Fuels and Biofuels: Cellular Biosystems; Cellular Respiration

Question 1

What is the word equation of aerobic respiration? Where does this occur?

Answer 1

• Glucose + Oxygen —> Carbon dioxide + Water + ATP

- Mitochondria

Question 2

How is aerobic respiration controlled?

Answer 2

By a sequence of enzyme controlled reactions

Question 3

How many ATP molecules are produced per molecule of glucose metabolised?

Answer 3

38 ATP molecules

Question 4

What percent of the energy extracted from aerobic respiration is wasted and as what?

Answer 4

60% is wasted as heat

Question 5

What is anaerobic respiration? Where does it occur?

Answer 5

• Cellular respiration where there is no O2

- Cytosol

Question 6

What kind of reaction is aerobic respiration? Explain why it is this kind of reaction

Answer 6

• Redox reaction
• Glucose gets oxidised (loses electrons and hydrogens) and forms CO2 and Oxygen is reduced (gaining electron and hydrogens) to from H2O

Question 7

What is the importance of O2 in cellular respiration?

Answer 7

It neutralises the H+ that is created from the breakdown of glucose preventing the cell from increasing in pH and denaturing its proteins

Question 8

What are the three main cycles of cellular respiration? Outline each one

Answer 8

• Glycolysis: break down of glucose into two pyruvic acid molecules (FYI 2 ATP produced)
• Krebs cycle: breaks down pyruvic acid (FYI 2 ATP)
• Electron transfer: energy from electrons, produced by breakdown of pyruvic acid produce bulk of ATP (FYI 34 ATP)

Question 9

What does glyco and lysis mean? How does it relate to the process it undertakes?

Answer 9

• Sugar split

- It is the breaking down of glucose

Question 10

What are the two main phases of glycolysis?

Answer 10

Energy investment phase and energy harvest phase

Question 11

What is the energy investment phases?

Answer 11

Where the glucose uses 2 ATP molecules to slit into a 3-carbon phosphate sugar

Question 12

What is the energy harvest phase?

Answer 12

When the NADH (high energy electron carriers) transfer the H+ into the mitochondria to form H2O

Question 13

What are the inputs and outputs of glycolysis?

Answer 13

Input: 2 ATP, 2 NAD+
Output: 2 pyretic acid, 4 ATP (∴ 2 net), 2 NADH

Question 14

What is the function of the krebs cycle?

Answer 14

It completes the energy extraction of glucose

Question 15

What is the step before the krebs cycles but after glycolysis? What is the purpose of this?

Answer 15

• The transition stage

- To produce acetic acid acetyl-CoA (Acetyl coenzyme A)

Question 16

What happens to acetyl-CoA in the krebs cycle?

Answer 16

It bonds with oxaloacetic acid to form citric acid

Question 17

What is extracted from citric acid that is useful for respiration?

Answer 17

ATP (final product, FYI 2 of them), NADH (6 of them FYI) and FADH2 (2 of them FYI)

Question 18

What are the products of the krebs cycle that go to what final step in aerobic respiration?

Answer 18

The NADH and FADH2 go into the electron transfer step

Question 19

What occurs in the electron transfer stage?

Answer 19

High energy electrons are passed form molecule to molecule (in a series of redox reactions) that then energise protein pumps to pump hydrogen ions against the concentration gradient into the space between the inner and outer membrane of mitochondria

Question 20

How are the high energy electrons released?

Answer 20

NADH is converted into NAD+ (releasing a hydrogen and two electrons) and FADH2 is converted into FAD (releasing two protons and two electrons) by a series of redox reactions controlled by enzymes

Question 21

How does pumping hydrogen ions against the concentration gradient produce energy?

Answer 21

The hydrogen ions have potential energy and are forced through an enzyme complex on the inner mitochondrial membrane that then uses the energy of this ion gradient to generate ATP from ADP

Question 22

How many ATP are produced per NADH and FADH2?

Answer 22

3 per NADH

2 per FADH2

Question 23

What process in anaerobic respiration that is different from aerobic respiration?

Answer 23

Pyruvate is broken down into lactic acid (instead of acetyl-CoA

Question 24

Why does pyruvate turn into lactic acid?

Answer 24

In order to free up the NADH, that transferred electron to form lactic acid, to turn back into NAD+ allowing for continual production of ATP

Question 25

What property of anaerobic respiration makes it limited?

Answer 25

As lactic acid builds up the pH decreases which causes other cellular reactions to stop (e.g. acidifies the cell)

Question 26

How is lactic acid removed from the body?

Answer 26

Once oxygen is available the lactic acid is converted back into pyruvate where it is then used for aerobic respiration