4. There pts). are three lipids (A-C) Brieftly describe one major functional rol

Question

4. There pts). are three lipids (A-C) Brieftly describe one major functional role of individual lipids, respectively, in cells (6 5. The structure of acetyl-CoA is shown below. Draw the hydrolvzed product(s) of acetyl-CoA, and explain why CoA is considered a high energy molecule (6 pts). acetyl S-CoA 6. This is one of reactions in glycolysis. i) Considering what type of reaction occurs, fill out the blank with names of coenzymes necessary for this reaction. i) Briefly explain why this reaction uses a phosphate ion, instead of ATP phosphorylation, ii) predict if this reaction is reversible or irreversible (10 pts). 2- OPO,2 OPO32

Explanation / Answer

4) THe three types of lipids in the figure are

a - triglycerides. These compounds are formed by the esterification reaction of all threee hydroxyl groups of glycerol with different fatty acids. They function as energy source inside the cell.

b - Phospholipids. Phospholipids play a key role in biosynthesis of lipid bilayer of the cells as well as are involved in metabolism and cell signalling.

c - saccharolipids. these are lipid molecules derived from the linkage of sugar molecules to fatty acids. They form an important component of lipopolysaccharide layer around the cell, thus providing the bacteria protection from the external environment.

5) the hydrolysed product of acetyl-CoA are acetate (CH3COOH) and CoA (Coenzyme A).

About two thirds of the energy requirements of aerobic cells is met by the complete oxidation of the acetyl group of acetylCoA to CO2 in the TCA cycle.

During a sequence of the TCA cycle, acetylCoA condenses with oxaloacetate to form citrate in a reaction catalyzed by the enzyme citrate synthase. During the subsequent reactions citrate is converted back to oxaloacetate with electron donated to coenzymes NAD+ and FAD for ATP generation from oxidative phosphorylation, and release of two carbons as CO2. Hence acetylCoA is considered a high enegy molecule.

5)

i - A is NAD+ (reduced Nicotinamide adenine dinucleotide)and B is NADH (oxidised Nicotinamide adenine dinucleotide)

ii - in this reaction during the payoff stage of glycolsis, G3P is converted t o1,3BPG with the formation of NADH

NADH is formed by the reduction of NAD+ by hydrogen.

Therefore in order to maintain hydrogen balance and charge balance, phosphate ion is used instead of ATP.

iii - yes this reaction is reversible. depending on the concentration of G3P and 1,3BPG, the reaction can go in forward or reverse direction.

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