respiration (energy systems in and between organisms)

Question 1

where in the cell does glycolysis happen?

Answer 1

in the cytoplasm

Question 2

how does glucose turn into glucose phosphate in glycolysis

Answer 2

2 ATP molecules are broken down into ADP + Pi so glucose is phosphorylated by the 2 Pi

Question 3

what happens to the phosphates in pyruvate?

Answer 3

they go back to ADP to form 2 molecules of ATP

Question 4

what is the main product of the link reaction

Answer 4

acetyl coA

Question 5

how does NAD turn into reduced NAD and where does it get its hydrogens from?

Answer 5

pyruvate gives up 2 hydrogens to reduce 2 NADs

Question 6

why does the link reaction require oxygen

Answer 6

one carbon from the pyruvate combines with oxygen to form CO2

Question 7

What are all of the products of the link reaction and where do they go?

Answer 7

2 acetyl CoA go to the krebs cycle
carbon dioxide is released as a waste product
reduced NAD goes to oxidative phosphorylation

Question 8

how many times does the krebs cycle happen

Answer 8

twice

Question 9

where does the krebs cycle occur

Answer 9

in the matrix

Question 10

what is step 1 of the krebs cycle

Answer 10

acetyl CoA (2C) combines with oxaloacetate (4C) to make citrate (6C). coenzyme A goes back to the link reaction to be used again

Question 11

what is step 2 of the krebs cycle

Answer 11

the 6C citrate is converted into a 5C compound because it is decarboxylated. dehydrogenation also occurs to produce reduced NAD

Question 12

what is step 3 of the krebs cycle

Answer 12

regeneration of oxaloacetate 5C molecules is converted into a 4C molecule (carbon removed as CO2)
decarboxylation and dehydrogenation occur and produce 1 reduced FAD and 2 reduced NAD

Question 13

how many molecules of ATP are produced altogether in aerobic respiration and in each step?

Answer 13

38 altogether
glycolysis 2
link reaction 0
krebs cycle 2
oxidative phosphorylation 34

Question 14

name the 4 main stages in aerobic respiration and where they occur

Answer 14

glycolysis - cytoplasm
link reaction - matrix
krebs cycle - matrix
oxidative phosphorylation - via electron transfer chain: membrane of cristae

Question 15

outline the stages of glycolysis

Answer 15

1. glycolysis is phosphorylated to glucose phosphate by 2x ATP
2. glucose phosphate splits into 2x triose phosphate
3. 2x TP is oxidised to 2x pyruvate

Net gain of 2x reduced NAD and 2x ATP

Question 16

how does pyruvate from glycolysis enter the mitochondria

Answer 16

via active transport

Question 17

what happens during the link reaction?

Answer 17

1. oxidation of pyruvate to acetate
   (per pyruvate molecule: net gain of 1x CO2 and 2H atoms used to reduce 1xNAD)
2. acetate combines with coenzyme A to make acetyl CoA

Question 18

what is the electron transfer chain?

Answer 18

series of carrier proteins embedded in membrane of the cristae of mitochondria. produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration

Question 19

what happens in the electron transfer chain?

Answer 19

electrons are released from reduced NAD and FAD undergo successive redox reactions.
the energy released us coupled to maintaining proton gradient or released as heat.
oxygen acts as final electron acceptor

Question 20

how is a proton concentration gradient established during chemisosmosis in aerobic respiration?

Answer 20

some energy released from ETC is coupled to the active transport of hydrogen ions (protons) from the matrix into the intermembrane space

Question 21

how does chemisosmosis produce ATP during aerobic respiration

Answer 21

H+ ions move down their concentration gradient from the intermembrane space into the matrix via ATP synthase

Question 22

state the role of oxygen in aerobic respiration

Answer 22

final electron acceptor in electron transfer chain (produced water as a byproduct)

Question 23

what is the benefit of an electron transfer chain rather than a single reaction?

Answer 23

energy is released gradually
less energy is released as heat

Question 24

name 2 types of molecules that can be used as alternative respiratory substrates

Answer 24

amino acids from proteins
glycerol and fatty acids from lipids

Question 25

how can lipids act as an alternative respiratory substrate?

Answer 25

lipids > glycerol and fatty acids
1. phosphorylation of glycerol = TP for glycolysis
2. fatty acids = acetate
3. acetate enters link reaction
4. H atoms produced for oxidative phosphorylation

Question 26

how can amino acids act as an alternative respiratory substrate?

Answer 26

deamination produces:
1. 3C compounds = pyruvate for link reaction
2. 4C/5C = intermediates in krebs cycle

Question 27

what happens to the lactate produced in anaerobic respiration?

Answer 27

transported to liver via bloodstream, where it is oxidised to pyruvate.
can enter link reaction in liver cells or be converted glycogen

Question 28

what happens during anaerobic respiration in some microorganisms (yeast, plant cells)

Answer 28

only glycolysis continues
pyruvate is decarboxylated to form ethanal
ethanal is reduced to ethanol using reduced NAD to produce oxdised NAD for further glycolysis

Question 29

what is the advantage of producing ethanol/ lactate during anaerobic respiration

Answer 29

converts reduced NAD back into NAD so glycolysis can continue

Question 30

what is the disadvantage of producing ethanol during anaerobic respiration

Answer 30

cells die when ethanol concentration is above 12%
ethanol dissolves cell membranes

Question 31

what is the disadvantage of producing lactate during anaerobic respiration

Answer 31

acidic, so pH decreases
results in muscle fatigue

Question 32

compare aerobic and anaerobic respiration

Answer 32

both involve glycolysis
both require NAD
both produce ATP

Question 33

contrast aerobic and anaerobic respiration

Answer 33

aerobic:
produces more ATP
doesnt produce ethanol or lactate

anaerobic:
produces fewer ATP
produced ethanol or lactate