KEY POINTS
v Proteins, Carbohydrates and lipids are the biological molecules which are more in eukaryotic cells.
v DNA and RNA are the biological molecules which are more in prokaryotic cells.
S.NO | CHEMICAL COMPONENTS | % TOTAL CELL WEIGHT | |
BACTERIAL CELL | MAMMALIAN CELL | ||
1. | Water | 70 | 70 |
2. | Proteins | 15 | 18 |
3. | Carbohydrates | 3 | 4 |
4. | Lipids | 2 | 3 |
5. | DNA | 1 | 0.25 |
6. | RNA | 6 | 1.1 |
7. | Other organic mocules (enzymes, hormones, metabolites) | 2 | 2 |
8. | Inorganic ions (Na+,K+ ,Mg++,Cl-, SO4- etc) | 1 | 1 |
v Carbon and hydrogen bond is the potential source of chemical energy for cellular activities.
v Amount of water varies from 65 to 89% in different organisms.
v Human bone cell contain 20% water and brain cells contain 85% water.
v The specific heat of vaporization of water is 574 K Cal / Kg.
v Evaporation of only 2ml out of one litre of water lowers the remaining 998ml of water’s temperature by 1oC.
v At 25oC, the concentration of each H+ and OH- ions in pure water is about 10-7 moles / lit.
v Glycoproteins and glycoliplids have structural role in extracellular matrix of animals and bacterial cell.
v Monosaccharide are chemically polyhydroxy aldehydes or ketones.
v All carbon atoms on a monosaccharide have a hydroxyl group except one.
v The aldehydes form of triose is called glyceraldehydes and ketone form is called dihydroxyacetone.
v Tetroses are rare in nature and occur in some bacteria.
v From the biological point of view the most important hexose is glucose. It is an aldose sugar.
v In free states, glucose is present in all fruits, being abundant in graps, figs and dates.
v Our blood normally contains 0.08% glucose.
v For the synthesis of 10gm of glucose, 717.6k Cal of solar energy is used.
v The covalent bond between two monosaccharides is called glyosidic bond.
v Amylase starches have unbranched chains of glucose and are soluble in hot water.
v Starches give blue colour with iodine.
v Glycogen is called animal starch.
v Glycogen is insoluble in water and gives red colour with iodine.
v The most abundant carbohydrate in nature is cellulose.
v Cellulose gives no colour with iodine.
v The lipids are heterogenous group of compounds related to fatty acids.
v Lipids store double the amount of energy as compared to the same amount of any carbohydrates.
v Chemically acylglycerols can be defined as esters of fatty acids and alcohol.
v In Esterification, OH from alcohol and H combine to form water.
v In animals the fatty acids are straight chains while in plants, these may be branched or ringed.
v The melting point of palmatic acid is 63.1oC and that of butyric acid is -8oC.
v Oleic acid is an un-saturated fatty acid.
v Animal fats are solid at room temperature where as most of the plant fats are liquids.
v Fats and oils are lighter than water and have specific gravity of about 0.8.
v Phosphatidylcholine is commonly called glecithin.
v Movement of organs and organisms and movement of chromosomes during anaphase of cell division are caused by proteins.
v The number of amino acids varies from a few to 3000 or even more in different species.
v About 170 types of amino acids have been found to occur in cells and tissue. Of these about 25 are constituents of proteins. Most of the proteins are however composed of 20 types of amino acids.
v In Glycine R is replaced by hydrogen atom, NH3 in alanine.
v Amino acids mainly differ due to the type or nature of R group.
v The primary structure of protein comprises the number and sequence of amino acids.
v In insulin, the two polypeptides are held together by disulphide bridge.
v There are over 10,000 proteins in human body.
v The sequence of amino acids is determined by the order of nucleotides in the DNA.
v One of the common secondary protein structure is a-helix. The a-helix is a very uniform geometric structure with 3.6 amino acids in each turn of helix.
v B-pleated sheet is formed by the fold backs of the polypeptide.
v Tertiary structure is maintained by three types of bonds namely ionic, hydrogen and disulphide.
v In Fibrous proteins, secondary structure is most common.
v Fibrous proteins are non-crystalline, elastic and insoluble in aqueous media.
v Fibrous protein of nails and hairs is called keratin.
v In Globular proteins, tertiary structure in most common.
v Globular proteins are soluble in aqueous media, such as salt solution, solution of acids or bases or aqueous alcohol.
v ATP is an imported nucleotide used as an energy currency by the cell.
SOURCE OF DNA | ADENINE | GUANINE | THYMINE | CYTOSINE |
Man | 30.9 | 19.9 | 29.4 | 19.8 |
Sheep | 29.3 | 21.4 | 28.3 | 21.0 |
Wheat | 27.3 | 22.7 | 27.1 | 22.8 |
Yeast | 31.3 | 18.7 | 32.9 | 17.1 |
v DNA is made up of four kinds of nucleotides namely d-adenosine monophosphate (d-AMP), d-guanosine monophosphate (d-GMP) d-cytidine monophosphate (d-GMP) and d-thymidine monophosphate (d-TMP).
v Nitrogenous basis are of two types single-ringed pyrimidines and double ringed purines.
v NAD is a dinucleotiode and an important co-enzyme.
v In 1951, Erwin Chargoff provided data about the ratios of different bases present in a DNA molecule.
TYPES OF CELL | AMOUNT OF DNA / NUCLEUS IN PICTOGRAM IN CHICKEN | AMOUNT OF DNA / NUCLEUS IN PICTOGRAM IN CARP |
Red Blood Cells | 2.3 | 3.3 |
Liver Cells | 2.4 | 3.3 |
Kidney Cells | 2.4 | 3.3 |
Sperm Cells | 1.3 | 1.6 |
v In each turn of DNA, there are about 10 base pairs of about 35 Angstron unit.
v Haemophilus Influenza is the first microbe to have the genome completely sequenced.
v RNA is synthesized by DNA in a process called transcription.
v m-RNA consists of a strand of variable length.
v For a protein molecules of about 1,000 amino acid, m-RNA may will have the length of 3,000 nucleotides.
v mRNA is about 3-4% t-RNA is about 10-20% and r-RNA may upto 80% of the total cellular RNA.
v t-RNA molecules have a chain length of 75-90 nucleotides.
v r-RNA is strongly associated with the ribosomal proteins where 40 to 50% of it is present.
v Two different molecules, belonging to different categories, usually combine together the form conjugated molecules.
v Most of the cellular secretions are glycoproteins in nature. Both glycoproteins and glyolipids are integral structural components of plasma membrane.
v The nucleohistones are present in chromosomes.