Module 7: Cellular Respiration

Question 1

What is cellular respiration?

Answer 1

A series of metabolic pathways that convert glucose into ATP.

Question 2

What are redox reactions?

Answer 2

A combination of:
1. Oxidation reactions. Takes away an electron.
2. Reduction reactions. Gains an electron.

Question 3

What is NAD?

Answer 3

An electron carrier derived from vitamin B. Easily oxidised or reduced.

NAD+ is the oxidised form (less electrons).
NADH is the reduced form (added 2 electrons and a proton).

Question 4

What does NAD stand for?

Answer 4

Nicotinamide Adenine Dinucleotide.

vitamin B, which NAD is derived from, is also known as B3 or niacin

Question 5

What is the reduction equation for NAD+?

Answer 5

RH + (NAD+) → NADH + R

Where RH is reducing agent.
And R is oxidised.

Question 6

What is a reducing agent?

Answer 6

A compound that reduces (gives electrons to) another compound.

Question 7

What is FAD+?

Answer 7

Flavin adenine dinucleotide.
Derived from vitamin B2, riboflavin.
Its reduced form is FADH2.

Question 8

What is NADP?

Answer 8

A second variation of NAD, containing an extra phosphate group.

Question 9

Why can’t living cells store significantly amounts of free energy?

Answer 9

Excess free energy would increase heat in the cell, resulting in excess thermal motion that could damage and destroy the cell.

Question 10

What is ribose?

Answer 10

A five-carbon sugar found in RNA.

Question 11

What is the order of creation of ATP?

Answer 11

AMP + 1 phosphate group → ADP + 1 phosphate group → ATP

Question 12

What is AMP?

Answer 12

Adenosine monophosphate.
Composed of an adenine molecule bonded to a ribose molecule and a single phosphate group.

AMP is one of the nucleotides in RNA.

Question 13

What is dephosphorylation?

Answer 13

The removal of a phosphate group/s by hydrolysis.
Releases energy.

Question 14

What is the standard chemical equation of hydrolysis?

Answer 14

AB + H2O → AH + BOH

Question 15

How is water affected by hydrolysis of ATP?

Answer 15

Water is broken down into a hydrogen atom (H+) and a hydroxyl group (OH-), which is added to a larger molecule.
Water is reformed when the third phosphate is added to ADP, forming ATP.

Question 16

What are the 2 methods of phosphorylation?

Answer 16

1. Substrate phosphorylation. A phosphate group connected to other molecule transfers to ADP to form ATP.
2. Oxidate phosphorylation/chemiomosis. Occurs in the mitochondria (eukaryotic) or in the plasma membrane (prokaryotic).

Question 17

What is glycolysis?

Answer 17

The first step of cellular respiration.
Converts glucose into pyruvate.
Anaerobic.

Question 18

What are the 3 steps of aerobic cellular respiration?

Answer 18

1. Glycolysis.
2. Krebs Cycle/citric acid cycle.
3. Electron Transport Chain

Question 19

How does glucose enter heterotophic cells?

Answer 19

1. Through active secondary transport against the glucose concentration gradient.
2. Through a group of integral protein transporters called GLUT proteins.

Question 20

What is the net production from 1 glucose molecule in glycolysis?

Answer 20

2 pyruvate molecules.
2 NADH.
2 ATP.

Question 21

What is pyruvate?

Answer 21

The conjugate base of pyruvic acid.
Three carbon molecules composed of a ketone functional group and a carboxyl group.
C3H3O3.

Question 22

Where does glucolysis take place?

Answer 22

In the cytosol of the cell.

Question 23

What do the first 5 steps of glycolysis do?

Answer 23

The preparation phase.
Converts a 6-carbon sugar (glucose) into two 3-carbon sugars (glyceraldehyde-3-phosphate).

ATP is consumed in the 1st and 3rd steps. Both these reactions are irreversible.

Question 24

What do the last 5 steps of glycolysis do?

Answer 24

The Pay-Off Phase.
Produces energy.
In steps 7 and 10, 1 ATP is made per glyceraldehyde-3-phosphate.

Step 7 is reversible, step 10 is not.

Question 25

How many steps are in glycolysis?

Answer 25

10 steps.

Question 26

What is the total production of ATP and NADH in glycolysis?

Answer 26

4 ATP and 2 NADH. Because 2 ATP are used in glycolysis, the net total is: 2 ATP and 2 NADH.

Question 27

When is NADH formed in glycolysis?

Answer 27

In the 6th step, by an enzyme called dehydrogenase.

Question 28

How many pyruvate molecules are produced through glycolysis?

Answer 28

2 pyruvate molecules.

Question 29

How is pyruvate changed during pyrvate oxidation?

Answer 29

Pyruvate → acetyl CoA This occurs in the mitochondria.

Question 30

What are the steps of pyruvate oxidation?

Answer 30

1. Carboxyl group removed from pyrvate, releasing CO2. This creates a 2 carbon hydroxyethyl group bound to the enzyme (pyruvate dehydrogenase). 2. The hydroxyethyl group is oxidised to an acetyl group and the electrons picked up by NAD+, forming NADH. 3. The enzyme-bound acetyl group is transferred to CoA, producing a molecule of acetyl CoA.

Question 31

What is CoA?

Answer 31

Coenzyme A. A carrier compound derived from vitamin B5.

Question 32

What happens to acetyl CoA in the first step of the citric acid cycle?

Answer 32

Acetyl CoA → Citrate It loses its acetyl group (2 Carbons) to a 4-carbon molecule, oxaloaceate, to form citrate.

Question 33

What is citrate?

Answer 33

A 6-carbon molecule with 3 carboxyl groups.

Question 34

What is the overall equation for cellular respiration?

Answer 34

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP *glucose + oxygen → carbon dioxide + water + ATP*

Question 35

How is the citric acid cycle different from the linear glycolysis?

Answer 35

The citric acid cycle is a closed loop. The last part of the pathway regenerates the compound used in the first step.

Question 36

What are the outputs of the citric acid cycle?

Answer 36

Per 1 glucose molecule (2 pyruvate): 4 carbon dioxide. 2 ATP 6 NADH. 2 FADH2.

Question 37

What are the inputs of the citric acid cycle?

Answer 37

Per 1 glucose molecule (2 pyruvate): 2 Acetyl CoA 2 Oxaloacetate

Question 38

What are the outputs of pyruvate oxidation?

Answer 38

Per 1 glucose molecule (2 pyruvate) 2 acetyl CoA 2 Carbon Dioxide 2 NADH

Question 39

What is the chemical transformation of acetyl CoA in the citric acid cycle?

Answer 39

Acetyl CoA + Oxaloacetate → Citrate → Succinate → Oxaloacetate

Question 40

What is the electron transport chain?

Answer 40

A series of protein complexes embedded in the mitochondrial membrane that transfer electrons to form a hydrogen ion gradient.

Question 41

What are the structures in the electron transport chain?

Answer 41

Complex I Complex II Q - ubiquinone B Complex III Complex IV ATP Synthase

Question 42

How is ATP generated using ATP synthase?

Answer 42

1. H+ ions flow down their electrochemical gradient into ATP synthase. 2. These H+ ions turn the rotors of the ATP synthase. 3. ATP synthase facilitates the addition of a phosphate to ADP, forming ATP, using this energy. 4. The hydrogen ions are accepted by oxygen, forming water as an end product.

Question 43

What is the final electron acceptor in the electron transport chain?

Answer 43

Oxygen.