BIO 200 Exam 3

Fermentation

partial degradation of sugars that happens without oxygen

Aerobic respiration

consumes organic molecules and oxygen and yields ATP

cellular respiration

includes both aerobic and anaerobic respiration but mostly refers to aerobic
C₆H₁₂O₆ + 6O₂ —> 6CO₂ + 6H₂O + Energy

Redox reactions

chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions

1. oxidation

2. reduction

Oxygen

is the final electron acceptor, meaning that it is always accepting H

Oxidation reaction

loss of electrons from a substance

Reduction reaction

addition of electrons to a substance

Electron carrier

reducing agent

Electron donor

oxidizing agent (positive charge goes down)

Electron transport chain

consists of a series of molecules built into the inner membrane of the mitochondria

Stages of Cellular Respiration

1. Glycolysis - breaks down glucose into 2 molecules of pyruvate

2. Pyruvate and citric acid cycle - complete the breakdown of glucose to CO₂

3. oxidation phosphorylation - most ATP is made here because it is powered by redox reactions

substrate phosphorylation level

occurs when an enzyme transfers a phosphate group directly from a substrate to ADP

Glycolysis

Occurs in the cytoplasm with or without the presence of oxygen and has two phases

1. energy investment phase - 2 ATP are used to split glucose into 2 three-carbon sugar molecules

2. energy payoff phase - 4 ATP are synthesized, 2 NAD+ are reduced to NADH, the small sugars are oxidized to form 2 pyruvate and 2 H2O

Net products of glycolysis

1. 2 ATP

2. 2 NADH

3. 2 pyruvate

pyruvate oxidation

Pyruvate is converted to acetyl CoA before entering the citric acid cycle

Pyruvate dehydrogenase catalyzes three reactions

1. Oxidation of pyruvate’s carboxyl group, releasing the first CO2 of cellular respiration

2. Reduction of NAD+ to NADH

3. Combination of the remaining two-carbon fragment with coenzyme A to form acetyl CoA

Citric Acid Cycle

oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn

Another 2 CO2 are produced as a waste product

oxidative phosphorylation

NADH and FADH2 produced during glycolysis and the citric acid cycle account for most of the energy extracted from glucose

Chemiosmosis

the use of energy in a H⁺ gradient to drive cellular work

electron transport chain

1. NADH is oxidized into FADH₂

2. FADH is oxidized into FAD

3. electrons released - all electrons buildup and are released in chemiosmosis where a lot of ATP is made

4. water is made - not technically apart of electron transport

Cellular respiration energy flow

glucose —> NADH —> electron transport chain —> proton motive force —> ATP

Fermentations

Fermentation is an extension of glycolysis that oxidizes NADH by transferring electrons to pyruvate or its derivatives

1. Lactic acid fermentation

2. alcohol fermentation

alcohol fermentation

pyruvate is converted to ethanol in two steps

1. The first step releases CO2 from pyruvate

2. The second step produces NAD+ and ethanol

lactic acid fermentation

pyruvate is reduced directly by NADH to form lactate and NAD+

1. There is no release of CO2 in lactic acid
   fermentation

Differences between cellular respiration and fermentation

1. fermentation makes a lot less ATP because there is no oxidative phosphorylation

2. In fermentation, an organic molecule (pyruvate or acetaldehyde) acts as a final electron acceptor

3. In cellular respiration, electrons are transferred to the
   electron transport chain

obligate anaerobes

carry out anaerobic respiration or fermentation and cannot survive in the presence of O₂

facultative anaerobes

yeast and many bacteria can survive using either fermentation or cellular respiration - prefers fermentation