ATP & Redox

Question 1

What is the primary function of ATP in metabolism?

Answer 1

To serve as the main energy currency for cellular work

Question 2

Name three types of work powered by ATP.

Answer 2

Chemical (anabolism), mechanical (contraction), and osmotic (active transport)

Question 3

How much ATP does a human recycle per day?

Answer 3

30–40 kg

Question 4

Why is ATP considered a high-energy compound?

Answer 4

Due to the high-energy phosphoanhydride bonds it contains

Question 5

What is the ΔG’° of ATP → ADP + Pi?

Answer 5

-30.5 kJ/mol

Question 6

What makes ATP hydrolysis exergonic?

Answer 6

Charge repulsion, resonance stabilization, ionization of products, and Mg²⁺ effect

Question 7

Which ATP hydrolysis releases the most energy?

Answer 7

ATP → AMP + PPi followed by PPi → 2Pi (ΔG’° = –64.6 kJ/mol)

Question 8

What enzyme converts AMP to ADP?

Answer 8

Adenylate kinase

Question 9

How is ATP regenerated from NDPs?

Answer 9

By nucleotide diphosphate kinase

Question 10

How does ATP drive endergonic reactions?

Answer 10

By coupling its hydrolysis to them, making the overall ΔG negative

Question 11

What is substrate-level phosphorylation?

Answer 11

Direct formation of ATP from high-energy intermediates

Question 12

What is oxidative phosphorylation?

Answer 12

ATP production using energy from redox reactions in the mitochondria

Question 13

What is the role of ATP in phosphorylation reactions?

Answer 13

ATP donates phosphate groups to substrates

Question 14

What enzyme class catalyzes phosphorylation using ATP?

Answer 14

Kinases

Question 15

What distinguishes high-energy phosphorylated compounds?

Answer 15

They release a large amount of free energy upon hydrolysis

Question 16

Give an example of a high-energy thioester.

Answer 16

Acetyl-CoA

Question 17

Define oxidation in biochemical terms.

Answer 17

Loss of electrons

Question 18

Define reduction in biochemical terms.

Answer 18

Gain of electrons

Question 19

What is redox potential (E’°)?

Answer 19

A measure of a molecule’s tendency to accept electrons

Question 20

What is the reference redox reaction for E’°?

Answer 20

H⁺ + e⁻ ⇌ ½ H₂ (E’° = 0)

Question 21

How is E’° related to ΔG’°?

Answer 21

ΔG’° = –nFΔE’°

Question 22

What does a positive ΔE’° indicate?

Answer 22

The reaction is exergonic (ΔG’° < 0)

Question 23

Which has higher redox energy: a reduced or oxidized molecule?

Answer 23

Reduced molecule

Question 24

What is the H:C ratio indicative of?

Answer 24

Degree of reduction; higher H:C = more reduced

Question 25

What is the direction of electron flow in redox chains?

Answer 25

From lower to higher E'°

Question 26

Name three ways electrons can be transferred.

Answer 26

As free electrons, hydrogen atoms, or hydride ions

Question 27

Which enzyme class catalyzes redox reactions?

Answer 27

Oxidoreductases

Question 28

What is the function of NAD⁺ in metabolism?

Answer 28

To accept electrons and become NADH during catabolism

Question 29

What is the main role of FAD in redox reactions?

Answer 29

To accept two electrons and form FADH₂

Question 30

How does NADH contribute to ATP synthesis?

Answer 30

By donating electrons to the electron transport chain

Question 31

How is redox energy used to make ATP?

Answer 31

By creating a proton gradient that drives ATP synthase

Question 32

What are flavins?

Answer 32

Redox carriers like FAD and FMN that can accept two electrons and protons

Question 33

What distinguishes NAD⁺ from FAD in terms of binding?

Answer 33

NAD⁺ is soluble; FAD is usually bound as a prosthetic group

Question 34

What drives the exergonic nature of electron transfer?

Answer 34

The flow of electrons toward molecules with higher redox potential

Question 35

Why are coupled reactions important in metabolism?

Answer 35

They allow endergonic processes to proceed using energy from exergonic reactions

Question 36

What makes hydrolysis of PPi important?

Answer 36

It prevents reverse reactions and drives biosynthesis irreversibly

Question 37

What is the role of Mg²⁺ in ATP function?

Answer 37

Stabilizes negative charges and assists in enzyme binding

Question 38

What does ΔG < 0 signify in metabolic reactions?

Answer 38

That the reaction is spontaneous and can proceed without input

Question 39

Why is ΔG different from ΔG'° in vivo?

Answer 39

Because actual concentrations differ from standard conditions

Question 40

What is the role of CoA in metabolism?

Answer 40

It forms thioesters with acyl groups to carry them for oxidation or synthesis

Question 41

How do you calculate E using the Nernst equation?

Answer 41

E = E'° + (0.026/n) × ln([acceptor]/[donor])

Question 42

What is the main product of substrate-level phosphorylation?

Answer 42

ATP

Question 43

What is the main product of oxidative phosphorylation?

Answer 43

ATP via redox-driven proton gradients

Question 44

Which coenzyme is more commonly used in anabolic reactions?

Answer 44

NADPH

Question 45

Why is redox balance essential in metabolism?

Answer 45

To maintain energy flow and support biosynthetic needs

Question 46

How are redox carriers regenerated?

Answer 46

By donating electrons to downstream acceptors, like the ETC

Question 47

What allows redox reactions to power biological work?

Answer 47

Their ability to release free energy in a controlled manner

Question 48

What ensures directionality in electron transport?

Answer 48

Increasing E'° along the chain