Chapter 13: How Cells Obtain Energy From Food

Question 1

What is Cellular respiration?

Answer 1

The process of extracting energy from the bonds in sugar molecules as the sugar molecule is oxidized to water and carbon dioxide

Question 2

Where does the energy from breaking the bond in a sugar molecule go?

Answer 2

Energy released is stored in COVALENT bonds in activated carriers like NADH and ATP

Question 3

How is energy gain from sugars regulated so the cell can handle the energy gain?

Answer 3

Enzymes carry out the oxidation of sugars in a tightly controlled series of reactions - which results in slow energy release

Question 4

What are the two methods which cells can make ATP?

Answer 4

Oxidation of food molecules

Oxidative phosphorylation

Question 5

Define Catabolism

Answer 5

The process of enzymes breaking down complex organic molecules into smaller ones - for an energy source or as precursors to make other organic molecules

Question 6

What is the first phase of Catabolism?

Answer 6

Breakdown of foods into their basic subunits - proteins to amino acids, polysaccharides to simple sugars, fats to fatty acids

Question 7

What is stage 2 of Catabolism / Glycolysis?

Answer 7

When simple subunits are broken into Acetyl CoA - limited amounts of ATP and NADH produced

Question 8

What are the steps in stage 2 of Catabolism?

Answer 8

1. 1 Molecule of glucose is split into 2 molecules of Pyruvate, plus ATP and NADH (a little) - Glycolysis
2. Pyruvate is transferred from the cytosol into the matrix of the mitochondria
3. Enzyme converts Pyruvate into Acetyl CoA and carbon dioxide

Question 9

Where does Glycolysis occur?

Answer 9

Cytosol

Question 10

What are the steps in stage 3 of Catabolism?

Answer 10

1. Acetyl CoA is converted into an oxaloacetate molecule which forms citrate
2. Citric acid cycle
3. Electrons from NADH are passed along ETC - supports oxidative phosphorylation

Question 11

Where does stage 3 in catabolism occur?

Answer 11

Inside the mitochondria

Question 12

What are the inputs / outputs of Glycolysis?

Answer 12

Input: 2 ATP, glucose
Output: 4 ATP, 2 NADH, 2 Pyruvate

Question 13

What are the steps of glycolysis?

Answer 13

1. 2 molecules of ATP are added to 1 molecule of glucose
2. 6-Carbon sugar is cleaved into 2 3-Carbon sugars
3. Energy is generated - 4 molecules of ATP are released with 2 molecules of NADH and 2 molecules of Pyruvate