Topic 9: cellular respiration

Question 1

Define catabolic pathways

Answer 1

• Energy production = ATP
• Breaking down organic compounds
• E.g. respiration

Question 2

Define anabolic pathways

Answer 2

• Energy consumption
• Synthesis of organic compounds
• E.g. photosynthesis

Question 3

What is the energy flow in an ecosystem?

Answer 3

Sunlight > photosynthesis in chloroplast + respiration in mitochondria > heat energy

Question 4

Explain the catabolic pathways

Answer 4

• Cells must regenerate ATP = in order to keep working
• Produce energy by oxidizing organic molecules = exergonic = releases energy
• Reactants > energy rich than products
  PROCESSES
  1) Cellular respiration
  2) Anaerobic respiration

Question 5

Describe cellular respiration

Answer 5

• Most efficient catabolic pathway
• Complete degradation of carbohydrates in presence of O2
• Chemical energy in glucose bonds transferred to phosphate bonds in ATP
• Yields highest ATP
• Energy from ATP hydrolysis used to perform endergonic reactions

Question 6

What is the equation for cellular respiration?

Answer 6

C6H12O6 + Ο2 —-> CO2+ H2O+ ΑΤP

Question 7

What are the 2 energy production/conversion organelles?

Answer 7

1) Chloroplasts = photosynthesis
2) Mitochondria = 2/3 stages of respiration

Question 8

3 stages of respiration

Answer 8

1) Glycolysis = anaerobic = cytosol
2) Krebs cycle = aerobic =mitochondria matrix
3) Oxidative phosphorylation =aerobic = inner membrane

Question 9

Describe the structure of a mitochondria

Answer 9

• Diameter = 1-10 μm
• Outer membrane
• Inner membrane = cristae = ETC complexes + ATP synthase
• Intermembrane space
• Matrix = mitochondrial DNA + free ribosomes

Question 10

Define redox reactions

Answer 10

• Transfer e- from 1 reactant to another via oxidation/reduction
• Oxidation = lose e-
• Reduction = gain e-

Question 11

Describe redox in respiration

Answer 11

• Glucose oxidized
• O2 reduced

Question 12

Describe the ATP production at each stage

Answer 12

• Glycolysis + Krebs = 10% of total = substrate level phosphorylation
• Oxidative phosphorylation = 90% ATP = ATP synthase

Question 13

Describe how e- energy is transferred and transported

Answer 13

• e- released from oxidation of organic compounds
• Co-transferred with H+
• Transferred to coenzymes FAD + NAD+ = reduced NADH + FADH2
• They transport to ETC
• Transferred to O2 = H2O

Question 14

What do NAD + FAD stand for?

Answer 14

• NAD = nicotinamide adenine dinucleotide
• FAD - flavin adenine dinucleotide

Question 15

Define dehydrogenase

Answer 15

• Enzymes that remove e- from organic compounds = transfer them to NAD + FAD

Question 16

Describe glycolysis

Answer 16

• Breaks down glucose
• Location = cytosol
• Anaerobic
• Products = 2ATP + 2NADH + 2 Pyruvate
  PHASES
  1) Energy investment
  2) Energy payoff

Question 17

Explain energy investment

Answer 17

• 2 ATP spent
• Substrates phosphorylated = energy-rich = unstable
• Splits glucose

Question 18

Explain energy payoff

Answer 18

• 4 ADP + 4 Pi = 4 ATP
• 2 NAD + 4e- + 4 H+ = 2NADH
• 2 Pyruvates

Question 19

Give the net products of glycolysis

Answer 19

• 2 ATP
• 2 NADH
• 2 Pyruvate

Question 20

Describe the Krebs cycle

Answer 20

• Completes the oxidation of organic molecules
• Location = mitochondrial matrix
• Products = CO2 + energy

Question 21

Describe the conversion of pyruvate

Answer 21

• Pyruvate is converted into acetyl-CoA before starting Krebs cycle
• Undergoes pyruvate dehydrogenase reaction
• 3 carbon > 2 carbon acetyl-CoA = 1 carbon released = CO2
• NAD+ reduced = NADH

Question 22

Describe Krebs cycle

Answer 22

• Acetyl-CoA combines with oxaloacetate = citric acid
• NADH + FADH2 produced = transferred to ETC
• Each acetyl-CoA =
  > 2 CO2
  > 3 NADH
  > 1 FADH2
  > 1 ATP

Question 23

How many ATP are produced by 1 NADH + FADH2 in Krebs cycle?

Answer 23

• 1 NADH = 3 ATP
• 1 FADH2 = 2 ATP

Question 24

Give the net products for Krebs cycle

Answer 24

• 12 molecules ATP

Question 25

2 Ways that e- enter the ETC

Answer 25

1) NADH oxidation = via complex I = NADH dehydrogenase
2) FADH2 oxidation = via complex II = succinate dehydrogenase

Question 26

Why is the ETC a stepwise energy transfer?

Answer 26

• If e- transfer not stepwise = large release of e- = uncontrolled reaction
• Instead of controlled release of little energy for synthesis

Question 27

Explain oxidative phosphorylation in the ETC

Answer 27

• e- from NADH/FADH oxidation = transferred to ETC
• e- initially transferred to coenzyme ubiquinone
• e- passed from higher energy carrier > lower energy carriers = down electronegativity
• e- transferred to O2 = most electronegative = H2O

Question 28

Give the order of complexes in the ETC

Answer 28

1) Complex I / Complex II
2) Coenzyme Q = ubiquinone
3) Complex III = cytochrome oxidoreductase
4) Cytochrome c
5) Complex IV = cytochrome oxidase

Question 29

Explain chemiosmosis

Answer 29

• ETC causes H+ pumped from matrix > intermembrane space
• H+ concentration gradient created
• pH matrix = 8 / pH IMS = 7
• Higher concentration in IMS
• H+ flow into matrix via ATP synthase down conc grad
• ATP synthase uses energy from H+ = ATP

Question 30

Define proton motive force

Answer 30

• Proton gradient created by flow of e-
• Drives chemiosmosis

Question 31

Describe ATP synthase

Answer 31

• Enzyme = synthesizes ATP from ADP + Pi
• Located = inner mitochondrial membrane
• Found in mitochondria + chloroplast + bacteria
• Has a proton pump = uses proton gradient = ATP synthesis
  2 PARTS:
  1) F0 = transmembrane part = subunits a/b/c
  2) F1= matrix part = subunits α/β/γ/δ/ε
• Proton though it = changes binding affinity in ATP/ADP
• H+ flowing through = 120° rotation

Question 32

What is the localization/orientation of ATP synthase?

Answer 32

• Inner membrane
• From intermembrane space to matrix

Question 33

What is the area of proton accumulation/ATP synthesis?

Answer 33

• Intermembrane space
• Matrix