Metabolism: Catabolism and Anabolism

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Questions and Answers

What is metabolism also known as?

Cellular response

Biochemical pathway

Biochemical reaction

Biotransformation (correct)

What is the main difference between catabolic and anabolic reactions?

Catabolic reactions consume energy, while anabolic reactions produce energy

Catabolic reactions produce energy, while anabolic reactions consume energy

Catabolic reactions occur in the mitochondria, while anabolic reactions occur in the cytosol

Catabolic reactions involve breakdown of molecules, while anabolic reactions involve synthesis of molecules (correct)

What is the net product of glycolysis in terms of ATP molecules?

8 ATP molecules

6 ATP molecules

4 ATP molecules

2 ATP molecules (correct)

What is the function of phosphofructokinase 1 enzyme in glycolysis?

It mediates flux through the glycolytic pathway Signup and view all the answers

What is the byproduct of glycolysis that can be used to generate ATP in subsequent reactions?

NADH and ATP Signup and view all the answers

What is the purpose of the first step in glycolysis, where glucose is phosphorylated to glucose-6-phosphate?

To activate glucose for metabolism Signup and view all the answers

What is the end product of glycolysis that can be further metabolized in aerobic respiration?

Pyruvate Signup and view all the answers

What is the meaning of NAD in NADH?

Nucleotide Adenine Dinucleotide Signup and view all the answers

What happens to glucose in the first stage of glycolysis?

It is activated for metabolism and rearranged to form 2x 3C sugars Signup and view all the answers

Where does anaerobic respiration occur?

In muscle during anaerobic exercise Signup and view all the answers

What is the result of the Cori Cycle?

Recycling of R-lactate to glucose Signup and view all the answers

How many ATP are needed for the Cori Cycle?

6x ATP per glucose molecule Signup and view all the answers

What enzyme converts R-lactate to pyruvate?

Lactate dehydrogenase Signup and view all the answers

What is gluconeogenesis?

The biosynthesis of glucose from non-carbohydrate precursors Signup and view all the answers

Where does gluconeogenesis occur?

In liver cytosol Signup and view all the answers

What is the role of pyruvate carboxylase?

To control the balance between degradation and synthesis of glucose Signup and view all the answers

Study Notes

Metabolism

Metabolism is the interconversion of biomolecules using chemical reactions, also known as biotransformation.
It can be subdivided into catabolism and anabolism.

Catabolism

Catabolic degradation reactions produce:
- Chemical energy (ATP)
- Ion gradients
- Mechanical energy (muscle contraction)
- Reducing agents (NADH and NADPH)

Anabolism

Anabolic (biosynthetic) reactions:
- Store energy
- Produce macromolecules and cellular structures

Metabolic Reactions

Biological reactions are in a state of flux.
Many reactions are endothermic and unfavourable, so they need energy from ATP hydrolysis.
Metabolism needs to balance energy (ATP), reducing agents, and the amounts of small molecules.

Biosynthetic Reactions

Typically convert between reduced and oxidized forms.
NAD stands for Nucleotide Adenine Dinucleotide.

Glycolysis

Glycolysis is the degradation of glucose in the cytosol.
It consists of 3 stages.

First Half of Glycolysis

Glucose is phosphorylated to Glucose-6-phosphate.
Glucose-6-phosphate is isomerized to Fructose-6-phosphate.
Fructose-6-phosphate is converted to Fructose-1,6-bisphosphate.

Second Half of Glycolysis

Fructose-1,6-bisphosphate is converted to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.
Dihydroxyacetone phosphate is converted to glyceraldehyde-3-phosphate.
Each step is repeated twice as 2x glyceraldehyde-3-phosphate molecules are generated for each glucose molecule.

Net Products of Glycolysis

2 ATP
2 NADH
2 pyruvate

Control Factor in Glycolysis

Phosphofructokinase 1 enzyme mediates flux through the glycolytic pathway.

Anaerobic Respiration

Occurs in muscle during anaerobic exercise.
Pyruvate is reduced to R-lactate in the absence of oxygen.
NADH is oxidized to NAD+, which allows glycolysis to continue under anaerobic conditions.
R-lactate can be reoxidized to pyruvate using NAD+.

Cori Cycle

Recycles R-lactate to glucose.
Steps:
- Lactate is transported from muscle to liver in the blood.
- Lactate is converted to pyruvate by lactate dehydrogenase.
- Pyruvate is converted to glucose by gluconeogenesis in the liver.
6 ATP are needed for the Cori Cycle, with 2 ATP coming from glycolysis.

Gluconeogenesis

Biosynthesis of glucose from non-carbohydrate precursors in liver cytosol.
Occurs in liver cytosol, with the exception of the oxaloacetate step, which occurs in liver mitochondria.
Steps:
- R-lactate is converted to pyruvate.
- ATP, CO2, and pyruvate make oxaloacetate in mitochondria.
- Oxaloacetate is exported to cytosol and converted to phosphoenolpyruvate.
- Bisphosphatase and phosphatase convert fructose-1,6-bisphosphate to glucose.

Enzymes

Lactate dehydrogenase converts R-lactate to pyruvate.
Pyruvate carboxylase controls the balance between degradation and synthesis of glucose.
Phosphatase allows the export of glucose to other tissues.

Mitochondria

Roles:
- Aerobic respiration
- Deamination and urea formation

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Description

Learn about the process of metabolism, its subdivision into catabolism and anabolism, and the roles of these reactions in energy production and macromolecule synthesis.