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MBB 231 > Lecture 8 - Bioenergetics & Enzymes > Flashcards

Lecture 8 - Bioenergetics & Enzymes Flashcards

1
Q

def: no net fixation of carbon into organic compounds

A

chemoheterotrophs

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2
Q

def: a subset of thermodynamics, the quantitative analysis of how the biological world gains and uses energy

A

bioenergetics

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3
Q

where do chemotrophs get their energy from?

A

oxidizing metabolic fuels

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4
Q

what are catabolic metabolic pathways?

A

oxidative reaction sequences that result tin the transfer of electrons away from carbon

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5
Q

how many oxidation states does carbon have?

A

5

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6
Q

what is the most highly oxidized form of carbon found in living organisms?

A

carbon dioxide

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7
Q

in carbon hydrogen bonds, how are the electrons shared?

A

the more electronegative carbon owns the two electrons shared with hydrogen

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8
Q

in carbon oxygen bonds, how are the electrons shared?

A

electron sharing is unequal in favour of oxygen

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9
Q

T or F: entropy decreases when monomers are ordered into more complex molecules

A

true

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10
Q

what relates changes in enthalpy and changes in entropy?

A

Gibbs Free Energy

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11
Q

a reaction can occur spontaneously only if deltaG is ________, thus the process is _______-

A

negative, exergonic

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12
Q

a reaction cannot occur spontaneously if deltaG is ________, thus the process is _________

A

positive, endergonic

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13
Q

what is deltaG when the system is at equilibrium?

A

0

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14
Q

what is the deltaG of the cellular environment?

A

-11.5 kcal/mol

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15
Q

def: the ratio of product concentration to reactant concentration at equilibrium

A

equilibrium constant

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16
Q

is homeostasis equivalent to equilibrium?

A

No!

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17
Q

what is a better term for the steady state in which a cell holds itself?

A

dynamic steady state

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18
Q

def: the maintenance of dynamic steady state by regulatory mechanisms that compensate for external changes

A

homeostasis

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19
Q

______ and ________ catalyze virtually all cellular processes and reactions

A

enzyme and ribozymes

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20
Q

what are the 7 properties of catalysts?

A
  1. only small amounts required
  2. function at physiologically relevant temp and pH
  3. aren’t irreversible altered during the reaction
  4. highly specific to their substrate
  5. they generate a very specific product
  6. can be regulated to meet the needs of the cell
  7. they change the RATE, not the THERMODYNAMICS of the reaction
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21
Q

def: state in which reactants are thermodynamically unstable but do not have enough energy to exceed the activation energy barrier

A

metastable state

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22
Q

def: the minimum amount of energy required by reactants before collisions between them will lead to product formation

A

activation energy (Ea)

23
Q

def: the precise point at which weak chemical reactions between substrate and enzyme are at the stage where the reaction has an equal chance of going to product or back to substrate

A

transition state

24
Q

T or F: if reactants can be bound on a surface and brought closer together, their interaction will be favoured and the required Ea will be reduced

A

treu

25
Q

a _______ enhances the rate of a reaction by providing a binding surface and effectively lowering Ea

A

catalyst

26
Q

what are 3 ways enzymes reduce the activation energy?

A
  1. maintain precise substrate orientation
  2. change the substrate reactivity (influence the distribution of electrons)
  3. exert physical stress (conformational change = destabilizing bonds)
27
Q

def: characteristic cluster of amino acids on every enzyme, region of the enzyme that binds substrate (and cofactor)

A

active site

28
Q

the active site is usually a __________ _______ ___ ________ that accommodates the substrates with high affinity

A

complimentary groove or pocket

29
Q

what does the active site contain?

A

residues that directly participate in the making and breaking of bonds

30
Q

which amino acids comprise the active site?

A

Cysteine (C)
Serine (S)
Aspartate (D)
Glutamate (E)
Histidine (H)
Lysine (K)

31
Q

def: organic, participate in catalysis, but not a substate, derived from vitamins, bind loosely

A

co-enzymes

32
Q

def: inorganic, help increase the rate of catalysis, often electron carriers, bind tightly

A

metals

33
Q

def: enzyme not bound to its co-factor

A

apoenzyme

34
Q

def: enzyme found bound to its co-factor

A

holoenyzme

35
Q

what are the 4 other purposes of the rest of the enzyme structure?

A
  1. support structure to allow the 3 dimensional creation of active site from primary sequence
  2. regulatory sites
  3. sites of interaction with other proteins
  4. substrate channels
36
Q

what characterizes enzymes?

A

their sensitive to temperature and pH

37
Q

at low temperatures, how does the rate of enzyme activity change with temperature?

A

it increases with temperature due to increased kinetic activity of enzyme and substrate molecules

38
Q

beyond a certain point of temperature increase, what happens to enzymes?

A

they denature and lose enzyme activity

39
Q

most enzymes are active within a pH range of about ____ units

A

3-4

40
Q

pH dependence is usually due to the presence of ________ _____ ____ __ _____ ____ or on the substrate

A

charged amino acids at the active site

41
Q

pH changes affect the charge of such residues, and can disrupt ______ and _______ bonds

A

ionic and hydrogen bonds

42
Q

what are two other factors that enzymes are sensitive to?

A
  1. molecules and ions that act as inhibitors or activators
  2. ionic strength of the environment which affects hydrogen bonding and ionic interactions needed to maintain tertiary conformation
43
Q

what kind of bonding does substrate bonding involve?

A

usually hydrogen, ionic or both

44
Q

def: the quantitative aspects of enzyme catalysis and the rate of substrate conversion into products

A

enzyme kinetics

45
Q

def: discrete locally folded unit of the overall tertiary structure, usually with a specific function

A

domain

46
Q

T or F: proteins will similar functions often have completely different domains

A

false, they often share common domains

47
Q

proteins will multiple functions usually have a separate ________ for each function

A

domain

48
Q

what processes regulate enzyme concentrations in a cell?

A

synthesis and degradation

49
Q

how can cells regulate protein activity?

A
  • inhibition
  • allosteric regulation
  • cleavage
  • phosphorylation
  • kinase localization
  • Ca2+ sequesteration
  • receptor internalization
50
Q

what are enzymes most influenced/inhibited by?

A

products, alternative substrates, substrate analogues, drugs, toxins, and allosteric effectors

51
Q

def: regulation of an enzyme by binding an effector molecule at a site other than the enzymes active site

A

allosteric regualtion

52
Q

what does binding of a regulatory ligand do?

A

change of a proteins conformation

53
Q

T or F: all covalent modification can be reversed

A

False, some can be reversed

54
Q

Phosphorylation/Dephosphorylation:
Kinases _______
Phosphatases ________

A

Kinases phosphorylate
Phosphatases dephosphorylate

MBB 231 (19 decks)

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