Respiration 3.5.2 (Energy transfers in and between organisms 3.5)

Question 1

What are the 4 key stages of aerobic respiration ?

Answer 1

Glycolysis ~> Link reaction ~> Krebs cycle ~> Oxidative phosphorylation

Question 2

Where does glycolysis take place ?

Answer 2

In the cytoplasm and is an anaerobic process

Question 3

EQ : Describe the process of glycolysis (4)

Answer 3

1) Phosphorylation of glucose using ATP.
2) Oxidation of triose phosphate to pyruvate
3) Net gain of ATP
4) NAD reduced

Question 4

What are the products of glycolysis ?

Answer 4

2 x pyruvate
Net gain of 2 ATP
2 x NADH

Question 5

where does link reaction take place

Answer 5

mitochondrial matrix

Question 6

where does the krebs cycle take place

Answer 6

mitochondrial matrix

Question 7

where does oxidative phosphorylation take place

Answer 7

cristae ( mitochondrial inner membrane)

Question 8

what are the products made per krebs cycle ?

Answer 8

• 3x NADH
• 1x FADH
• 1x ATP
• 2x Co2

Question 9

what are the products per glucose molecule in the krebs cycle ?

Answer 9

• 6x NADH
• 2x FADH
• 2x ATP
• 4x Co2

Question 10

what are the products for every glucose molecule in the link reaction

Answer 10

• 2x Acetylcoenzyme A
• 2x Co2 released
• 2x NADH

Question 11

what are the stages of the link reaction

Answer 11

• pyruvate made in glycolysis gets oxidised to acetate
• NAD is reduced to NADH
• Acetate then combined with Co enzyme A to produce acetylcoenzyme A

Question 12

How does pyruvate transport from the cytoplasm to the matrix ?

Answer 12

By active transport

Question 13

How many NADH are made in total after glycolysis , link reaction and krebs cycle from one glucose molecule

Answer 13

10

Question 14

How many FADH2 are made in total after glycolysis , link reaction and the krebs cycle from 1 glucose molecule

Answer 14

2

Question 15

what was the main point of the krebs cycle

Answer 15

To make electrons available for oxidative phosphorylation

Question 16

Where do the electrons and protons come from in phosphorylation

Answer 16

From the H+ in NADH and FADH2

Question 17

what do electrons do in oxidative phosphorylation

Answer 17

They provide energy to make ATP

Question 18

What is anaerobic respiration

Answer 18

In the absence of oxygen respiration occurs anaerobically

Question 19

Where does anaerobic take place

Answer 19

Cytoplasm

Question 20

What is the only process that occurs in anaerobic respiration

Answer 20

Glycolysis

Question 21

What are the products of glycolysis in anaerobic respiration in animals

Answer 21

lactate

Question 22

What are the products of glycolysis in anaerobic respiration in plants

Answer 22

Ethanol and carbon dioxide

Question 23

What happens after pyruvate is produced in glycolysis in anaerobic respiration of animals

Answer 23

• Pyruvate produced in glycolysis is reduced to form lactate in animals by gaining the hydrogen from NADH.
• This oxides NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced

Question 24

Why do plants produce different products to animals in anaerobic respiration

Answer 24

Because of the different enzymes involved

Question 25

What happens after pyruvate is produced in glycolysis in anaerobic respiration of plants and microbes

Answer 25

- Pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide in plants by gaining the hydrogen from NADH. - This oxides NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced

Question 26

What percentage is aerobic respiration efficient and why

Answer 26

32% efficient • Some protons leaking across mitochondrial membrane during oxidative phosphorylation • ATP being used to actively transport pyruvate and NADH into matrix because some energy is lost as heat .

Question 27

Why is anaerobic respiration less efficient than aerobic respiration

Answer 27

Only 2 ATP molecules are produced from one glucose molecule

Question 28

EQ : Without oxygen , less ATP is produced by respiration. Explain why. (2)

Answer 28

Only glycolysis is able to take place Only produces 2 ATP molecules

Question 29

EQ : Explain why converting pyruvate to ethanol is important in allowing the continued production of ATP in anaerobic respiration (2)

Answer 29

so NAD can be reused So glycolysis can proceed

Question 30

EQ : Give two ways in which anaerobic respiration of glucose in yeast is similar to anaerobic respiration of glucose in a muscle cell (2)

Answer 30

1) produces NAD 2) ATP formed

Question 31

EQ : Give two ways in which anaerobic respiration of glucose in yeast is different from anaerobic respiration of glucose in a muscle cell (2)

Answer 31

1) Ethanol is formed in yeast whereas in a muscle cell , lactic acid is formed 2) Carbon dioxide is produced in yeast , whereas in a muscle cell , it doesn’t produce Carbon dioxide

Question 32

Why is respiration important

Answer 32

Respiration produces ATP For active transport , protein synthesis etc

Question 33

summarise the stages of anaerobic respiration

Answer 33

Glycolysis NAD regeneration

Question 34

Explain what happens after glycolysis if respiration is anaerobic

Answer 34

1) Pyruvate converted to lactate (animals) or ethanol (plants and yeast) 2) oxidising reduced NAD - NAD regenerated 3) So glycolysis can continue allowing continued production of ATP

Question 35

Suggest why anaerobic respiration produced less ATP per molecule of glucose than aerobic respiration

Answer 35

- Only glycolysis involved which produced little ATP (2 c molecules ) - No oxidative phosphorylation which forms majority of the ATP ( around 34 molecules )

Question 36

Describe the krebs cycle

Answer 36

1) acetyl coenzyme A reacts with a 4C molecule • releasing coenzyme A • producing a 6C molecule that enters the krebs cycle 2) In a series of oxidation - reduction reactions , the 4C molecule is regenerated and : • 2 x CO2 lost • Coenzymes NAD and FAD reduced • Substrate level phosphorylation • ATP produced

Question 37

Describe the process of oxidative phosphorylation

Answer 37

1) NADH / FADH oxidised to release H atoms => split into protons and electrons 2) Electrons transferred down electron transfer chain by redox reactions 3) Energy released by electrons used in the production of ATP from ADP + Pi ( chemiosmotic theory ) • Energy used by electron carried to actively pump protons from matrix to intermembrane space • Protons diffuse into matrix down an electrochemical gradient via ATP synthase • Releasing energy to synthase ATP from ADP + Pi 4) In matrix at the end of electron transport chain , oxygen is final electron acceptor • So protons , electrons and oxygen combine to form water

Question 38

Give examples of other respiratory substrates

Answer 38

Breakdown products of lipids and amino acids , which enter the Krebs cycle . For example : • Fatty acids from hydrolysis of lipids => converted to Acetyl Coenzyme A • Amino acids from hydrolysis of proteins => converted to intermediates in Krebs cycle

Question 39

EQ: Pea plants respire aerobically , producing ATP which can be used for amino acid synthesis . Describe the role of oxygen in aerobic respiration (2)

Answer 39

• Terminal electron acceptor • forms water

Question 40

EQ: The bacteria respire anaerobically . This produces hydrogen and ATP used in nitrogen fixation. The hydrogen comes from reduced NAD . Explain how the regeneration of NAD in this way allows ATP production to continue (2)

Answer 40

• oxidised NAD can accept more electrons • This continues process of glycolysis

Question 41

EQ : Oxygen is needed for the production of ATP on the cristae of the mitochondrion . Explain why (3)

Answer 41

- forms h2O - Electrons cannot be passed along electron transfer chain if no oxygen accepts them - ATP formed as electrons pass along transport chain