Enzymes and Energy (week 3)

Question 1

what is metabolism?

Answer 1

All the chemical reactions that transpire inside cells, including those that use and release energy,

Question 2

1st law of thermodynamics

Answer 2

Energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another; the total energy of the universe is constant

Question 3

catabolic

Answer 3

breaks down big complex molecules into smaller, easier to absorb molecules; releases energy

Question 4

anabolic

Answer 4

Anabolism builds molecules required for the body’s functionality; requires energy

Question 5

2nd law of thermodynamics

Answer 5

1. It states that as energy is transferred or transformed, more and more of it is wasted.
2. states that there is a natural tendency of any isolated system to degenerate into a more disordered state.
3. The state of entropy (disorder) of the entire universe will always increase over time.

Question 6

exergonic (Gibbs Free energy)

Answer 6

the free energy of the products is lower than that of the reactants; Negative ∆G: free energy is given off during the reaction; usually occurs in cellular respiration

Question 7

endergonic (Gibbs free energy)

Answer 7

the free energy of the products is higher than that of the reactants;
Positive ∆G: an input of free energy is required for the reaction; usually occurs in photosynthesis

Question 8

what are enzymes?

Answer 8

biological catalysts that speed up chemical reactions in living organisms; they do so by lowering activation energy

Question 9

where do substrates bind to the enzyme?

Answer 9

active site

Question 10

are enzymes consumed during chemical reactions?

Answer 10

no

Question 11

what can happen if there is more substrate than enzyme present?

Answer 11

the enzyme can saturate

Question 12

what increases the rate of an enzymatic reaction

Answer 12

1. add more enzyme
2. add more substrate until the point of saturation
3. adjust pH to optimal level

Question 13

what is an enzyme inhibitor?

Answer 13

A substance that blocks the action of an enzyme

Question 14

Competitive inhibitors

Answer 14

inhibitor binds to/directly to the active site

Question 15

noncompetitive inhibitor

Answer 15

inhibitor binds not to the active site but rather elsewhere (allosteric site) on the enzyme and this binding causes the active site to change shape

Question 16

activation energy

Answer 16

The energy which must be added to a system to start a reaction

Question 17

free energy doesn’t change when enzymes are present. T or F

Answer 17

T

Question 18

how are enzymes specific?

Answer 18

1.They usually only catalyze one and only one reaction
2. Typically only the substrates can bind to the enzyme
3. This is due to the specific shape and nature of binding of the substrates to the active site

Question 19

examples of specific enzymes

Answer 19

1. phosphofructokinase: cellular respiration
2. ligase: DNA replication
3. acetylcholinesterase: skeletal muscle replication
4. pancreatic proteases: protein digestion
5. hyaluronidase - fertilization

Question 20

how do enzymes act upon substrates?

Answer 20

enzyme substrate complex

Question 21

steps of enzyme action

Answer 21

1. initiation: reactants bind to active site to form complex
2. transition state facilitation: interactions between enzyme/substrate lower activation energy
3. termination: products are released and enzyme is unchanged

Question 22

properties of enzymes:

Answer 22

1. Enzymes are not consumed in the reaction.
2. Enzymes can catalyze both the forward and the reverse reactions.
3. Enzymes are extremely sensitive to the external environment.
4. Enzymes can saturate. šEnzymes can denature.

Question 23

enzyme regulation

Answer 23

Most can be regulated (turned on or
off) by the cell

1. Constitutive enzymes: present in relatively high amounts regardless of conditions
2. Inducible enzymes: present at low levels, unless their synthesis is induced by an inducing agent

Question 24

what factors influence enzyme functioning?

Answer 24

1. Environment: temperature and pH
2. Cofactors and coenzymes
3. Competitive inhibition
4. Noncompetitive inhibition

Question 25

what is a cofactor?

Answer 25

1. a non-protein chemical compound that is required for the enzyme’s activity
2. Many enzymes require cofactors to function properly
3. Considered to be “helper molecules” that assist enzymes in their action
4. Can be ions or organic molecules

Question 26

Feedback Inhibition

Answer 26

1. when the product of a pathway acts as an inhibitor of the pathway prevents too much buildup of product
2. Provides a means of self-regulating in a system