Chapter 5: Energy and Life

Question 1

Energy

Answer 1

• The ability to do work
• Kinetic energy: motion
• Potential energy: stored energy

Question 2

Thermodynamics

Answer 2

• The study of energy or heat changes

Question 3

Chemical reactions

Answer 3

• Making and breaking of chemical bonds

Question 4

1st Law of Thermodynamics

Answer 4

• Energy cannot be created or destroyed

- Energy flows in one direction and some of that energy is dissipated as heat

Question 5

2nd Law of Thermodynamics

Answer 5

• Entropy: measure of the degree of disorder in a system

Question 6

Substrate (reactants)

Answer 6

• Starting molecules of a chemical reaction

Question 7

Products

Answer 7

• Molecules at the end of a reaction

Question 8

Endergonic reactions

Answer 8

• product contains more energy than reactants
• require input of energy
• not spontaneous

Question 9

Exergonic reactions

Answer 9

• produces products that contain less free energy than that produced by original reactants
• release energy
• can be spontaneous

Question 10

Activation energy

Answer 10

• initial input of energy needed to start reaction, break bonds

Question 11

Catalysis

Answer 11

• lowers the activation energy of a reaction

Question 12

Enzymes

Answer 12

• catalysts used by cells to perform particular reactions

- usually proteins but can be nucleic acids

Question 13

Induced fit model

Answer 13

• active site + reactant binding site = puzzle piece fit

Question 14

Biochemical pathway

Answer 14

• catalyzed reactions occur together in sequence

Question 15

Effect of temperature on enzymes

Answer 15

• as temp increases, reaction rate increases
• but, if temp gets too high, enzyme denatures and loses its shape and function
• optimal range for humans is 35-40° C

Question 16

Effect of pH on enzymes

Answer 16

• optimal range for humans is 6-8

- except for stomach which is pH 2

Question 17

Allosteric enzymes

Answer 17

• cells can control enzymes by altering their shape

- allosteric enzymes are affected by the binding of signal molecules

Question 18

Feedback inhibition

Answer 18

• a form of enzyme inhibition where the product of a reaction acts as a repressor

Question 19

Competitive inhibition

Answer 19

• binding of inhibitor to active site prevents reaction from occurring
• e.g., Lipitor

Question 20

Noncompetitive inhibition

Answer 20

• inhibitor reduces activity of enzymes

- e.g., certain antibiotics

Question 21

ATP

Answer 21

• Adenosine triphosphate
  1. A sugar
  2. An adenine nucleotide
  3. A chain of 3 phosphate groups (energy is stored between the phosphate groups, they have same charge and don’t want to be near each other)

Question 22

How is energy released from ATP?

Answer 22

• When the endmost phosphate group is broken off an ATP molecule

Question 23

Equation for ATP breakdown

Answer 23

ATP –> ADP + Pi + energy

Question 24

Coupled reactions

Answer 24

• occur when exergonic reactions are used to pay for the initiation of endergonic reactions

Question 25

Oxidation-reduction reactions

Answer 25

• redox reactions
• electrons pass from atoms or molecules to one another
• involve transfer of energy because the electrons retain their potential energy