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]