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Biology > Respiration > Flashcards

Respiration Flashcards

1
Q

What is the purpose of cellular respiration?

A

Allows energy stored in organic molecules in cells (e.g. glucose) to be released to make ATP, which is then hydrolysed to provide the energy needed for active processes in cells

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2
Q

What is the balanced equation for respiration?

A

C6H12O6 = 6O2 —> 6CO2 + 6H2O + ENERGY

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3
Q

What is metabolism?

A

Refers to all of the reactions that occur inside an organism

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4
Q

What are anabolic reactions?

A

Metabolic reactions that build up large molecules from smaller ones
- Net requirement for energy

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5
Q

What are catabolic reactions?

A

Metabolic reactions that break down large molecules into smaller ones

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6
Q

Is respiration an anabolic or catabolic reaction?

A 
Catabolic
Substrates (usually glucose) are broken down, releasing energy
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7
Q

Why is ATP such a useful immediate source of energy?

A
  • The hydrolysis of ATP releases small quantities of energy, in manageable amounts, to drive single reactions
  • This prevents wastage and cell damage
  • Single step reaction - a quick and easy way to release energy
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8
Q

What are the 4 stages in aerobic respiration?

A

1- Glycolysis
2- The link reaction
3- The krebs cycle
4- Oxidative phosphorylation

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9
Q

Where does glycolysis occur?

A

Cytoplasm

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10
Q

Where do the last 3 stages of aerobic respiration take place?

A

Mitochondria

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11
Q

Is glycolysis an anaerobic or aerobic process?

A

Can be both

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12
Q

Describe the steps in glycolysis

A
  • Phosphorylation of glucose, involves 1 ATP molecule, into glucose phosphate (6C)
  • Glucose phosphate is phosphorylated into hexose bisphosphate (6C) using 1 ATP
  • Hexose bisphosphate splits into 2xTP (hydrolysis)
  • 2xTP are oxidised to 2x pyruvate (3C)
  • A single TP molecule produces 2xATP and 1xNADH through dehydrogenation
  • Dehydrogenation - TP loses H+, NAD coenzymes accept the removed hydrogens - they are reduced, forming 2 NADH
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13
Q

What are the end products of glycolysis?

A

Net gain of:

  • 2 ATP (2 used up, 4 made)
  • 2x NADH
  • 2x pyruvate
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14
Q

What is NAD?

A
  • Coenzyme

- A non-protein organic molecule which helps the enzymes in the last part of glycolysis to work

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15
Q

What is substrate level phosphorylation?

A

Formation of ATP without the involvement of an electron transport chain

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16
Q

What is the purpose of phosphorylating glucose?

A

Makes the original glucose molecule more reactive

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17
Q

How is glycogen converted into glucose molecules?

A

Breaking 1,4 glycosidic bonds via hydrolysis

Enzymes and water are needed

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18
Q

Where does the link reaction occur?

A

Mitochondrial matrix

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19
Q

Is the link reaction an aerobic or anaerobic process?

A

Aerobic

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20
Q

What may happen to the CO2 produced after the link reaction?

A
  • Diffuse away and be removed from organism as metabolic waste
  • In autotrophic organisms, it may be used as a raw material in PHS
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20
Q

Describe the steps in the link reaction

A
  • Pyruvate enters matrix by active transport via specific carrier proteins
  • Pyruvate is decarboxylated and dehydrogenated to acetyl (2C)
  • CO2 is produced as a by-product, NAD is reduced to NADH
  • Acetyl combines with Co-A to produce acetyl-coenzyme A
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20
Q

What is the net gain from the link reaction?

A
  • 1 CO2

- 1 NADH

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21
Q

Why does the link reaction happen twice?

A

2 pyruvate molecules were formed from glycolysis

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22
Q

Where does the kreb’s cycle take place?

A

Mitochondrial matrix

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23
Q

Describe the steps in the Kreb’s cycle

A

1- Acetyl group (2c) + oxaloacetate (4c) = citrate (6c)
2- Citrate is decarboxylated + dehydrogenated = 5c compound, 1 CO2 + NADH
3- 5c is decarboxylated & dehydrogenated = 4c compound, 1 CO2 + NADH
4- 4c compound dehydrogenated = NADH + FADH2
5- Regeneration of oxaloacetate

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24
Q

Where do the reduced co-enzymes carry the H atoms to?

A

Cristae of mitochondria

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25
Q

What step of aerobic respiration happens on the cristae?

A

Oxidative phosphorylation

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26
Q

What does oxidative phosphorylation mean?

A

Adding inorganic phosphate (Pi) to ADP in the presence of O2, to make ATP indirectly, via a chain of electron carriers

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27
Q

What is the advantage of oxidative phosphorylation occuring in the cristae?

A

They are folded, giving a large SA for as much ATP to be made as possible

28
Q

Describe steps involved in oxidative phosphorylation

A
  • NADH/FADH2 re-oxidised back to NAD/FAD, releasing 2 protons/electrons
  • The e- are transferred along ETC
  • H+ accumulate me in space, creating proton gradient, builds up chemiosmotic potential
  • Protons diffuse down conc- gradient through ATP synthase
  • As protons flow through ATP synthase via protein channels, energy is released
  • Energy converts ADP + Pi to ATP (chemiosmosis)
  • O2 us the final electron acceptor, combining with e- to form H2O
29
Q

What is the evidence for the process of chemiosmosis occuring?

A

pH difference across 2 sides of mitochondrial membrane - H+ ions create an acidic pH

30
Q

Give 3 differences between NAD and FAD

A
  • NAD accepts H from glycolysis/link/kreb’s
  • FAD only accepts H from kreb’s
  • Reduced NAD is re-oxidised at the start of ETC, whereas FAD is re-oxidised further along
31
Q

What does the matrix contain?

A
  • Enzymes that catalyse stages of link/kreb’s
  • NAD/FAD
  • Oxaloacetate
  • Mitochondrial DNA
  • Mitochondrial ribosomes
32
Q

What does the outer membrane contain?

A
  • Proteins
  • Some of which form channels or carriers
  • Allow passage of molecules, such as pyruvate, into mitochondrion
33
Q

How does the lipid composition of the inner membrane differ from the outer membrane?

A
  • Less permeable to small ions such as H ions than is the outer membrane
34
Q

How would you investigate the effect of temperature on rate of respiration in yeast?

A
  • 2cm3 of yeast and glucose solution
  • X6 tubes the same
  • Transfer to 6 thermostatic water baths (15-65°C)
  • Leave for 5 mins before starting (acclimatise)
  • 2 drops of methylene blue as an indicator
  • Blue when oxidised
  • Colourless when reduced
  • As yeast respires, H released, splits into H+ & e-
  • Go into ETC, picked up by methylene blue, reducing it
35
Q

How do you convert time taken into rate?

A

1/time

36
Q

Give 2 ways that anaerobic respiration occurs in the eukaryotic cells

A

1- Muscle cells (animals) - lactate fermentation

2- Fungi/Plant/Yeast- ethanol fermentation

37
Q

How many ATP will be made per glucose respired in anaerobic respiration?

A

2 ATP

38
Q

How does anaerobic respiration occur in mammalian muscle cells?

A
  • Glycolysis
  • Reduced NAD is re-oxidised to NAD, so it can be reused to accept more H
  • Pyruvate is the H acceptor, allowing the NAD to be regenerated (pyruvate reduced)
  • Requires enzyme lactate dehydrogenase
  • Allows glycolysis to continue, generating enough ATP to sustain muscle concentration for a short time
39
Q

Is anaerobic respiration in mammals reversible or irreversible?

A

Reversible as it’s a single step reaction and nothing is lost

40
Q

What happens to the lactate in anaerobic respiration?

A
  • Carried from the muscles to the liver
  • When O2 is available it’s turned back into glucose
  • Can either enter glycolysis l, be stored as glycogen or be converted to purity are and enter link reaction of respiration
41
Q

Why is it so important that lactate is removed from the muscles quickly?

A
  • It would reduce the pH of the muscle cells
  • Inhibit enzymes in muscle cells
  • Inhibit muscle contraction (requires enzymes)
42
Q

How does anaerobic respiration occur in plants, fungi and yeast?

A
  • Glycolysis
  • Each pyruvate molecule is decarboxylated to form ethanal
  • This is catalysed by enzyme pyruvate decarboxylase (which has a coenzyme attached)
  • The ethanal accepts H from NADH (which is reoxidised) and the ethanal is reduced to ethanol using the enzyme ethanol dehydrogenase
43
Q

Why are yeast cells described as facultative anaerobes?

A

It can live without oxygen, but if this continues for too long, it will die as the concentration of ethanol builds up (once it reaches 15%)

44
Q

What is the benefit of anaerobic respiration?

A

Allows respiration to occur for a short time in difficult conditions, allowing an organism to continue functioning

45
Q

Why is glycolysis the only source of ATP production in RBC?

A
  • RBC don’t have mitochondria so cannot do links/kerbs/ETC

- Advantage = more room for harm of living to be stored so more O2 can be carried around the body by each RBC

46
Q

Why is it useful that cardiac muscle is adapted to reduce the chances of anaerobic respiration ever being needed?

A
  • Don’t want anaerobic respiration in heart/cardiac cells
  • Lactic acid would stop muscle contracting properly
  • Cause fatigue of heart muscle and reduction in blood pumped around body
  • Dangerous
47
Q

What biochemical adaptations do diving mammals have to spent lots of time underwater?

A
  • Greater conc of haemoglobin and myoglobin - maximises O2 stores
  • Higher tolerance to lactose - can respire anaerobically for longer
  • Greater tolerance of high CO2 levels - effective blood buffering systems that prevent catastrophic rise in pH
48
Q

What physiological adaptations do diving mammals have to spent lots of time underwater?

A
  • Modified circulatory system - when diving, peripheral vasoconstriction occurs, so blood is shunted to brain, heart and muscles
  • Heart slows by up to 85% (bradycardia) - reduces energy demand of heart muscles
  • Exchange 80-90% of air in lungs when they breathe - high compared to humans at 15%
49
Q

What physical adaptations do diving mammals have to spent lots of time underwater?

A
  • Streamlining to reduce drag due to friction from water whilst swimming - reduces energy demand during a dive
  • Libs of marine animals are fin shaped- maximises efficient use of energy in propulsion
50
Q

Why will plants die if left in water-logged soil for too long?

A

There are no air pockets in waterlogged soil so the root cells done have access to oxygen

  • Anaerobic respiration cannot be sustained for long
  • Ethanol accumulates which is toxic to root cells
51
Q

What is a respiratory substrate?

A

An organic molecule that can be used in respiration to release energy

52
Q

How are polysaccharides and disaccharides respired?

A

Hydrolysed using enzymes into monosaccharides and then respired

53
Q

Give an example of a polysaccharide that is hydrolysed into a monosaccharide in plants

A

Starch, hydrolysed into alpha glucose and then respired

54
Q

Give an example of a polysaccharide that is hydrolysed into a monosaccharide in animals

A

Glycogen, hydrolysed into alpha glucose and then respired

55
Q

Give 3 examples of disaccharides that are hydrolysed into monosaccharides

A

1- Sucrose, hydrolysed into glucose and fructose, then respired
2- Maltose, hydrolysed into 2x alpha glucose, then respired
3- Lactose, hydrolysed into glucose and galactose, then respired

56
Q

What are lipids hydrolysed into?

A

Fatty acids and glycerol

57
Q

What happens to glycerol when a lipid is being respired?

A

Can be converted to pyruvate and enter respiratory pathway

58
Q

What happens to the fatty acids when a lipid is being respired?

A

Combine with co-A to form a complex, which is then carried into mitochondrial matrix, forming acetyl-co-A
Then enters Krebs cycle
Pathway = Beta-oxidation pathway

59
Q

Why are proteins usually not respired?

A
  • Amino acids are either used to make important protein structures in the body, or they are converted into urea for excretion
  • Only respired if an organism undergoes fasting, starvation or prolonged exercise
60
Q

Where can various amino acids enter the respiratory pathway?

A

1- Pyruvate
2- Acetyl CoA
3- 5C compound

61
Q

Why do lipids release more than twice as much energy as carbohydrates and proteins when respired?

A
  • Made up of glycerol and fatty acids

- Fatty acids consist of very long hydrocarbon chains = LOTS of H

62
Q

What is a respiratory quotient (RQ)?

A

The ratio of CO2 produced by a respiring organism to O2 consumed in a given time

63
Q

What is the equation for RQ?

A

CO2 released / O2 uptake per unit time

64
Q

What can the RQ tell us?

A

What respiratory substrate is being metabolised by an organism and what type of respiration (anaerobic & anaerobic) is being employed

65
Q

What always give an RQ value of 1 or less

A

Aerobic respiration

66
Q

What does a RQ value of more than 1 suggest?

A

That anaerobic respiration is taking place because more CO2 is produced than O2 consumer

67
Q

What is used to measure respiration rates and the factors affecting respiration?

A

Respirometer

68
Q

How do you set up a respirometer?

A

1- Place the coloured liquid, that had one drop of detergent added, into manometer tube
2- Connect apparatus with taps open, enabling air in apparatus to connect with atmosphere
3- Measure mass of living organisms (g)
Place whole set up in a water bath for 10 mins until it reaches same temp
4- place syringe near the top of the scale in the syringe barrel and note it’s level
5- Mark levels of coloured liquid in manometer with felt too pen
6- Close taps and leave apparatus in water bath for 10 mins
7- Measure change in level of manometer liquid
8- Depress syringe barrel to reset apparatus
9- Calculate volume of O2 absorbed per min per gram of living organism

69
Q

What is the net gain from the Kreb’s cycle?

A
  • 2xATP
  • 3xNADH
  • 1xATP
  • 1xFADH2

Biology (19 decks)

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