Ch 12: Energy and Respiration

Question 1

How to overcome activation energy? (e.g. glucose)

Answer 1

1. Using enzymes to lower the activation energy

2. Using phosphorylation to raise energy level of glucose

Question 2

Why is the ATP a good molecule as ‘energy currency’?

Answer 2

• Readily hydrolyzed to release energy
• Small (easy to transport)
• Water-soluble (easy to transport)

Question 3

The difference between ‘energy currency’ and ‘energy storage’!

Answer 3

Energy currency: immediate donor of energy when a cell needs energy –> first choice of energy supply?

Energy storage: short-term or long-term store of chemical potential energy –> second and third choice of energy supply?

Question 4

Energy for ATP synthesis comes from what processes? (2 processes)

Answer 4

1. Energy released from reorganizing chemical bonds (respiration) –> Krebs cycle and glycolysis
2. Electrical potential energy

Question 5

Explain electron potential energy! (how it happens)

Answer 5

Transfer of electrons by electron carriers (mitochondria and chloroplast)

• Difference in proton (H+ ions) across cell membrane
• Protons flow down their concentration gradient (facilitated diffusion) –> ATP synthase synthesizes ATP (a.k.a. chemiosmosis)

Question 6

Conditions for chemiosmosis to happen

Answer 6

3 protons create 1 ATP, as long as ADP and a Pi group are available inside the organelle

Question 7

Phases of chemiosmosis (3 phases)

Answer 7

ATP synthase has 3 binding sites and a part of molecule which rotates as H+ (proton) passes causing changes in the 3 binding sites and hence passing 3 phases:

1. ADP and Pi binds
2. Tightly bound ATP forms
3. ATP is released

Question 8

Active transport, what goes in and out of cells? (what pumps are used as well?)

Answer 8

pump Na+ (sodium ions) OUT of cell
pump K+ (potassium ions) INTO the cell

Protein (sodium-potassium) pumps on cell surface membrane

Question 9

Explain sodium-potassium pump!

Answer 9

• A protein
• Spans across cell membrane
• OUTER side: K+ binding site
• INNER side: Na+ and ATP
• Acts as ATPase (releasing energy)

Question 10

What is ATPase?

Answer 10

Enzyme which catalyzes the hydrolysis of ATP into ADP + Pi, generating energy to drive the pump (change protein pump shape) –> 30.5 kJ/mol

Question 11

What is Pi?

Answer 11

Inorganic phosphate, H3PO4

Question 12

For each ATP, how many K+ and Na+ are moved? (also, into or out of cell do they go?)

Answer 12

Two K+ move into the cell

Three Na+ move out of cell

Question 13

What is the result of the amount of K+ and Na+ not being equal?

Answer 13

Potential difference is created across the membrane. Negative inside compared to the outside.

Sodium and potassium leaks down their diffusion gradient. However, cell surface membranes are much less permeable to Na+, so this ‘leaking’ diffusion actually increases the potential difference across the membrane.

Question 14

Is ATP used a lot for active transport?

Answer 14

Yes, about 50% of ATP is used to maintain ionic content of cells

Question 15

What is the purpose of respiration?

Answer 15

Breaking down of organic molecules in a series of stages to release chemical potential energy to synthesize ATP

Question 16

What are the 4 stages of glucose breakdown? (in order and in which part of the cell they happen)

Answer 16

1. Glycolysis (cytoplasm)

(mitochondria)

2. The link reaction
3. The Krebs cycle
4. Oxidative phosphorylation (electron transport chain)

Question 17

Explain glycolysis extensively! (pt1)

a. Process

Answer 17

a. Process:
1. Phosphorylation using ATP because glucose is stable (increases energy level so that glucose will react)
_glucose (6C) + ATP –> fructose phosphate (6C)
_fructose phosphate + ATP –> fructose biphosphate (6C)
_fructose biphosphate (6C) –> 2 triose phosphate molecules (3C)

2. Removal of hydrogen from triose phosphate
   2NAD + 2H+ –> 2NADH [reduced NAD]
   also produces 2ATP
   NAD = nicotinamide adenine dinucleotide
3. what’s left of triose phosphate is the intermediate and intermediate changing to 2 pyruvates generates 2ATP

Question 18

Explain glycolysis extensively! (pt2)

b. Reactants and Products @ which process of glycolysis

Answer 18

Used =
2ATP @ phosphorylation

Gained =
2 ATP @ removal of hydrogen from 2 triose phosphates
2 NADH @ removal of hydrogen from 2 triose phosphates
2 ATP @ intermediate turning into 2 pyruvates

net gain 2ATP, 2NADH

Question 19

Explain the link reaction!

Answer 19

Pyruvate enters mitochondria by active transport.
Through outer and inner membranes into the mitochondrial matrix

(Pyruvate - CO2 - H) + CoA –> acetyl coenzyme A

1. decarboxylated and dehydrogenated (H moved to NAD)
2. added with coenzyme A
3. acetyl coenzyme A is yielded

Pyruvate + CoA + NAD –> acetyl coenzyme A + NADH + CO2

Question 20

Extra info about link reaction

1. component and a feature of coA
2. another way of making acetyl coA and its process

Answer 20

1. coA = a nucleoside (ribose plus adenine); acts as carrier of acetyl groups to Krebs cycle
2. Fatty acids; in cycle of reactions, each cycle turn shortens the fatty acid chain by two-carbon acetyl unit. each react with a coA, producing acetyl coA

Question 21

Krebs cycle also known as…

Answer 21

aka citric acid or tricarboxylic acid

Question 22

What are the steps of Krebs cycle?

Answer 22

1. Acetyl coA + oxaloacetate……

refer to diagram drawn

Question 23

Mention Krebs cycle products

Answer 23

2 CO2, 1FAD, 3NADH, 1ATP

Question 24

Explain why do is there a term like “oxidative phosphorylation AND electron transport chain”?

Where do oxidative phosphorylation happens?

Answer 24

Energy for phosphorylation comes from activity of electron transport chain

Inner mitochondrial membrane