Cellular Respiration and Metabolism

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Questions and Answers

What is the primary purpose of glycolysis?

To convert pyruvate into lactic acid

To utilize oxygen for ATP production

To break down glucose into two molecules of pyruvate (correct)

To synthesize glucose from pyruvate

Where in the cell does glycolysis occur?

On the outer membrane

In the nucleus

In the cytosol (correct)

In the mitochondria

Which phase of glycolysis requires an investment of energy?

Oxidation phase

Energy investment phase (correct)

Energy payout phase

Activation phase

What happens to pyruvate in the presence of oxygen?

It enters the mitochondrial matrix for further processing Signup and view all the answers

Which structure within the mitochondria is involved in ATP synthesis through chemiosmosis?

Inner membrane Signup and view all the answers

How many enzyme-catalyzed steps are involved in glycolysis?

10 Signup and view all the answers

What characterizes the outer mitochondrial membrane?

It allows passage of molecules less than 5000 daltons Signup and view all the answers

Which process occurs in the mitochondrial matrix?

Pyruvate oxidation Signup and view all the answers

What role does the proton gradient play in ATP synthesis?

It powers ATP synthesis via ATP synthase. Signup and view all the answers

What is the primary location of the electron transport chain (ETC) in eukaryotic cells?

Inner membrane Signup and view all the answers

What is the consequence of cyanide acting as an inhibitor of ETC Complex IV?

Electrons can't be transferred to oxygen. Signup and view all the answers

Which of the following compounds carries electrons from food during cellular respiration?

FADH2 Signup and view all the answers

How many ATP molecules can each cell produce per second?

10 million Signup and view all the answers

What is the result of no energy being available to pump protons to the intermembrane space?

No proton gradient will build up. Signup and view all the answers

What process occurs simultaneously with ATP synthesis at various sites within the cell?

Chemiosmosis Signup and view all the answers

How is ATP synthesized from ADP and inorganic phosphate (P_i)?

Use of proton gradient energy via ATP synthase. Signup and view all the answers

What is the net yield of ATP from glycolysis per molecule of glucose?

2 ATP Signup and view all the answers

Which pathway in cellular respiration is responsible for the majority of ATP production?

Oxidative Phosphorylation Signup and view all the answers

What is the total theoretical maximum yield of ATP per molecule of glucose across all pathways in cellular respiration?

30-32 ATP Signup and view all the answers

Which of the following statements about the efficiency of glucose metabolism is correct?

Cellular respiration achieves around 40% efficiency. Signup and view all the answers

Which of the following products is NOT produced during glycolysis?

FADH2 Signup and view all the answers

Which statement about glycolysis is false?

It requires the presence of oxygen. Signup and view all the answers

What is the primary process that occurs during oxidative phosphorylation?

Electron transport chain function Signup and view all the answers

What is the primary function of catabolic pathways in metabolism?

To yield energy through the breakdown of organic fuels Signup and view all the answers

Which polysaccharide serves as the main glucose storage molecule in animals?

Glycogen Signup and view all the answers

What is produced as a byproduct of glucose oxidation?

Carbon dioxide Signup and view all the answers

Which statement is true about glucose?

It is a polar molecule and soluble in water. Signup and view all the answers

What occurs during an exergonic reaction involving glucose?

Energy is released as products form. Signup and view all the answers

How do anabolic pathways contribute to metabolism?

They synthesize larger molecules from smaller building blocks. Signup and view all the answers

What is the general equation for glucose oxidation?

$C_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O + Energy$ Signup and view all the answers

Which characteristic of glucose allows it to be an effective energy source in the body?

It undergoes exergonic reactions. Signup and view all the answers

What is one of the primary purposes of metabolic pathways?

Elimination of waste Signup and view all the answers

What is the role of ATP in cellular processes?

It serves as an energy carrier molecule Signup and view all the answers

Which statement accurately describes the interconnectivity of metabolic pathways?

Various organic molecules enter the same cellular respiration pathway Signup and view all the answers

How many pathways are primarily involved in cellular respiration?

Four Signup and view all the answers

In what form is glucose stored in animals?

Glycogen Signup and view all the answers

What was NOT mentioned as an aspect of the learning objectives?

Identify the sites of ribosome production Signup and view all the answers

Which of the following is considered a catabolic reaction?

Breakdown of glucose to release energy Signup and view all the answers

Which of the following statements best describes anabolic reactions?

They involve the synthesis of complex molecules. Signup and view all the answers

Study Notes

Glycolysis

Breaks down glucose into two pyruvate molecules
Occurs in the cytosol
Independent of oxygen
Involves ten enzyme-catalyzed steps
Two major phases - energy investment phase and energy payoff phase

Mitochondria - Powerhouse of the Cell

Outer membrane
- Permeable to molecules larger than 5000 daltons
Intermembrane space
- Site of H+ accumulation
Inner membrane
- Site of the electron transfer chain and ATP synthase
Matrix
- Pyruvate oxidation and the citric acid cycle occur here

Pyruvate Oxidation

Occurs in the mitochondrial matrix (eukaryotes)
An enzyme complex catalyzes three reactions

Metabolism

Set of life-sustaining chemical reactions that take place in a living organism
Catabolic pathways break down larger molecules into smaller building blocks
Anabolic pathways assemble larger molecules from smaller building blocks
Useful energy and building blocks for biosynthesis are locked in organic molecules

Glucose

The primary metabolic fuel of the body
A polar molecule soluble in water
Transported in the bloodstream to cells for use as an energy source
Stored in the form of polysaccharides - starch in plants and glycogen in animals

Oxidation of Glucose

Releases a lot of energy
- C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
- ΔG⁰’ = -2880 kJ/mol (exergonic, energy released)

Oxidative Phosphorylation

The energy released from glucose is used to create a proton (H+) gradient across the inner membrane
The electrochemical and concentration gradient powers ATP synthesis through the enzyme ATP synthase
Occurs in two stages:
- Electron transport chain
- Chemiosmosis

Chemiosmosis

ATP synthesis occurs simultaneously at many sites
Each cell can produce 10 million ATP molecules per second

Interesting Fact: How does Cyanide Kill?

Cyanide is a highly effective reversible inhibitor of ETC Complex IV
Electrons cannot be transferred to oxygen and redox reactions in the ETC will stop
No energy will be available to pump protons to the intermembrane space
Therefore, ATP production stops leading to cardiac and respiratory arrest!

Efficiency of Glucose Metabolism

Fermentation (anaerobic)
- Substrate-level phosphorylation in glycolysis yields 2 ATP
- Efficiency is approximately 2%
Cellular respiration (aerobic)
- Substrate-level and oxidative phosphorylation yield 30-32 ATP
- Efficiency is approximately 40%!

Clicker Question Responses

Clicker Question 1: The correct order of the four pathways involved in cellular respiration in the presence of oxygen is: Glycolysis, pyruvate oxidation, citric acid cycle, and oxidative phosphorylation.
Clicker Question 2: The false statement concerning glycolysis is: The end products are carbon dioxide and water. The end products of glycolysis are pyruvate and ATP,
Clicker Question 3: The option that will decrease glycolysis is: Decreased activity of enzyme 3 or 6.
- Decreased activity of enzyme 3 or 6 will block glycolysis, preventing the formation of ATP.

Metabolic Pathway Interconnectivity

Glycolysis and the citric acid cycle constitute a small fraction of the reactions that occur in a cell.
Pathways have dedicated purposes:
- Energy extraction
- Fuel storage
- Building block synthesis
- Waste elimination

Learning Objectives & Overview of Glucose Metabolism

At the end of the lesson, learners should be able to explain the flow of energy in living systems, describe the role of ATP, and list the four pathways involved in cellular respiration.
Learners should also be able to explain two ways in which metabolic pathways are regulated, appreciate the interconnection of metabolic pathways, and understand different metabolic fates of various organic molecules.
Glycogen is the storage form of glucose in animals.

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Description

Test your knowledge on glycolysis, pyruvate oxidation, and the mitochondria's role in cellular respiration. This quiz covers the metabolic processes involved in breaking down glucose and the various pathways that sustain life. Challenge yourself to understand the energy transformation processes that occur within cells.