Respiration

Question 1

Where glycolysis fits in the overall process of respiration

Answer 1

-Glycolysis is the first stage of aerobic and anaerobic respiration
-occurs in cytoplasm of the cell

Question 2

Process of glycolysis

Answer 2

1) glucose converted into phosphorylated glucose by hydrolysis of 2x ATP molecules to ADP (provides energy to activate glucose
and lowers AE for enzyme controlled reactions that follow)
2) Phosphorylated glucose split into 2X triose phosphate (3C molecule)
each triose phosphate oxidised (H removed from each of 2 triose phosphate and transferred to H carrier molecule AKA NAD > NADH
3) enzyme controlled reactions convert each triose phosphate into another 3C molecule (pyruvate) so 2 molecules of ATP are regenerated from ADP

Question 3

Where does glycolysis occur?

Answer 3

cytoplasm

Question 4

What is glycolysis involved in?

Answer 4

aerobic AND anaerobic respiration

Question 5

What are the end products of glycolysis?

Answer 5

-net gain of 2 x ATP
-2 x reduced NAD (NADH)
-2 x pyruvate

Question 6

How many ATP are hydrolysed for the phosphorylation of glucose?

Answer 6

2

Question 7

Why does glucose phosphate split?

Answer 7

it is unstable

Question 8

For 1 GLUCOSE molecule, how many ATP are produced (in the oxidation of triose phosphate(s))

Answer 8

4 (2 per TRIOSE PHOSPHATE)

Question 9

What is NAD converted into in the oxidation of triose phosphate to form pyruvate?

Answer 9

NADH (2 per GLUCOSE)

Question 10

How many pyruvate are made for each glucose molecule?

Answer 10

2

Question 11

What is produced in glycolysis and is needed in the next stages of respiration?

Answer 11

-NADH
-PYRUVATE

Question 12

How are pyruvate and NADH transported into the mitochondrial matrix?

Answer 12

active transport

Question 13

Process of link reaction

Answer 13

-pyruvate molecule from glycolysis diffuses from cytoplasm across mitochondrial membrane into mitochondrial matrix
-pyruvate (3c) is oxidised (and decarboxylated) to acetate (2c molecule) so CO2 is produced as a by-product and the 2H lost from pyruvate is accepted by NAD>NADH to be used in ATP later on (in anaerobic resp)
-acetate combined with coenzyme A (CoA) to produce acetyl coenzyme A (2c molecule)

Question 14

Why does links reaction happen

Answer 14

so pyruvate from glycolysis can be oxidised first before entering kerbs cycle

Question 15

What reaction makes acetate?

Answer 15

the oxidation of pyruvate

Question 16

What are the products of the oxidation of pyruvate?

Answer 16

acetate and NADH and CO2

Question 17

What is produced overall in the link reaction? (per glucose)

Answer 17

2 x Acetyl CoA
2 x NADH
2 x CO2

Question 18

What is the job of coenzyme A?

Answer 18

to deliver the acetate so it can react with a 4-carbon compound

Question 19

Process of kerbs cycle

Answer 19

-Takes place in mitochondrial matrix and involves a series of redox reactions
- acetyl CoA from link reaction combines with 4 c molecule, releasing coenzyme A and producing 6c molecule
-in a series of reactions, 6 c molecule loses co2 and H to give 4C molecule
-H+ being lost means coenzymes NAD and FAD are reduced
- 1ATP (adp +pi ) produced as a result of substrate level phosphorylation
-remaining 4c molecule is available t combine with new molecule of acetyl-co-enzyme A a to being cycle again

Question 20

from each molecule of pyruvate linsk and klerbs produce:

Answer 20

-reduced co enzymes > NADH and FADH > these have potential to provide energy to produce ATP molecule by oxidative phosphorylation so they’re important in kerbs
-one molecule of atp
-3 molecules of co2

Question 21

roles of coenzymes

Answer 21

-important in carrying H atoms from one molecule to another e.g.

-NAD > important in respiration
-FAD > important in kerbs
-NADP > important in photosynthesis

Question 22

Why is NAD most important carrier

Answer 22

-works with dehydrogenase enzymes that catalyse removal of H atoms from substrates and transfer them to other molecules involved in oxidative phosphorylation

Question 23

Significance of Kerbs cycle

Answer 23

-breaks down macromolecules into smaller > pyruvate broken down into co2
-produces H atoms that’s carried by NAD to e- transfer chain > provide energy for oxidative phosphorylation >leads to production of ATP of ATP for metabolic energy for cells
-regenerates 4C molecule that combines with acetyl coenzyme A which would otherwise accumulate
-source of intermediate compounds used by cells in manufacture of other important substances eg fatty acids, amino acids and chlorophyll

Question 24

Products per glucose of kerbs cycle

Answer 24

useful = 6x NADH
2X FADH
2X ADP
waste = 4x CO2

Question 25

Products per cycle of kerbs cycle

Answer 25

3x NADH 1X FAD 1x ATP 2x CO2

Question 26

nature of hydrogen carrier molecules and its role in kerbs cycle

Answer 26

-hydrogen carrier molecules in respiration are co enzymes (molecules that some enzymes require in order to function). -The molecules specific to Krebs cycle are FAD and NAD, which work with dehydrogenase enzymes to remove hydrogen atoms from substrates and transfer them to the molecules involved in oxidative phosphorylation.

Question 27

Process of oxidative phosphorylation

Answer 27

-occurs in the cristae -NADH and FADH from kerbs, linked and glycolysis are oxidised to release H atoms and split into H+ and e- -in a series of redox reactions, e- are transferred down e- transfer chain. as e- decrease in energy levels, energy is released -energy that is released allows active transport of H+ across inner mitochondrial membrane into intermembranal space -H+ diffuse by facilitated transport into matrix down electrochemical gradient via ATP synthase channel (embedded in inner mitochondrial membrane). so there's a high conc of H+ in intermembrane space and lower conc in matrix -releases energy to synthesise ATP from ADP + Pi -in matrix, at the end of electron transport chain, oxygen is the final electron acceptor (e- can't pass along otherwise), so protons, electrons and oxygen combine to form water

Question 28

mechanism of oxidative phosphorylation

Answer 28

some of energy of e- within H atoms is conserved in formation of ATP

Question 29

What is the energy released (in the electron carrier chain) used for?

Answer 29

actively transporting H+ out of the matrix into the inter-membrane space

Question 29

What happens to the electrons that are released in OP

Answer 29

they travel along an electron transport chain which releases energy

Question 30

Anaerobic respiration

Answer 30

-pyruvate converted to lactate (animal cells and some bacteria) or ethanol (+co2 in plants and yeast) -oxidising NADH > NAD is regenerated -so glycolysis can continue (which needs NAD), allowing continued production of ATP

Question 31

How do protons move back into the matrix?

Answer 31

facilitated diffusion through ATP synthase

Question 32

What does ATP synthase do?

Answer 32

Phosphorylate ADP to form ATP

Question 33

What does oxygen pick up in this step?

Answer 33

electrons and H+ ions, forming H2O

Question 34

What is oxygens role in respiration?

Answer 34

it is the final electron acceptor and will form water

Question 35

Why is NAD and FAD not transferred in one explosive step

Answer 35

-when energy is released a little at a time -more of it can be harvested for benefit of organism -transfer of e- down energy gradient allows their energy to be released gradually and more usefully

Question 36

respiration of lipids

Answer 36

1) lipids hydrolysed to glycerol and fatty acids 2) glycerol is then phosphorylated and converted to triose phosphate which enters glycolysis pathway and kerbs 3) fatty acid component is broken down into 2C which are converted to acetyl co enzyme A 4) this enters kerbs cycle

Question 37

production of oxidation of lipids

Answer 37

- 2C fragment of carbohydrate and many H atoms -H atoms used to produce ATP during oxidative phosphorylation - so lipids release more than double energy of same mass of carbohydrate

Question 38

respiration of protein

Answer 38

1) hydrolysed to constituent amino acids 2) have amino group removed (deamination) before entering respiratory pathways at different points depending on number of c atoms they contain - 3 c compounds converted to pyruvate - 4 and 5 c compounds converted to intermediates in kerbs