Deck 4: Cellular Metabolism

Question 1

State the first and second laws of thermodynamics. Living systems may appear to violate the second law of thermodynamics because living things maintain a high degree of organization despite a universal trend toward increasing disorganization. What is the explanation for this apparent paradox?

Answer 1

The first law of thermodynamics states that "energy cannot be created nor destroyed but it can be converted from one form to another".
The second law of thermodynamics states that "closed system moves toward increasing disorder, or entropy".
Living systems appear to violate the second law of thermodynamics because living things maintain a high degree of organization despite a universal trend toward increasing disorganization.
Living systems are not closed but open systems which utilize the energy in the environment to make themselves more organized. However after death of the living system, the second law of thermodynamics is followed and entropy occurs.

Question 2

Explain what is meant by "free energy" in a system. Will a reaction that proceeds spontaneously have a positive or negative change in free energy?

Answer 2

The free energy in a system is the energy available for doing work.
A reaction that proceeds spontaneously will have a positive change in the free energy and such reactions are called as exergonic reactions.

Question 3

Many biochemical reactions proceed slowly unless the energy barrier to the reaction is lowered. How is this accomplished in living systems?

Answer 3

In many biochemical reactions energy barrier to the reaction must be lowered in order to continue the reaction. This is accomplished by the chemical substances known as catalysts. They are helpful in reducing activation energy and accelerating the chemical reaction. Enzymes are the biological catalysts that are used in the living world to carry out many biochemical reactions at a faster rate.

Question 4

What happens in the formation of an enzyme-substrate complex that favors the disruption of substrate bonds?

Question 5

What is meant by a "high-energy bond," and why might the production of molecules with such bonds be useful to living organisms?

Question 6

Although ATP supplies energy to an endergonic reaction, why is it not considered a fuel?

Question 7

What is an oxidation-reduction reaction and why are such reactions considered so important in cellular metabolism?

Question 8

Give an example of a final electron acceptor found in aerobic and anaerobic organisms. Why is aerobic metabolism more efficient than anaerobic metabolism?

Question 9

Why must glucose be "primed" with a high-energy phosphate bond before it can be degraded in the glycolytic pathway?

Question 10

What happens to the electrons removed during the oxidation of triose phosphates during glycolysis?

Question 11

Why is acetyl-CoA considered a "strategic intermediate" in respiration?

Question 12

Why are oxygen atoms important in oxidative phosphorylation? What are the consequences if they are absent for a short period of time in tissues that routinely use oxidative phosphorylation to produce useful energy?

Question 13

Explain how animals can generate ATP without oxygen. Given that anaerobic glycolysis is much less efficient than oxidative phosphorylation, why has anaerobic glycolysis not been discarded during animal evolution?

Question 14

Why are animal fats sometimes called "the king of fuels"? What is the significance of acetyl-CoA to lipid metabolism?

Question 15

The breakdown of amino acids yields two products: ammonia and carbon skeletons. What happens to these products?

Question 16

Explain the relationship between the amount of water in an animal's environment and the kind of nitrogenous waste it produces.

Question 17

Explain three ways that enzymes may be regulated in cells.