(87) Bio 221 Open Stax Chp 24 Metabolism

Metabolism Overview

• Definition: Metabolism is the sum of all chemical reactions in the body, including both energy-requiring and energy-releasing processes.

• Factors Influencing Metabolism:

  • Muscle mass

  • Food intake

  • Physical activity demands

Types of Metabolism

• Catabolism:

  • Breakdown reactions, represented by blue arrows.

  • Example: Proteins from food are broken down into amino acids.

• Anabolism:

  • Building-up reactions, represented by green arrows.

  • Example: Glucose is converted into glycogen in the liver.

• Overall Definition: Metabolism is a combination of both catabolism and anabolism.

ATP: The Energy Molecule

• Adenosine Triphosphate (ATP):

  • Composed of adenine and three phosphate groups.

  • Serves as the primary energy currency of the cell.

• ATP Production Process:

  • Food is broken down to create ATP through glycolysis.

  • Glucose is converted to ATP, and energy is utilized when ATP is broken down to ADP (Adenosine Diphosphate) by breaking the bond between second and third phosphates.

Steps of Cellular Respiration

1. Glycolysis:

   • Occurs in the cytoplasm.

   • Glucose (6 carbons) is broken down into two pyruvate molecules (3 carbons each).

2. Conversion of Pyruvate to Acetyl CoA:

   • Occurs in mitochondria in the presence of oxygen.

   • Each pyruvate loses one carbon as CO2.

3. Citric Acid Cycle (Krebs Cycle):

   • Acetyl CoA enters and undergoes multiple reactions.

   • Produces high-energy carriers NADH and FADH2, along with some ATP.

4. Oxidative Phosphorylation:

   • High-energy electrons from NADH and FADH2 are used to produce a large number of ATP.

Aerobic vs. Anaerobic Respiration

• Aerobic Respiration:

  • Requires oxygen; pyruvate enters the mitochondria and leads to significant ATP production (approximately 36 ATP).

• Anaerobic Respiration:

  • Occurs without oxygen; leads to lesser ATP production (about 4 ATP) and generation of lactic acid.

Gluconeogenesis

• Definition: The production of glucose from non-carbohydrate sources when dietary glucose is insufficient.

• Sources for Glucose Production:

  • Amino Acids (from proteins)

  • Glycerol (from fats)

  • Lactate (from anaerobic respiration)

• Importance: Occurs during fasting or starvation.

Glycogenesis and Glycogenolysis

• Glycogenesis:

  • The process of converting excess glucose into glycogen (storage form of glucose) in the liver.

• Glycogenolysis:

  • The breakdown of glycogen back into glucose when energy is needed.

  • An example of catabolism.

Lipid Metabolism

• Role of Lipids: Lipids are non-polar and require carriers for transport in the body.

• Types of Lipoproteins:

  • Chylomicrons: Transport dietary lipids from intestines to adipose tissue.

  • VLDL (Very Low-Density Lipoprotein): Transfers triglycerides from the liver to fat cells.

  • LDL (Low-Density Lipoprotein): Carries cholesterol to cells (considered bad fat).

  • HDL (High-Density Lipoprotein): Removes excess cholesterol from cells back to the liver (considered good fat).

Protein Metabolism

• Breaking Down Proteins: Dietary proteins are digested into amino acids.

• Energy Production: Amino acids can enter metabolic pathways to produce ATP, but glucose is the preferred energy source.

Nutritional Needs for Metabolism

• Essential Nutrients: Water, carbohydrates, lipids, proteins, vitamins, and minerals are vital for metabolic processes.

• Vitamins: Divided into water-soluble (B and C) and fat-soluble (A, D, E, K); the latter can accumulate in the body and should be consumed in moderation.

• USDA MyPlate: A guideline for balanced nutrition, specifying the proportions of different food groups necessary for healthy metabolism.