Respiration

Question 1

Role of the outer membrane of mitochondria

Answer 1

• separate contents of mitochondria from rest of cell
• create a cellular compartment with idea conditions for aerobic respiration

Question 2

Role of innermembrane of mitochondria

Answer 2

• contains electron transport chains and ATP synthase

Question 3

Cristae

Answer 3

• projections/infolding of inner membrane
• increases the surface area available for oxidative phosphorylation

Question 4

Matrix

Answer 4

• contains enzymes for the Krebs cycle and link reaction
• contains mitochondrial DNA and ribosomes
• fluid of the mitochondria

Question 5

Summary of aerobic respiration

Answer 5

glycolysis - link reaction - Krebs cycle - oxidative phosphorylation

Question 6

Summary of anaerobic respiration

Answer 6

glycolysis - fermentation

Question 7

Glycolysis

Answer 7

• first stage
• occurs in cell cytoplasm
• splits glucose into 2 pyruvate molecules
• produces 2x NADH
• net yield 2 ATP

Question 8

Link reaction

Answer 8

• links anaerobic glycolysis to aerobic respiration stages
• occurs in mitochondrial matrix
• pyruvate is decarboxylated and reduced to form acetate
• acetate is then bound to coenzyme A
• produces acetyl coA, 1x CO2, 1x NADH (per each molecule of pyruvate)

Question 9

Kerbs cycle

Answer 9

• occurs in mitochondrial matrix
• involves decarboxylation, dehydrogenation and substrate level phosphorylation
• Produces CoA, 3x NADH, 1x ATP, 1x reduced FAD, 2x C02 (per cycle)

Question 10

Role of NAD in respiration

Answer 10

• accepts protons and electrons released during glucose breakdown
• role in all stages of cellular respiration
• accepts 1 H

Question 11

Role of FAD in respiration

Answer 11

• Only accepts hydrogens in the Krebs cycle
• accepts 2 hydrogens

Question 12

How many ATP molecules are synthesised from reduced NAD and reduced FAD

Answer 12

• reduced NAD results in synthesis of 3 ATP molecules (or 2.5)
• reduced FAD results in synthesis of 2 ATP molecules (or 1.5)

Question 13

Net yield of ATP from aerobic and anaerobic respiration

Answer 13

• Aerobic= 38
• anaerobic= 2

Question 14

Different types of organisms (respiration wise)

Answer 14

• Obligate anaerobes = can’t survive in the presence of oxygen e.g. some prokaryotes
• Facultative anaerobes = synthesis ATP by aerobic respiration in O2 present, but can switch to anaerobic in absence e.g. yeast
• Obligate aerobes= can only synthesis ATP in presence of oxygen e.g. mammals

Question 15

Fermentation

Answer 15

• a form of anaerobic respiration
• process by which complex organic molecules are broken into smaller inorganic molecules without the use of oxygen or an electron transport chain
• organic compounds not fully broken down, so less ATP produced
• small quality of ATP produced by substrate level phosphorylation

Question 16

What is alcoholic fermentation

Answer 16

• occurs in yeast and some plant root cells
• end products= CO2 and ethanol

Question 17

What is lactate fermentation

Answer 17

• occurs in animal cells
• produces lactate

Question 18

How does a lack of oxygen lead to stopping of aerobic respiration

Answer 18

• no oxygen to act as the final electron acceptor
• flow of electrons and ATP synthesis stops
• reduced NAD and FAD are no longer able to be oxidised as nowhere for electrons to go
• NAD and FAD not regenerated so decarboxylation and oxidation of pyruvate and Krebs cycle stops

Question 19

Features of lactate fermentation

Answer 19

• pyruvate acts as a hydrogen acceptor- takes hydrogen from NADH
• reaction catalysed by lactate dehydrogenate
• pyruvate is converted to lactate
• NAD is regenerated- keeps glycolysis going, so small net yield of ATP
• reversible process

Question 20

Why can’t lactate fermentation occur indefinitely

Answer 20

• the reduced ATP quantity not enough to maintain vital processes for long
• lactic acid accumulation causes a fall in pH so enzymes don’t function efficiently

Question 21

Summary of Lactate fermentation

Answer 21

pyruvate + hydrogen = lactate

Question 22

Features if alcoholic fermentation

Answer 22

• irreversible process
• pyruvate is converted to ethanal
• catalysed by pyruvate decarboxylase
• ethanal can accept a H ion from NADH, forming ethanol
• regenerated NAD can now act as a coenzyme in glycolysis
• can occur indefinitely
• however, ethanol becomes toxic to yeast cells if accumulates over 15%

Question 23

Respiratory quotient equation

Answer 23

= CO2 produced / O2 consumed

Question 24

What is the average respiratory quotient for carbs, lipids, proteins, normal respiration and anareobic

Answer 24

• carbs= 1.0
• protein= 0.9
• lipids= 0.7
• normal activity (aerobic)= 0.8/0.9
• anaerobic respiration= >1