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Everything you need to know about biochemistry of the molecules of life. Some of the questions are as follows:-
Q.1. What are the four elements that make up over 98% of all living matter? Also name the other two elements which are next to them in importance.
Ans: The four major elements are carbon, oxygen, hydrogen and nitrogen. The other two elements next to them in importance are: phosphorus and sulphur.
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Q.2.What is the importance of weak bonds?
Ans: The weak bonds make important biological systems and determine the very important properties of the molecules and are responsible for their proper functioning,
Q.3. What are macromolecules?
Ans: The macromolecules consist of many repeating subunits. Each subunit consists of a small simple molecule.
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Q.4. What is an element? Name their three components.
Ans: An element is a pure substance comprising a single type of atoms. The three components of an atom are electron, proton and neutron.
Q.5. What are strong bonds?
Ans: The strong bonds are often covalent bonds formed when atoms share electrons to fill in their outer shell achieving thereby maximum stability. The stronger the bond, the more energy is needed to break it.
Q.6. Discuss whether the hydrogen bonds are weak or strong.
Ans: The hydrogen bonds are weak but biologically they are very important. The two strands of DNA are held together by hydrogen bonds. The hydrogen bonds also determine the shape of proteins.
Q.7. What are monomers? Give three examples of macromolecules and their monomers.
Ans: The small repeating subunits which make large or macromolecules are called monomers.
The three examples of macromolecules and their monomers are as follows:
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1. The proteins, which are chains of amino acids that form polypeptides.
2. The polysaccharides, which are the chains of monosaccharide’s which form branching structures.
3. The nucleic acids DNA and RNA each of which is made up of nucleotides.
Q.8. Which are two major groups of amino acids?
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Ans: The carboxyl group and the amino group are two groups bonded to the same carbon atom.
Q.9. How many amino acids are there in a protein?
Ans: There are twenty amino acids each differing in its side chains.
Q.10. How are peptide bonds synthesized?
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Ans: The peptide bonds are formed by the formation of a covalent bond between the amino group of one amino acid and the carboxyl group of another amino acid, accompanied by removal of HOH which is called dehydration synthesis.
Q.11. Give two examples of substitute proteins.
Ans: They are glycoproteins and lipoproteins which contain covalently bonded molecules, sugars and lipids other than amino acids.
Q.12. What are polysaccharides? Give three categories of carbohydrates.
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Ans: The polysaccharides are polymers of monosaccharide’s. The three categories of carbohydrates are monosaccharide (pentoses and hexoses), disaccharides, and polysaccharides.
Q.13. Name the two nucleic acids. What are their monomers (subunits)?
Ans: They are:
1. Deoxyribonucleic acid (DNA)
2. Ribonucleic acid (RNA).
Their monomers (subunits) are nucleotides which are un-branched.
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Q.14. Give composition of nucleotides of DNA.
Ans: The nucleotides of DNA are made up of three units which are:
(1) A nitrogen base called purine made up of adenine or guanine or pyrimidine (thymine or cytosine),
(2) deoxyribose (bonded covalently), and
(3) A phosphate molecule.
Q.15. How are double helix strands of DNA occurring in a cell joined?
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Ans: The two strands in a helix are joined together by hydrogen bonding between adenine and thymine and between guanine and cytosine.
Q.16. How does RNA differ from DNA?
Ans: The nucleotides in ribonucleic acid are same as in DNA except that ribose replaces deoxyribose and there is uracil in place of thymine. There are three different types of RNA which are found in the cell, e.g., rRNA, mRNA and tRNA.
Q.17. Are lipids macromolecules? Are they biologically important?
Ans: No, the lipids are too small and heterogeneous that cannot be considered as macromolecules. They are of great-biological significance.
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Q.18. Name two neurotransmitters.
Ans: Acetylcholine is a transmitter at motor end plates (neuromuscular junctions) which are junctions between nerve and striated muscle. The Y –amino butyrate, also known as gamma-amino butyric acid or GABA is also a neurotransmitter.
Q.19. How do Bacteria Detect and Move towards Nutrients in their Environment?
Ans: The movement of bacteria towards some specific substances and away from others is known as chemo-taxis. In 1960s Julius Alder began to investigate the molecular basis of bacterial chemo-taxis. The chemo-taxis begins with the detection of chemicals by specific chemoreceptors on the surface of cell.
Information from these sensors is transmitted to a processing system which analyzes and integrates many stimuli. This sensory processing system consequently sends signals to the motors that drive the flagella. These signals determine whether a bacterium continues to swim smoothly in a straight line or changes its course all of a sudden. Approximately twenty different chemoreceptors have been detected in Escherichia coli.
Each of these proteins is located either in the plasma membrane or in the periplasmic space. The galactose binding protein which is a soluble protein in the periplasmic space serves as a recognition protein for positive chemotaxis to galactose in addition to being part of the pump that actively transports it into the cell.
The chemoreceptor for glucose is a component of membrane-bound phosphotransferase system for the active uptake of sugars. The surface of the bacterium E. coli also contains chemoreceptors for attractants like serine, cysteine, alanine and glycine. Some of the typical examples of chemoreceptors for negative chemotaxis are fatty acids, alcohols, hydrophobic amino acids, indole, H+ (pH < 6.5), OH~ (pH > 7.5) and sulphides.
Q.20. What are the general Characteristics of Lipids?
Ans: The important general characteristics of lipids are as follows:
1. The lipids are insoluble in water but soluble inorganic solvents. This difference in their nature for solubility is due to nonpolar hydrophobic nature.
2. The lipids are not made up of similar subunits.
3. Some of the simple lipids which are made up of C, H and O include fats and steroids. The fat is made up of glycerol covalently bonded to fatty acids. The steroids consist of four-membered ring structure.
4. The compound lipids consist of fatty acids and glycerol and usually have elements other than C, H and O, e.g., phospholipids, lipoproteins and lipopolysaccharides. They are of great importance in the cell envelope of bacteria.
5. The phospholipids are of two parts. The polar end is soluble in water while the nonpolar end containing C and H is insoluble in water but soluble in organic solvents.
