respiration

Question 1

Why can single cells respire anaerobically constantly? [3]

Answer 1

It produces toxic waste products which are expelled from the cell
- Protected by slime capsule
- Multi-cellular organism would have toxic waste accumulate in body

Question 2

Cellular Respiration [2]

Answer 2

• Releases energy
• Takes place in all organisms all the time

Question 3

How does Cellular Respiration work? [2]

Answer 3

• Food molecules are broken down to release energy
• Requires oxygen provided by exchange surface and vascular system in multi-cellular organisms

Question 4

Breathing [2]

Answer 4

• Ventilation
• Provides oxygen and removes carbon dioxide

Question 5

Aerobic Respiration [2]

Answer 5

• Requires oxygen
• Releases a relatively large amount of energy

Question 6

Anaerobic Respiration [2]

Answer 6

• Respiration without oxygen
• Releasing a relatively small amount of energy

Question 7

Aerobic Cellular Respiration [2]

Answer 7

• Humans respire mainly sugars (some amino acids and fatty acids)
• Net release of free energy (up to 38 ATP molecules)

Question 8

Respiration Equation

Answer 8

Glucose + oxygen > Carbon dioxide + water + energy

Question 9

Overview of the 4 stages of Respiration

Answer 9

Glycolysis
- Glucose splits into pyruvate
The link reaction
- Pyruvate is oxidised into acetate
The Krebs cycle
- Electrons are stripped off the acetate
The electron transport chain
- The energy in the electrons is used to produce ATP

Question 10

What is NADH? [3]

Answer 10

• Respiration involves the removal of electrons from glucose molecules
• The energy in the electrons makes ATP
• NADH is an electron carrier

Question 11

Where does each stage of Aerobic Respiration take place?

Answer 11

Glycolysis - Cytoplasm
Link Reaction & Krebs Cycle - Matrix
ETC - Inner membrane of mitochondria

Question 12

Glycolysis [4]

Answer 12

• Substrate level phosphorylation
  -2 ATP molecules add 2 phosphate groups to glucose
• glucose phosphate splits into two triose phosphate (3C) molecules
• both TP molecules are oxidised (reducing NAD) to form 2 pyruvate molecules (3C)
• releases 4 ATP molecules

Question 13

Link Reaction [4]

Answer 13

• Reduced NAD and pyruvate are actively transported to matrix
• pyruvate is oxidised to acetate (forming reduced NAD)
• carbon removed and CO2 forms
• acetate combines with coenzyme A to form acetylcoenzyme A (2C)

Question 14

Krebs Cycle [2]

Answer 14

• Acetylcoenzyme A combines with 4C molecule to produce a 6C molecule - enters cycle
• oxidation-reduction reactions

produces :
6 reduced NAD
2 reduced FAD
2 ATP 4 carbon dioxide

Question 15

Electron Transport Chain [10]

Answer 15

• NADH and FADH2 from glycolysis, link reaction and Krebs cycles are used
• A series of electron carriers are found in the cristae
• Electrons move from the hydrogen atoms carried by NADH and FADH2
  to the first electron carrier
• The electrons pass along the chain of carrier molecules, in a series of
  oxidation-reduction reactions
• As they move, energy is released
• This energy causes active transport of protons (H+) across the membrane into the mitochondrial inner membrane space
• This creates a chemiosmotic gradient
• Protons must move through ATP synthase
• As the protons diffuse through the ATP synthase, ATP is created from ADP and Pi
• The protons combine with the electrons and also oxygen to form water
• Oxygen is the final electron acceptor

Question 16

Anaerobic Respiration [3]

Answer 16

• Occurs in the cytoplasm
• Aim is regenerating NAD
• NAD reduced in glycolysis so must be converted back to NAD to continue glycolysis

Question 17

Anaerobic Respiration in plants and some microorganisms

Answer 17

Pyruvate + NADH → ethanol + carbon dioxide + NAD

Question 18

Anaerobic Respiration in Animals

Answer 18

Pyruvate + NADH → lactate + NAD

Question 19

Process of Anaerobic Respiration [3]

Answer 19

• Glycolysis
• NAD+ Regenration creates lactate and allows NAD+ to be used again in reaction
• Only releases 2 ATP, while aerobic reaction produces 38

Question 20

Starvation [5]

Answer 20

• We obtain most of our energy by respiring food we have eaten recently
• Carbohydrate is our primary source of energy + small amounts of fat and protein
• Carbohydrate runs out after about a day
• Fat can only be respired when some carbohydrate
  is still available
• Must respire protein
  Can lose 50% of protein before death occurs

Question 21

How can Lipids be Respired? [3]

Answer 21

Hydrolysed to glycerol and fatty acids
Glycerol - phosphorylated and
converted into TP (then enters glycolysis)
Fatty acids - converted into 2C molecules, then acetyl CoA (then enters Krebs)

Question 22

How can Proteins be Respired? [3]

Answer 22

• amino group removed from the amino acids,
• enter the chain depending on the carbon content
• 3C into pyruvate;
  4C & 5C into Krebs
  intermediaries