Chapter 15: Metabolism

Question 1

3 Stages of generation from food

Answer 1

1. Large molecules in food broken down into smaller molecules by digestion (no useful energy yet)
2. Small molecules are processed into key molecules of metabolism (small amount of ATP)
3. ATP is produced from complete oxidation (lot of ATP)

Question 2

Why living organisms need free energy?

Answer 2

1. Performance of mechanical work
2. Active transport
3. Synthesis of macromolecules and other biomolecules

Question 3

Catabolism

Answer 3

Large molecules broken down to smaller molecules
Release energy, exergonic
Usually involved in oxidation

Question 4

Anabolism

Answer 4

Small molecules react to give rise to larger ones
Requires energy, endergonic
Usually involved in reduction

Question 5

△G under set of conditions depend on

Answer 5

1. value of △G°
2. concentration of reactants and products

Question 6

Criteria for constructing metabolic pathways

Answer 6

1. Individual reactions must be specific
2. pathway in total must be thermodynamically favorable

Question 7

How do thermodynamically unfavorable reactions become favorable?

Answer 7

By coupling reactions that are more favorable

Question 8

ATP Hydrolysis

Answer 8

ATP + H20 –> ADP + Pi
Proces is exergonic
△G°= -30.5 kJ/ mol

Question 8

ATP (Adenine Triphosphate)

Answer 8

Universaly currency of free energy
Energy derived from light of fuels is converted into ATP
Great intermediate for carrier of phosphoryl groups

Question 9

Rank stability of ATP, AMP, ADP from least stable to most stable

Answer 9

ATP ( - 4) –> ADP (-3) –> AMP (-2)

Question 10

Why is ATP least stable between AMP and ADP?

Answer 10

Has 4 negative charges and electrostatic repulsion

Question 11

Phosphate transfer potential

Answer 11

Standard free energy of hydrolysis
Means of comparing tendency of organic molecules to transfer a phosphoryl group to an acceptor molecule

Question 12

4 Key Factors why ATP has high phosphoryl transfer potential

Answer 12

1. Charge repulsion: 4 Negative charges in close proximity
2. Resonance stabilization: free Pi has greater resonance stabilization than any of phosphates in ATP
3. Increase in entropy: when one molecule of ATP –> ADP + Pi
4. Stabilization by hydration: ATP hydrolysis are more effectively stabilized by association with water than ATP

Question 13

ATP Synthesis

Answer 13

ADP + Pi –> ATP + H20
Requires energy for catabolism
Endergonic

Question 14

The more reduced a carbon, the more _____ is released by its oxidation

Answer 14

free energy

Question 15

More energy of carbon molecules is:

Answer 15

Higher △G°
More CH bonds
More energy released
Less reduced

Question 16

Less energy of carbon molecules is:

Answer 16

Lower △G°
Less CH bonds
More energy released
More reduced

Question 17

ATP Synthesis Couple with Carbon Oxidation

Answer 17

• Essence of catabolism is capturing energy of CO2 as ATP
• the energy that is released when Carbon that is oxidized to CO2 is used to regenerate ATP from ADP and Pi
• Energy of oxidation is initially trapped as high phosphoryl transfer potential compound

Question 18

Activated Carriers

Answer 18

Small molecule carrying activated functional groups that can be donated to another molecule

Question 19

Compounds that have high phosphoryl transfer potential

Answer 19

• Phosphoenol pyruvate (PEP)
• 1,3 Biphophoglycerate (1, 3 BPG)
• Creatine phosphate

Will donate phosphate to ADP for ADP to phosphate ATP

Question 20

Activated Carrier characteristics

Answer 20

1. carriers that are kinetically stable in absence of specific catalysts
2. metabolsim of activated groups is accomplished with small number of carriers

Question 21

NAD+ reduced to NADH

Answer 21

Gain of e-
Nicotinamide ring accepts a hydrogen ion and 2 electrons

Question 21

ATP is activated carrier of

Answer 21

phosphoryl groups

Question 22

NAD+

Answer 22

Universal oxidizing agent for catabolsim as it picks up electrons during oxidatin of food

Question 22

NAD+ and FAD are activated carriers of

Answer 22

carry electrons from oxidation of fuels

Question 23

NADH

Answer 23

• After receiving electrons, acts as activator carrier to electron transfer chain and regenerate to NAD+
• Cofactor for many enzymes that catalyze redox reactions

Question 24

Redox dehydrogenation Reaction

Answer 24

Oxidation and Reduction happen at same time
Use enzyme dehydrogenase

Question 25

The electrons are carried by ____ componet of FAD and FADh2

Answer 25

Isoalloxazine Ring

Question 26

Coenzyme A

Answer 26

Activated carrier of acyl groups
Transfer of acyl group is exergonic because thioester is unstable

Question 27

Biotin (B7)

Answer 27

Activated carrier of CO2
Coenzyme: Biotine lysine adducts
ATP dependent carboxylation and carboxyl group transfer

Question 28

Many activated carriers are derived from

Answer 28

Vitamins

Question 29

Riboflavin (B2 Vitamin)

Answer 29

Coenzyme: FAD
Oxidation Reduction rxn

Question 30

Whichvitamin functrions as coenzymes

Answer 30

B Vitamins

Question 31

Nicotinic Acid (niacin, B3)

Answer 31

Coenzyme: NAD+
oxidation reduction rxn

Question 32

Pantothenic acid (B5)

Answer 32

Coenzyme A
Acyl group transfer

Question 33

Metabolic Processes/ Homeostatsis is regulated by:

Answer 33

1. Amount of enzymes present: regulated by gene level transcription
2. Catalytic activity of enzymes: regulated allosterically or by reversible covalent modification, hormones cordinate metabolic activity
3. Accessibility of substrates

Question 34

Energy Status

Answer 34

Important regulator of enzyme activity

Question 35

2 ways to assess energy status:

Answer 35

1. energy change
2. phosphorylation potential

Question 36

Energy change formula

Answer 36

[ATP] + 1/2 [ADP] / [ATP] + [ADP] + [AMP]

Question 37

Phosphorylation formula

Answer 37

[ATP] / [ADP] + [Pi]