Chapter 7: How Cells Harvest Energy (Cellular Respiration)

Which of the following processes uses an inorganic molecule besides oxygen as a terminal electron acceptor?
A. aerobic respiration
B. fermentation
C. anaerobic respiration
D. all of the above

C. anaerobic respiration

NADH is made during
A. glycolysis
B. pyruvate oxidation
C. krebs cycle
D. all of the above

D. all of the above

Glycolysis costs _______ ATP's, but makes_______ ATP's; thus it has a net yield of ______ ATP's.
A. 3, 6, 3
B. 2, 4, 2
C. 2, 2, 0
D. 4, 8, 4

B. 2, 4, 2

The 2 carbons in acetyl-CoA are eventually used to form
A. glucose
B. ATP
C. pyruvate
D. oxaloacetate
E. carbon dioxide

E. carbon dioxide
When acetyl-CoA moves into the Krebs cycle, 1 CO2 is released and eventually another one is.

What is the function of the coenzymes, NADH and FADH2?
A. charging electrons to power ATP synthase
B. catalyzing the formation of acetyl-CoA
C. providing electrons and H+ to the electron transport chain
D. transporting CO2 into the mitochondria
E. acting

C. providing electrons and H+ to the electron transport chain

The process of removing the amino group from an amino acid is
A. decarboxylation
B. defenestration
C. denaturation
D. deamination
E. deracciation

D. deamination

Beta-oxidation is used to extract energy from
A. glucose
B. proteins
C. nucleic acids
D. carbohydrates
E. triglycerides (fatty acids + glycerols)

B. proteins

When making wine, grape juice and yeast are sealed into a container. Why must the container be air tight?
A. to prevent the buildup of lactic acid
B. fermentation only occurs in the absence of oxygen
C. yeast cannot live in aerobic environments
D. to prev

B. fermentation only occurs in the absence of oxygen

A cheeseburger contains bread, meat, and cheese. Which portion of this meal produces the most ATP per unit of mass?
A. bread
B. meat
C. cheese
D. all are equal

C. cheese
Cheese has the most fat content which is why it contains the most ATP.

What happens in the electron's energy as it moves through the electron transport chain?
A. the electrons gain energy through each transfer
B. the electrons lose energy through each transfer
C. the energy content is unchanged
D. the energy drops to a diffe

C. the energy content is unchanged
The electron does not change, it is just moving through the system.

autotrophs

able to produce their own organic molecules through photosynthesis

heterotrophs

live on organic compounds produced by other organisms (autotrophs)

respiration

all organisms use cellular respiration to extract energy from organic molecules

oxidations

loss of electrons

dehydrogenations

lost electrons are accompanied by protons; a hydrogen atom is lost (1 proton, 1 electron)

NAD+ (nicotinamide adenosine dinucleotide)

an electron carrier; NAD+ accepts 2 electrons and 1 proton to become NADH. this reaction is reversible

aerobic respiration

final electron acceptor is oxygen (O2)

anaerobic respiration

final electron acceptor is an inorganic molecule

fermentation

final electron acceptor is an organic molecule, but not oxygen (O2)

What is the formula for cellular respiration?

C6H12O6+6O2+energy----->6CO2+6H2O

substrate-level phosphorylation

transfers a phosphate group directly to ADP; occurs during glycolysis

oxidative phosphorylation

ATP synthase uses energy from a proton gradient

Stages of oxidation of glucose (respiration)

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

Glycolysis

the splitting of glucose. Converts 1 glucose (6 carbons) to 2 pyruvates (3 carbons); 10-step biochemical pathway; occurs in the cytoplasm; net production of 2 ATP molecules by substrate-level phosphorylation; 2 NADH produced by the reduction of NAD+

3 main steps of glycolysis

1. Priming Reactions
2. Cleavage
3. Oxidation and ATP formation

Priming Reactions

the first 3 reactions "prime" glucose by converting it into a 6-carbon molecule with 2 phosphates

Cleavage

6-carbon diphosphate cleaved into two 3-carbon phosphorylated molecules (G3P)

Oxidation and ATP formation

G3P is oxidized, transferring 2 electrons and 1 proton to NAD+ forming NADPH. A phosphate is then added to G3P to produce BPG (1, 3-biphosphoglycerate). The incorporated phosphate can be transferred from ADP to form ATP.

aerobic respiration

when oxygen is present, the pyruvate is oxidized to acetyl-CoA which enters the Krebs cycle

fermentation

when oxygen is not present, the pyruvate is reduced in order to oxidize NADH back to NAD+

pyruvate oxidation

only occurs in the presence of oxygen. Occurs in the mitochondria in eukaryotes. Occurs in the plasma membrane in prokaryotes.

Products of pyruvate oxidation

For each 3-carbon pyruvate molecule:
-1 CO2
-1 NADH
-1 acetyl-CoA which consists of 2 carbons from pyruvate attached to coenzyme A (acetyl-CoA proceeds to the Krebs cycle)

Krebs Cycle

oxidizes the acetyl group from the pyruvate. occurs in the matrix of the mitochondria. Biochemical pathway of 9 steps in 3 segments:
1. Acetyl-CoA+oxaloacetate---->citrate
2. Citrate rearrangement and decarboxylation
3. Regeneration of oxaloacetate

9 Steps of the Krebs Cycle

1. Condensation
2 & 3. Isomerization
4. The 1st oxidation
5. The 2nd oxidation
6. Substrate-level phosphorylation
7. The 3rd oxidation
8 & 9. Regeneration of oxaloacetate and the 4th oxidation

Products of the Krebs cycle

For each acetyl-CoA that enters:
-Releases 2 molecules of CO2
-Reduces 3 NADH
-Reduces 1 FADH2
-Produces 1 ATP
-Regenerates oxaloacetate

After the Krebs cycle, what has glucose been oxidized to?

-6CO2
-4 ATP
-10 NADH
-2 FADH2 (these electron carriers proceed to the electron transport chain)

Electron transport chain

a series of membrane-bound electron carriers; embedded in the inner mitochondrial membrane. Electrons from NADH and FADH2 are transferred to complexes of the ETC.

Each electron transport chain complex is

a proton pump that creates a proton gradient and transfers electrons to the next carrier

FADH2

located in the inner mitochondrial membrane. Skips the first step of chemiosmosis and feeds electrons to ubiquinone

Chemiosmosis

an accumulation of protons in the inter membrane space drives protons into the matrix via diffusion. This membrane is relatively impermeable to ions. Most protons can only reenter the matrix through ATP synthase (uses energy from the gradient to make ATP

Theoretical Energy Yield of Respiration

-38 ATP per glucose for bacteria
-36 ATP per glucose for eukaryotes

Actual Energy Yield of Respiration

-30 ATP per glucose for eukaryotes

What is the reduced yield due to?

A "leaky" inner membrane and the use of the proton gradient for purposes other than ATP synthesis

alcohol fermentation

Occurs in yeast. CO2 is released, which causes bread to rise. The final step produces ethanol which makes beer and wine. Ethanol is toxic to yeast so at 12% the yeast molecules begin to die

Lactic Acid fermentation

Occurs in human muscle cells. Lactate dehydrogenase transfers electrons from NADH to pyruvate produced in glycolysis. It converts the pyruvate to lactic acid producing NAD+ from NADH. Muscle fatigue is when the system becomes overwhelmed (lactic acid buil

Catabolism of a protein

amino acids undergo deamination to remove the amino group and the remainder of the amino acid is converted to a molecule that enters glycolysis or the Krebs cycle

Catabolism of a fat

fats are broken down to fatty acids and glycerol. Fatty acids are converted to acetyl groups by beta oxidation (a oxygen-dependent process). The respiration of a 6-carbon fatty acid yields 20% more energy than 6-carbon glucose