metabolism

Nutrition and Metabolism

  • Key Components of Nutrition:

    • Carbohydrate Metabolism

    • Lipid and Protein Metabolism

    • Metabolic States & Metabolic Rate

    • Body Heat and Thermoregulation

Metabolism

  • Functions of Food:

    • Source of energy

    • Provides essential nutrients

    • Stored for future use

  • Definition of Metabolism:

    • Net sum of all chemical reactions in the body

    • Produces energy (ATP) from some reactions while others consume it

    • Molecules are eventually broken down, recycled, or excreted

Catabolism and Anabolism

  • Catabolic Reactions:

    • Breakdown of complex organic compounds

    • Provide energy (exergonic)

    • Examples: Glycolysis, Krebs Cycle, Electron Transport

  • Anabolic Reactions:

    • Synthesize complex molecules from smaller ones

    • Require energy (endergonic)

  • Energy Exchange:

    • ATP (adenosine triphosphate) is crucial for energy exchange in reactions

ATP Molecule & Energy

  • Each cell contains about 1 billion ATP molecules lasting less than one minute.

  • More than half the energy released from ATP is converted to heat.

Energy Transfer

  • Chemical Bonds:

    • Energy is stored in bonds between atoms.

  • Oxidation and Reduction:

    • Oxidation: Decrease in energy content via loss of electrons.

    • Reduction: Increase in energy content via gain of electrons.

    • Oxidation-reduction reactions are always coupled.

Oxidation and Reduction

  • Biological Oxidation:

    • Loss of electrons/hydrogen atoms (dehydrogenation) requiring coenzymes.

    • Common coenzymes include:

      • NAD (Nicotinamide adenine dinucleotide)

      • NADP (Nicotinamide adenine dinucleotide phosphate)

      • FAD (Flavin adenine dinucleotide)

  • Biological Reduction:

    • Gain of electrons increases potential energy.

Mechanisms of ATP Generation

  • Phosphorylation:

    • Attaches third phosphate group containing stored energy.

  • Mechanisms include:

    • Substrate-level Phosphorylation: Occurs in cytosol.

    • Oxidative Phosphorylation: Occurs in mitochondria.

    • Photophosphorylation: Occurs in chlorophyll-containing plants/bacteria.

Phosphorylation in Animal Cells

  1. Glycolysis in Cytoplasm

    • Input: 1 Glucose

    • Output: 2 Pyruvic acid, 2 NADH + 2 H+, 2 ATP

  2. Formation of Acetyl Coenzyme A

    • Output: 2 NADH + 2 H+, 2 Acetyl CoA

  3. Krebs Cycle

    • Produces 3 NADH + H+, 1 FADH2, 1 ATP, releases CO2.

  4. Electron Transport Chain

    • Generates 32 or 34 ATP from electrons.

Carbohydrate Metabolism--In Review

  • GI Tract:

    • Polysaccharides → Simple sugars absorption (glucose, fructose, galactose).

  • In the Liver:

    • Fructose & galactose converted to glucose.

    • Storage forms glucose as glycogen.

  • In Body Cells:

    • Glucose: oxidized for energy, converted into other forms, or stored.

Fate of Glucose

  • Cell Respiration:

    • Uses glucose to produce ATP, CO2, and H2O.

  • Forms Glycogen:

    • Glycogenesis for storage in liver/skel. muscles.

  • Lipogenesis:

    • Converts glucose to glycerol & fatty acids.

Glucose Movement into Cells

  • Transport Mechanisms:

    • Na+/glucose symporters in GI tract & kidney tubules.

    • GluT transporters facilitate glucose entry; insulin increases GluT transporters.

    • Glucose 6-Phosphate: Formed immediately inside cell using ATP.

Glucose Catabolism

  • Cellular Respiration Steps:

      1. Glycolysis (anaerobic respiration)

      1. Formation of Acetyl CoA (transitional)

      1. Krebs Cycle (aerobic respiration)

      1. Electron Transport Chain.

Glycolysis Overview

  • Breakdown six-carbon glucose to two three-carbon pyruvic acids.

  • 10-step process in cytosol:

    • Produces 4 ATP after input of 2 ATP; uses 2 NAD+ as hydrogen acceptors.

Fate of Pyruvic Acid

  • In oxygen-deficient conditions, converts to lactic acid for continued ATP production.

  • Lactic acid can be processed back to pyruvic acid in the liver.

Formation of Acetyl Coenzyme A

  • Pyruvic acid enters mitochondria and undergoes decarboxylation.

  • Results in 2-carbon fragment attached to CoA, forms Acetyl CoA for Krebs cycle.

Krebs Cycle (Citric Acid Cycle)

  • Oxidation-reduction and decarboxylation reactions that regenerate to 4C compound.

  • Each Acetyl CoA yields:

    • 2 CO2, 3 NADH + H+, 1 FADH2, 1 ATP.

Electron Transport Chain

  • Integral membrane proteins undergo oxidation-reduction.

  • Electrons delivered to ATP synthesis via chemiosmosis.

Chemiosmosis

  • Energy released during electron transfer used to pump H+ ions, facilitating ATP synthesis as H+ diffuses through channels.

Overview of Electron Transport & ATP Production

  • Complete oxidation of glucose yields 36-38 ATP, with roughly 40% efficiency.

Summary of Cellular Respiration

  • Glucose + O2 → 36-38 ATP, CO2, H2O; ATP production steps detailed through glycolysis, Krebs cycle, and electron transport.

Carbohydrate Loading for Athletes

  • Increases glycogen reserves by consuming complex carbohydrates before endurance events.

Glycogen Metabolism

  • Glycogenesis, glycogenolysis, and gluconeogenesis are key processes in glucose storage/release.

Transport of Lipids by Lipoproteins

  • Lipoproteins assist in lipid transport due to their nonpolar nature.

  • Major classes categorized by density: chylomicrons, VLDLs, LDLs, and HDLs.

Blood Cholesterol Levels

  • Sources include diet and liver synthesis; maintained within recommended ranges for health.

Fate of Lipids

  • Used for ATP production, stored, or synthesized into vital molecules.

Lipid Catabolism

  • Breakdown of triglycerides into fatty acids and glycerol affecting energy production.

Lipogenesis

  • Lipid synthesis in the liver from excess amino acids or glucose.

Ketogenesis

  • Excess acetyl groups during fatty acid catabolism lead to ketone body formation; related to ketosis.

Protein Metabolism

  • Amino acids contribute to energy production and synthesis of new proteins.

  • Breakdown involves removing amino acids (deamination).

Nitrogen Balance

  • Positive balance reflects growth; negative reflects muscle atrophy during catabolic states.

Metabolic Adaptations During States

  • Different states of metabolism (absorptive, postabsorptive, fasting) define body's energy balance.

Regulation of Food Intake

  • Regulated by hormones and neural signals in the hypothalamus; factors stimulating or inhibiting appetite.

Guidelines for Healthy Eating

  • Recommendations based on balanced intake of different food groups and calories.

Functions of Minerals

  • Various roles contributing to structural, enzymatic, and regulatory functions in the body.

Vitamins Overview

  • Essential for numerous biochemical processes; dietary intake varies for solubility and synthesis abilities.

Antioxidant Vitamins

  • Protect against cellular damage from free radicals; related to disease resistance and overall health.

Obesity Implications

  • Associated risks including chronic diseases, cardiovascular issues, and more.

Metabolic Rate Factors

  • Influenced by exercise, hormones, temperature, and caloric intake.

Heat Production & Transfer Mechanisms

  • Body heat management through conduction, convection, radiation, and evaporation.

Hypothalamic Thermostat & Thermoregulation

  • Body's heat regulation centers monitoring temperature and initiating responses for homeostasis.

Fever and Hypothermia

  • Extreme body temperatures can affect health; fever aids infection response, while hypothermia can lead to critical conditions.