Respiration

Question 1

what is energy from respiration used for?

Answer 1

• active transport eg. sodium potassium ion pumps
• secretion
• endocytosis
• anabolism eg. synthesising proteins from amino acids
• DNA replication
• cytoskeleton - movement

Question 2

structure of mitochondria

Answer 2

• inner and outer membrane
• gel-like matrix in middle
• inner membrane folds inwards creating cristae
• contain ribosomes and mitochondrial DNA

Question 3

stages of glycolysis

Answer 3

• occurs in cytoplasm of cell
  Phosphorylation
• 2 phosphates from 2 ATP molecules added to glucose to form 1 hexose bisphosphate (6 carbons) and 2 ADP molecules
• hexose bisphosphate splits into 2 triose phosphate
• triose phophate phosphorylated - phosphate added forming triose bisphosphate
  Oxidation
• triose bisphosphates oxidised (loses H atom) to form 2 pyruvate - catalysed by dehydrogenase
• they each lose both phosphates to ADP forming 4 ATP molecules (net gain of 2)
• hydrogen atom picked up by NAD forming 2 NADH
  if oxygen available, 2 pyruvates transported to matrix

Question 4

link reaction stage of respiration

Answer 4

• in matrix
• pyruvate decarboxylated (CO2 removed) to give 2C product
• CO2 diffuses out cell as a waste product
• H removed from pyruvate and picked up by NAD making acetate (2C) and NADH
• acetate combines with coenzyme A forming acetyl coenzyme A
• no ATP produced yet
• occurs for each pyruvate moleule so for 1 glucose - 2 acetyl coA produced, 2 NADH and 2 CO2 released

Question 5

Krebs cycle

Answer 5

• in matrix
• acetyl coA (2C) combines with oxaloacetate (4C) to form citrate (6C), while coA returns to link reaction
• decarboxylation - now 5C
• oxidation / dehydrogenation - H atom picked up by NAD - NADH
• decarboxylation - 4C
• substrate level phosphorylation - ATP molecule produced
• oxidation / dehydrogenation - 2 H atoms picked up by FAD - FADH2
• oxidation / dehydrogenation - H atom picked up by NAD - NADH , this happens once more
• citrate is now converted back to oxaloacetate
• this occurs twice per 1 glucose molecule

Question 6

oxidative phosphorylation

Answer 6

• occurs across inner membrane of mitochondria
• H atoms carried by NADH and FADH2 are oxidised and release H atoms which split into H+ ions and electrons
• electrons pass across 3 electron carriers
• chemiosmosis - energy gained from passing electrons across carriers is used to pump H+ from matrix to space between inner and outer membrane forming electrochemical gradient
• H+ move down grad back to matrix via ATP synthase
• movement drives synthesis of ATP from ADP and Pi
• at the end of the electron transport chain, H+, electrons and O2 combine to form water
• oxygen is the final electron acceptor

Question 7

what happens to electron transport chain if oxygen isn’t present?

Answer 7

• it cannot operate as oxygen is the final electron acceptor

Question 8

substrate level phosphorylation

Answer 8

• production of ATP when a phosphate group is transferred from a highly reactive intermediate eg. triose bisphosphate

Question 9

why does aerobic respiration make less ATP than the theoretical maximum?

Answer 9

• ATP used to transport pyruvate into mitochondrion
• some energy in electron transport chain is released as heat rather than being used to transport H+ across inner membrane
• not all NADH used at start of electron transport chain

Question 10

why does anaerobic respiration produce less ATP than aerobic respiration?

Answer 10

• anaerobic produces 2 molecules of ATP
• ATP only produced by substrate level phosphorylation
• Krebs cycle and electron transport chain doesn’t occur in anaerobic respiration - no chemiosmosis

Question 11

how is mitochondria adapted to respiration?

Answer 11

• matrix - contains required enzymes and coenzymes - NAD and FAD, oxaloacetate
• outer membrane - contains protein channels and carriers allowing passage of molecules into mitochondria
• inner membrane - impermeable to smal ions (eg. H+ allowing build up of them in intermembrane space), folded - large SA, many electron carriers and ATP synthase embedded in it

Question 12

first step of anaerobic respiration

Answer 12

Glycolysis
- occurs in cytoplasm
Phosphorylation
- 2 phosphates from 2 ATP molecules added to glucose to form 1 hexose bisphosphate (6 carbons) and 2 ADP molecules
- hexose bisphosphate splits into 2 triose phosphate
Oxidation
- triose phosphate oxidised (loses H atom) to form 2 pyruvate - catalysed by dehydrogenase
- this generates 4 ATP molecules (net gain of 2)
- hydrogen atom picked up by NAD forming 2 NADH

Question 13

lactate fermentation

Answer 13

• in mammals in absence of oxygen
• in cytoplasm
• glycolysis occurs
• NADH gets oxidised by lactate dehydrogenase and transfers H to pyruvate to make NAD and lactate
• NAD then reused in glycolysis to make more ATP
• lactate diffuses into plamsa and transported to liver cells where it’s converted back to pyruvate for the rest of aerobic respiration - requires oxygen

Question 14

why can’t lactate fermentation occur indefinitely?

Answer 14

• doesn’t produce enough ATP to maintain processes over a long period of time
• the build up of lactate causes a fall in pH - proteins will denature (enzymes and muscle filaments)

Question 15

oxygen debt

Answer 15

• the repayment of oxygen after exercise
• we still breathe heavily after exercise to deal with the lactate build up

Question 16

alcoholic fermentation

Answer 16

• in plants and fungi cells eg. yeast
• in cytoplasm
• glycolysis occurs
• CO2 removed from pyruvate to make ethanal - catalysed by pyruvate decarboxylase
• NADH transfers H to ethanal to make ethanol and NAD
• NAD reused in glycolysis

Question 17

how much energy is produced in anaerobic respiration vs aerobic?

Answer 17

anaerobic - 2 ATP
aerobic - 32-38 ATP

Question 18

what is a respiratory substrate?

Answer 18

• any bio molecule that can be broken down to release energy
• eg. glucose, proteins, lipids (lipids produce most energy)

Question 19

how are proteins respired?

Answer 19

• excess proteins deaminated to produce urea
• some converted into glycogen or fat
• some converted to pyruvate or acetate

Question 20

how are lipids respired?

Answer 20

• glycerol converted into glucose and is respired
• fatty acids - made up of hydrocarbon chains - large source of H atoms for oxidative phosphorylation so lots of ATP made

Question 21

respiratory quotient equation and vales for glucose, proteins, lipids

Answer 21

• RQ = vol of CO2 released/vol of O consumed
• glucose = 1
• protein = 0.9
• lipid = 0.7

Question 22

how does a respirometer work?

Answer 22

• two boiling tubes are connected by a capillary tube with an air bubble on a scale
• one tube contains the object respiring (eg. bread mould) in a gauze basket above soda lime to absorb any CO2 produced from respiration
• as O2 is used up and CO2 is absorbed, the air bubble moves towards this boiling tube
• the other boiling tube contains a control substance that doesn’t respire
• to calculate the rate of respiration, measure how far the air bubble moves in a certain time (eg. 25 min), repeat 3 times and calculate a mean