Chapter 18 Respiration

Question 1

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

Answer 1

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

Question 2

What is the purpose of glycolysis?

Answer 2

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

Question 3

What are the main steps of glycolysis?

Answer 3

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

Question 4

What is the yield from glycolysis?

Answer 4

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

Question 5

What is substrate level phosphorylation?

Answer 5

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

Question 6

What is the process of the link reaction?

Answer 6

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

Question 7

What is the yield from the Link reaction?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

What is the full Citric Acid Cycle?

Answer 9

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)

Question 10

What is the net yield from the Krebs Cycle?

Answer 10

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

Question 11

What is the process of oxidative phosphorylation?

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

What is the process of anaerobic respiration in humans?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What are the benefits and cons of anaerobic respiration?

Answer 20

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

Question 21

What is a respiratory substance?

Answer 21

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

Question 22

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

Answer 22

Lipids>proteins>carbohydrates

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

Question 23

What is RQ?

Answer 23

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

Question 24

What do plants produce when they respire anaerobically?

Answer 24

Ethanol and Carbon dioxide

Question 25

How can you investigate the respiration in peas?

Answer 25

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

Question 26

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

Answer 26

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

Question 27

How can you measure the rate of respiration in insects?

Answer 27

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

Question 28

How can data loggers be used?

Answer 28

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

Question 29

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

Answer 29

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

Question 30

What are the limitations of using a respirometer?

Answer 30

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

Question 31

How do you put the coloured liquid in a respirometer?

How do you measure oxygen uptake?

Answer 31

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

Question 32

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

Answer 32

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, …

Question 33

How is the mitochondrion membrane adapted for its function?

Answer 33

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

Question 34

What is the importance of coenzymes in respiration?

Answer 34

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

Question 35

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

Answer 35

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

Question 36

Why do fats have the highest RQs?

Answer 36

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

Question 37

What does insects form during anaerobic respiration?

Answer 37

Lactic acid, not co2

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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