Aerobic Respiration

Question 1

Where is the energy stored in glucose?

Answer 1

In the C-C and C-H bonds

Question 2

What is chemiosmosis?

Answer 2

Creation of a hydrogen ion concentration so hydrogen ions are able to travel through ATP synthase by facilitated diffusion

Question 3

What is the first step of respiration?

Answer 3

Glycolysis

Question 4

Where does glycolysis occur?

Answer 4

The cytoplasm of cells

Question 5

How many ATP’s are produced in glycolysis?

Answer 5

Two ATPs consumed
Four ATPs produced
NET PRODUCTION 2 ATP

Question 6

Glycolysis details:

Answer 6

1) Two ATPs consumed to phosphorylate glucose and turn it into HEXOSE BISPHOSPHATE
2) HB lysed into two molecules of TRIOSE PHOSPHATE
3) Each TP has a phosphate (Pi from the cytoplasm) added making two molecules of TRIOSE BISPHOSPHATE
4) Triose bisphosphate are dehydrogenated, forming two molecules of PYRUVATE
5) Hydrogen atoms lost are accepted by NAD to form NADH
6) Two triose bisphosphate molecules have their phosphate groups from them. These phosphates used to regenerate 4 ATP from ADP and Pi. This is Substrate Level Phosphorylation

Question 7

What is the structure of a mitochondrion?

Answer 7

1) Outer mitochondrial membrane
2) Inner mitochondrial membrane
3) Matrix
4) Intermembrane space

Question 8

What occurs in the matrix?

Answer 8

• Contain enzymes for Krebs Cycle and the link reaction

- Contains mitochondria DNA

Question 9

What occurs in the intermembrane space?

Answer 9

• Protons pumped into this space by the electron transport chain
• Space is small so concentration builds up quickly

Question 10

What occurs in the outer mitochondrial membrane?

Answer 10

• Separates contents of the mitochondrion from the rest of the cell
• Creates cellular compartments with ideal conditions for aerobic respiration

Question 11

What occurs in the inner mitochondrial membrane?

Answer 11

Contains electron transport chains and ATP synthase

Question 12

What is the second stage of respiration?

Answer 12

The Link Reaction

Question 13

Link Reaction detail:

Answer 13

1) Pyruvate pumped into the mitochondrial matrix by carrier proteins
2) Pyruvate put through oxidative decarboxylation:
3) CO2 removed by decarboxylation
4) Hydrogen removed in oxidation reaction
5) Hydrogen atoms accepted by NAD to produce NADH
6) 2-carbon group produced that binds to COENZYME A to produce ACETYL CoA

Question 14

What is the third stage of respiration?

Answer 14

Krebs Cycle

Question 15

How many ATPs produced in one turn of Krebs Cycle?

Answer 15

One ATP

Question 16

Krebs Cycle details:

Answer 16

1) Link reaction delivers acetyl groups into Krebs Cycle
2) The acetyl group combines with oxaloacetate (4 carbon) to form citrate (6 carbon)
3) Coenzyme A returned to link reaction
4) Citrate is decarboxylated and dehydrogenated to produce 5 carbon intermediate, CO2 and NADH
5) 5 carbon intermediate decarboxylated and dehydrogenated to produce 4 carbon intermediate, CO2 and NADH
6) 4 carbon intermediate undergoes substrate level phosphorylation to produce ATP from ADP + Pi
7) 4 carbon dehydrogenated to produce NADH
8) dehydrogenated again to produce FADH2
9) Last three reactions convert 4 carbon intermediate into oxaloacetate so Krebs Cycle can turn again

Question 17

How is NAD reduced?

Answer 17

-NAD accepts one proton and two electrons
-NAD reduced to NADH
NAD + H+ +2e- ——> NADH

Question 18

How is FAD reduced?

Answer 18

-FAD accepts two protons and two electrons
-FAD reduced to FADH2
FAD + 2e- + 2H+ ——> FADH2

Question 19

How is NADH used?

Answer 19

• Used in last stage of aerobic respiration (oxidative phosphorylation) to produce ATP from ADP and Pi
• One reduced NAD molecule can be used to produce three ATP molecule

Question 20

How is FADH2 used?

Answer 20

• Used in last stage (oxidative phosphorylation) of aerobic respiration to produce ATP from ADP and Pi
• One reduced FAD molecules can be used to produce two ATP molecules

Question 21

What is ATP synthase?

Answer 21

• Enzyme that catalyses formation of ATP from ADP and Pi
• Formation of ATP is energetically unfavourable
• ATP synthase ensures reaction goes in forward direction
• Needs source of energy to do this
• Electrochemical gradient created by difference in H+ concentration across inner mitochondrial membrane

Question 22

Electron transport chains:

Answer 22

1) NADH and FADH2 deliver high energy electrons to electron transport chain
2) Electron passed between proteins energy is used to pump proton into intermembrane space
3) This is a series of REDOX reactions
4) Final low energy electrons accepted by free oxygen molecules, forming water
5) Oxygen is the final electron acceptor

Question 23

Oxidative phosphorylation:

Answer 23

1) Hydrogen atoms accepted by NAD and FAD delivered to electron transport chain in cristae of mitochondria
2) Hydrogen atoms dissociate into hydrogen ions and electrons
3) Energy is released during redox reactions as the electrons reduce and oxidise electron carriers
4) Energy used to create proton gradient, leading to diffusion of proton through ATP synthase, resulting in the synthesis of ATP from ADP and Pi
5) Oxygen acts as final electron acceptor, forming water
6) Oxidative phosphorylation because phosphate used is not coming from another molecule

Question 24

What is the net gain of ATP molecules in aerobic respiration?

Answer 24

38 ATP molecules per glucose molecule respired

Question 25

How can the rate of aerobic respiration be measured?

Answer 25

• Respirometer can be used
• Maggots, peas, locusts, etc. can be used
• Soda lime absorbs CO2 produced
• Respirometer left to equilibrate to produce the right enzymes
• When O2 is taken in from the tube, the volume and pressure decreases, causing the fluid to move towards the respirometer
• 3 different experiments carried out, one with soaked peas, one with dry peas and glass beads (makes up mass) and one with just glass beads as a control
• Control used to work out corrected difference
• Can be carried out at different temperatures, etc.
• Rate of oxygen uptake = distance moved by fluid/time

Question 26

Why is respiration exothermic?

Answer 26

• Large organic molecules are broken down into small inorganic molecules
• Total energy required to break all bonds is less than energy released in making the bonds
• Respiration is exothermic and the released energy is used to make ATP from ADP and Pi