Chapter 9 - Pathways that Harvest Chemical Energy

Question 1

Glucose

Answer 1

Most common fuel molecule in cells; used in cellular respiration to generate ATP

Question 2

5 Principles of Metabolic Pathways

Answer 2

Complex transformations are a series of separate reactions; each reaction is catalyzed by a specific enzyme; many metabolic pathways are similar in all organisms; in eukaryotes, metabolic pathways are compartmentalized in specific organelles; key enzymes can be inhibited or activated (regulated) to alter the rate of the pathway

Question 3

Glucose redox reaction

Answer 3

Glucose loses electrons (becomes oxidized) and oxygen gains them (becomes reduced)

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + free energy

Question 4

Three catabolic processes that harvest energy from glucose

Answer 4

Glycolysis - glucose is converted into 2 pyruvate (oxygen independent)

Cellular respiration (Pyruvate Oxidation, Kreb’s Cycle, Oxidative Phosphorylation) - Converts pyruvate into 3 molecules of CO2

Fermentation - converts pyruvate into lactic acid or ethyl alcohol (ethanol)

Question 5

Substrate level phosphorylation

Answer 5

The formation of ATP with a donated phosphate group from a compound

Question 6

Oxidative phosphorylation

Answer 6

The formation of ATP by oxidation of electron carriers in the presence of O2; includes the electron transport chain and chemiosmosis

Question 7

NAD+

Answer 7

Coenzyme that operates as a key electron carrier in glucose metabolism

Question 8

Dehydrogenase

Answer 8

Enzyme that removes hydrogen from a molecule (ie. NADH)

Question 9

Glycolysis

Answer 9

Takes place in the cytoplasmic area and oxygen independent; converts glucose (6C) into 2 pyruvate (3C) molecules; produces 2 ATP and 2 NADH; occurs in 10 steps catalyzed by a specific enzyme

Question 10

Glycolysis investment phase

Answer 10

Requires an input of 2 ATP in the first 5 steps to complete glycolysis

Question 11

Glycolysis energy payoff phase

Answer 11

4 ATP and 2 NADH are generated from the last 5 steps of glycolysis

Question 12

3 possible outcomes for pyruvate

Answer 12

Oxidative phosphorylation, lactic acid fermentation or alcohol fermentation

Question 13

Kreb’s Cycle

Answer 13

aka Citric Acid Cycle or Tricarboxlic Acid Cycle (TCA); 8 enzyme catalyzed steps producing 6 NADH, 2 FADH2, 2 ATP and releasing 4 CO2

Question 14

Pyruvate Oxidation

Answer 14

If O2 is present, pyruvate is oxidized and converted to Acetyl-CoA in the mitochondrial matrix and then combines with oxaloacetate in the Kreb’s cycle; forms 2 NADH and 2 CO2

Question 15

Electron transport chain

Answer 15

Requires a series of reactions so that energy can be captured by an endergonic reaction; energy is released as electrons (from NADH and FADH2) are passed between carriers; electrons from NADH and FADH2 are passed along the respiratory chain, a series of protein complexes in the inner mitochondrial membrane containing electron carriers and enzymes; the final electrons are donated to O2 where O2 is reduced to H2O; ATP is NOT created in this step

Question 16

Proton motive force

Answer 16

Protons are actively transported across the mitochondrial inner membrane at the same time that electrons are being passed down the ETC; protons accumulate in the intermembrane space and create a concentration gradient and charge difference creating a potential energy

Question 17

Chemiosmosis

Answer 17

Couples proton movement across a membrane with ATP synthesis using the enzyme ATP synthase (rotary motor mechanism)

Question 18

ATP Synthase

Answer 18

A rotary motor mechanism that acts as a channel allowing H+ to diffuse back into the matrix (chemiosmosis); uses the energy of the diffusion to rotate the axle and combine ADP and Pi to make ATP

Question 19

Fermentation

Answer 19

Process to continue to produce energy without undergoing oxidative phosphorylation (in the absence of O2); occurs in the cytosol; replenishes NAD+ to keep glycolysis going

Question 20

Lactic acid fermentation

Answer 20

Fermentation that uses NADH as a reducing agent to reduce pyruvate to lactate, thus regenerating NAD+ to keep glycolysis operating; when lactate builds up, the increase in [H+] lowers pH and causes muscle pain

Question 21

Alcohol fermentation

Answer 21

Pyruvate from glycolysis is converted into acetaldehyde, and CO2 is released. NADH from glycolysis is used to reduce acetaldehyde to ethanol, thus regenerating NAD+ to keep glycolysis operating.