Chapter 8 - energy and enzymes

Question 1

Where is energy stored in molecules ?

Answer 1

in the bonds
- covalent bonds have the most energy, then ionic, then hydrogen

Question 2

creating bonds _____________ energy; breaking bonds __________ energy

Answer 2

requires; releases

Question 3

what is the first law of thermodynamics

Answer 3

energy is neither created nor destroyed; it simply changes form
- mitochondria does not “make energy”, it transforms glucose into ATP

Question 4

what is potential energy

Answer 4

energy stored in a position or configurationk

Question 5

what is kinetic energy

Answer 5

energy in motion

Question 6

which has more decreasing potential energy: non polar bonds or polar bonds

Answer 6

polar bonds
- non polar covalent bonds have the most potential energy

Question 7

do lipids tend to have high or low potential energy

Answer 7

high potential energy

Question 8

do carbs tend to have high or low potential energy

Answer 8

low (polar)

Question 9

what is enthalpy

Answer 9

the total energy in a molecule
- includes potential energy in the bonds of the molecule plus the kinetic energy’s effect on pressure/volume of its surroundings (represented as H)

Question 10

define exothermic

Answer 10

releases heat, change in H is negative

Question 11

define endothermic

Answer 11

uptake of heat, change in H is positive

Question 12

define entropy

Answer 12

the amount of disorder

Question 13

what is the second law of thermodynamics

Answer 13

entropy always increases in a system that includes surroundings as well as the products of the reaction

Question 14

What is Gibbs free energy

Answer 14

determines whether the reaction is spontaneous or requires added energy to be produced

Question 15

what is gibbs free energy equation

Answer 15

ΔG = ΔH - (TΔS)
- H = change in enthalpy
- S = change in entropy
- T = temperature in degrees kelvin
- reactions are non spontaneous when ΔG is greater than 0

Question 16

do spontaneous reactions have to happen quick?

Answer 16

no; they may take years (such as rusting)

Question 17

when does entropy increase

Answer 17

when no energy is brought into a system

Question 18

what is energetic coupling

Answer 18

when energy is released from an exergonic reaction and is used to power an endogenic reaction
- occurs through a transfer of electrons or transfer of a phosphate group (ADP to ATP)

Question 19

what are redox reactions related to energetic coupling?

Answer 19

reduction - oxidation reactions that are non spontaneous
- oxidation: loss of electrons
- reduction: gain of electrons

Question 20

what are ATP transfers relating to energetic coupling?

Answer 20

energy via phosphate groups (non-spontaneous)
- hydrolysis of ATP
phosphorylation coupled with endergonic reactions

Question 21

define activation energy:

Answer 21

the amount of kinetic energy required to initiate a chemical reaction
- energy needed to reach a transition state

Question 22

how does a higher temperature impact enzyme substrate collision

Answer 22

higher temperatures impact the collisions by creating more of them until the enzyme hits the optimal temperature

Question 23

describe the transition state

Answer 23

high energy causing an immediate state of reactants during a chemical reaction that must be achieve for the reaction to proceed
- the more unstable the transition state, the higher the activation energy, the less likely a reaction is to proceed quickly

Question 24

what do enzymes do?

Answer 24

bring substrates and active sites together; they lower the amount of activation energy needed to create a reaction
- enzymes are a catalyst
- does not make endergonic reactions exergonic

Question 25

induced fit:

Answer 25

changed shape of the active site of an enzyme as the result of the initial weak binding of a substrate so it binds the substrate more tightly

Question 26

What are the steps to enzyme activation

Answer 26

Initiation: substrate binds to the active site

Transition state Facilitation: interactions between the enzyme and substrate lower the activation energy

Termination: products have lower affinity for the active site and are released. Enzyme is unchanged after the reaction

Question 27

Enzymes do not work alone, what are the other factors that impact enzymes

Answer 27

cofactors, coenzymes, and prosthetic groups

Question 28

Describe cofactors

Answer 28

inorganic ions that reversibly interact with enzymes

Question 29

describe coenzymes

Answer 29

organic molecules that reversibly interact with enzymes such as the electron carriers NADH

Question 30

Describe prosthetic groups

Answer 30

atoms or non-amino acid molecules that are permanently attached to proteins such as retinal; retinal is involved in converting light energy into nerve impulses.

Question 31

within enzyme functions, what do reactions depend on?

Answer 31

• substrate concentration
  -enzyme affinity for substrate
• specific environment (pH, temperature, CO2 levels)
• regulation: controlling when and where an enzyme will function

Question 32

what are the two types of regulation?

Answer 32

reversible (non covalent): interactions that do not permanently affect enzymes primary structure
- competitive inhibition: molecules that compete for active sites
- allosteric regulation: molecules that bind to another location changing the shape of the enzyme

Covalent: irreversible changes to the primary structure due to peptide bonds or phosphorylation