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1

Metabolism

is the totality of an organism's chemical reactions

2

Metabolism is an emergent property of life that arises from interactions between

molecules within the cells.

It is both the breaking down and building up of things.

3

A metabolic pathway

begins with a specific molecule and ends with a product.

Each step is catalyzed by a specific enzyme.

4

Catabolic pathways

release energy by breaking down complex molecules into simpler compounds.

5

Cellular respiration, the breakdown of glucose in the presence of oxygen, is an example of a

pathway of catabolism.

6

Anabolic pathways

consume energy to build complex molecules from simpler ones

7

The synthesis of protein from amino acids is an example of

anabolism

8

Bioenergetics is the study of

how organisms manage their energy resources.

9

Catabolic Pathways

-breaking down (molecules)
-release energy
-spontaneous (just happens)
-exergonic
-Delta G=negative (the triangle G)

-on a graph:
it starts with high energy (reactants), then it ends up with low energy (products).

10

Anabolic Pathways

-building up
-needs/requires energy
-non-spontaneous
-endergonic
-Delta G=positive (the triangle G)

-on a graph:
it starts with low energy (reactants), then it ends up with high energy (products).

11

Energy is the

capacity to cause change.

Energy exists in various forms, some of which can perform work.

12

Kinetic energy is energy associated with

motion

13

Heat (thermal energy) is

kinetic energy associated with random movement of atoms or molecules

14

Potential energy is energy that

matter possesses because of its location or structure

15

Chemical energy is

potential energy available for release in a chemical reaction.

16

Energy can be converted from

one form to another.

Some energy is ALWAYS lost as heat when conversion occurs.

17

Thermodynamics is

the study of energy transformations (and how it moves around).

18

An isolated system, such as that approximated by liquid in a thermos, is

isolated from its surroundings.
(the liquid is completely closed off)

19

In an open system, energy and matter can be

transferred between the system and its surroundings.

20

Organisms are

open systems.

(They are constantly bringing in energy from the outside and releasing energy from the inside)

21

According to the First Law of Thermodynamics,

the energy of the universe is constant.

Energy can be transferred and transformed, but it cannot be created or destroyed.

((Energy is constant in the Universe))

The first law is also called the principle of conservation of energy.

22

During every energy transfer or transformation, some energy is

unusable, and is often lost as heat.

23

According to the Second Law of Thermodynamics,

every energy transfer or transformation increases the entropy (disorder) of the universe.

Entropy will always increase in energy transfer.

24

Living cells unavoidably convert organized forms

of energy to heat.

25

Spontaneous processes occur

without energy input; they can happen quickly or slowly.

26

For a process to occur without energy input, it must

increase the entropy of the universe.

27

Cells create ordered structures from

less ordered materials.

28

Organisms also replace ordered forms of matter and energy with

less ordered forms.

29

Energy flows into an ecosystem in the form of

light and exits in the form of heat.

30

The evolution of more complex organisms dow not violate the

second law of thermodynamics.

31

Entropy (disorder) may decrease in an organism, but

the universe's total entropy increases.

32

Biologists want to know which reactions occur spontaneously and which require input of energy.

To do so, they need to determine energy changes that occur in chemical reactions.

33

A living system's free energy is

energy that can do work when temperature and pressure are uniform, as in a living cell.

34

The change in free energy (delta G) during a process is related to the change in

enthalpy, or change in total energy (delta H), change in entropy (delta S), and temperature in Kelvin (T).

(Delta G)=(Delta H) - T (Delta S)

35

Only processes with a negative delta G are

spontaneous.

36

Spontaneous processess can be harnessed to

perform work.

37

Free energy is a measure of a

system's instability, its tendency to change to a more stable state.

38

During a spontaneous change,

free energy decreases and the stability of a system increases.

39

Equilibrium is a state of

maximum stability.

40

A process is spontaneous and can perform work only when

it is moving toward equilibrium.

41

The concept of free energy can be applied to the

chemistry of life's processes.

42

An exergonic reaction

proceeds with a net release of free energy and is spontaneous.

delta G is negative.
This is also catabolic.

It starts with high energy (reactants), then ends up with low energy (products).
((what it looks like on a graph))

43

An endergonic reaction

absorbs free energy from its surroundings and is nonspontaneous.

delta G is positive.
This is also anabolic.

It starts with low energy (reactants), then ends up with high energy (products).
((what it looks like on a graph))

44

Reactions in a closed system eventually reach

equilibrium and then do no work.

45

Cells are not in equilibrium; they are

open systems experiencing a constant flow of materials.

46

A defining feature of life is that

metabolism is never at equilibrium.

47

A catabolic pathway in a cell

releases free energy in a series of reactions.

48

Closed and open hydroelectric systems can serve as

analogis.

49

A cell does three main kinds of work

-Chemical
-Transport
-Mechanical

50

To do work, cells manage energy resources by

energy coupling, the use of an exergonic process to drive an endergonic one.

51

Energy coupling is the

use of an exergonic process to drive an endergonic one.

52

Most energy coupling is mediated by

ATP.

53

ATP (adenosine triphosphate) is

the cell's energy shuttle.

((ATP=energy currency of a cell?))
((ATP=how we transport energy in a cell))

54

ATP is composed of

ribose (a sugar)
adenine (a nitrogenous base)
and
three phosphate groups

55

The bonds between the phosphate groups of ATP's tail can be

broken by hydrolysis.

56

Energy is released from ATP when the

terminal phosphate bond is broken.

This release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves.
-3 negative phosphate groups act like a coiled spring.

57

The three types of cellular work (mechanical, transport, and chemical) are powered by

the hydrolysis of ATP.

(how we do energy coupling.)

58

In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used

to drive an endergonic reaction.
(energy coupling)

Overall, the coupled reactions are exergonic.

59

ATP drives endergonic reactions by

phosphorylation, transferring a phosphate group to some other molecule, such as a reactant.

This recipient molecule is now called a phosphorylated intermediate.

60

Phosphorylated Intermediate is

a molecule (often a reactant) with a phosphate group covalently bound to it, making it more reactive (less stable) than the unphosphorylated molecule.

61

ATP is a renewable resource that is

regenerated by addition of a phosphate group to adenosine diphosphate (ADP).

62

The energy to phosphorylate ADP comes from

catabolic reactions in the cell.

63

The ATP cycle is a

revolving door through which energy passes during its transfer from catabolic to anabolic pathways.

64

Just because a reaction is spontaneous, it doesn't meant that the

rate of the reaction is fast.

65

A catalyst is a

chemical agent that speeds up a reaction without being consumed by the reaction.

((don't/doesn't change reactions???))

66

An enzyme is a

catalytic protein.

67

Hydrolysis of sucrose by the enzyme sucrase is an example of an

enzyme-catalyzed reaction.

68

Every chemical reaction between molecules involves

bond breaking and bond forming.

69

The initial energy needed to start a chemical reaction is called

the free energy of activation, or activation energy (Ea).

(Even if it is spontaneous, it still requires some energy to get it going)

70

Activation energy is often supplied in the form of

thermal energy that the reactant molecules absorb from their surroundings.

71

Enzymes catalyze reactions by

lowering the Ea (activation energy) barrier.

((this doesn't change anything, just lowers it))

72

Enzymes do not affect the change in free energy (delta G); instead,

they hasten (speed up) reactions that would occur eventually.

((delta D is unaffected by enzyme. It will always be the same))

73

Enzymes function by

lowering the activation energy.

74

Kind of steps of how an enzyme works

Substrate
Enzyme
Enzyme-Substrate Complex
Active Site
Induced Fit
Cofactor

75

The reactant that an enzyme acts on is called the enzyme's

substrate.

76

The enzyme binds to its substrate, forming an

enzyme-substrate complex.

77

The active site is the

region on the enzyme where the substrate binds.

78

Induced fit of a substrate brings

chemical groups of the active site into positions that enhance their ability to catalyze the reactions. ((changes shape))

79

Enzyme specificity

every enzyme is very specific for certain substrates.

80

In an enzymatic reaction, the

substrate binds to the active site of the enzyme.

81

The active site can lower an Ea (activation energy) barrier by


(((not really important???)))

-orienting substrates correctly
-straining substrate bonds
-providing a favorable microenvironment
-covalently bonding to the substrate

82

An enzyme's activity can be affected by

-general environmental factors, such as temperature and pH
-chemicals that specifically influence the enzyme

83

Each enzyme has an optimal temperature in which

it can function.

84

Each enzyme has an optimal pH in which

it can function.

85

Optimal contions favor the most active

shape for the enzyme molecule.

86

Cofactors are

non-protein enzyme helpers

Cofactors may be inorganic (such as metal in ionic form) or organic.

87

An organic cofactor is called a

coenzyme.

Coenzymes include vitamins.

88

If an inhibitor binds with covalent bonds

inhibition is usually irreversible.
(This means an enzyme is then stopped for forever)

89

Some inhibitors use

weak interactions, in which case the inhibition is reversible.
(These only stop it for a little instead of for forever)

90

Competitive inhibitors bind to

the active site of an enzyme, competing with the substrate.

(Competitive inhibitors bind to the active spot on an enzyme keeping the substrate from binding)

91

Noncompetitive inhibitors bind to

another part of an enzyme, causing the enzyme to change shape and making the active site less effective.

(Noncompetitive inhibitors bind away from the active site and changes the shape so that the substrate cannot bind to it)

92

Examples of inhibitors include

toxins, poisons, pesticides, and antibiotics.

93

Enzymes are proteins encoded by

genes.

94

Changes (mutations) in genes lead to

changes in amino acid composition of an enzyme.

95

Altered amino acids in enzymes may alter their

substrate specificity.

96

Under new environmental conditions a novel form of an

enzyme might be favored.

97

Chemical chaos would result if a cell's

metabolic pathways were not tightly regulated.

A cell does this by switching on or off the genes that encode specific enzymes or by regulating the activity of enzymes.

98

Allosteric regulation may

either inhibit or stimulate an enzyme's activity.

(Allosteric regulation is the general broad name/term for a way to turn on or off an enzyme??)

99

Allosteric regulation occurs when a

regulatory molecule binds to a protein at one site and affects the protein's function at another site. (like noncompetitive inhibition)

It is a way to turn enzymes off.
(We use activators or inhibitors to do this?)

100

Noncompetitive inhibition is a type of

allosteric regulation.

(??)

101

Most allosterically regulated enzymes are made from

polypeptide subunits.

102

Each enzyme has

active and inactive forms.

103

The binding of an activator stabilizes the

active form of the enzyme. (turns on?)

104

The binding of an inhibitor stabilizes the

inactive form of the enzyme. (turns off?)

105

Cooperativity is a

form of allosteric regulation that can amplify enzyme activity.

One substrate molecule primes an enzyme to act on additional substrate molecules more readily.

((One molecule binding on unit and makes it easier to have faster binding on other units?))

106

Cooperativity is allosteric because

binding by a substrate to one active site affects catalysis in a different active site.

107

Allosteric regulators are attractive drug candidates for enzyme regulation because

of their specificity.

108

Inhibition of proteolytic enzymes called caspases may help

management of inappropriate inflammatory responses.

109

In feedback inhibition, the

end product of a metabolic pathway shuts down the pathway ((of an enzyme??)).

(another way to regulate enzyme)

110

Feedback inhibition prevents a cell from

wasting chemical resources by synthesizing more product than is needed.

111

Feedback inhibition is a

method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

112

Structures within the cell help bring order to

metabolic pathways.

113

Some enzymes act as

structural components of membranes.

114

In eukaryotic cells, some enzymes reside in

specific organelles; for example, enzymes for cellular respiration are located in the mitochondria.