C1.2 Respiration

Question 1

Adenosine Triphosphate structure

Answer 1

• 3 phosphate groups
• ribose sugar
• adenine (base)

Question 2

ATP function

Answer 2

Cell energy currency, temporarily stores energy and used for transfter of energy between processes + different cell parts.

3rd phosphate group easily removed/reattached, releasing energy.

Question 3

Properties of ATP which
make it suitable for storing/transfering energy

Answer 3

• Soluble in water: move freely in cytoplasm + other cell aqueous solutions.
• Stable at pH close to neutral (in cytoplasm).
• Can’t pass freely through PB of membranes. Movement between membrane-bound organelles controlled.

Question 4

ATP as a coenzyme

Answer 4

Coenzymes are organic compounds that help enzymes by cycling between loaded and unloaded forms. ATP transfers chemical energy to enzymes, lowering the activation energy and triggering catalysis.

Question 5

Mneumonic: BANG ME

Uses of ATP

Answer 5

Biosynthesis of macromolecules (e.g. polymers)
Active transport (e.g. endocytosis)
Nerve transmission (e.g. propagation of AP)
Growth and repair (e.g. mitotic division)
Movement (e.g. muscle contraction)
Emission of light (e.g. bioluminescence)

AP = action potentials

Question 6

What are NAD+ and FAD?

Answer 6

Carrier molecules known as hydrogen/electron carriers (gain).

NAD+ + 2H+ + 2e– → NADH + H+
FAD + 2H+ + 2e– → FADH2

Question 7

Glycolysis - step 1

Answer 7

Glucose is phosphorylated (6C) → fructose-1,6-biphosphate (6C, 2P)

(2ATP → 2ADP + 2Pi)

Question 8

Glycolysis - step 2

Answer 8

Fructose-1,6-biphosphate (6C, 2P) undergoes lysis → 2x Triose phosphate (3C, P)

Question 9

Glycolysis - step 3

Answer 9

Triose phosphate oxidised (dehydrogenase works w/ NAD+ (coenzyme) to remove H) → pyruvate (3C)

1. NAD+ → NADH + H+ (reduced - accepts hydrogens, takes electrons to ETC)
2. 2ADP + 2Pi → 2ATP (dephos. / ATP formation)

Question 10

Link reaction (x2)

Answer 10

Pyruvate diffuses into matrix mitochondria and is decarboxylated (form CO2) + oxidised.

This forms NADH + H+ and an acetyl group (2C).
2C joins w/ coenzyme A → AcetylCoA

Question 11

Krebs cycle (x2) - step 1

Answer 11

AcetylCoA + Oxaloacetate (4C) combine → Citrate (6C)

Coenzyme A goes back into Link Reaction.

Question 12

Krebs Cycle (x2) - step 2

Answer 12

6C citrate → converted to 5C compound
Carbon dioxide = removed (decarboxylation)

Oxidation/dehydrogenation also occurs:
H is removed by NAD+ → NADH + H+

Question 13

Krebs Cycle (x2) - step 3

Answer 13

5C molecule → converted to oxaloacetate (4C)

Decarboxylation + dehydrogenation occur (CO2, NADH + H+) FAD also reduced (remove H) → (FADH2).

Substrate level phosphorylation occurs: ATP produced by direct transfer of phosphate from an intermediate compound to ADP.

Question 14

What does the Krebs Cycle produce (x2)?

KREBS HAPPENS x2 PER GLUCOSE = DOUBLE PRODUCT

Answer 14

• 2ATP
• 4CO2
• 2FADH2
• 6NADH + H+

Question 15

ETC - step 1

Answer 15

NADH + H+ and FADH2 are oxidised - protons removed by dehydrogenase enzyme → NAD+ and FAD+ (reused in Krebs)

H atom → H+ and e-

Question 16

ETC - step 2

Answer 16

e- move along the ETC (3 embedded proteins that act as electron carriers), losing energy at each carrier.

Energy used by protein pumps to move H+: matrix → intermem. space = create high electrochem. gradient.

Question 17

ETC - step 3

Answer 17

Chemosmosis occurs:

H+ moves down gradient into matrix via a protein channel. Channel has ATP synthase attach, movement drives synthesis of ATP from ADP + Pi.

Question 18

ETC - step 3 (final step of respiration)

Answer 18

In the matrix, 12H+ + 12e- + 6O2 (from blood) → 6H2O
* Oxygen = final electron acceptor

Question 19

What is oxidative phosphorylation?

Answer 19

O = oxidation of NADH + H+ and FADH2 to form H+ and e- at the start of the ETC.

P = addition of a phosphate to form ATP (ADP+Pi → ATP) at the end of chemosmosis.

Question 20

How much ATP is generated overall in aerobic + anaerobic respiration?

Answer 20

anaerobic = 2

Question 21

Anaerobic respiration - step 1

Answer 21

Glucose → pyruvate (via glycolysis) + NADH

Without oxygen, NADH cannot be oxidized by the mitochondria, reducing the amount of available NAD.

Question 22

Anaerobic respiration - step 2

Answer 22

Fermentation involves conversion: pyruvate → alt carbon compound via a reaction that oxidises NADH.

This process restores NAD, which is needed for glycolysis to keep making ATP without oxygen.

Without fermentation, glycolysis would stop = essential

Question 23

Products of fermentation (- step 3)

Answer 23

Animals: lactic acid (lactate) – reversible (pyruvate can be reformed when oxygen is present)

Plants/yeast: ethanol + carbon dioxide – irreversible

Question 24

Anaerobic cell respiration uses in animals and bacteria

Answer 24

Animals: used to maximise muscle contraction power (energy capacity exceeds oxygen levels)

Bacteria: lactic acid can be used to modify milk proteins, making certain yogurts + cheese

Question 25

Anaerobic cell respiration uses in yeast

Answer 25

Bread – CO2 causes dough to rise via leavening (ethanol evaporates during baking process) Alcohol – Ethanol is the intoxicating agent (concs above ~14% damage the yeast)

Question 26

Variables affecting the rate of cell respiration

Answer 26

Temp/pH alter functionality of respiratory enzymes. Glucose/oxygen availability influence reaction rates. Inhibitors prevent enzyme-substrate interactions (e.g. cyanide blocks electron transfer in the ETC)

Question 27

Carbohydrates - What is the energy yield? Is anaerobic respiration possible?

Answer 27

1) 17 kJ/g. About half of lipids. Energy is released by oxidizing C and H, carbohy. mass is more than 50% O, which doesn't yield energy. 2) Yes - glycolysis uses sugars as the substrate and generates some ATP w/out needing oxygen.

Question 28

Lipids - What is the energy yield? Is anaerobic respiration possible?

Answer 28

1) 37 kJ/g. Nearly 90% of lipid mass is C and H. 2) No - The first stage of respiration is fatty acids → acetyl groups in matrix, then fed into Krebs cycle. This only happen when oxygen is available.

Question 29

Respiration formula

Answer 29

C6H12O6 +6 O2→6 CO2+ 6 H2O C6H12O6→2 C3H6O3 C6H12O6→2 C2H5 OH + CO2