Human Physiology Week 3 - Metabolism Study Guide

Study Notes

Energy Production and ATP

ATP (adenosine triphosphate) is the primary energy currency of the cell.
Energy released from breaking phosphate bonds in ATP can be used to drive chemical reactions and generate heat.
ATP can be produced through different pathways:
- Combustion of carbohydrates:
  - Glycolysis: breakdown of glucose to pyruvate
  - Citric acid cycle: further breakdown of pyruvate to carbon dioxide
- Combustion of fatty acids: Beta-oxidation
- Combustion of proteins: breakdown to amino acids, eventually contributing to energy production

Phosphocreatine

Acts as an immediate energy source for ATP production.
Reversible reaction: Phosphocreatine + ADP ↔ ATP + Creatine
- Moves rightward when ATP levels are depleted to maintain high ATP levels.
- Moves leftward when ATP demand is low to resynthesize phosphocreatine.
Known as "creatine phosphate".

Glycolysis

Breakdown of glucose to pyruvate, producing ATP.
Yields:
- 2 ATP molecules if glucose is used.
- 3 ATP molecules if glycogen is used (better source of energy).

Anaerobic ATP Production

Sources:
- Existing ATP in the cell (~1 second)
- Phosphocreatine (5-10 seconds)
- Glycolysis (~30-60 seconds)

Body's Energy Sources

Fat mass is the most abundant energy source.
Glycogen is the storage form of glucose, found in the liver, skeletal muscle, and kidneys.
Glucose is found in the bloodstream.
Protein is abundant but not typically used for ATP production.

Blood Glucose Regulation

Key hormones:
- Insulin:
  - Takes glucose from the blood and stores it as glycogen in muscle, adipose tissue, and liver.
  - Lowers blood glucose levels and promotes glycogen formation.
  - Turns off gluconeogenesis.
- Glucagon and epinephrine:
  - Promote glucose production in the liver.
Processes:
- Glycogenesis: production of glycogen from glucose.
- Glycogenolysis: breakdown of glycogen.
- Gluconeogenesis: formation of new glucose from amino acids.

Diabetes Mellitus

Characterized by excess blood glucose:
- Glucose accumulates in the urine, making it sweet.
- Causes polyuria (excess urine) and polydipsia (excess thirst) due to osmotic activity of glucose.
Type I diabetes:
- Pancreatic dysfunction, inability to produce sufficient insulin.
- Often immune-mediated.
Type II diabetes:
- Cells are less sensitive to insulin despite sufficient production.
- Glucose cannot enter muscle and adipose tissue, leading to high blood glucose levels.

Diabetes and Atherosclerosis

Excess glucose can damage endothelial cells.
This damage promotes the formation of atherosclerotic plaques.
Consequences:
- Impaired blood flow to organs, leading to dysfunction.
- Increased risk of heart attack and stroke.

HbA1c Test

Measures the percentage of hemoglobin that has been glycosylated (exposed to glucose).
Reflects average blood glucose levels over several weeks.
Provides a more informative measure than a single fasting blood glucose value.
Can detect impaired glucose tolerance even when fasting blood glucose is normal.

Pre-Diabetes

Fasting blood glucose is above normal (>100 mg/dL) but below the diabetes threshold.

Description

This quiz explores the essential processes of energy production in cells, focusing on ATP, its synthesis, and the various metabolic pathways involved, such as glycolysis and the citric acid cycle. Understand the role of phosphocreatine in maintaining ATP levels during energy demands. Perfect for students of biochemistry and cellular metabolism.