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Biochem 1 > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Virtually all reactions in the body are mediated by _________

A

Enzymes

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2
Q

___________ increase the rate of reaction but remain ________ by the overall process

A

Enzymes; unchanged

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3
Q

Enzymes catalyse all ______ _______

A

Metabolic events

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4
Q

Enzymes are __________ for their __________

A

Selective; substrates

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5
Q

What is the suffix for an enzyme?

A

Ase

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6
Q

What is a holoenzyme?

A

An active enzyme with its nonprotein component

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7
Q

What is an apoenzyme?

A

An enzyme without its nonprotein component and it is inactive

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8
Q

What is a cofactor?

A

If the nonprotein moiety is a metal ion - cofactor

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9
Q

What is a coenzyme?

A

If the nonprotein moiety is a small organic molecule - coenzyme

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10
Q

The active site

A

A pocket or groove on the surface of the protein into which the substrate fits. Specificity of an enzyme is controlled by its structure

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11
Q

Lock and Key Model

A

The enzymes tertiary structure consists of a unique pocket or site which is tailer-made to fit only its substrate

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12
Q

Induced-Fit Model

A

As enzymes interact substrates, they change their conformation such that the enzyme is snug around the substrate

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13
Q

The combination of substrate and enzyme creates a new reaction pathway with a __________ transition state energy

A

Lowered

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14
Q

Enzyme Kinetics are affected by

A

Temp and pH
Enzyme concentration
Subtrate concentration

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15
Q

Temp and pH

A

Each enzyme reaction has an optimum pH and temperature. Extremes disrupt enzyme structure

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16
Q

Enzyme concentration

A

At saturating substrate concentration, the initial velocity is directly related to enzyme concentration. As long as substrate is not limiting more enzyme leads to more product

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17
Q

Substrate Concentration

A

The rate can be increased by adding more substrate, or by removing product as it is formed

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18
Q

What is enzyme saturation?

A

When the active sites on all enzymes are engaged, this is called enzyme saturation

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19
Q

Michaelis-Menton Model

A

The rate equation for a one-substrate enzyme-catalyzed reaction

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20
Q

Low Km

A

High affinity because a low substrate is needed to half saturate the enzyme and tight binding. More efficiency

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21
Q

High Km

A

Low affinity and weak binding. Low efficiency

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22
Q

What is an inhibitor?

A

Any substance that can diminish the velocity of an enzyme-catalyzed reaction

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23
Q

Irreversible inhibitors have what kind of bond?

A

Covalent

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24
Q

Reversible inhibitors have what kind of bond?

A

Non-covalent bonds

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25
Q

What are the two types of inhibition?

A

Competitive and non-competitive

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26
Q

Competitive Inhibition

A

Inhibitor binds reversibly to the same site as substrate. Increases Km for a given substrate, so more substrate is needed to reach Vmax.

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27
Q

Non-Competitive Inhibiton

A

Inhibitor and substrate bind to different sits on the enzyme. Inhibitor can bind to either free enzyme, thus preventing reaction. Decreases Vmax because it can’t be overcome by increasing substrate.

28
Q

What is an allosteric enzyme?

A

Regulated by molecules called effectors or modifiers that bind non-covalently to sites other than the active sites

29
Q

What are the two types of effectors?

A

Negative and positive

30
Q

Negative Effector

A

Inhibit enzyme activity - takes more substrate to get to 1/2 Vmax, higher K

31
Q

Positive Effector

A

Increases enzyme activity - takes less substrate to get to 1/2 Vmax, lower K

32
Q

Homotropic Effectors

A

Substrate serves as effector, enhancing other substrate-binding sites

33
Q

Heterotropic Effectors

A

Effector different from substrate, effector may be the product, feeds back to cause inhibition

34
Q

An acid is an electron pair _________

A

Acceptor

35
Q

A base is an electron pair ________

A

Donor

36
Q

Electrophile

A

A lewis acid which seeks electrons

37
Q

Nucleophile

A

A lewis base, which seeks substances that are electron deficient

38
Q

Acid/Base reactions produce?

A

Water, salt and sometimes carbon dioxide

39
Q

What is a strong acid?

A

It 100% ionizes in water

40
Q

What is a weak acid?

A

Only a small % is ionized in water

41
Q

The Acid/Base Dissociation Constant

A

The relationship between the relative concentrations of the reactants and products is a temperature dependent constant

42
Q

The stronger the acid or base, the _____ the value os the dissociation constant

A

Larger

43
Q

Keq greater than 1

A

Favors the product

44
Q

Keq less than 1

A

Favours the reactants

45
Q

Le Chatelier’s Principle

A

If a chemical in equilibrium is disturbed, the system will adjust to restore equilibrium

46
Q

What two things alter the equilibrium?

A

Change in concentration of reactants or products, change in temperature

47
Q

pH

A

A measure of a solutions acidity. The -log of H+. The lower the pH the higher the acidity

48
Q

pH of the body is ____?

A

7.4

49
Q

Buffer

A

A buffer solution has the ability to resist changes in pH upon the addition of small amounts of either acid or base

50
Q

A buffer solution needs 2 things

A
  1. A weak acid or a weak base
  2. The salt of the weak acid or weak base (the conjugate)
51
Q

Why Buffer?

A

Many reactions in living organisms proceed normally only in a narrow pH range. A change in pH or the aqueous solution of a living organism can be fatal. Living organisms need a mechanism to keep the pH of their physiological solutions relatively constant

52
Q

KA

A

Dissociation constant of the weak acid

53
Q

KB

A

Dissociation constant of the weak base

54
Q

What are the 3 Homeostatic Regulators of H+?

A
  1. Chemical buffer systems
  2. Respiratory mechanism
  3. Renal mechanism
55
Q

Chemical Buffer Systems

A

The first to respond, takes less than 1 second, temporarily ties up excess acids and bases

56
Q

3 main systems of chemical buffer systems

A
  1. Carbonic acid
  2. Phosphate
  3. Protein
57
Q

Respiratory Mechanism

A

Second to respond, takes 1-3 minutes, respiratory centre involved, removes CO2 and H2CO3

58
Q

Renal Mechanism

A

Third to respond but not potent, takes hours to days, kidneys remove metabolic acids

59
Q

Phosphate Buffer System

A

Important in tubular fluids of kidneys and ICF

60
Q

Carbonic Acid Bicarbonate Buffer System

A

Most important in the ECF, the most significant buffering compound in the blood

61
Q

Bloods buffering capability is dependent on the equilibrium between?

A
  1. CO2 dissolved in the blood and carbonic acid as a product of CO2 and water
  2. Carbonic acid and bicarbonate as a product of H+ dissociation
62
Q

The role of the kidneys

A

Assist acid-base balance by regulation/excretion of bicarbonate and NH4+

63
Q

If larger numbers of bicarbonate ions are filtered by the kidneys and excreted into the urine, this removes _____ from the _____

A

Base; blood

64
Q

If larger numbers of hydrogen ions are filtered by the kidneys and excreted into the urine, this removes _____ from the _____

A

Acid; blood

65
Q

Protein Buffer Systems - 3 types

A
  1. Plasma
  2. Amino acid
  3. Hemoglobin
66
Q
A

Biochem 1 (2 decks)

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