Review Questions Chp 6 (key)

Review Questions - Chapter 6 (KEY)

Ground Rules of Metabolism 1. 2.

___Metabolism_______ is the controlled capacity to acquire and use energy for stockpiling, breaking apart, building, and eliminating substances in ways that contribute to survival and reproduction. Define energy; be able to state the first and second laws of thermodynamics. Potential energy is the capacity to make things happen, to do work.; it can also be called chemical energy, measured in kilocalories. Kinetic energy is the energy of motion; it includes heat energy.

First law of thermodynamics states that the total

amount of energy in the universe is constant; it cannot be created nor destroyed; it can only change form.

Second law of thermodynamics states that the

spontaneous direction of energy flow is from high- to low-quality forms.

3. 4.

____Entropy______ is a measure of the degree of randomness or disorder of systems. Explain how the world of life maintains a high degree of organization.

5.

Reactions that show a net loss in energy are said to be __exothermic

6.

The world of life (plant and animal) maintains a high degree of organization only because it is being re-supplied with energy from the sun. (exergonic)_______; reactions that show a net gain in energy are said to be __endothermic (endergonic)________. ATP is composed of __ribose________, a five-carbon sugar, three __phosphate________ groups, and __adenine________, a nitrogencontaining compound.

7. 8.

Adding a phosphate to a molecule is called __phosphorylation________. Explain what a gradient is in general; then describe (a) concentration gradients, (b) pressure gradients, and (c) electric gradients. A. What Is a Concentration Gradient?

1. Concentration refers to the number of molecules (or ions) of a substance in a given volume of fluid. 2. The thermal energy of the molecules drives the movement of molecules. a. Molecules constantly collide and tend to move down a concentration gradient (high to low). b. The net movement of like molecules down a concentration gradient is called diffusion; each substance diffuses independently of other substances present as illustrated by dye molecules in water. B. What Determines Diffusion Rates? 1. Several factors influence the rate and direction of diffusion: concentration differences, temperature (higher = faster), molecular size (smaller = faster), electric gradients (a difference in charge), and pressure gradients. 2. When gradients no longer exist, there is no net movement (dynamic equilibrium). Explain the functioning of the ATP/ADP cycle. ATP Couples Energy Inputs With Outputs 1. ATP is composed of adenine, ribose, and three phosphate groups. a. Energy input links phosphate to ADP to produce ATP (phosphorylation). b. ATP can in turn donate a phosphate group to another molecule, which then becomes primed and energized for specific reactions. 2. ATP's role is like currency in an economy: earning ATP during exergonic reactions and spending it during endergonic ones. 3. ADP can be recycled to ATP very rapidly in the ATP/ADP cycle. C. Some Electron Transfers Drive ATP Formation 1. Electrons are transferred in nearly every reaction that harnesses energy for use in the formation of ATP.

10. ATP directly or indirectly delivers __energy________ to almost all biosynthetic pathways. 11. Give the function of each of the following participants in metabolic pathways: reactants, intermediates, enzymes, cofactors, and end products.

Reactants are substances that enter reactions. 2. Intermediates are the compounds formed between the start and the end of a pathway. 3. Products are the substances present at the 1.

conclusion of a pathway.

4.

Enzymes

5.

Cofactors

up) reactions.

are proteins that catalyze (speed

are small molecules and metal ions that help enzymes by carrying atoms or electrons.

6. End products are the final compound(s) that is(are) formed in a metabolic pathway.

12. Cite one example of a coenzyme. Coenzymes are large organic molecules such as NAD+, FAD, and NADP+. 13. What is the function of metabolic pathways in cellular chemistry? Metabolic pathways form series of reactions that regulate the concentration of substances within cells by enzymemediated linear and circular sequences. 14. Explain the effects of enzymes on activation energy. Enzymes are catalytic molecules that alter the rate of a chemical reaction by lowering a reaction’s activation energy.

15. Describe the induced-fit model. Inducing changes in enzyme shape (induced-fit model), can regulate an enzymatic reaction. Sometimes a substrate does not quite fit the enzyme’s active site. The enzyme can still bind to the substrate and as it does, the enzyme causes (induces) bonds to be stretched or, otherwise altered, such that the substrate now fits the active site and the reaction can proceed. 16. Describe the control mechanism known as feedback inhibition. Allosteric enzymes have (in addition to active sites) regulatory sites where control substances can bind to alter enzyme activity; if this

control substance is the

end product in the enzyme’s metabolic pathway, feedback inhibition occurs.

17. What are "allosteric enzymes," and what is their function? Allosteric enzymes have (in addition to active sites) regulatory sites where control substances can bind to alter enzyme activity. This is a control mechanism for how many enzyme molecules are available for a particular reaction.

18. Explain what happens to enzymes if temperature and pH continually increase. Because enzymes operate best within defined temperature ranges, high temperatures decrease reaction rate by disrupting the bonds that maintain three-dimensional shape

(denaturation occurs).

Most enzymes function best at a pH near 7 (pepsin in the stomach is an exception); higher or lower values disrupt enzyme shape

(denaturation occurs).

and halt function.

19. Distinguish diffusion from osmosis, and active transport from passive transport.

Refer to chapter 5 Review Questions (KEY)

20. Describe and contrast exocytosis and endocytosis. Explain the role of vesicle formation in both processes.

Refer to chapter 5 Review Questions (KEY)

21. Describe phagocytosis and describe the kind of phagocytosis that occurs in your body.

Refer to chapter 5 Review Questions (KEY)

22. Water tends to diffuse from (select one) __ hypertonic __ hypotonic solutions to (select one) __ hypertonic __ hypotonic solutions.