Roles of ATP in living cells

Question 1

What is anabolism?

Answer 1

synthesis of complex molecules from simpler ones (necessary energy usually derived from ATP)

Question 2

What is catabolism?

Answer 2

breakdown of energy- rich molecules to simpler ones (CO2 H2O and NH3)

Question 3

What is energy used for?

Answer 3

Motion (muscle contraction)
Transport (of ions/molecules across membranes)
Biosynthesis of essential metabolites
Thermoregulation

Question 4

Why are storage forms required?

Answer 4

Because feeding times and usage times do not coincide all the time

Question 5

Where is free energy gained from?

Answer 5

Food

Question 6

What is gibbs free energy?

Answer 6

Energy capable of doing work at constant temperature and pressure
The energy derived from the oxidation of dietary fuels

Question 7

When does entropy increase?

Answer 7

Breakdown

Question 8

When does enthalpy increase?

Answer 8

When energy is put into the system

Question 9

What is an exergonic reaction?

Answer 9

One which releases energy

Question 10

When is free energy negative?

Answer 10

When the reaction releases energy

Question 11

When is free energy positive?

Answer 11

When reaction is endergonic and require energy to begin

Question 12

Give an example of an exergonic reaction?

Answer 12

Catabolism

Question 13

Give an example of endergonic reactions

Answer 13

Anabolism

Question 14

Describe coupling of reactions

Answer 14

An endergonic reaction can be driven in the forward direction by coupling it to an exergonic reaction through a common intermediate

Question 15

When is phosphate group transfer used?

Answer 15

When ATP is used

Question 16

What can magnesium deficiency do?

Answer 16

Interfere with metabolism

Question 17

Describe substrate level phosphorylation

Answer 17

Formation of ATP by phosphoryl group transfer from a substrate to ADP

Question 18

Respiration-linked phosphorylation involve…

Answer 18

Membrane-bound enzymes and transmembrane gradients of protons and require oxygen

Question 19

How do enzymes interfere with gibbs free energy?

Answer 19

They do not

Question 20

What are coenzymes derived from?

Answer 20

Vitamins

Question 21

What is a prosthetic group?

Answer 21

Non-protein cofactor that is covalently bound to the enzyme

Acts as a temporary store for e- or intermediates

Question 22

What is NAD formed from?

Answer 22

Niacin

Question 23

What is FAD formed from?

Answer 23

B2 Riboflavin

Question 24

In each redox case how many electrons and protons are transferred?

Answer 24

2 electrons

Various protons

Question 25

What is NAD+ reduced to?

Answer 25

NADH

Question 26

What is FAD reduced to?

Answer 26

FADH2

Question 27

What is the functional group of NAD+

Answer 27

Nicotinamide

Question 28

What are priming reactions?

Answer 28

Where ATP is put into the reaction to begin it

Question 29

Where does glycolysis occur in the cell?

Answer 29

Cytoplasm

Question 30

What continues to the next stage of the glycolysis reaction

Answer 30

G3P

Question 31

How many times do the payoff reactions occur per molecule of glucose?

Answer 31

Twice

Question 32

What is the product of glycolysis?

Answer 32

Pyruvate

Question 33

What is the priming stage?

Answer 33

investment of ATP at the hexokinase and PFK-1 reactions

Question 34

What is the payoff stage?

Answer 34

recovery of ATP by SLP using the 1,3 - bisphosphate kinase and pyruvate kinase reactions

Question 35

What are the two possible fates of pyruvate?

Answer 35

Under aerobic conditions, oxidation and complete degradation In hypoxic conditions, it can be reduced to lactate

Question 36

Under aerobic conditions where does pyruvate get degredated?

Answer 36

Mitochondria

Question 37

Describe how pyruvate is transported into the mitochondria?

Answer 37

Occurs via by specific carrier protein embedded in the mitochondrial membrane

Question 38

How does pyruvate form acetyl CoA?

Answer 38

Pyruvate undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex to form Acetyl CoA:

Question 39

Describe the structure of the pyruvate dehydrogenase complex?

Answer 39

Three different enzymes | Five different coenzymes

Question 40

List the vitamins essential for the pyruvate dehydrogenase complex

Answer 40

Thiamine (in TPP) Riboflavin (in FAD) Niacin (in NAD) Pantothenate (in CoA)

Question 41

What is the TCA cycle?

Answer 41

Krebs cycle/Tricarboxylic acid cycle/Citric acid cycle Final common pathway for the oxidation of fuel molecules In 8 steps, acetyl residues (CH3-CO-) are oxidised to CO2

Question 42

What does 1 turn of the TCA cycle produce?

Answer 42

3 NADH FADH2 GTP 2 CO2

Question 43

Describe the 3 ways TCA cycle is regulated

Answer 43

Entry of acetyl-CoA into the TCA cycle (citrate synthase reaction) Conversion of pyruvate to acetyl-CoA (PDH reaction) Also regulated at isocitrate dehydrogenase and -ketoglutarate dehydrogenase reactions

Question 44

Name some other sources of Acetyl coA

Answer 44

Fatty acids | Amino acids

Question 45

How are the TCA intermediates replenished?

Answer 45

By anaplerotic reactions

Question 46

What happens to the NADH and FADH2 after the TCA and glycolysis? State the problem here

Answer 46

Oxidised by the mitochondrial ETC The inner mitochondrial membrane is impermeable to NADH! There is no carrier in the membrane to transport it across

Question 47

Describe how NADH is transported?

Answer 47

It is not! | The shuttles transport the electrons across the membrane

Question 48

Describe the two shuttles stating where they are prevalent and what they do

Answer 48

The glycerol-3-phosphate shuttle, especially prevalent in brain and muscle The malate-aspartate shuttle, in liver and heart Both shuttles act to regenerate NAD+ and make 1.5 or 2.5 moles of ATP

Question 49

Describe the action of the glycerol-3-phosphate shuttle

Answer 49

NADH reduces dihydroxyacetone-P (DHAP) to glycerol-3-phosphate (G-3-P) Catalysed by G-3-P dehydrogenase G-3-phosphate diffuses into the intramembrane space A mitochondrial G-3-P dehydrogenase (called flavoprotein dehydrogenase) uses FAD to oxidise it to DHAP FADH2 carries electrons to ubiquinone in the electron transport chain eventually producing 1.5 ATP

Question 50

Describe the action of the malate aspartate shuttle

Answer 50

Electrons of cytosolic NADH transfer to cytosolic oxaloacetate yielding malate Malate is transported into the matrix via an exchanger protein that transports α-KG in the opposite direction In the matrix, malate is oxidised back to oxaloacetate NADH formed transfers its reducing power to the electron transport chain producing 2.5 ATP Oxaloacetate is converted to aspartate Aspartate is transported to the cytosol via an exchanger protein that transports glutamate into the matrix Cytosolic aspartate is transaminated to oxaloacetate

Question 51

Describe the electron transport chain

Answer 51

Comprises four large multi-unit proteins intrinsic to the inner mitochondrial membrane

Question 52

State the reaction the electron transport chain catalyses

Answer 52

NADH + H+ + 1/2O2 = NAD+ + H2O | Energy released from this reaction not released as heat but tightly coupled to the production of ATP

Question 53

The 4 complexes are linked by 2 soluble proteins. What are they?

Answer 53

Ubiquinone (coenzyme Q) – a lipid soluble benzoquinone with a long isoprenoid tail Cytochrome C - These are free to move in the membrane by diffusion (they are not part of the complexes)

Question 54

Which complex does NADH pass its electrons to in the electron transport chain?

Answer 54

Complex 1

Question 55

Which complexes move protons in the electron transport chain?

Answer 55

1,3,4