Chapter 7 Cellular Respiration and Fermentation

Explain the difference between fermentation and cellular respiration.

Fermentation: Does not require oxygen, Yields less ATP (2), breaks down glucose into organic molecules like lactic acid or ethanol, an organic molecule is the final electron acceptor, occurs in cytoplasm

Cellular Respiration: Requires oxygen, Yields up more ATP (30-32), completely breaks down glucose into CO2 and water, oxygen in the final electron acceptor, occurs in cytoplasm and mitochondria

Write the summary equation for cellular (aerobic) respiration. Write the specific chemical equation for the degradation of glucose.

C₆H₁₂O₆ + 6 O₂  —> 6 CO₂ + 6 H₂O + Energy
Organic compounds + oxygen —> carbon dioxide + water + energy

Define Oxidation (OIL)

Oxidation is the loss of an electron

Oxidation Is Loss

Describe the role of NAD+ in cellular respiration

It acts as an electron carrier and its where hydrogens are held in the cell temporarily.

In general terms, explain the role of the electron transport chain in cellular respiration

NADH passes electrons to the electron transport chain, from which they eventually combine with hydrogen ions and oxygen to form water.

Name the three stages of cellular respiration and state the region of the eukaryotic cell where each stage occurs.

1.Glycolysis → cytosol

2.Citric acid cycle and Pyruvate oxidation → mitochondrial matrix

3.Oxidative phosphorylation → inner mitochondrial membrane

Explain why ATP is required for the preparatory steps of glycolysis.

Two molecules of ATP are consumed as glucose is split into two three-carbon sugars.The conversion of these molecules to pyruvate produces two NADH and four ATP by substrate-level phosphorylation.

Identify the second form of phosphorylation, substrate-level phosphorylation

The enzyme has two space for a Substrate-P + ADP → Substrate + ATP

Distinguish between substrate level phosphorylation and oxidative phosphorylation.

Substrate level phosphorylation: ATP is made by a direct transfer of a phosphate group from an organic substrate to ADP by an enzyme

Oxidative phsophorylation: ATP is generated by using energy derived from redox reactions of an electron transport chain

What is the role of the electron transport chain in forming a proton(H+) gradient

The electron transport chain creates the proton gradient by using energy from electron transfers to pump H+ across the inner memebrane

Distinguish between fermentation and anaerobic respiration.

Fermentation: Occurs without oxygen, is the partial degradation of sugars to release energy; A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.

Anaerobic respiration: The use of inorganic molecules other than oxygen to accept electrons at the "downhill" end of electron transport chains.

State the basic function of fermentation

A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.

Compare the fate of pyruvate in alcohol fermentation and lactic acid fermentation

In alcoholic fermentation, pyruvic acid is converted to ethanol. Carbon dioxide is released, and NADH is recycled into NAD+. In lactic acid fermentation, pyruvic acid is converted to lactic acid. NADH is recycled into NAD+

Compare the processes of fermentation and cellular respiration

Fermentation is the process of deriving energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound.

This is in contrast to cellular respiration, where electrons are donated to an exogenous electron acceptor, such as oxygen, via an electron transport chain

Describe how food molecules other than glucose can be oxidized to make ATP

Each NADH and FADH2 molecule formed represents stored energy... contain high energy electrons from food molecules which are carried to an electron transport chain; Plants manufacture their own food by photosynthesis using energy from sunlight. Cells harvest the chemical energy stored in organic molecules and use it to regenerate ATP, the molecule that drives most cellular work. ADP + P + energy ATP

Explain how glycolysis and the citric acid cycle can contribute to anabolic pathways

Glycolysis and the citric acid cycle contribute by making ATP, they also generate electrons for the Electron Transport Chain (ETC). The ETC then uses those electrons to make a proton gradient in the mitochondria which in turn powers the enzyme ATP-synthase to make a whole bunch of ATP.

Define reduction (RIG)

The addition of electrons
Reduction Is Gain

When compounds lose electrons, they _________ energy

Lose

When compounds gain electrons, they _________ energy.

Gain

What happens in Glycolysis(Stage 1)?

It breaks down glucose into 2 molecules of pyruvate

What happens in Citric Acid cycle and Pyruvate Oxidation(Stage 2)?

Completes breakdown of glucose

What happens in Oxidative phosphorylation?

Electron transport chain and Chemiosmosis - accounts for most of ATP synthesis

The normal, “downhill” route  most electrons follow in cellular respiration

Glucose → NADH → Electron Transport Chain → Oxygen 

Why is glycolysis an appropriate term for this step in cellular respiration?

Glycolysis means “sugar splitting” which is what happens in this pathway.
Glucose(6-carbon sugar) splits into → Two 3 - Carbon sugars

What is the starting and ending product of glycolysis

6-carbon sugar (glucose) → two 3-carbon compounds (pyruvate)

Energy investment phase (First phase of glycolysis)

What is the glycolysis net results?

Glucose(goes through glycolysis) → 2 pyruvate + 2 ATP + 2NADH

Notice that glycolysis occurs in the cytosol of the cell. What is the relationship concerning glycolysis and oxygen

Glycolysis occurs whether or not O₂ is present (meaning it doesnt require oxygen).

However, if O₂ is present, the chemical energy stored in pyruvate and NADH can be extracted by pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation (the rest of the steps in cellular respiration)

How many times does the citric acid cycle occur for each molecule of glucose

It occurs 2 times

How many NADHs are formed from a pyruvate molecule?

4 NADH

How many total carbons are lost as pyruvate is oxidized?

3 Carbons

The carbons have been lost in the molecule called __________ __________ .

Carbon dioxide

How many FADH2 have been formed?

1 FADH2

How many ATPs are formed?

1 ATP

Explain why oxygen is the ultimate electron acceptor. Oxygen stabilizes the electrons by combining

with two hydrogen ions to form what compound?

Oxygen is the final electron acceptor because it is very electronegative. It stabilizes the electrons with 2 hydrogen ions to form water

The two electron carrier molecules that feed electrons into the electron transport system are

________________ and __________________.

NADH and FADH2

Chemiosmosis

process in which energy stored in the form of a hydrogen ion gradient across the membrane is used to drive cellular work

Proton-motive force

energy stored in proton gradient across a membrane
H⁺ gradient created by ETC

• Drives ATP synthase

How does Chemiosmosis and Proton-motive force relate to the process of oxidative phosphorylation?

The proton-motive force is the energy source, and chemiosmosis is the process that uses that energy to make ATP

What is the electron acceptor in fermentation?

An organic molecule, typically pyruvate or a derivitave

Why ATP yield is not exact

• NADH → ATP ratio varies

• Different shuttle systems give different yields

• Proton-motive force powers other work

Why glycolysis is ancient

• Occurs in all organisms

• Occurs in cytosol (no organelles needed)

• Predates oxygen in the atmosphere