Carbohydrate Metabolism and Respiration

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Questions and Answers

What is the net gain of ATP molecules produced during glycolysis?

4 ATP molecules

1 ATP molecule

2 ATP molecules (correct)

3 ATP molecules

Which carbohydrate is primarily utilized as the body’s preferred energy source?

Galactose

Glycogen

Fructose

Glucose (correct)

Where does glycolysis occur within the cell?

Mitochondria

Ribosomes

Cytosol (correct)

Nucleus

What process converts fructose and galactose into glucose in the body?

Hepatic conversion Signup and view all the answers

What is the first step of cellular respiration?

Glycolysis Signup and view all the answers

What molecule is formed from pyruvate in anaerobic conditions?

Lactic acid Signup and view all the answers

What is the net gain of ATP during anaerobic respiration?

2 molecules Signup and view all the answers

What is the role of NAD+ during anaerobic respiration?

To regenerate and be reused in glycolysis Signup and view all the answers

What happens to pyruvate in the presence of oxygen?

It is converted to acetyl CoA Signup and view all the answers

Which of the following is a product of the Krebs cycle?

NADH+H+ Signup and view all the answers

How many ATP molecules are directly produced from the Krebs cycle?

1 Signup and view all the answers

Which substance serves as the final electron acceptor in the electron transport chain?

Oxygen Signup and view all the answers

What is produced as a byproduct of aerobic respiration?

Carbon dioxide and water Signup and view all the answers

What is the primary role of the proton pump in the electron transport chain?

To push H+ ions out of the mitochondria Signup and view all the answers

How many ATP molecules can the liver, kidney, and heart cells generate during glycolysis compared to other cells?

6 ATP in liver cells, 4 ATP in others Signup and view all the answers

What type of molecules do lipids provide more energy compared to glucose?

Fats Signup and view all the answers

What is the cumulative ATP yield from glycolysis, the Krebs cycle, and the electron transport chain in total?

36 or 38 ATP Signup and view all the answers

What happens to H+ ions during oxidative phosphorylation?

They accumulate outside the membrane Signup and view all the answers

Study Notes

Carbohydrate Metabolism and Cellular Respiration

Carbohydrates exist as monosaccharides, disaccharides, or polysaccharides
Polysaccharides must be hydrolysed to form monosaccharides (glucose, fructose, and galactose) for energy to be used
Glucose makes up 80% of monosaccharides, while fructose and galactose make up the remaining 20%
Fructose and galactose are converted to glucose by the liver
Blood glucose is maintained at approximately 5.6 mmol/L (100 mg/dL) by homeostatic mechanisms
Glucose is the body's preferred energy source for ATP production, but it also supports amino acid, glycogen, and triglyceride synthesis

Learning Outcomes

Students should be able to describe how carbohydrates are used as an energy source
Students should be able to describe glycolysis and where it occurs
Students should be able to identify the formation of acetyl CoA
Students should be able to describe the citric acid cycle and where it occurs
Students should describe oxidative phosphorylation through the electron transport chain and where it occurs

Glucose Movement into a Cell

Glucose must enter a cell before it can be used
Glucose passes through the plasma membrane into the cytosol
Cell markers allow glucose to enter the cell, and these markers are then altered to prevent glucose from leaving the cell

Glucose Catabolism

The oxidation of glucose to produce ATP is called cellular respiration
Cellular respiration involves four steps: glycolysis, formation of acetyl coenzyme A, Krebs cycle, and electron transport chain

Glycolysis

Glycolysis is the breakdown of glucose
Chemical reactions split the 6-carbon glucose molecule into two 3-carbon pyruvic acid (pyruvate) molecules
The splitting of glucose requires 2 ATP molecules
Glycolysis produces 4 ATP molecules for a net gain of 2 ATP
If ADP levels are high, glycolysis happens quickly to make ATP. If ADP levels are low, glucose is converted into glycogen

Anaerobic Respiration

During strenuous exercise, pyruvate is reduced by the addition of 2 hydrogen atoms to create lactic acid
2 pyruvate + 2 NADH + 2H⁺ → 2 lactic acid + 2 NAD⁺
The NAD+ can be reused in glycolysis
The net gain of ATP in anaerobic respiration is small (only 2 molecules)
Lactic acid accumulation leads to muscle fatigue

What Happens to Pyruvate?

Depending on oxygen availability, pyruvate can be used either in anaerobic or aerobic respiration
Anaerobic respiration occurs in the absence of oxygen
Aerobic respiration occurs in the presence of oxygen

Formation of Lactate

Lactate is produced in muscles when the oxygen concentration is low
Lactate production regenerates NAD+ and allows anaerobic energy production to proceed

Aerobic Respiration

In the presence of oxygen, pyruvate is converted to acetyl coenzyme A (acetyl CoA) in the mitochondria
Acetyl CoA enters the Krebs cycle (citric acid cycle) in the mitochondria
The Krebs cycle involves oxidation-reduction and decarboxylation reactions, releasing CO₂
The reactions yield ATP, CO₂, NADH⁺H⁺, and FADH₂
The production of NADH⁺H⁺ and FADH₂ is crucial for ATP generation (more ATP is generated later)
Only 1 ATP is produced directly from the Krebs cycle

Krebs Cycle (Citric Acid Cycle)

The Krebs cycle is a series of oxidation-reduction and decarboxylation reactions in the mitochondria
The cycle processes acetyl CoA and results in the production of CO₂, ATP, NADH⁺H⁺, and FADH₂

Oxidative Phosphorylation and the Electron Transport Chain

This is a series of electron carriers (membrane proteins) in the mitochondrial membrane
Electrons are passed from one carrier to the next, releasing energy
The released energy is used to form ATP from ADP
Electron carriers power a proton pump, pushing H⁺ out of the mitochondria
H⁺ builds up outside the membrane
H⁺ re-enters the mitochondria through a specialized channel, driving ATP formation
Oxygen is the final electron acceptor, forming H₂O

Aerobic Respiration Summary

Glycolysis, the Krebs cycle, and the electron transport chain produce 36 or 38 ATP molecules
Liver, kidney, and heart cells produce 6 ATP molecules in glycolysis
Other cells produce 4
The products of aerobic respiration are CO₂ and H₂O

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Description

This quiz covers the essentials of carbohydrate metabolism, including the roles of monosaccharides, disaccharides, and polysaccharides. Students will explore glycolysis, the citric acid cycle, and the biochemical mechanisms behind energy production from carbohydrates. Understanding these processes is crucial for studying cellular respiration.