5b. Glycolysis, Krebs Cycle and Oxidative Phosphorylation

Question 1

What are the three major destinations for consumed nutrients?

Answer 1

Energy
Structural or functional molecules
Storage compounds

Question 2

From which macronutrients is most energy derived?

Answer 2

carbohydrates
Fat
Protein

Question 3

What percentage of energy released is typically lost as heat?

Answer 3

60-70%

Question 4

What is the remainder of energy stored as after heat loss?

Answer 4

Chemical energy (ATP)

Question 5

Define metabolism.

Answer 5

Every chemical reaction in the body

Question 6

What is catabolism?

Answer 6

Chemical reactions that break down complex organic molecules

Question 7

What is anabolism?

Answer 7

Chemical reactions that build-up simple molecules into complex molecules

Question 8

What is stored in the bonds between atoms in molecules?

Answer 8

Energy

Question 9

What molecule typically transfers energy in chemical reactions?

Answer 9

ATP

Question 10

What does ATP stand for?

Answer 10

Adenosine Triphosphate

Question 11

What are the components of ATP?

Answer 11

• 3 phosphate groups
• Adenine base
• 5C sugar (ribose)

Question 12

What happens when the terminal phosphate bond of ATP is hydrolyzed?

Answer 12

Large amounts of energy are released

Question 13

What is the first stage in energy generation?

Answer 13

Large molecules are converted to smaller units

Question 14

What is produced from proteins in the first stage of energy generation?

Answer 14

Peptides and amino acids

Question 15

What is produced from fats in the first stage of energy generation?

Answer 15

Glycerol and fatty acids

Question 16

What is produced from polysaccharides in the first stage of energy generation?

Answer 16

Simple sugars

Question 17

What occurs in the second stage of energy generation?

Answer 17

Smaller units are degraded to a few simple key compounds

Question 18

What is the third stage of energy generation?

Answer 18

Citric acid cycle (Krebs) and oxidative phosphorylation

Question 19

What is the primary focus of carbohydrate metabolism?

Answer 19

Glucose metabolism

Question 20

What is the overall reaction for the oxidation of glucose?

Answer 20

Fuel + O2 –> CO2 + H2O + energy (ATP + heat)

Question 21

What are the three pathways glucose is catabolized in?

Answer 21

• Glycolysis
• Krebs cycle
• Electron transport chain and oxidative phosphorylation

Question 22

What is the process of ATP production without oxygen called?

Answer 22

Anaerobic

Question 23

What is produced during anaerobic ATP production?

Answer 23

Glycolysis

Question 24

What is the transitional step in anaerobic ATP production?

Answer 24

Formation of acetyl CoA

Question 25

What is the process of ATP production using oxygen called?

Answer 25

Aerobic

Question 26

What are the components of aerobic ATP production?

Answer 26

* Krebs cycle * Electron transport chain

Question 27

What is the initial step in glycolysis?

Answer 27

Activate glucose by adding 2 phosphate groups from ATP

Question 28

How much energy is liberated during glycolysis?

Answer 28

2ATP + 2NADH2

Question 29

What determines the fate of pyruvic acid?

Answer 29

Availability of O2

Question 30

What happens to pyruvic acid when O2 is unavailable?

Answer 30

* Reduced to lactic acid * Lactic acid diffuses into blood * Liver converts lactic acid back to pyruvic acid

Question 31

What happens to pyruvic acid when O2 is available?

Answer 31

It proceeds to the Krebs cycle in the mitochondrion

Question 33

What enters the mitochondria and undergoes decarboxylation?

Answer 33

Pyruvic acid ## Footnote This process removes CO2 and converts pyruvate to a 2C acetyl group.

Question 34

What is formed when the 2C acetyl group is attached to coenzyme A?

Answer 34

Acetyl coenzyme A ## Footnote Acetyl CoA enters the Krebs cycle.

Question 35

What is coenzyme A derived from?

Answer 35

Vitamin B ## Footnote Coenzyme A acts as a carrier for the acetyl group.

Question 36

Where do the biochemical reactions of the Krebs cycle occur?

Answer 36

Matrix of mitochondria ## Footnote The Krebs cycle is a series of reactions that release energy.

Question 37

What does the 2C component of Acetyl CoA release during the Krebs cycle?

Answer 37

CO2 and H ## Footnote Hydrogen ions are sent to the electron transport chain as NADH2 and FADH2.

Question 38

What does Acetyl CoA combine with to form citric acid in the Krebs cycle?

Answer 38

4C compound ## Footnote This 4C compound is oxalo-acetic acid.

Question 39

What is the reaction equation for the formation of citric acid?

Answer 39

(2C) acetyl CoA + (4C) oxalo-acetic acid --> (6C) citric acid ## Footnote This equation represents the combination of acetyl CoA and oxalo-acetic acid.

Question 40

What are the products produced from each acetyl CoA molecule that enters the Krebs cycle?

Answer 40

* 2 molecules of CO2 * 3 molecules of NADH2 * 1 molecule of ATP * 1 molecule of FADH2 ## Footnote Each glucose produces 2 acetyl CoA molecules, doubling the yield.

Question 41

Where is the electron transport chain located?

Answer 41

Mitochondria ## Footnote Specifically, it is located in the inner mitochondrial membrane.

Question 42

What forms the chain in the electron transport chain?

Answer 42

Integral membrane proteins (cytochromes) ## Footnote Cytochromes pass electrons along the chain.

Question 43

What is produced in large quantities through oxidative phosphorylation?

Answer 43

ATP ## Footnote This process generates the majority of ATP in the cell.

Question 44

What happens to the hydrogens delivered to the chain in the electron transport chain?

Answer 44

They are split into protons (H) and electrons ## Footnote Electrons release energy as they move through the chain.

Question 45

What is formed when the final complex of the electron transport chain passes electrons to O2?

Answer 45

Water (H2O) ## Footnote This occurs after the buildup of H creates a positive charge.

Question 46

What is the function of ATP synthase in the electron transport chain?

Answer 46

Forms ATP from ADP and inorganic phosphate ## Footnote ATP synthase uses the potential energy from the proton gradient.

Question 47

What is the overall equation for aerobic cellular respiration?

Answer 47

Glucose (+O2) is broken down into CO2 + H2O + energy ## Footnote This energy is used to form ATP.

Question 48

How many ATPs are formed during glycolysis?

Answer 48

2 ATPs ## Footnote Glycolysis also produces 2 NADH2.

Question 49

How many NADH2 are formed during the Krebs cycle?

Answer 49

6 NADH2 ## Footnote Additionally, 2 FADH2 are formed during the Krebs cycle.

Question 50

How many ATPs does each NADH2 generate via the proton gradient?

Answer 50

3 ATP ## Footnote This means 10 NADH2 generates 30 ATP.

Question 51

How many ATPs does each FADH2 generate via the proton gradient?

Answer 51

2 ATP ## Footnote Thus, 2 FADH2 generates 4 ATP.

Question 52

What is the total number of ATPs generated from one glucose molecule via oxidative phosphorylation?

Answer 52

36-38 ATPs ## Footnote This includes all ATP produced from glycolysis, Krebs cycle, and oxidative phosphorylation.

Question 53

What is the benefit of the complete oxidation of glucose?

Answer 53

H2 obtained from a variety of organic molecules is funneled to ATP ## Footnote This complex series of reactions primarily occurs in the mitochondria.