Biology Chapter 9: Cellular Respiration

Questions and Answers

What is the difference between fermentation and cellular respiration?

Fermentation does not need oxygen, cellular respiration does.

What is the formula for the catabolic degradation of glucose by cellular respiration?

Cellular respiration and photosynthesis are both what type of reaction?

Redox reactions

What is the difference between oxidation and reduction?

LEO says GER; lose electrons oxidation, gain electrons reduction. Signup and view all the answers

What is the difference between the reducing agent and the oxidizing agent?

The oxidizing agent is the electron acceptor, whereas the reducing agent is the electron donor. Signup and view all the answers

In cellular respiration, the electrons are not transferred directly from glucose to oxygen. Each electron is coupled with a proton to form a hydrogen atom, these are held in the cell by what electron carrier?

NAD+ Signup and view all the answers

What is a coenzyme?

A coenzyme is an organic nonprotein helper for catalytic activity. Signup and view all the answers

What is the normal route that electrons follow in cellular respiration?

glucose, NADH, electron transport chain, oxygen Signup and view all the answers

What’s the general process of cellular respiration?

<ol> <li>Glycolysis (substrate level phosphorylation), 2. Citric Acid Cycle (substrate level phosphorylation), 3. Oxidative Phosphorylation (electron transport chain) and chemiosmosis</li> </ol> Signup and view all the answers

Where does glycolysis occur?

in the cytosol of the cell Signup and view all the answers

Why is glycolysis an appropriate term?

It literally means 'sugar splitting', which is what happens, glucose is split into two pyruvate molecules. Signup and view all the answers

The starting product of glycolysis is:

Glucose, a six carbon sugar Signup and view all the answers

The end product of glycolysis is:

two 3 carbon sugars, pyruvate Signup and view all the answers

What are the two stages of glycolysis?

The energy investment phase, and the energy payoff phase Signup and view all the answers

What is used in the energy investment phase of glycolysis?

Two ATP molecules are invested, with the product of 2 ADP and 2 inorganic phosphate. Signup and view all the answers

What are the products and reactants of the energy payoff stage of glycolysis?

4 ADP and 4 inorganic phosphates are used to form 4 ATP molecules. Also, 2 NAD+, 4 e-, and 4 H+ are used to form 2 NADH and 2 H+, along with 2 Pyruvate molecules and 2 H2O molecules. Signup and view all the answers

What is the net gain of energy in glycolysis? Where is most of the energy?

2 pyruvate molecules, 2 ATP, 2 NADH, and 2 H+. Most of the energy is still present in the two molecules of pyruvate. Signup and view all the answers

What is the relationship between glycolysis and oxygen?

Glycolysis does not need oxygen, it occurs without it. Signup and view all the answers

Before pyruvate enters the citric acid cycle, it must be converted to?

acetyl CoA Signup and view all the answers

Explain the process of converting pyruvate to acetyl CoA.

<ol> <li>Pyruvate's carboxyl group is removed (COO-) and is given off as CO2. 2. The remaining 2-carbon fragment is oxidized, forming acetate (CH3COO-); extracted electrons are transferred to NAD+ forming NADH. 3. Coenzyme A attaches to acetate, forming acetyl CoA, which has high potential energy.</li> </ol> Signup and view all the answers

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

2 times, once for each pyruvate. Signup and view all the answers

How many NADH's are formed from the citric acid cycle?

3 NADHs Signup and view all the answers

How many total carbons are lost as pyruvate is oxidized in the citric acid cycle?

3, released as 3 CO2 molecules Signup and view all the answers

How many FADH2 are formed in the citric acid cycle?

1 Signup and view all the answers

How many ATPs are formed in the citric acid cycle?

1 Signup and view all the answers

The citric acid cycle is performed twice; in total how many molecules of each product are formed?

6 NADH, 2 FADH2, and 2 ATP Signup and view all the answers

Explain what happens to the six carbon molecules from the original glucose molecule.

They have broken into pyruvate and then into acetyl CoA; as these molecules are oxidized, the carbon eventually is all lost as CO2. Signup and view all the answers

In the electron transport chain, as the electron travels the molecules become _ in free energy and _ in electronegativity.

lower in free energy but higher in electronegativity Signup and view all the answers

The molecule at zero free energy (end of the electron transport chain) is?

Oxygen, the lowest in free energy and highest in electronegativity Signup and view all the answers

Oxygen stabilizes the received electrons by:

Combining with two hydrogen ions to form water. Signup and view all the answers

Explain the overall concept of how ATP synthase uses the flow of hydrogen ions to produce ATP.

H+ builds up outside of the membrane (intermembrane space) and creates a hydrogen gradient. The hydrogen naturally wants to go to an area of lower concentration, so it travels back into the mitochondria matrix. As it does, it goes through the ATP synthase, causing the motor to spin and activating catalytic sites to form ATP from ADP and inorganic phosphate. Signup and view all the answers

Define chemiosmosis.

Chemiosmosis is an energy coupling mechanism that uses energy stored in the form of H+ gradient across the membrane to drive cellular work. Signup and view all the answers

Define proton motive force.

H+ gradient performs work. Signup and view all the answers

How many molecules of ATP can NADH form? FADH2?

NADH contributes to a maximum of approximately 2.5. FADH2 contributes to a maximum of approximately 1.5 molecules. Signup and view all the answers

Why does the total count of ATP produced vary?

<ol> <li>Depends on the shuttle used to carry electrons from the cytosol to the mitochondrion. NADH is more effective than FAD. 2. Not all of the energy from the proton motive force is used to create ATP.</li> </ol> Signup and view all the answers

Fermentation allows the production of ATP without __?

Oxygen or an electron transport chain Signup and view all the answers

What is the ultimate electron acceptor in fermentation since there is an absence of oxygen?

NAD+ Signup and view all the answers

Explain how alcohol fermentation starts with glucose and yields ethanol.

Glucose is made into pyruvate then acetaldehyde. This is reduced by NADH into ethanol, creating NAD+ once more (it is recycled). Signup and view all the answers

Explain how lactic acid fermentation starts with glucose and yields lactate.

Glucose to pyruvate, reduced by NADH to make lactate. (no CO2 release) NADH reducing pyruvate creates NAD+ again. Signup and view all the answers

What three organic molecules are often utilized to make ATP in cellular respiration?

Proteins, carbohydrates, and fats Signup and view all the answers

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is:

H+ concentration across the membrane that holds the ATP synthase Signup and view all the answers

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

Glycolysis Signup and view all the answers

In mitochondria, exergonic redox reactions ___

provide the energy needed to establish the proton gradient Signup and view all the answers

The final electron acceptor of the electron transport chain in aerobic oxidative phosphorylation is?

Oxygen Signup and view all the answers

What is the oxidizing agent in lactic acid fermentation?

Pyruvate Signup and view all the answers

When electrons flow along the electron transport chains of the mitochondria, what change occurs?

The pH of the matrix increases. Signup and view all the answers

Most CO2 from catabolism is released during:

the citric acid cycle Signup and view all the answers

Why is the citric acid cycle called a cycle?

The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle. Signup and view all the answers

During glycolysis, which molecule has the most chemical energy?

Fructose-1,6-bisphosphate Signup and view all the answers

If mice were fed glucose with radioactive oxygen, where would this oxygen appear again in a few minutes?

As carbon dioxide (by-product of cellular respiration) Signup and view all the answers

A molecule becomes more oxidized when it__?

loses an electron Signup and view all the answers

Most of the ATP produced in cellular respiration comes from which of the following processes?

Oxidative phosphorylation Signup and view all the answers

A chemist has discovered a drug that blocks an enzyme that catalyzes the second reaction of glycolysis. Why is this a bad idea?

Human cells also perform glycolysis and the drug will poison them as well. Signup and view all the answers

Most of the NADH that delivers electrons to the electron transport chain comes from which part of cellular respiration?

The citric acid cycle (6 molecules produced) Signup and view all the answers

What accompanies the conversion of pyruvate to acetyl CoA before the citric acid cycle?

The release of CO2 and the synthesis of NADH Signup and view all the answers

In preparing pyruvate to enter the citric acid cycle, what steps occur?

Pyruvate is oxidized and decarboxylated; then the removed electrons are used to reduce NAD+ into NADH. Signup and view all the answers

What is reduced in cellular respiration?

Oxygen Signup and view all the answers

The function of cellular respiration is to:

extract usable energy from glucose Signup and view all the answers

Why is oxygen one of the strongest oxidizing agents known?

It is extremely electronegative Signup and view all the answers

Where do the reactions of the citric acid cycle occur in eukaryotic cells?

the matrix of the mitochondrion Signup and view all the answers

A small amount of ATP is made in glycolysis when?

Transfer of a phosphate group from a fragment of glucose to ADP by substrate level phosphorylation. Signup and view all the answers

What happens to the energy in glucose that does not become ATP?

It is converted/released as heat. Signup and view all the answers

After the completion of the citric acid cycle, most usable energy is in the form of?

NADH Signup and view all the answers

How many molecules of ATP are gained by substrate level phosphorylation in cellular respiration?

4 Signup and view all the answers

What happens in a closed room full of people?

Temperature rises and CO2 levels rise. These are products of cellular respiration. Signup and view all the answers

In cellular respiration, what is oxidized and what is reduced?

Glucose is oxidized and oxygen is reduced. Signup and view all the answers

Why is there no production of carbon dioxide in glycolysis?

The products of glycolysis have the same total number of carbon atoms as the glucose started with. Signup and view all the answers

What are most of the electron carriers in the electron carrier chain?

Most of them are proteins called cytochromes. They have a heme group with an iron atom that accepts and donates electrons. Signup and view all the answers

What are obligate anaerobes?

They carry out only fermentation or anaerobic respiration. Cannot survive in the presence of oxygen. Signup and view all the answers

What are facultative anaerobes?

Many yeasts and bacteria; they use both fermentation and respiration. Signup and view all the answers

What is beta oxidation?

The process in which fatty acids are broken down to two-carbon fragments that enter the citric acid cycle as acetyl CoA. Signup and view all the answers

Where is the electron transport chain for cellular respiration located?

the inner membrane of the mitochondria (the cristae) Signup and view all the answers

Study Notes

Differences Between Fermentation and Cellular Respiration

Fermentation is anaerobic, requiring no oxygen; cellular respiration is aerobic, requiring oxygen.

Cellular Respiration and Photosynthesis

Both processes involve redox reactions, essential for energy transfer.

Oxidation and Reduction

Oxidation: Loss of electrons (LEO); Reduction: Gain of electrons (GER).

Electron Transport in Cellular Respiration

Electrons move from glucose to NAD+, forming NADH, which carries them to oxygen through the electron transport chain.

Coenzymes

Coenzymes assist enzymatic functions; NADH is a coenzyme derived from niacin.

Glycolysis Pathway

The typical electron pathway in cellular respiration is glucose → NADH → electron transport chain → oxygen.

Glycolysis Overview

Glycolysis involves substrate-level phosphorylation to convert glucose into pyruvate, yielding 2 ATP and NADH.

Location of Glycolysis

Occurs in the cytosol, where glucose splits into two pyruvate molecules.

Energy Investment and Payoff in Glycolysis

Initial investment of 2 ATP during the energy investment phase with a payoff of 4 ATP, 2 NADH, and pyruvate formation.

Pyruvate Conversion

Pyruvate must be converted to acetyl CoA before entering the citric acid cycle, releasing CO2 and forming NADH.

Citric Acid Cycle

The cycle occurs twice per glucose molecule, producing 6 NADH, 2 FADH2, and 2 ATP while releasing CO2.

Electron Transport Chain

As electrons travel through the chain, free energy decreases and electronegativity increases, with oxygen as the final electron acceptor.

Production of ATP

ATP synthase utilizes the H+ gradient across the membrane to generate ATP through oxidative phosphorylation.

Chemiosmosis

The process of using the H+ gradient to perform cellular work, crucial for ATP production.

Variability in ATP Yield

ATP yield from NADH (approx. 2.5) and FADH2 (approx. 1.5) varies based on electron shuttle efficacy and energy utilization from the proton motive force.

Fermentation Process

Fermentation produces ATP without oxygen by recycling NAD+; pyruvate is converted to either ethanol or lactate.

Carbon Dioxide in Cellular Respiration

Most CO2 is released during the citric acid cycle, reflecting the breakdown of glucose.

Strong Oxidizing Agent

Oxygen, due to its high electronegativity, is known as one of the strongest oxidizing agents.

Substrate-Level Phosphorylation

Small amounts of ATP are formed by directly transferring phosphate groups during glycolysis and the citric acid cycle.

Mitochondrial Function

The citric acid cycle reactions occur in the mitochondrial matrix, where the majority of NADH accumulates for electron transport.

Anaerobes

Obligate anaerobes only engage in fermentation or anaerobic respiration, while facultative anaerobes can switch between fermentation and respiration based on oxygen availability.

Fatty Acid Metabolism

Beta oxidation is the process where fatty acids are converted into acetyl CoA for entry into the citric acid cycle.

Location of Electron Transport Chain

The electron transport chain is located in the inner mitochondrial membrane (cristae), integral to ATP production and energy metabolism.

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Test your knowledge on the key concepts of cellular respiration and fermentation with these flashcards. Learn the differences between aerobic and anaerobic processes, and understand the formulas and definitions related to glucose degradation and energy production.