BB 16 Metabolic Energy (generation and storage)

Question 0

The overall free-energy change for a coupled series of reaction is the

Answer 0

sum of the free energy changes of the individual steps

Question 1

A reaction can occur spontaneously only if

Answer 1

ΔG is negative

Question 2

Three ways in which reactions can be coupled

Answer 2

1. a shared chemical intermediate
   • glycolysis and substrate level phosphorylation
2. An activated protein conformation
   • molecular motors
3. Ionic (electrochemical) gradients across membranes
   • oxidative phosphorylation

Question 3

Energy is required for

Answer 3

• motion
• active transport of solutes across membranes against a gradient
• biosynthesis
• signal amplification

Question 4

Energy is obtained from

Answer 4

• oxidation of foodstuffs (chemotrophs)

* trapping of light energy (phototrophs)

Question 5

ATP is an energy carrier containing

Answer 5

2 phosphoanhydride bonds

Question 6

ATP is an

Answer 6

activated carrier

• group carried is phosphoryl

Question 7

Further examples of activated carriers

Answer 7

NADH
FADH2
• major electron carriers in the oxidation of food molecules

Question 8

Chemotrophs derive free energy from

Answer 8

oxidation of fuel molecules such as
• glucose
• fatty acids

Question 9

In aerobic organisms, the ultimate electron acceptor is

Answer 9

oxygen … BUT
not transferred directly to oxygen, but transferred to special electron carriers:
• pyridine nucleotides (NADH)
• flavins (FADH2)

Question 10

Reduced electron carriers transfer their electrons to oxygen…

Answer 10

• via an electron transport chain in the inner mitochondrial matrix (IMM)
• the energy released is used to synthesize ATP (oxidative phosphorylation)

Question 11

NAD+

Answer 11

Nicotinamide adenine dinucleotide

• major electron acceptor in the oxidation of fuel molecules

Question 12

Formation of NADH

Answer 12

NAD+ accepts
• 1 H+
• 2 e-

Question 13

NADH is used primarily for

Answer 13

the generation of ATP

Question 14

NADPH

Answer 14

• reduced form of NADP+
• used for biosynthesis
• needs reducing power in addition to ATP

Question 15

FAD

Answer 15

Flavin adenine dinucleotide

• other major electron carrier in the oxidation of fuel molecules

Question 16

Reactive part of FAD

Answer 16

isoalloxazine ring
accepts
• 2 e-
• 2 H+
to form FADH2

Question 17

Enzymes speed the processes and

control the

Answer 17

• flow of free energy

.•reductive power

Question 18

Activated carriers

Answer 18

• NADH
• NADPH
• FADH2

Question 19

Most interchanges of activated groups in metabolism are accomplished by

Answer 19

a small set of carriers

Question 20

Extraction of energy from foodstuffs

STAGE 1

Answer 20

large molecules of food are broken into smaller units
• proteins to amino acids
• polysaccharides to simple sugars
• fats to glycerol and fatty acids
NO USEFUL ENERGY IS GENERATED IN THIS STAGE

Question 21

Extraction of energy from foodstuffs

STAGE 2

Answer 21

small molecules degraded to few simple units that play a central role in metabolism
• most are converted into Acetyl CoA
SOME ATP IS GENERATED IN THIS STAGE

Question 22

Extraction of energy from foodstuffs

STAGE 3

Answer 22

citric acid cycle and oxidative phosphorylation

90% OF ATP IS GENERATED IN THIS LAST STAGE

Question 23

3 ways metabolic pathways are regulated

Answer 23

• the amounts of enzymes
• the catalytic activities of these enzymes
• the accessibility of substrates

Question 24

Metabolic pathways regulated by | amounts of enzymes

Answer 24

amount depends on rate of synthesis and breakdown • amount of most enzymes regulated mostly by adjusting rate of transcription of genes encoding them

Question 25

Metabolic pathways regulated by | catalytic activity of enzymes

Answer 25

a) reversible allosteric control (feedback regulation) | b) reversible covalent modification (control amount of substrate capable of reaching enzyme)

Question 26

Metabolic pathways regulated by | accessibility of substrates

Answer 26

eg controlling entry to cell

Question 27

Biosynthetic and degradative pathways are

Answer 27

almost always DISTINCT (not the same) | • must be thermodynamically favorable = cant go back to substrates

Question 28

Many reactions in metabolism are controlled by the

Answer 28

ENERGY STATUS of the cell

Question 29

Energy charge

Answer 29

* one measure of the energy of the cell | * balance between the concentrations of ATP and AMP in the cell

Question 30

energy charge =

Answer 30

[ATP] + ½ [ADP] / [ATP] + [ADP] + [AMP]