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Biology OCR A > Chapter 18 Respiration > Flashcards

Chapter 18 Respiration Flashcards

1
Q

What are the 4 stages of respiration and where they take place?

A

Glycolysis- cytoplasm
Link Reaction- mitochondrial matrix
The Kreb’s Cycle- mitochondrial matrix
Oxidative phosphorylation- inner mitochondrial membrane

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2
Q

What is the purpose of glycolysis?

A

To generate some ATP by substrate-level phosphorylation
Breaks down molecules enough so that they are small enough to enter the mitochondria

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3
Q

What are the main steps of glycolysis?

A

Phosphorylation of glucose: 2 phosphate groups from ATP join the glucose molecule (isomerisation in between), forming a hexose-1,6-biphosphate sugar

Lysis- the hexose sugar splits into two smaller triose phosphates (DHAP and GALP)

Phosphate groups are added from free phosphates in the cytoplasm, forming two triose biphosphate molecules

Enzymes catalyse the dehydrogenation and formation of 2 ATP from each the biphosphates, forming 2 pyruvate molecules and total of 2 NADH

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4
Q

What is the yield from glycolysis?

A

2 Pyruvate molecules
Net of 2 ATP (4 ATP but 2 used in the start)
2 NADH

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5
Q

What is substrate level phosphorylation?

A

The direct exchange of phosphate, from one molecule to another, forming ATP
No electron transport chain needed

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6
Q

What is the process of the link reaction?

A

Pyruvate enters the mitochondrial matrix by active transport via carrier proteins

Undergoes oxidative decarboxylation, the removal of a CO2 and hydrogen, forming acetate (ethanoate) molecules, NADH, and CO2

Acetyl bound to coenzyme A, forming acetylCoA

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7
Q

What is the yield from the Link reaction?

A

2( 1x NADH)
2 (1 x CO2)- diffuses out
2 (1x AcetylCoA)

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8
Q

What is the process of the Krebs Cycle (OCR A) ?

A

AcetylCoA reacts with Oxaloacetate (2-oxobutanedioic acid) to form citrate

Citrate undergoes oxidative decarboxylation forming NADH and CO2 and alpha keto gluterate (5c). This is repeated forming a 4 carbon compound.

The 4 carbon compound is further modified, undergoing oxidation and forming further NADH, FADH2 and a small amount of ATP, and regenerating oxaloactetate

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9
Q

What is the full Citric Acid Cycle?

A

AcetylCoA —/ alpha ketogluterate + NADH + CO2

alpha ketogluterate + coA —/ succinylCoA + CO2 + NADH

Succinyl CoA —-/ succinate + coA, also forming ATP by substrate-level phosphorylation

Succinate —/ Fumerate + FADH2

Fumerate + Water—/Malate

Malate —-/Oxaloacetate + NADH

(Succinate, then alphabetical)

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10
Q

What is the net yield from the Krebs Cycle?

A

2(3 NADH)
2(FADH2)
2(ATP)

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11
Q

What is the process of oxidative phosphorylation?

A

NADH and FADH2 release hydrogen, which splits into protons and high energy electrons. The high energy electrons are passed to a series of carrier molecules called the electron transport chain

As the electrons pass down the chain, the redox reactions enable energy to be used to pump protons from the matrix to the intermembrane space. This establishes a proton gradient.

Protons will diffuse through the hydrophilic protein channel and enzyme ATP synthase, use the energy from the proton-motive force to synthesise ATP from ADP

The final electron acceptor is oxygen, which combines with protons to form water.

This is an example of chemiosmosis. The channels proteins are leaky so this is not 100% efficient

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12
Q

What is the theoretical yield for aerobic respiration for bacteria and multicellular organisms? Why?

A

38 for bacteria
36 for multicellular organisms, as some ATP used through the movement of molecules within the cell

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13
Q

What is the actual yield of aerobic respiration for multicellular organisms?

A

30 ATP
1) The membranes of the mitochondrial membrane are leaky, and some protons move back in from the intermembrane space to the matrix, decreasing the proton gradient
2) ATP is needed to actively transport pyruvate into the matrix
3) ATP is needed to actively transport NADH (from glycolysis) to the mitochondrial membrane

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14
Q

How many protons/electrons are donated by NADH/FADH2? How much ATP is generated per molecule?

A

NADH- 2 electrons, 1 Hydrogen, 3ATP
FADH2- 2 electrons, 2 Hydrogens, 2 ATP

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15
Q

Why is the yield of ATP higher for NADH than FADH2?

A

NADH delivers its high energy electrons at an earlier stage of the electron transport chain
This results in greater chemiosmosis , more ATP

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16
Q

What are the 3 types of classification for respiring eukaryotic organisms?

A

Obligate anaerobes- cannot survive in the presence of oxygen
Facultative anaerobes- can use O2 for aerobic but also anaerobic
Obligate aerobes- require oxygen to respire

17
Q

What is the process of anaerobic respiration in humans?

A

Glycolysis as normal, producing 2 pyruvate and 2 NADH
But for the process to repeat, the NADH must be oxidised
So the Hydrogens from NADH are transferred to the pyruvate, forming lactic acid and NAD
Catalysed by the enzyme lactate dehydrogenase

18
Q

What happens to lactic acid? Why is lactic acid toxic?

A

Travels in the blood to the liver
Lactate dehydrogenase also catalyses lactate to pyruvate, when can enter the Krebs Cycle
Or recycled into glucose and glycogen

Weak acid- alter the pH and cause enzymes to function incorrectly if it builds up

19
Q

What is the process of anaerobic respiration in yeast and plants?

A

Glycolysis
Enzyme pyruvate decarboxylase catalyses the formation of ethanal from pyruvate (oxidative decarboxylation)
Ethanal accepts H from NADH, forming ethanol and NAD

Ethanal is toxic so can kill yeast if it builds up

20
Q

What are the benefits and cons of anaerobic respiration?

A

Anaerobic- as glucose only partially broken down, more glycolysis per minute, and yield of ATP large
But it does not fully break down glucose, so per glucose molecule, yield 1/15th of aerobic

21
Q

What is a respiratory substance?

A

An organic substance that can be oxidised by respiration to release energy to make ATP

22
Q

Rank biomolecules in order the most ATP production? Why is this?

A

Lipids>proteins>carbohydrates

Based on number of C-Hs present, more protons for chemiosmosis

23
Q

What is RQ?

A

moles CO2 / moles O2
If =1 carbohydrates
Smaller the better
If greater than one, anaerobic respiration
Often a mix, respiring more than one

24
Q

What do plants produce when they respire anaerobically?

A

Ethanol and Carbon dioxide

25
Q

How can you investigate the respiration in peas?

A

Place inside a respirometer with KOH in the bottom to remove CO2 produced
Coloured fluid in a graduated tube inside, movement shows O2 uptake
Control variables

26
Q

How can you measure the rate of anaerobic respiration in yeast?

A

Use a vacuum sealed flask or paraffin to prevent O2 entering the yeast suspension
You can measure the volume of CO2 produced in a given time with a gas syringe, or you can use a respirometer with glass beads in one side and measure the movement of the coloured liquid (cannot use KOH)
Or similar to peas with a graduated tube but with coloured fluid up for CO2 production

27
Q

How can you measure the rate of respiration in insects?

A

Use a respirometer with two tubes, once with the insect and another with glass beads similar in mass to ensure the respirometer is uniform with the coloured volume
Start with taps open and measure initial volume, then close tap and see how far the coloured volumes have moved
Push down the syringes to reser

28
Q

How can data loggers be used?

A

Software used to set up to record something every 30 seconds for a certain period of time, e.g CO2 conc
Plots variable time graph

29
Q

What are the names of the enzymes used in anaerobic respiration?

A

Lactase dehydrogenase- pyruvate to lactic acid
Pyruvate decarboxylase- pyruvate to ethanal (then ethanol which is toxic)

30
Q

What are the limitations of using a respirometer?

A

Oxygen can leak from the connectors so not necessarily all linked to the coloured liquid
Oxygen uptake not a good representation of respiration
Difficult to read small changes in gases/movement of liquid

31
Q

How do you put the coloured liquid in a respirometer?

How do you measure oxygen uptake?

A

Dip into a small beaker with the dye and allow it to run in

Internal diameter of tube to calculate surface area x vertical distance travelled

32
Q

How can you compare the respiration rate of a maggot to a germinating seed?

but who seriously has the interest and the time and the sanity to do this, i dont know

A

Respirometer, coloured fluid, mung beans inside tube with soda lime to remove CO2
Syringe to push liquid back

Same equipment for maggot, but as a larger organism, more active, greater rate of respiration,
So needs larger syringe as will need more resetting without redoing the whole experiment
Ethical use of insects

Keep mass of both the same, temperature, timings, light, …

33
Q

How is the mitochondrion membrane adapted for its function?

A

Electron carriers for ETC
ATP synthase
Generally impermeable to protons through the phospholipid bilayer, only with proteins

34
Q

What is the importance of coenzymes in respiration?

A

NAD:
Glycolysis, enables oxidation of triose phosphate to form pyruvate, ATP and NADH
Link reaction, oxidation of pyruvate, ATP and NADH formed
Kreb’s cycle: 3 NADH per pyruvate, enables oxidation of pyruvate and intermediates
Oxidative phosphorylation: Delivers high energy electrons, chemiosmosis, delivers some protons

FAD: Enables oxidation of intermediates in Kreb’s cycle, and delivers high energy electrons to electron carriers

CoA- transports acetyl from the link reaction to the Kreb’s cycle in the matrix

ADP: Phosphorylation of glucose, dephosphorylation of triose phosphate, substrate level phosphorylation in Krebs, ATP formation through ATP synthase

35
Q

What should you look for with respiration graphs and different substrates?

A

When does one substrate begin being respired, does it run out
Aerobic or anaerobic
Relative rates of respiration and efficiency

36
Q

Why do fats have the highest RQs?

A

Most amount of Hs present, (and C-C/ C-H)
Many cycles with the Kreb’s cycle, more NADH
Lots of protons for chemiosmosis, greater proton gradients, ATP synthesis greater

37
Q

What does insects form during anaerobic respiration?

A

Lactic acid, not co2

38
Q

What are factors you should control when comparing the rate of respiration of yeast with different substrates?

A

Type of yeast and volume
Conc and volume of substrate
Temperature, pH
Stir each time and ensure connection tight
Rinse flasks each time

39
Q

Why can anaerobic respiration not continue for a long time in plants?

A

Ethanol toxic and builds up
Less ATP produced from glycolysis
So little active transport of mineral ions, phloem loading
Less photosynthesis

Biology OCR A (42 decks)

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