Bio315 Ch3

Front 1

The capacity to do work, or the capacity to change or move something

Back 1

Energy

Front 2

The study of the changes in energy that accompany events in the universe

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Thermodynamics

Front 3

Conservation of energy - can neither be created nor destroyed

Back 3

First law of thermodynamics

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Conversion of energy from one form to another

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Transduction

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Reactions that gain heat

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Endothermic

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Reactions that lose heat

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exothermic

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Events in the universe tend to proceed from a state of higher energy to a state of lower energy

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Second law of thermodynamics

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Without the input of external energy

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Spontaneous

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A measure of randomness or disorder

Energy not available to do additional work

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Entropy

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Catalysts that speed up chemical reactions

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enzymes

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inorganic enzyme conjugates

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Cofactors

Front 12

organic enzyme conjugates

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Coenzymes

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First and Second laws of thermodynamics equation

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

DeltaG=free energy

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Spontaneity depends on both

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entropy and enthalpy

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Particular reactants of an enzyme

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substrates

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Properties of enzymes

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Present in cells in small amounts

not permanently altered during reaction

cannot affect the thermodynamics

highly specific to their substrates

produce only appropriate metabolic products

can be regulated to meet cell needs

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energy input required for chemical transformation

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activation energy (E(sub)A)

Front 18

Reactant molecules that reach the activation energy are in the...

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transition state

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formed when an enzyme interacts with its substrate

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enzyme-substrate (ES) complex

Front 20

Portion of the enzyme where the substrate binds

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active site

Front 21

multiple substrates brought together in correct orientation to catalyze reaction

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substrate orientation

Front 22

substrate influenced by amino acid side chains at active sites that alter chemical properties (ex. charge) of substrate

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changing substrate reactivity

Front 23

enzyme changes conformation of substrate to bring closer to conformation of transition state

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inducing strain in the substrate

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The study of rates of enzymatic reactions under various experimental conditions

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Kinetics

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velocity at saturation

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maximal velocity (V(sub)max)

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number of substrate molecules converted to product per minute per enzyme molecule at Vmax

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Turnover number

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substrate concentration at one half of Vmax

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Michaelis constant (K(sub)M)
(units are concentration units)

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The KM may reflect...

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the affinity of the enzyme for the substrate

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-bind to sites other than active sites and inactivate the enzyme

-Vmax cannot be reached

-cannot be overcome with high substrate/inhibitor ratios

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Noncompetitive inhibitors

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slow the rates for enzymatic reactions

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Enzyme inhibitors

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bind tightly to the enzyme

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Irreversible inhibitors

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Bind loosely to enzyme

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reversible inhibitors

Front 33

-compete with the enzyme for active sites

-usually resemble substrate structure

-can be overcome with high substrate/inhibitor ratios

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Competitive inhibitors

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collection of biochemical reactions that occur within a cell

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metabolism

Front 35

sequences of chemical reactions, each catalyzed by a specific enzyme, confined to specific locations

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metabolic pathways

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pathways convert substrates into end products via a series of

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metabolic intermediates

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break down complex substrates into simple end products - provide raw materials and chemical energy for the cell

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catabolic pathways

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synthesize complex end products from simple substrates - require energy and use ATP and NADPH from catabolic pathways

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anabolic pathways

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When a substrate gains electrons, it is

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reduced

Front 40

When a substrate loses electrons, it is

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oxidized

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The substrate that donates electrons

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Reducing agent

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The substrate that gains electrons

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Oxidizing agent

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The first stage in the catabolism of glucose

Occurs in

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Glycolysis

soluble portion of cytoplasm

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Second stage of glucose catabolism

Occurs in

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Tricarboxylic Acid (TCA) cycle

Mitochondria of eukaryotic cells

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enzymes oxidize and reduce cofactors

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dehydrogenase

Front 46

-nonprotein cofactor associated with glyceraldehyde phosphate dehydrogenase

-can undergo oxidation and reduction at different places in the cell

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NAD+

Front 47

Donates electrons to the electron transport chain in the mitochondria

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NADH

Front 48

enzymes transfer phosphate groups in ATP formation

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Kinase

Front 49

occurs when ATP is formed by a kinase enzyme

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Substrate-level phosphorylation

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ATP is formed when...

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1,3-biphosphoglycerate is converted to 3-phosphoglycerate by 3-phosphoglycerate kinase

Front 51

Compared with other phosphate transfer in cells, ATP formation is

Back 51

moderately endergonic

Front 52

shown when molecules higher on the scale have less affinity for the group being transferred than are the ones lower on the scale

The less affinity, the better the donor

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Transfer potential

Front 53

covalent modification of enzymes regulated by phosphorylation such as

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protein kinases

Front 54

Enzymes are controlled by

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alteration in active sites

Front 55

enzymes regulated by compounds binding to allosteric sites

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Allosteric modulation

Front 56

the product of the pathway allosterically inhibits one of the first enzymes of the pathway

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Feedback inhibition

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High-energy phosphate compounds

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Phosphoenolpyruvate

1,3-Biphosphogylcerate

Phosphocreatine

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Low-energy phosphate compounds

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Glucose 6-phosphate

Glucose 3-phosphate