5.2.2 Respiration Flashcards Preview

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Flashcards in 5.2.2 Respiration Deck (24)
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1
Q

Where does glycolysis occur in the cell?

A
  • in the cytoplasm
2
Q

Which stages of respiration occur in the mitochondria?

A
  • link reaction
  • krebs cycle
  • oxidative phosphorylation
3
Q

Is glycolysis an aerobic or anaerobic process?

A
  • anaerobic

- doesn’t need oxygen to take place and it is the first stage

4
Q

Explain the two stages in glycolysis

A

Stage 1 Phosphorylation:

  • glucose is phosphorylated by adding two phosphates from 2 molecules of ATP
  • this creates 1 molecule of hexose bisphosphate and 2 molecules of ADP
  • then hexose bisphosphate is split up into 2 molecules of triose phosphate

Stage 2 Oxidation:

  • triose phosphate is oxidised, forming 2 molecules of pyruvate
  • NAD collects the hydrogen ions, forming 2 reduced NAD
  • 4 ATP are produced by 4 ADP and 4 inorganic phosphate molecules
  • 2 ATP molecules were used in stage one, so there is a net gain of 2 ATP
5
Q

Describe the link reaction

A
  • takes place in the mitochondrial matrix
  • pyruvate is decarboxylated: one carbon atom is removed from pyruvate in the form of CO2
  • NAD is reduced: it collects hydrogen from pyruvate into acetate
  • acetate is combined with coenzyme A to form acetyl coenzyme A
  • no ATP is produced in this reaction
6
Q

How many pyruvate molecules are made for every glucose molecule that enter glycolysis

A
  • two pyruvate molecules meaning link reaction and krebs cycle happen twice for every glucose molecule
  • two molecules of acetyl CoA go into Krebs cycle
  • two molecules of CO2 are released as a waste product of respiration
  • two molecules of reduced NAD are formed and go to oxidative phosphorylation
7
Q

Describe the Krebs Cycle

A
  • involves a series of oxidation-reduction reactions
  • takes place in the matrix
  • acetyl CoA combines with oxaloacetate to form citrate catalysed by citrate synthase
  • coenzyme A goes back to the link reaction to be used again
  • the 6C citrate molecule is converted to a 5C molecule
  • decarboxylation occurs, where CO2 is removed
  • dehydrogenation also occurs, where hydrogen is removed
  • the hydrogen is used to produced reduced NAD from NAD
  • the 5C molecule is then converted to a 4C molecule
  • decarboxylation and dehydrogenation occur, producing one molecule of reduced FAD and two reduced NAD
  • ATP is produced by the direct transfer of a phosphate group from an intermediate compound to ADP
  • when a phosphate group is directly transferred from one molecule to another it’s called substrate-level phosphorylation
  • citrate is now converted to oxaloacetate
8
Q

where do 1 CoA, oxaloacetate, 2 CO2, 1ATP, 3 reduced NAD, 1 reduced FAD go after the Krebs cycle

A
  • 1 CoA: reused in the next link reaction
  • 2 CO2: released as a waste product
  • oxaloacetate: regenerated for use in the next Krebs cycle
  • 1 ATP: used for energy
  • 3 reduced NAD: to oxidative phosphorylation
  • 1 reduced FAD: to oxidative phosphorylation
9
Q

Briefly explain oxidative phosphorylation

A
  • oxidative phosphorylation is the process where energy carried by electrons, from reduced coenzymes (reduced FAD and NAD) is used to make ATP
  • oxidative phosphorylation takes place in the inner mitochondrial membrane
10
Q

Fully describe oxidative phosphorylation

A
  • H atoms are released from reduced NAD and reduced FAD as they’re oxidised to NAD and FAD
  • the H atoms split into protons (H+) and electrons
  • the electrons move along the electron transport chain (made up of three electron carriers), losing energy at each carrier
  • the electron transport chain occurs in the inner mitochondrial membrane
  • this energy is used by electron carriers to pump protons from the mitochondrial matrix into the inter membrane space
  • the concentration of photons is now higher in the inter membrane space then in the mitochondrial matrix, forming an electrochemical gradient
  • protons move down the electrochemical gradient, by chemiosmosis, back into the mitochondrial matrix, via ATP synthesis
  • this movement drives the synthesis of ATP from ADP and inorganic phosphate
  • in the matrix at the end of the electron transport chain, the protons, electrons and O2 (from blood) combine to form water
  • oxygen is said to be the final electron acceptor
11
Q

How many ATP molecules can be made from one glucose molecule and why?

A
  • 32 molecules
  • glycolysis: 2 ATP produced
  • glycolysis: 2 reduced NAD = 2 x 2.5 = 5 ATP molecules
  • link reaction (x2): 2 reduced NAD = 2x 2.5
  • Krebs cycle (x2): 2 ATP = 2
  • Krebs cycle (x2): 6 reduced NAD= 6 x 2.5 = 15
  • Krebs cycle: 2 reduced FAD = 2 x 1.5 = 3

= 32

12
Q

Which processes are not used in anaerobic respiration?

A
  • link reaction
  • Krebs cycle
  • oxidative phosphorylation
13
Q

What are the two types of anaerobic respiration?

A
  • alcoholic fermentation

- lactate fermentation

14
Q

Describe lactate fermentation

A
  • occurs in mammals to produce lactate
  • reduced NAD (from glycolysis) transfers hydrogen to pyruvate to form lactate and NAD
  • NAD can then be reused in glycolysis
15
Q

Why is glycolysis able to continue without oxygen in anaerobic respiration>

A
  • NAD is regenerated, which glycolysis needs

- so a small amount of ATP is still produced to keep other processes going

16
Q

How much can the body tolerate lactate?

A
  • our cells can tolerate high lactate for short periods of time
  • however, too much lactate is toxic and is removed into the bloodstream
  • liver takes up lactate from bloodstream and converts it back into glucose in gluconeogenesis
17
Q

Describe alcoholic fermentation

A
  • CO2 is removed from pyruvate to form ethanal
  • reduced NAD from glycolysis transfers hydrogen to ethanal to form ethanol and NAD
  • NAD can then be reused in glycolysis
18
Q

Why does anaerobic respiration release less energy than aerobic respiration?

A
  • anaerobic respiration only include one energy-releasing stage, glycolysis, which only produce 2 ATP per glucose molecule
  • other energy-releasing reaction, Krebs and oxidative phosphorylation require oxygen
19
Q

What is a respiratory substrate?

A
  • any biological molecule that can be broken down in respiration to release energy is a respiratory substrate
20
Q

What is the order of energy value in different respiratory substrate?

A
  • lipids: 39.4 kJ/g
  • proteins: 17
  • carbs: 15.8
21
Q

Why are there different energy values for different respiratory substrate>

A
  • most ATP is made in oxidative phosphorylation, requiring hydrogen atoms from reduced NAD and reduced FAD
  • respiratory substrate that contain more H atoms per unit of mass caused more ATP to be produced
22
Q

What is the respiratory quotient and its classifications

A
  • RQ = volume of CO2 released / volume of O2 consumed
  • triglycerides: 0.7
  • proteins or amino acids: 0.9
  • carbs: 1.0
23
Q

Why is the RQ helpful?

A
  • 0.7-1.0 is usual RQ for humans, showing fats and carbs are used
  • High RQ, means that organism is short of oxygen, and is respiring anaerobically
  • plants may have low RQ because CO2 released in respiration is used for photosynthesis so is not measured
24
Q

Describe a respirometer experiment

A
  • each tube contains potassium hydroxide which absorbs CO2
  • control tube has no woodlice
  • syringe is used to set fluid to known level
  • left for a period of time
  • there will be a decrease in the volume of air in test tube due to oxygen consumption by woodlice and CO2 is absorbed
  • decrease in volume of air will reduce the pressure in the tube and cause coloured liquid in manometer to move towards test tube
  • distance moved by liquid in a given time is measure
  • the volume of oxygen can be calculated