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Biology 110 > Energy transformations and Enzymes > Flashcards

Energy transformations and Enzymes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

1st law of thermodynamics

A

Energy is not created or destroyed in a closed system but it can be transformed

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2
Q

Energy is…

A

the capacity to do work

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3
Q

Potential energy

A

Energy stored as chemical bonds, concentration gradients, etc.

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4
Q

Kinetic energy

A

The energy of movement

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5
Q

Metabolism

A

Sum total of all chemical reactions occurring in a biological system at a given time

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6
Q

Anabolic metabolism

A

Complex molecules are made from simple molecules; energy is required

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7
Q

Catabolic metabolism

A

Complex molecules are broken down to smaller ones; energy is released

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8
Q

2nd law of thermodynamics

A

When energy is converted from one form to another, some of that energy becomes unavailable to do work

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9
Q

Entropy (S)

A

A measure of the disorder in a system

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10
Q

Enthalpy (H)

A

Total energy

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11
Q

Free energy (G)

A

The usable energy that can do work

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12
Q

Unusable energy is represented by entropy multiplied by the absolute temperature

A

H=G+TS

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13
Q

If change in G is -

A

free energy is released

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14
Q

If change in G is +

A

free energy is required

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15
Q

If free energy is not available

A

the reaction does not occur

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16
Q

Exergonic reaction

A

release free energy

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17
Q

Catabolism

A

Complexity decreases (generates disorder)

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18
Q

Endergonic reaction

A

Consume free energy

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19
Q

Anabolism

A

Complexity (order) increases

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20
Q

ATP can be ______ to ADP and P

A

Hydrolyzed

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21
Q

ATP ____ and ____ free energy

A

Captures; transfers

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22
Q

ATP can also ______

A

Phosphorylate; donate a phosphate group to other molecules

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23
Q

When ATP hydrolysis releases so much energy

A
  1. Phosphate groups have negative charges and repel each other- the energy needed to get them close enough to bond is stored in the P-O bond
  2. The free energy of the P-O bond is much higher than the energy of the O-H bond that forms after hydrolysis
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24
Q

How many cycles of synthesis and hydrolysis does each ATP molecule go through everyday?

A

10,000

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25
Q

Energy is released by hydrolysis of ATP can be used to drive an _______

A

Endergonic reaction

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26
Q

Metabolic pathways

A

Chemical reactions in cells are organized in metabolic pathways that are interconnected

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27
Q

The complex pathways are modeled using computer algorithms

A

Systems biology

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28
Q

Enzymes help ____ and ______ metabolic pathways

A

organize and regulate

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29
Q

Most biological catalysts are enzymes (proteins)

A

Act as a framework in which reactions can take place

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30
Q

Catalysts

A

Increase rates of chemical reactions

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31
Q

Activation energy

A

The amount of energy required to start the reaction

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32
Q

Activation energy puts the reactants in a reactive model called the

A

transition state

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33
Q

Transition state intermediates

A

Activation energy changes the reactants into unstable forms with higher free energy

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34
Q

Activation energy can come from___

A

heating the system

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35
Q

Enzymes ____ the energy barrier by bringing reactants together

A

lower

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36
Q

Enzymes are _____

A

highly specific

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37
Q

Reactants are called ____

A

substrates

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38
Q

Substrate molecules bind to the ____ of the enzyme

A

active site

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39
Q

The 3D shape of the enzyme determines the ____

A

specificity

40
Q

The enzyme substrate complex is held together by

A

hydrogen bonds, electrical attraction, or covalent bonds

41
Q

Enzymes ____ the energy barrier for reactions

A

lower

42
Q

An enzyme may use one or more mechanisms to catalyze a reaction

A

Orient substrates so they can react
Induce strain by stretching the substrate-makes the bonds unstable and more reactive to other substates
Temporarily add chemical group

43
Q

Enzyme specifity depends on

A

precise interlocking of molecular shapes
interactions of chemical groups at the active site of

44
Q

Induced fit

A

some enzymes change shape when it binds the substrate, which alters the shape of the active site

45
Q

Rate of catalyzed reaction depends on

A

substrate concentration

46
Q

Concentration of an enzyme is usually much _____ than the substrate

A

lower

47
Q

At saturation

A

all enzyme is bound to substrate; it is working at maximum rate

48
Q

Enzyme activity can be controlled in two ways

A

Regulation of gene expression and regulation of enzyme activity

49
Q

Enzyme inhibitors

A

Molecules that bind to the enzyme and slow reaction rates

50
Q

Naturally occurring inhibitors

A

regulate metabolism

51
Q

Artificial inhibitors

A

Can be used to treat disease, kill pets, or study how enzymes work

52
Q

Reversible inhibition

A

Inhibitor bonds noncovalently to the active site and prevents substrate from binding

53
Q

Competitive inhibitors

A

Compete with the natural substrate for binding sites

54
Q

Uncompetitive inhibitors

A

bind to the enzyme-substrate complex, preventing release of products

55
Q

Noncompetitive inhibitors

A

bind to enzyme at a different site (not the active site)

56
Q

Allosteric regulation

A

A non-substrate molecule binds enzyme at a site different than the active site, which changes enzyme shape
Active form-cannot bind substrate
Inactive form- cannot bind substrate

57
Q

Most allosteric enzymes are proteins with

A

quaternary structure

58
Q

Inhibitors and activators bind to other polypeptides called

A

regulatory subunits, at regulatory sites (allosteric sites)

59
Q

Feedback inhibition

A

the final product acts as a noncompetitive inhibitor of the first enzyme, which shuts down the pathway

60
Q

Reversible phosphorylation

A

Regulates many enzymes

61
Q

By being heated

A

enzymes can lose tertiary structure and become denatured

62
Q

Every enzyme is most active at a particular Ph which ____

A

Influences ionization of functional groups

63
Q

At low Ph (high H+) COO- may react with H+ to form

A

COOH (no longer charged); this affects folding and thus enzyme function

64
Q

Cells harvest chemical energy from

A

glucose oxidation

65
Q

Metabolic pathways

A

a coordinated series of biological reactions catalyzed by enzymes that convert molecules into other molecules

66
Q

5 principles

A

complex transformations occur in a series of seperate reactions
each reaction is catalyze by a specific enzyme
many metabolic pathways are similar in all organisms
In eukaryotes, metabolic pathways are compartmentalized in specific organelles
Key enzymes can be inhibited or activated to alter the rate of the pathway

67
Q

Three catabolic processes harvest energy from glucose

A

glycolysis (anaerobic)
cellular respiration (aerobic)
fermentation ( anaerobic)

68
Q

Oxidation-reduced (redox) reactions

A

one substance transfers electrons to another substance

69
Q

Reduction

A

gain of electrons

70
Q

Oxidation

A

Loss of electrons

71
Q

If a carbon containing molecule gains H or loses O, its likely been ____ (gained electrons or electron density) and its an oxidizing agent

A

reduced

72
Q

If a carbon containing molecule lose H or gains O, its likely been ______ (lost electrons or electron density) and is a reducing agent

A

oxidized

73
Q

Conversions of C-C bonds to C=O bonds is _____

A

oxidation because there is a net movement of electrons away from C

74
Q

Coenzyme NAD+ is a key electron carrier in

A

biological redox reactions

75
Q

Glycolysis

A

takes place in cytoplasm
converts glucose into 2 molecules of pyruvate
produces 2 ATP and 2 NADH
occurs in 10 steps

76
Q

step 1-5 requires ____

A

ATP; 2 ATP input

77
Q

Steps 6-10 yield

A

NADH and ATP; yields 4 ATP and 2 NADH

78
Q

Pyruvate oxidation

A

Occurs in the mitochondrial matrix
Pyruvate is oxidized to acetate and CO2
Acetate bonds with coenzyme A to form acetyl CoA
One NAD+ is reduced to NADH

79
Q

What is the starting point for the citric acid cycle?

A

Acetyl CoA

80
Q

Acetyl CoA donates its acetyl group to ______, forming citrate

A

oxaloacetate

81
Q

8 reactions completely oxidize the acetyl group to ____

A

2 molecules of CO2

82
Q

Energy released is captured by

A

GDP
NAD+
FAD+

83
Q

Oxidative phosphorylation

A

The reason our cells need oxygen
ATP synthesized by reoxidation of electron carriers in the presence of O2
Two componets: electron transport and chemiosmosis
Occurs in the mitochondrial inner membrane

84
Q

Electron transport

A

electrons from NADH and FADH2 pass thru the respiratory chain of membrane-associated electron carriers in the mitochondria

85
Q

Chemiosmosis

A

protons flow back across the membrane thru a channel protein, ATP synthase, which couples diffusion with ATP synthesis

86
Q

When H+ diffuse in chemiosmosis, potential energy is converted into _____, rotating the central polypeptide and transferring energy to the FI subunit

A

Kinetic enery
Energy used to make ATP (about 28)

87
Q

Lactic acid fermentation

A

pyruvate is the electron acceptor; lactate is the product
lactate dehydrogenase catalyzes fermentation

88
Q

Alcoholic fermentation

A

yeast and some plant cells
requires two enzymes to metabolize pyruvate to ethanol
products are CO2, ethanol, and 2 ATP

89
Q

Catabolic interconversions

A

polysaccharides are hydrolyzed to glucose and enters glycolysis
lips are broken down
proteins are hydrolyzed to amino acids-> glycolysis or citric acid cycle

90
Q

Anabolic interconversions

A

glucogenesis- citric acid cycle and glycolysis intermediates are reduced to form glucose
acetyl CoA can be used to form fatty acids
citric acid cycle intermediates can be use to synthesize nucleic acid componets

91
Q

How do cells decide which pathway to use?

A

Levels of substrates in the metabolic pool are quite constant
Organisms regulate enzymes to maintain balance between catabolism and anabolism

92
Q

Mechanisms that regulate rates of each step in a metabolic pathway

A

change the amount of active enzyme by regulating gene expression
change enzyme activity by covalent modifications
feedback inhibition by allosteric enzymes
substrate availability

93
Q

Glycolysis and citric acid cycle are subject to

A

allosteric regulation of key enzymes

94
Q

The main control point in glycolysis is

A

phosphofructokinase which inhibited by ATP

95
Q

The main control point in the citric acid cycle is

A

isocitrate dehydrogenase

96
Q

Acetyl CoA is another control point

A

if ATP levels are high and the citric acid cycle shuts down, the accumulation of citrate activates fatty acid synthesis from acetyl CoA, diverting it to storage

97
Q

Irreversible inhibition

A

inhibitor covalently bonds to side chains in the active site and permanently inactivates the enzyme

Biology 110 (4 decks)

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