QUESTION 24 When light excites chlorophyl, the chlorophyll molecule O a. changes
ID: 146273 • Letter: Q
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QUESTION 24 When light excites chlorophyl, the chlorophyll molecule O a. changes to carotene O b. becomes agitated and moves rapidly c. becomes radioactive d. absorbs the energy and moves an electron to a higher energy state e, becomes ionized QUESTION 25 Which of the following is not a chain of glucose molecules? a. Starch o b. Glycogen O c. Cellulose o d. Lipids QUESTION 26 Which reactions are Not exergonic reactions? o a. Protein synthesis O b. starch synthesis Oc.digestion O d. respiration o e. hydrolysis O f. A and BExplanation / Answer
24. Light is absorbed by chlorophyll during photosynthesis. Chlorophylls are photoreceptors as they have networks of single and double bonds. Their absorptions bands are stronger in visible range of light. Chlorophyll absorbs the light energy. An electron in chlorophyll is excited and it moves from a ground energy state to an excited level. If a suitable electron acceptor is present, the high-energy electron will be transferred to this electron acceptor. If not, it comes back to ground state and the absorbed energy will be converted to heat. During photosynthesis, the energy is passed to other chlorophyll molecules and finally to photosystem II reaction center. There is no ionization or radiation involved.
Carotene is another orange pigment found in plants. They transmit absorbed light to chlorophylls. They also absorb singlet oxygen formed during photosynthesis.
Right answer is: d. absorbs the energy and moves an electron to a higher energy state.
25. Lipids are hydrocarbons containing hydrogen and carbon. They include fats, oils, waxes etc and are important building blocks of cells. They are not carbohydrates. Hence, they lack glucose.
Glucose is a carbohydrate that is a monosaccharide. Starch is a polysaccharide made up of glucose that are linked by alpha 1. 4 glycosidic bonds.
Glycogen is a branched polysaccharide made up of glucose that is linked by alpha 1,4 and alpha 1, 6 glycosidic bonds. Cellulose is a polysaccharide of glucose linked by beta 1,4 glycosidic bonds.
Right answer is: d. lipids
26. Endergonic reactions require an input of energy to drive them. Hence, they are non-spontaneous reaction. Exergonic reactions are spontaneous and result in release of energy. Less energy is stored in reactants than in the products. Synthesis reactions are endergonic while hydrolysis reactions are exergonic.
Protein synthesis is an endergonic reaction as it reduces entropy. A number of enzymes and ribozymes are involved in creation of a peptide bond between amino acids. Nearly 5 ATP molecules are required for attaching one amino acid to growing polypeptide chain. ATP is an energy rich molecules. As energy from ATP is used in peptide bond formation, it is an endergonic process.
Synthesis of starch requires linkage of glucose molecules by glycosidic bonds. Hence, it is an anabolic process. Anabolic processes require inputs of energy. Thus, starch synthesis is an anabolic process.
Cellular respiration leads to formation of ATP from glucose via glycolysis, TCA and electron transport chain. Hence, it is an exergonic process. Digestion is an exergonic process involving hydrolysis of bonds between carbohydrates, proteins and lipids, forming smaller compounds. Hydrolysis reactions are exergonic as the reactants have less energy than products. Breakage of bonds will release energy.
Right answer is f. A and B
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