Question

ENT.pa! Adobe Reader Window Help Tος Question 3 Why do animals not convert all excess fuel into fatty acids instead they store their energy as glycogen? [4] Question 4 Discuss important differences between fatty acid biosynthesis and fatty acid oxidation [10] Question 5 Outline the synthesis of fructose-6-phosphate from 3-phosphoglycerate. [10]

biochemistry

Answer 1

Question 3

Glycogen is an important fuel reserve for several reasons. The controlled breakdown of glycogen and release of glucose increase the amount of glucose that is available between meals. Hence glycogen serve as a buffer to maintain the blood glucoe levels. Moreover the glucose from the glycogen is readily mobilized and is therefore a good energy source for a sudden strenous activity. Ulike fatty acids the release of glucose can provide energy in the absence of oxygen and thus supply energy for an anaerobic activity.

Question 4

Fatty acids are broken down to acetyl co-enzymeA by means of beta oxidation inside the mitochondria whereas fatty acids are synthesised from acetyl co-enzymeA outside mitochondria. The two processes are different in the way they occur, type of reactions, and the substrate used.

Below are the differences tabulated.

Fatty acid oxidation Fatty acid bio-synthesis

products is acetyl co-enzymeA.	precursor is acetyl co-enzymeA
malonyl co-enzymeA is not involved.	malonyl co-enzymeA is the source of carbons.
oxidative process, require NAD+ and FAD.	reductive process, requires NADPH and ATP.
starts at carboxyl end.	starts at methyl end.
occurs is mitochondrial matrix.	occurs in cytosol.
fatty acids form thio ester bond with COASH	fatty acids form thio ester bond with acyl-carrier protein ACP.
beta hydroxy intermediates have L configuration.	beta hydroxy intermediates have D configuration.

Question 5

This synthesis occurs as a part of gluconeogenesis. I m attaching an image of the procedure. Please do go through the image.

(2) Pyruvate (2) HC0, +(2) ATP) pyruvate carboxylase (2) ADP + (2) GTP) (2) Oxaloacetate PEP carboxykinase (2) CO2 + (2) GDP + (2) PEP (2) 3-Phosphoglycerate (2) ATP phosphoglycerate kinase (2) ADP + (2) 1,3-Bisphosphoglycerate NADH + H+ Fructose-1,6-bisphosphate -NAD P f ructose-1,6-bisphosphatase Fructose-6-phosphate Glucose-6-phosphate Piw g lucose-6-phosphatase