Intro to Metabolism

Question 1

What is metabolism?

Answer 1

The sum of all chemical reactions occurring within a cell or organism

Question 2

What is catabolism?

Answer 2

The breakdown of complex molecules into simpler ones, releasing energy

Question 3

What is anabolism?

Answer 3

The synthesis of complex molecules from simpler ones, requiring energy

Question 4

What is intermediate metabolism?

Answer 4

The intracellular metabolic processes that sustain life

Question 5

What are the three stages of catabolism?

Answer 5

1. Digestion of macromolecules; 2. Formation of acetyl-CoA; 3. Oxidation in the citric acid cycle and ETC

Question 6

Which stage of catabolism produces the most ATP?

Answer 6

Stage 3 – oxidation of acetyl-CoA in the electron transport chain

Question 7

What is the primary product of catabolism entering the citric acid cycle?

Answer 7

Acetyl-CoA

Question 8

What is ATP’s role in metabolism?

Answer 8

It stores and transfers energy for cellular processes

Question 9

Why are catabolic and anabolic pathways not the same in reverse?

Answer 9

Because they involve different enzymes and regulation mechanisms

Question 10

What are the characteristics of metabolic pathways?

Answer 10

Enzyme-catalyzed, compartmentalized, regulated, and interconnected

Question 11

How does catabolism differ structurally from anabolism?

Answer 11

Catabolism converges from many substrates; anabolism diverges to many products

Question 12

What is metabolic compartmentalization?

Answer 12

The localization of metabolic pathways in specific organelles

Question 13

Name a tissue where gluconeogenesis is active.

Answer 13

Liver

Question 14

How is metabolism regulated externally?

Answer 14

Through hormones and extracellular signals

Question 15

What internal signals regulate metabolism?

Answer 15

Concentrations of ATP, NADH, FADH₂, and substrate availability

Question 16

What are the three main types of enzyme regulation?

Answer 16

Gene induction, allosteric regulation, and substrate availability

Question 17

What is the Gibbs free energy equation?

Answer 17

ΔG = ΣG_products − ΣG_substrates

Question 18

What does ΔG < 0 mean?

Answer 18

The reaction is exergonic and spontaneous

Question 19

What does ΔG > 0 mean?

Answer 19

The reaction is endergonic and non-spontaneous

Question 20

What does ΔG = 0 mean?

Answer 20

The reaction is at equilibrium

Question 21

What is standard Gibbs free energy change (ΔG’⁰)?

Answer 21

The change in free energy under standard conditions (1 M, 25°C, pH 7)

Question 22

How is ΔG’⁰ related to the equilibrium constant?

Answer 22

ΔG’⁰ = –RT ln K′eq

Question 23

What does K′eq > 1 indicate?

Answer 23

That ΔG’⁰ < 0 and the reaction is spontaneous

Question 24

Why is ΔG important in metabolism?

Answer 24

It determines whether a metabolic reaction will proceed

Question 25

What happens to ΔG in reverse reactions?

Answer 25

It has the same magnitude but opposite sign

Question 26

Are ΔG values additive in metabolic pathways?

Answer 26

Yes, the overall ΔG is the sum of individual step ΔGs

Question 27

How are unfavorable reactions made to proceed?

Answer 27

By coupling them with favorable reactions like ATP hydrolysis

Question 28

What is the ΔG’⁰ of ATP hydrolysis?

Answer 28

Approximately –30.5 kJ/mol

Question 29

Why is ATP an effective energy currency?

Answer 29

Because it releases significant free energy upon hydrolysis

Question 30

What is the role of NADH in metabolism?

Answer 30

It carries electrons from catabolism to the electron transport chain

Question 31

What role do enzymes play in metabolic reactions?

Answer 31

They lower activation energy and enable specificity and control

Question 32

Do enzymes change ΔG of reactions?

Answer 32

No, they only affect reaction rate, not thermodynamics

Question 33

What is a coupled reaction?

Answer 33

- An endergonic reaction driven by an exergonic one through a shared intermediate - one where the free energy of a thermodynamically favourable reaction is used to drive a thermodynamically unfavourable one.

Question 34

Give an example of a coupled reaction in metabolism.

Answer 34

Glucose phosphorylation coupled with ATP hydrolysis

Question 35

Who discovered the citric acid cycle?

Answer 35

Hans Krebs in 1937

Question 36

Who discovered β-oxidation?

Answer 36

Knoop in 1904

Question 37

What is the major source of cellular energy?

Answer 37

The oxidation of nutrients through catabolic pathways

Question 38

What makes an enzyme regulatory?

Answer 38

Its ability to respond to metabolic signals and control pathway flux

Question 39

What is the difference between exergonic and endergonic reactions?

Answer 39

Exergonic reactions release energy (ΔG < 0), endergonic reactions require energy (ΔG > 0)

Question 40

What is the role of feedback inhibition in metabolism?

Answer 40

To regulate the pathway by inhibiting enzymes via their products

Question 41

How are key metabolic enzymes typically regulated?

Answer 41

Allosterically or by covalent modification

Question 42

What is the role of the liver in metabolism?

Answer 42

It regulates blood glucose and coordinates multiple pathways

Question 43

What is the role of mitochondria in metabolism?

Answer 43

Site of the citric acid cycle and oxidative phosphorylation

Question 44

What is substrate availability regulation?

Answer 44

Control of enzyme activity based on concentration of substrate

Question 45

Why are metabolic reactions compartmentalized?

Answer 45

To increase efficiency and allow regulation between pathways

Question 46

What happens when a reaction has a large negative ΔG?

Answer 46

It tends to be irreversible and a good point for regulation

Question 47

What is the main energy outcome of catabolism?

Answer 47

Generation of ATP and reduced electron carriers (NADH, FADH₂)

Question 48

How does metabolism support cellular structure?

Answer 48

By providing building blocks and energy for biosynthesis

Question 49

What is the purpose of metabolic divergence in anabolism?

Answer 49

To produce a variety of macromolecules from simple precursors