Question

74. Under actual cellular conditions, how many strongly exergonic reactions take place in glycolysis?

71. For every starting molecule of glucose, how many NTPs are made directly in the Citric Acid Cycle (not including any ATP made in the ETC)?

69. What percentage of carbon atoms in cholesterol are derived from acetyl-coA?

68. How many fatty acid chains are attached to a membrane phospholipid?

38. The hormone that stimulates the synthesis of glycogen and inhibits its breakdownis __________________.

please answer all the question

Answer 1

Q1) under actual cellular conditions, how many strongly exergonic reactions take place in glycolysis?

Ans: 2 exergonic reactions take place.

Soln : Exorgenic are the Reactions in which chemical bonds are broken, releasing the energy in those bonds. Exergonic reactions are those that have a negative value of ΔG and are spontaneous.

a) The enzyme phosphoglycerokinase transfers a phosphate from BPG to a molecule of ADP to form ATP. This happens to each molecule of bisphosphoglycerate (BPG). This reaction yields two 3-phosphoglycerate (3 PGA) molecules and two ATP molecules.

b) The enzyme pyruvate kinase transfers a Phosphate from PEP to ADP to form pyruvate and ATP. This happens for each molecule of phosphoenolpyruvate (PEP). This reaction yields two molecules of pyruvate and two ATP molecules.

Hence these two reactions that are step 7 and step 10 are the exergonic reactions in the glycolysis.

Q2) For every starting molecule of glucose, how many NTPs are made directly in the citric acid cycle? not including any atp made from etc?

Ans: 2 ATPs are formed.

soln: the Krebs cycle uses a molecule of acetyl CoA to generate 1 ATP, 3 NADH, 1 FADH2, 2 CO2, and 3 H+. Two molecules of acetyl CoA are produced in glycolysis so the total number of molecules produced in the citric acid cycle is doubled (2 ATP, 6 NADH, 2 FADH2, 4 CO2, and 6 H+). Both the NADH and FADH2 molecules made in the Krebs cycle are sent to the electron transport chain, the last stage of cellular respiration. hence, only 2 ATPs are formed in this process.

Q3) What percentage of carbon atoms in cholesterol are derived from acetyl-CoA

Ans: 100 percentage of carbon atoms in cholesterol are derived from acetyl-CoA

soln: Cholesterol is made up of 27 carbon atoms in the following steps.

a) synthesis of isopentenyl pyrophosphate, an activated isoprene unit that is the key building block of cholesterol. in this step 5 carbon compounds are formed

b) the condensation of six molecules of isopentenyl pyrophosphate to form squalene. in this step 30 carbon compound.

c) squalene cyclizes in an astounding reaction and the tetracyclic product is subsequently converted into cholesterol. It leads to the release of 3 carbon atoms and forming 27 carbon compounds.

Q4) How many fatty acids chains are attached to a membrane phospholipid?

Ans: 2 fatty acid chains are attached to membrane phospholipids.

Soln: Phospholipids are major components of the plasma membrane they are composed of fatty acid chains attached to a glycerol backbone. Unlike triglycerides, which have three fatty acids, phospholipids have two fatty acids that help form a diacylglycerol. The third carbon of the glycerol backbone is also occupied by a modified phosphate group.

Q5) The hormone that stimulates the synthesis of glycogen and inhibits its breakdown.

Ans: insulin stimulates the synthesis of glycogen and inhibits its breakdown.