucleotide strands. Hydrogen Bond Acceptor - A group with at least one free lone pair of electrons. In DNA and RNA, common acceptor groups include: carbonyls, hydroxyls, and tertiary amines. Hydrogen Bond Donor - A group with a free hydrogen group. In DNA and RNA, common donors include secondary amines and hydroxyl groups. Major groove - In a helix, refers to the larger of the unequal grooves that are formed as a result of the double-helical structure of DNA. As a result of the patterns of hydrogen bonding between complementary bases of DNA, the sugar groups stick out at 120 degree angles from each other instead of 180. The major groove is generated by the larger angular distance between sugars. Minor groove - In a helix, refers to the smaller of the unequal grooves that are formed as a result of the double-helical structure of DNA. As a result of the patterns of hydrogen bonding between complementary bases of DNA, the sugar groups stick out at 120 degree angles from each other instead of 180. The minor groove is generated by the smaller angular distance between sugars. Nitrogen Base - One of three components of a nucleotide, nitrogen bases come in two general types: purines and pyrimidines. Of the four nitrogen bases, adenine and guanine are purines, while cytosine and thymine are pyrimidines. Through hydrogen bonding, base pairs link in a complementary nature: adenine with thymine and guanine with cytosine, forming the double-stranded helix of DNA. In RNA, thymine is replaced by uracil. Nucleic Acid - A chain of nucleotides joined together by phosphodiester bonds. Both DNA and RNA are nucleic acids. Nucleotide - A five-membered sugar group with a purine or pyrimidine nitrogen base group attached to its 1' carbon via a glycosidic bond and one or more phosphate groups attached to its 5' carbon via an ester bond. Phosphate Backbone - Refers to the structural organization of the DNA double-helix in which the pyrimidine and purine basic groups face the interior while the phosphate groups line the exterior of the helix. The phosphate backbone carries a negative charge. Phosphate Group - One of three components of a nucleotide, comprised of a central phosphorous surrounded by four oxygens. The phosphate links to the sugar group, carries a negative charge because of the chemical interaction between phosphorous and oxygen, and forms the exterior of the phosphate backbone. Phosphodiester linkage - In a polynucleotide, refers to the bond between the 3' hydroxyl of a sugar group in a nucleotide and a phosphate group attached to the 5' carbon of another sugar group. Pitch - In a helix, refers to the vertical distance traveled in one full turn (360 degrees of twist). Primary Structure - In DNA and RNA, refers to the linear sequence of base pairs or amino acids in a polynucleotide chain. Purine - One of two categories of nitrogen base ring compounds found in DNA and RNA. A purine is a nine-membered double ring composed of one five-membered joined to a six membered ring containing four nitrogens. See pyrimidine. Pyrimidine - One of two categories of nitrogen base ring compounds found in DNA and RNA. A six-membered ring containing two nitrogens. See purine. Ribose - The sugar group of RNA, a five-membered sugar ring containing one oxygen and four carbons with one additional carbon attached to the 4' carbon in the ring and hydroxyl groups attached to the 1', 2', 3', and 5' carbons. See deoxyribose. Right Hand Rule - A trick used to quickly determine the "handedness" or orientation of a helix. In a right-handed helix, if one extends his or her right hand and traces with fingers along the backbone of the helix, the hand and thumb move upwards. Rise - In a helix, the vertical distance traveled when moving from one base pair to the adjacent base pair. Secondary Structure - In DNA and RNA, the local folding patterns of a polynucleotide based on complementary base-pairing. Common motifs include alpha helices and bet-pleated sheets. Sugar Group - One of three components of a nucleotide, a five-ringed carbon sugar, either ribose or deoxyribose in form. The sugar group bonds to the nitrogen base and to the phosphate group. Tertiary Structure - In DNA and RNA, the complex three-dimensional form of a polynucleotide.Nucleotides and Nucleic AcidsBoth DNA and RNA are known as nucleic acids. They have been given this name for the simple reason that they are made up of structures called nucleotides. Those nucleotides, themselves comprising a number of components, bond together to form the double-helix first discovered by the scientists James Watson and Francis Crick in 1956. This discovery won the two scientists the Nobel Prize. For now, when we discuss nucleic acids you should assume we are discussing DNA rather than RNA, unless otherwise specified.NucleotidesA nucleotide consists of three things: 1. A nitrogenous base, which can be either adenine, guanine, cytosine, or thymine (in the case of RNA, thymine is replaced by uracil).2. A five-carbon sugar, called deoxyribose because it is lacking an oxygen group on one of its carbons.3. One or more phosphate groups. The nitrogen bases are pyrimidine in structure and form a bond between their 1' nitrogen and the 1' -OH group of the deoxyribose. This type of bond is called a glycosidic bond. The phosphate group forms a bond with the deoxyribose sugar through an ester bond between one of its negatively charged oxygen groups and the 5' -OH of the sugar ().Nucleic AcidsNucleotides join together through phosphodiester linkages between the 5' and 3' carbon atoms to form nucleic acids. The 3' -OH of the sugar group forms a bond with one of the negatively charged oxygens of the phosphate group attached to the 5' carbon of another sugar. When many of these nucleotide subunits combine, the result is the large single-stranded polynucleotide or nucleic acid, DNA ()If you look closely, you can see that the two sides of the nucleic acid strand shown above are different, resulting in polarity. At one end of the large molecule, the carbon group is unbound and at the other end, the -OH is unbound. These different ends are called the 5'- and 3'-ends, respectively.The Helical Structure of DNAshows a single strand of DNA. However, as stated earlier, DNA exists as a double-helix, meaning two strands of DNA bind together. As seen above, one strand is oriented in the 5' to 3' direction while the complementary strand runs in the 3' to 5' direction. Because the two strands are oppositely oriented, they are said to be anti-parallel to each other. The two strands bond through their nitrogen bases (marked A, C, G, or T for adenine, cytosine, and guanine). Note that adenine only bonds with thymine, and cytosine only bonds with guanine. The nitrogen bases are held together by hydrogen bonds: adenine and thymine form two hydrogen bonds; cytosine and guanine form three hydrogen bonds. An important thing to remember about the structure of the DNA helix is that as a result of anti-parallel pairing, the nitrogen base groups face the inside of the helix while the sugar and phosphate groups face outward. The sugar and phosphate groups in the helix therefore make up the phosphate backbone of DNA. The backbone is highly negatively charged as a result of the phosphate groups.The Importance of the Hydrogen BondHydrogen bonding is essential to the three-dimensional structure of DNA. These bonds do not, however, contribute largely to the stability of the double helix. Hydrogen bonds are very weak interactions and the orientation of the bases must be just right for the interactions to take place. While the large number of hydrogen bonds present in a double helix of DNA leads to a cumulative effect of stability, it is the interactions gained through the stacking of the base pairs that leads to most of the helical stability.Hydrogen bonding is most important for the specificity of the helix. Since the hydrogen bonds rely on strict patterns of hydrogen bond donors and acceptors, and because these structures must be in just the right spots, hydrogen bonding allows for only complementary strands to come together: A- T, and C-G. This complementary nature allows DNA to carry the information that it does. Chargaff's RuleChargaff's rule states that the molar ratio of A to T and of G to C is almost always approximately equal in a DNA molecule. Chargaff's Rule is true as a result of the strict hydrogen bond forming rules in base pairing. For every G in a double-strand of DNA, there must be an accompanying complementary C, similarly, for each A, there is a complementary paired T.DNA is a Right-Handed HelixEach strand of DNA wraps around the other in a right-handed configuration. In other words, the helix spirals upwards to the right. One can test the handedness" of a helix using the right hand rule. If you extend your right hand with thumb pointing up and imagine you are grasping a DNA double helix, as you trace upwards around the helix with your fingers, your hand is moving up. In a left-handed helix, in order to have your hand move upwards with your thumb pointing up, you would need to use your left hand. DNA is always found in the right-handed configuration.The Major and Minor GroovesAs a result of the double helical nature of DNA, the molecule has two asymmetric grooves. One groove is smaller than the other. This asymmetry is a result of the geometrical configuration of the bonds between the phosphate, sugar, and base groups that forces the base groups to attach at 120 degree angles instead of 180 degrees. The larger groove is called the major groove while the smaller one is called the minor groove. Since the major and minor grooves expose the edges of the bases, the grooves can be used to tell the base sequence of a specific DNA molecule. The possibility for such recognition is critical, since proteins must be able to recognize specific DNA sequences on which to bind in order for the proper functions of the body and cell to be carried out. As you might expect, the major groove is more information rich than the minor groove. This fact makes the minor groove less ideal for protein binding.Characteristics of the DNA Double-HelixDNA will adopt two different forms of helices under different conditions--the B- and A-forms. These two forms differ in their helical twist, rise, pitch and number of base pairs per turn. The twist of a helix refers to the number of degrees of angular rotation needed to get from one base unit to another. In the B-form of helix, this is 36 degrees while in the A-form it is 33 degrees. Rise refers to the height change from one base pair to the next and is 3.4 angstroms in the B-form and 2.6 angstroms in the A-form. The pitch is the height change to get one full rotation (360 degrees) of the helix. This value is 34 angstroms in the B-form since there are ten base pairs per turn. In the A-form, this value is 28 angstroms since there are eleven base pairs per full turn.Of the two forms, the B-form is far more common, existing under most physiological conditions. The A-form is only adopted by DNA under conditions of low humidity. RNA, however, generally adopts the A-form in situations where the major and minor grooves are closer to the same size and the base pairs are a bit tilted with respect to the helical axis.The Bases of DNAThe four nitrogen bases found in DNA are adenine, cytosine, guanine, and thymine. Each of these bases are often abbreviated a single letter: A (adenine), C (cytosine), G (guanine), T (thymine). The bases come in two categories: thymine and cytosine are pyrimidines, while adenine and guanine are purines (). The pyrimidine structure is produced by a six-membered, two-nitrogen molecule; purine refers to a nine-membered, four-nitrogen molecule. As you can see, each constituent of the ring making up the base is numbered to help with specificity of identification.Base Pairing in DNAThe nitrogen bases form the double-strand of DNA through weak hydrogen bonds. The nitrogen bases, however, have specific shapes and hydrogen bond properties so that guanine and cytosine only bond with each other, while adenine and thymine also bond exclusively. This pairing off of the nitrogen bases is called complementarity. In order for hydrogen bonding to occur at all, a hydrogen bond donor must have a complementary hydrogen bond acceptor in the base across from it. Common hydrogen bond donors include primary and secondary amine groups or hydroxyl groups. Common acceptor groups are carbonyls and tertiary amines ().There are three hydrogen bonds in a G:C base pair. One hydrogen bond forms between the 6' hydrogen bond accepting carbonyl of the guanine and the 4' hydrogen bond accepting primary amine of the cytosine. The second between the 1' secondary amine on guanine and the 3' tertiary amine on cytosine. And the third between the 2' primary amine on guanine and the 2' carbonyl on cytosine ().Between an A:T base pair, there are only two hydrogen bonds. One is found between the 6' primary amine of adenine and the 4' carbonyl of thymine. The other between the 1' tertiary amine of adenine and the 2' secondary amine of thymine ().The Deoxyribose SugarThe deoxyribose sugar in DNA is a pentose, a five-carbon sugar. Four carbons and an oxygen make up the five-membered ring; the other carbon branches off the ring. Similar to the numbering of the purine and pyrimidine rings (seen in ), the carbon constituents of the sugar ring are numbered 1'-4' (pronounced "one-prime carbon"), starting with the carbon to the right of the oxygen going clockwise (). The fifth carbon (5') branches from the 4' carbon.Figure %: Deoxyribose SugarIt is from this numbering system of the sugar group that DNA gets its polarity. The linkages between nucleotides occur between the 5' and 3' positions on the sugar group. One end has a free 5' end and the other has a free 3' end.Attached to the remaining free carbons at the 1', 3' and 5' positions is an oxygen-containing hydroxyl group (-OH). The DNA sugar is called a deoxyribose because it is lacking a hydroxyl group at the 2' position. Instead there is just a hydrogen (see ).PhosphatesA phosphate group consists of a central phosphorous surrounded by four oxygens. The phosphorous is single-bonded to three of the oxygens and double-bonded to the fourth. Due to the nature of the chemical bonds, there is a negative charge on each oxygen that has only one bond coming off of it. This negative charge accounts for the overall negative charge on the phosphate backbone of a DNA molecule.Differences Between DNA and RNAStructurally, DNA and RNA are nearly identical. As mentioned earlier, however, there are three fundamental differences that account for the very different functions of the two molecules. 1. RNA is a single-stranded nucleic acid.2. RNA has a ribose sugar instead of a deoxyribose sugar like DNA.3. RNA nucleotides have a uracil base instead of thymine.Other than these differences, DNA and RNA are the same. Their phosphates, sugars, and bases show the same bonding patterns to form nucleotides and their nucleotides bind to form nucleic acids in the same way.The Uracil BaseThe uracil base replaces thymine in RNA. Thymine and uracil are structurally very similar. Uracil has fundamentally the same structure as thymine, with the deletion of a methyl group at the 5' position. Uracil will base pair with adenine in the same way as thymine pairs with adenine ().The Ribose SugarThe ribose sugar is structurally identical to the deoxyribose sugar, with the addition of a hydroxyl group at the 2' position ().The Three-Dimensional Structure of RNAUnlike DNA, RNA cannot adopt the B-form helix because the additional 2' hydroxyl interferes with the arrangement of the sugars in the phosphate backbone. Although RNA does not adopt the highly ordered B-form of helix, it can be found in the A-form and does base pair to form complex secondary and tertiary structures. The primary structure of a nucleic acid refers to its sequence of base pairs. In RNA, the secondary structures are the two- dimensional base-pair foldings in which local sequences have regions of self- complementarity, giving rise to base pairs and turns. Common secondary structural motifs include hairpins, bulges, and loops ().The main difference between the three-dimensional structures of DNA and RNA is that in RNA the three-dimensional structure is single-stranded. The base- pairing that occurs in RNA is all through regions of self-complementarity. This three-dimensional arrangement is called the tertiary structure of RNA and it can be very complex.
Lipids
· LIPID describes a chemically varied group of organic fatty compound substances · Lipids are highly concentrated energy stores.· They are water-insoluble bio-molecules but soluble in organic solvents such as ether, benzene. Chloroform, etc. (lipophilic).· Lipids serve as fuel molecules, signal molecules, and components of membranes, hormones and intracellular messengers.· They are esters of long chain fatty acids and alcohols.· Only a limited number of lipids are clinically important. This group includes fatty acids, triacylglycerols (or triglycerides), cholesterol, and phospholipids. · The various types of lipids differ in their chemical and physical properties and in their physiological roles. · Other lipids serve as precursors for other essential compounds or act as a sources or storage of energy. · Lipids are important insulators against heat loss and organ damage and allows for nerve conduction in the central nervous system.· When conjugated with proteins, lipids compounds are called lipoproteins, the transport form of lipids in aqueous substances such as blood. Classification Of Lipids:LIPIDS are classified broadly according to their chemical composition into:1- simple lipids2- complex lipids3- derived lipids4- miscellaneous lipids based.SIMPLE LIPIDS: These lipids are the esters of fatty acids with alcohols. They are of three types: Waxes, sterol esters and Triacylglycerol.COMPOUND/COMPLEX LIPIDS: These lipids are esters of fatty acids with alcohols with additional groups such as phosphate, nitrogenous base, etc. They are again divided into 3 types: Phospholipids, Glycerophosphlipids, Sphingophospholipids.DERIVED LIPIDS: These lipids are obtained on hydrolysis of simple and complex lipids. These lipids contain glycerol and other alcohols. This class of lipids include steroid hormones, ketone bodies, hydrocarbons, fatty acids, fatty alcohols, mono and diacylglycerides. MISCELLANEOUS LIPIDS: These include compounds, which contain characteristics of lipids. They include squalene, terpenes, hydrocarbons, carotenoids, etc. Classification Scheme:Functions of Lipids:Lipids are the constituents of cell membrane and regulate membrane permeability.They protect internal organs, serve as insulating materials, give shape and smoothness to the body.They serve as a source of fat soluble vitamins.Essential fatty acids are useful for transport of cholesterol, formation of lipoproteins, etc.Phospholipids in mitochondria are responsible for transport of electron transport chain components.Accumulation of fat in liver is prevented by phospholipids.Phospholipids help in removal of cholesterol from the body. Cholesterol is a constituent of membrane structure and it synthesizes bile acids, hormones and vitamin D. It is the principal sterol of higher animals, abundant in nerve tissues and gallstones.Classification Of Lipids:Based on their Biological functions Lipids can be classified into: Storage Lipids—The principle stored form of energy Structural Lipids– The major structural elements of Biological Membranes Lipids are signals, cofactors and pigments Storage Lipids:Storage Lipids include fats and oils, and wax. Fats and oils are composed of 3 fatty acids each in ester linkage with a single glycerol (Triacylglycerols) 3FA+Glycerol=Fats, Oils Waxes are esters of long-chain(C14-C36) saturated and unsaturated fatty acids with long chain (C16-C30) alcohols FA + Alcohol = waxesFatty Acids:• Fatty acids are composed only of carbon, hydrogen and oxygen • Fatty Acids are carboxylic acids with hydrocarbon chains ranging from 4-36.• Fatty acids are of 2 types: Saturated and Unsaturated.Triacylglycerols (TAG) Triacylglycerol(Triglyceride) is an ester of glycerol with three fatty acids. It is also called neutral fat. They are stored in adipocytes in . A mammal contains 5% to 25% or more of its body weight as lipids,90%TAG Wax: Waxes are esters of long chain (C14-C36) saturated and unsaturated fatty acids with long chain (C16-C30) alcohols.Functions of Wax: Chief storage fuels for some of the microorganisms. Protect skin and hair. Application in industries, pharmaceuticals, and cosmeticsCholesterol Cholesterol is a derived lipid. Its widely distributed as sterols in animals and humans, most of which is synthesized by the liver It is an essential component of cell membrane Vit. D, hormones and bile acids are synthesized from cholesterol. Bile acids are essential for normal digestion and absorption of fats and fat-soluble vitamins. An increase in dietary intake of cholesterol increases its synthesis in the body as well which leads to coronary heart diseases. Unsaturated fats reduce the level of cholesterol in blood. LDL, HDL AND VLDL: Low density lipoproteins (LDL) transports cholesterol from liver through blood to the tissues (Bad cholesterol) High density lipoprotein (HDL) transports cholesterol from blood to the liver where it is metabolised (Good cholesterol) LDL high Cholesterol high High risk of heart attack HDL high Cholesterol low Low risk of heart attack Bile Acids:Bile Acids are polar derivatives of cholesterol that act as detergents in the intestine, emulsifying dietary fats to make them more accessible to digestive lipases Essential fatty acids: Linoleic, Linolenic, and Arachidonic acids Essential fatty acids synthesize structural fats in tissues such as prostoglandins, leukotriens, prostocyclins, thromboxane which regulate body functions such as blood clotting, inflammation etc. Essential fatty acid deficiency can result in abnormalities like poor growth, increase food intake, scale inflammation of skin and impaired immune response. Best dietary sources are vegetable oils(corn oil, sunflower oil) and oil rich fish (Herring , Sardine) Trans Fatty Acids: Exist in very small amounts in natural foods. Trans fatty acids lowers HDL level and raises total blood cholesterol They also raise plasma conc. Of lipoprotein – anthrogenic lipoprotein. Trans fatty acids are formed when vegetable oils are hydrogenated during the formation of margarine etc.Lipids as Biochemical Markers of DiseaseClinical chemistry laboratories offer many tests for lipid disorders. One of the most common tests is the lipid profile. This panel of tests includes measures of triacylglycerol and cholesterol in the form of lipoprotein-cholesterol molecules, low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C). The results of testing for these lipids provide measures of risk for coronary artery disease.Although the concentration of cholesterol in blood is dependent on many factors such as genetics, age, sex, diet, and physical activity, total cholesterol measurement is used clinically to monitor disease. In addition to its role as a risk factor for coronary artery disease, increased cholesterol concentration may be the result of hypothyroidism, liver disease, renal disease, or diabetes. Decreased cholesterol concentration may be the result of hyperthyroidism, digestive malabsorption, or impaired liver function. Factors that increase HDL-C include increased estrogen in women, increased exercise, and the effects of certain blood pressure medicines.Factors that decrease HDL-C include increased progesterone, obesity, smoking, and diabetes. Increased triacylglycerol may be the result of pancreatitis, diabetes mellitus, acute alcohol consumption, or certain liver diseases. In addition, triacylglycerol may be increased artifactually in nonfasting blood samples.
Origin of Life
LIFE : Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased (death), or else because they lack such functions and are classified as inanimate. Biology is the science concerned with the study of life. Any contiguous living system is called an organism. These animate entities undergo metabolism, maintain homeostasis, possess a capacity to grow, respond to stimuli, reproduce and, through natural selection, adapt to their environment in successive generations. More complex living organisms can communicate through various means. A diverse array of living organisms can be found in the biosphere of Earth, and the properties common to these organisms—plants, animals, fungi, protists, archaea, and bacteria—are a carbon- and water-based cellular form with complex organization and heritable genetic information. Scientific evidence suggests that life began on Earth some 3.7 billion years ago. The mechanism by which life emerged is still being investigated. Since then, life has evolved into a wide variety of forms, which biologists have classified into a hierarchy of Taxa. Life can survive and thrive in a wide range of conditions. The meaning of life—its significance, purpose, and ultimate fate—is a central concept and question in philosophy and religion. Both philosophy and religion have offered interpretations as to how life relates to existence and consciousness, and both touch on many related issues, including life stance, purpose, conception of a god or gods, a soul or an afterlife. Different cultures throughout history have had widely varying approaches to these issues. Though the existence of life is only confirmed on Earth, many scientists believe extraterrestrial life is not only plausible but probable. Other planets and moons in the Solar System have been examined for evidence of having once supported simple life, and projects such as SETI have attempted to detect transmissions from possible alien civilizations. According to the panspermia hypothesis, life on Earth may have originated from meteorites that spread organic molecules or simple life that first evolved elsewhere.Origin:Evidence suggests that life on Earth has existed for about 3.7 billion years, with the oldest traces of life found in fossils dating back 3.4 billion years. All known life forms share fundamental molecular mechanisms, and based on these observations, theories on the origin of life attempt to find a mechanism explaining the formation of a primordial single cell organism from which all life originates. There are many different hypotheses regarding the path that might have been taken from simple organic molecules via pre-cellular life to protocells and metabolism. Many models fall into the "genes-first" category or the "metabolism-first" category, but a recent trend is the emergence of hybrid models that combine both categories. There is no scientific consensus as to how life originated and all proposed theories are highly speculative. However, most accepted scientific models build in one way or another on the following hypotheses:The Miller-Urey experiment, and the work of Sidney Fox, suggest that conditions on the primitive Earth may have favored chemical reactions that synthesized amino acids and other organic compounds from inorganic precursors.Phospholipids spontaneously form lipid bilayers, the basic structure of a cell membrane.Life synthesizes proteins, which are polymers of amino acids using instructions encoded by cellular genes; the polymers of deoxyribonucleic acid (DNA). Protein synthesis entails intermediary ribonucleic acid (RNA) polymers. One possibility for how life began is that genes originated first, followed by proteins; the alternative being that proteins came first and then genes. However, because genes are required to make proteins, and proteins are needed to make genes, the problem of considering which came first is like that of the chicken or the egg. Most scientists have adopted the hypothesis that because DNA and proteins function together so intimately, it's unlikely that they arose independently. Therefore, a possibility, apparently first suggested by Francis Crick, is that the first life was based on the DNA-protein intermediary: RNA. RNA has the DNA-like properties of information storage, replication and the catalytic properties of some proteins. Crick and others actually favored the RNA-first hypothesis even before the catalytic properties of RNA had been demonstrated by Thomas Cech. A significant issue with the RNA-first hypothesis is that experiments designed to synthesize RNA from simple precursors have not been nearly as successful as the Miller-Urey experiments that synthesized other organic molecules from inorganic precursors. One reason for the failure to create RNA in the laboratory is that RNA precursors are very stable and do not react with each other under ambient conditions. However, the successful synthesis of certain RNA molecules under conditions hypothesized to exist prior to life on Earth has been achieved by adding alternative precursors in a specified order with the precursor phosphate present throughout the reaction.[60] This study makes the RNA-first hypothesis more plausible. Recent experiments have demonstrated true Darwinian evolution of unique RNA enzymes (ribozymes) made up of two separate catalytic components that replicate each other in vitro.[62] In describing this work from his laboratory, Gerald Joyce stated: "This is the first example, outside of biology, of evolutionary adaptation in a molecular genetic system."[63] Such experiments make the possibility of a primordial RNA world even more attractive to many scientists.Miller/Urey Experiment By the 1950s, scientists were in hot pursuit of the origin of life. Around the world, the scientific community was examining what kind of environment would be needed to allow life to begin. In 1953, Stanley L. Miller and Harold C. Urey, working at the University of Chicago, conducted an experiment which would change the approach of scientific investigation into the origin of life. Miller took molecules which were believed to represent the major components of the early Earth's atmosphere and put them into a closed system The gases they used were methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O). Next, he ran a continuous electric current through the system, to simulate lightning storms believed to be common on the early earth. Analysis of the experiment was done by chromotography. At the end of one week, Miller observed that as much as 10-15% of the carbon was now in the form of organic compounds. Two percent of the carbon had formed some of the amino acids which are used to make proteins. Perhaps most importantly, Miller's experiment showed that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions that scientists believed to be present on the early earth. This enormous finding inspired a multitude of further experiments. In 1961, Juan Oro found that amino acids could be made from hydrogen cyanide (HCN) and ammonia in an aqueous solution. He also found that his experiment produced an amazing amount of the nucleotide base, adenine. Adenine is of tremendous biological significance as an organic compound because it is one of the four bases in RNA and DNA. It is also a component of adenosine triphosphate, or ATP, which is a major energy releasing molecule in cells. Experiments conducted later showed that the other RNA and DNA bases could be obtained through simulated prebiotic chemistry with a reducing atmosphere. These discoveries created a stir within the science community. Scientists became very optimistic that the questions about the origin of life would be solved within a few decades. This has not been the case, however. Instead, the investigation into life's origins seems only to have just begun. There has been a recent wave of skepticism concerning Miller's experiment because it is now believed that the early earth's atmosphere did not contain predominantly reductant molecules. Another objection is that this experiment required a tremendous amount of energy. While it is believed lightning storms were extremely common on the primitive Earth, they were not continuous as the Miller/Urey experiment portrayed. Thus it has been argued that while amino acids and other organic compounds may have been formed, they would not have been formed in the amounts which this experiment produced. Many of the compounds made in the Miller/Urey experiment are known to exist in outer spaceTheories of origin of life1. Scientific Evolution: This theory relies strongly on the Big Bang theory of the Creation of the Universe, which was the beginning of the formation of matter. This eventually led to the creation of planets, Pangaea and life on earth as it evolved over millions of years in a natural environment of chemicals and enabling elements. Evolution of life can mean many things. Some use the word to refer to any change at all. Obviously the creation/evolution debate is not about that kind of a definition. Creationists agree that many changes take place, but disagree with the theory of evolution when it is used to mean that a gradual progression from molecules to man produced all living things by natural means, that is, without the involvement of an intelligent Creator. 2. Special Creation: According to this theory, all the different forms of life that occur today on planet earth have been created by God, the almighty. This idea is found in the ancient scriptures of almost every religion. According to Hindu mythology, Lord Brahma, the God of Creation, created the living world in accordance to his wish. According to the Christian belief, God created this universe, plants, animals and human beings in about six natural days. The Sikh mythology says that all forms of life including human beings came into being with a single word of God. Special creation theory believes that the things have not undergone any significant change since their creation. Creationists generally believe the Bible's explanation that God created a number of basic groups of animals and plants as described in the first part of Genesis. They believe that while God created each group with the possibility of a good deal of variation, they brought forth according to their own kind. By definition, the faith-based Theory of Special Creation is purely a religious concept, acceptable only on the basis of faith. It has no scientific basis. 3. Biogenesis: The belief that living things come only from other living things (e.g. a spider lays eggs, which develop into spiders). It may also refer to biochemical processes of production in living organisms. The Law of Biogenesis, attributed to Louis Pasteur, states that life arises from pre-existing life, not from nonliving material. Pasteur's (and others') empirical results were summarized in the phrase Omne vivum ex vivo, Latin for "all life [is] from life", also known as the "law of biogenesis". Pasteur stated: "La génération spontanée est une chimère" ("Spontaneous generation is a dream"). 4. Abiogenesis: In the natural sciences, abiogenesis - also known as spontaneous generation - is the study of how life on Earth could have arisen from inanimate matter. This is also referred to as the "primordial soup" theory of evolution (life began in water as a result of the combination of chemicals from the atmosphere and some form of energy to make amino acids, the building blocks of proteins, which would then evolve into all the species). It should not be confused with evolution, which is the study of how groups of already living things change over time. Most amino acids, often called "the building blocks of life", can form via natural chemical reactions unrelated to life, as demonstrated in the Miller-Urey experiment and similar experiments, which involved simulating the conditions of the early Earth. In all living things, these amino acids are organized into proteins, and the construction of these proteins is mediated by nucleic acids. This of these organic molecules first arose and how they formed the first life is the focus of abiogenesis. Egyptians believed that mud of the Nile River could spontaneously give rise to many forms of life. The idea of spontaneous generation was popular almost till seventeenth century. Many scientists like Descartes, Galileo and Helmont supported this idea. 5. Theory of Chemical Evolution : This theory is also known as Materialistic Theory or Physico-chemical Theory. According this theory, the origin of life on earth is the result of a slow and gradual process of chemical evolution that probably occurred about 3.8 billion years ago. This theory was proposed independently by two scientists - A.I.Oparin, a Russian scientist in 1923 and J.B.S Haldane, an English scientist, in 1928. 6. Theory of Catastrophism: This theory on the origin of life is simply a modification of the theory of Special Creation. It states that there have been several creations of life by God, each preceded by a catastrophe resulting from some kind of geological disturbance. According to this theory, since each catastrophe completely destroyed the existing life, each new creation consisted of life form different from that of previous ones. French scientists Georges Cuvier (1769-1832) and Orbigney (1802 to 1837) were the main supporters of this theory. 7. Inorganic Incubation: Proposed by Professor William Martin, of Düsseldorf University, and Professor Michael Russell, of the Scottish Environmental Research Centre in Glasgow, this theory states that Instead of the building blocks of life forming first, and then forming a cell-like structure, the researchers say the cell came first and was later filled with living molecules. They say that the first cells were not living cells but inorganic ones made of iron sulfide and were formed not at the Earth's surface but in total darkness at the bottom of the oceans. The theory postulates that life is a chemical consequence of convection currents through the Earth's crust and, in principle, could happen on any wet, rocky planet. 8. Endosymbiotic Theory: This theory, espoused by Lynn Margulis, suggests that multiple forms of bacteria entered into symbiotic relationship to form the eukaryotic cell. The horizontal transfer of genetic material between bacteria promotes such symbiotic relationships, and thus many separate organisms may have contributed to building what has been recognized as the Last Universal Common Ancestor (LUCA) of modern organisms. James Lovelock's Gaia theory, proposes that such bacterial symbiosis establishes the environment as a system produced by and supportive of life. His arguments strongly weaken the case for life having evolved elsewhere in the solar system. 9. Panspermia - Cells From Outer Space: Some scientists believe that the simplest life-forms, whole cells (especially microbial cells), have been transported to the Earth from extraterrestrial sources. In this way, a process called panspermia (means seeds everywhere) might have initiated life on Earth. Most mainstream scientists have not supported panspermia, but early challenges have been thwarted in recent years due to discoveries such as terrestrial microbes that survive in extreme environments and incredibly aged yet viable microorganisms found in ancient rocks. In addition, water (essential for life) has been discovered on other planets and moons, and organic chemicals have been found on meteorites and in interstellar debris. 10. Cosmogony: Cosmogony is any theory concerning the coming into existence or origin of the universe, or about how reality came to be. In the specialized context of space science and astronomy, the term refers to theories of creation of the Solar System. For example, Greek mythology and some religions of the Ancient Near East refer to chaos, the formless or void state of primordial matter preceding the creation of the universe or cosmos in creation myths. Cosmogony can be distinguished from cosmology, which studies the universe at large and throughout its existence, yet does not inquire directly into the source of life or its origins. Biological classificationThe hierarchy of biological classification's eight major taxonomic ranks, which is an example of definition by genus and differentia. Life is divided into domains, which are subdivided into further groups. Intermediate minor rankings are not shown. Traditionally, people have divided organisms into the classes of plants and animals, based mainly on their ability of movement. The first known attempt to classify organisms was conducted by the Greek philosopher Aristotle (384–322 BC). He classified all living organisms known at that time as either a plant or an animal. Aristotle distinguished animals with blood from animals without blood (or at least without red blood), which can be compared with the concepts of vertebrates and invertebrates respectively. He divided the blooded animals into five groups: viviparous quadrupeds (mammals), birds, oviparous quadrupeds (reptiles and amphibians), fishes and whales. The bloodless animals were divided into five groups: cephalopods, crustaceans, insects (which included the spiders, scorpions, centipedes, and what we define as insects in the present day), shelled animals (such as most molluscs and echinoderms) and "zoophytes." Though Aristotle's work in zoology was not without errors, it was the grandest biological synthesis of the time and remained the ultimate authority for many centuries after his death. The exploration of the American continent revealed large numbers of new plants and animals that needed descriptions and classification. In the latter part of the 16th century and the beginning of the 17th, careful study of animals commenced and was gradually extended until it formed a sufficient body of knowledge to serve as an anatomical basis for classification. In the late 1740s, Carolus Linnaeus introduced his method, still used, to formulate the scientific name of every species. Linnaeus took every effort to improve the composition and reduce the length of the many-worded names by abolishing unnecessary rhetoric, introducing new descriptive terms and defining their meaning with an unprecedented precision. By consistently using his system, Linnaeus separated nomenclature from taxonomy. This convention for naming species is referred to as binomial nomenclature. The fungi were originally treated as plants. For a short period Linnaeus had placed them in the taxon Vermes in Animalia. He later placed them back in Plantae. Copeland classified the Fungi in his Protoctista, thus partially avoiding the problem but acknowledged their special status. The problem was eventually solved by Whittaker, when he gave them their own kingdom in his five-kingdom system. As it turned out, the fungi are more closely related to animals than to plants. As new discoveries enabled us to study cells and microorganisms, new groups of life were revealed, and the fields of cell biology and microbiology were created. These new organisms were originally described separately in protozoa as animals and protophyta/thallophyta as plants, but were united by Haeckel in his kingdom protista, later the group of prokaryotes were split off in the kingdom Monera, eventually this kingdom would be divided in two separate groups, the Bacteria and the Archaea, leading to the six-kingdom system and eventually to the current three-domain system. The classification of eukaryotes is still controversial, with protist taxonomy especially problematic. As microbiology, molecular biology and virology developed, non-cellular reproducing agents were discovered, such as viruses and viroids. Sometimes these entities are considered to be alive but others argue that viruses are not living organisms since they lack characteristics such as cell membrane, metabolism and do not grow or respond to their environments. Viruses can however be classed into "species" based on their biology and genetics but many aspects of such a classification remain controversial. Since the 1960s a trend called cladistics has emerged, arranging taxa in an evolutionary or phylogenetic tree. It is unclear, should this be implemented, how the different codes will coexist. Linnaeus 1735 Haeckel 1866 Chatton 1925 Copeland 1938 Whittaker 1969 Woese et al. 1977 Woese et al. 1990 Cavalier-Smith 2004 2 kingdoms 3 kingdoms 2 empires 4 kingdoms 5 kingdoms 6 kingdoms 3 domains 6 kingdoms (not treated) Protista Prokaryota Monera Monera Eubacteria Bacteria Bacteria Archaebacteria Archaea Eukaryota Protoctista Protista Protista Eukarya Protozoa Chromista Vegetabilia Plantae Plantae Plantae Plantae Plantae Fungi Fungi Fungi Animalia Animalia Animalia Animalia Animalia Animalia
Viruses
Notes on viruses and the diseases caused by it
PHOTOSYNTHESIS
Photosynthesis is the process by which plants, some bacteria and some protistans use the energy from sunlight to produce glucose from carbon dioxide and water. This glucose can be converted into pyruvate which releases adenosine triphosphate (ATP) by cellular respiration. Oxygen is also formed.
Arya Sunil
BASICS OF BIOCHEMISTRY
Biochemistry course for non- biology background students ,this course is to learn just enough about biochemistry for semester examination
Aditya Chaubey
Human Reproduction
the pdf contains consilated theory for the topic Human Reproduction suitable for those who are preparing for neet and the pdf also contains practice questions .
Shivansh Nigam
Genetics
the pdf conatins notes for genetics
Animal Kingdom
Animals are eukaryotic, multicellular, species belonging to the Kingdom Animalia. Every animal has their own unique characteristics. They obtain their energy either by feeding on plants or on other animals. ... They are animals which are composed of several cells and numerous animals are highly portable.
Arun Thomas
Nucleus Biology
Every B.Tech first years have to study some subjects which they don't have any interest to. So that's why i have created few notes on the topic so that it would be easier for students to focus on their field of Interests. These notes will fetch you marks on the D-day and are point to point.
Deepjyoti Ray