8: Energy From Organic Molecules I

Question 1

Depending on how they obtain energy, organisms are classified as either…

Answer 1

Autotrophs or heterotrophs

Question 2

____ convert solar energy into chemical energy.

Answer 2

Autotrophs

Question 3

Autotrophs store chemical energy as…

Answer 3

ATP or organic molecules

Question 4

List three examples of autotrophs.

Answer 4

1. Plants
2. Algae
3. Photosynthetic bacteria

Question 5

____ rely on the chemical energy stored in the bonds of organic molecules.

Answer 5

Heterotrophs

Question 6

Heterotrophs convert chemical energy into…

Answer 6

ATP

Question 7

True or false:

Only heterotrophs can extract chemical energy from organic molecules.

Answer 7

False

Both autotrophs and heterotrophs are capable of this.

Question 8

____% of species are heterotrophs.

Answer 8

95

Question 9

List four examples of heterotrophs.

Answer 9

1. Animals
2. Fungi
3. Most protists
4. Most prokaryotes

Question 10

All cells can use ____ to extract energy from the chemical bonds in organic molecules.

Answer 10

Cellular respiration

Question 11

Cellular respiration involves two enzyme-catalyzed reactions, ____ and ____.

Answer 11

Oxygenation and dehydrogenation

Question 12

Dehydrogenation involves…

Answer 12

The loss of both protons and electrons
(the loss of one or more hydrogen atoms)

Question 13

The energy contained in electrons is harvested via a series of…

Answer 13

Redox reactions

Question 14

During a redox reaction, the ____ and ____ are transferred to another molecule.

Answer 14

Electrons and most of their energy

Question 15

What happens to the energy lost by electrons during transfer?

Answer 15

It is either lost as heat or converted to ATP.

Question 16

After multiple redox reactions, the energy-depleted electrons are transferred to…

Answer 16

A final electron acceptor molecule

Question 17

The transfer of electrons often relies on…

Answer 17

Electron carriers

Question 18

Most electron carriers are…

Answer 18

Cofactors

Question 19

What are cofactors?

Answer 19

Small chemicals that assist enzymes

Question 20

All electron carriers are easily and reversibly ____ and ____.

Answer 20

Oxidized and reduced

Question 21

List two examples of electron carriers.

Answer 21

NAD+ (reduces to NADH)
FAD (reduces to FADH2)

Question 22

What two forms of energy are generated via cellular respiration?

Answer 22

1. ATP
2. Electron energy

Question 23

NAD+ has ____ energy than NADH.

Answer 23

Greater

Question 24

____ is a fundamental energy source for cells.

Answer 24

Glucose

Question 24

When glucose is oxidized in the process of molecular oxygen (O2), respiration becomes...

Answer 24

Aerobic

Question 25

During the aerobic respiration of glucose, ____ is the final acceptor for harvested electrons.

Answer 25

Oxygen

Question 26

Cellular respiration of glucose produces chemical energy as...

Answer 26

ATP and heat

Question 27

# True or false: It is more efficient for a cell to convert the chemical energy of glucose to ATP all at once.

Answer 27

False Glucose is so energy efficient that if a cell did this, it would likely combust.

Question 28

Glucose oxidation happens over ____ stage(s).

Answer 28

Four

Question 29

List the four stages of glucose oxidation.

Answer 29

1. Glycolysis 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain & chemiosmosis

Question 30

In eukaryotes, glycolysis occurs in the...

Answer 30

Cytosol

Question 31

In eukaryotes, pyruvate oxidation, the Krebs cycle, and chemiosmosis occur in the...

Answer 31

Mitochondria

Question 32

In prokaryotes, the process of glucose oxidation occurs in either the...

Answer 32

Cytoplasm or plasma membrane

Question 33

During glycolysis, 1 molecule of glucose is converted into....

Answer 33

2 molecules of pyruvate

Question 34

What are the two phases of glycolysis?

Answer 34

1. Energy input 2. Energy production

Question 35

During the first phase of glycolysis...

Answer 35

Glucose splits into 2 molecules of G3P.

Question 36

The first phase of glycolysis is ____, while the second is ____.

Answer 36

Endergonic ; exergonic

Question 37

During the second phase of glycolysis...

Answer 37

Each molecule of G3P is converted into a pyruvate molecule

Question 38

For each glucose molecule, glycolysis produces...

Answer 38

2 pyruvate molecules 4 ATP molecules 2 NADH molecules 2 water molecules

Question 39

Glycolysis results in a net gain of ____ ATP molecules.

Answer 39

Two

Question 40

List the two means of producing ATP.

Answer 40

1. Substrate-level phosphorylation 2. Oxidative phosphorylation

Question 41

During substrate-level phosphorylation...

Answer 41

An enzyme transfers an inorganic phosphate to ADP, creating ATP.

Question 42

The energy contained in the inorganic phosphate is ____ during substrate-level phosphorylation.

Answer 42

Maintained

Question 43

When ____ is present, eukaryotes and aerobic prokaryotes can synthesize much more ATP.

Answer 43

Oxygen

Question 44

# True or false: Glycolysis requires oxygen to proceed.

Answer 44

False However, the cell can perform aerobic respiration if there is oxygen present.

Question 45

Pyruvate oxidation occurs in the ____ of a mitochondrion.

Answer 45

Matrix (innermost area)

Question 46

For every molecule of pyruvate, pyruvate oxidation produces...

Answer 46

1 molecule of carbon dioxide 1 molecule of NADH 1 molecule of acetyl-CoA

Question 47

The Krebs cycle is also sometimes called the...

Answer 47

Citric acid cycle

Question 48

The Krebs cycle contains a total of ____ steps, divided into ____ phases.

Answer 48

Nine ; three

Question 49

During the Krebs cycle...

Answer 49

Acetyl-CoA is oxidized.

Question 50

The Krebs cycle occurs in the ____ of a mitochondrion.

Answer 50

Matrix

Question 51

List the three main steps of the Krebs cycle.

Answer 51

1. Acetyl-CoA and oxaloacetate combine to form citrate. 2. Citrate is rearranged and forms a 4-carbon succinate. 3. Oxaloacetate is regenerated from succinate.

Question 52

In addition to succinate, the second step of the Krebs cycle produces...

Answer 52

2 carbon dioxide molecules 2 NADH molecules 1 ATP molecule

Question 53

In addition to oxaloacetate, the third step of the Krebs cycle produces...

Answer 53

1 NADH molecule 1 FADH2 molecule

Question 54

In total, for each molecule of acetyl-CoA, the Krebs cycle produces...

Answer 54

2 molecules of carbon dioxide 3 molecules of NADH 1 molecule of FADH2 1 molecule of ATP 1 oxaloacetate

Question 55

For each glucose molecule, ____ acetyl-CoA molecules enter the Krebs cycle.

Answer 55

Two