Understanding Healthy Weight and Obesity

What is a Healthy Weight?

• The perception of a healthy weight varies by culture and time period.
• In the USA, more than 7 out of 10 adults are overweight or obese.
• Factors contributing to obesity include high-fat fast food, lack of exercise, and heredity.
• Obesity increases the risk of developing cardiovascular disease, Type 2 diabetes, and certain cancers.
• Body Mass Index (BMI) is a measure of healthy weight. A BMI between 20 and 24 is considered healthy, while a BMI over 30 indicates obesity.
• BMI does not consider muscle mass, age, gender, or body frame size.
• To maintain a healthy weight, energy intake should equal energy output.
• Weight loss tips include reducing calorie intake, increasing exercise, eating smaller portions, and avoiding high-fat/sugar foods.
• Safe weight loss should be between 0.5 and 2 pounds per week, equivalent to a reduction of 3500 calories.

Disorders Associated with Obesity

• Type 2 Diabetes:
  • Sustained elevated blood sugar levels (glucose).
  • Insulin, produced by the pancreas, regulates blood sugar by facilitating glucose uptake into cells.
  • Glucagon, also produced by the pancreas, raises blood sugar levels by breaking down stored glucose in the liver.
  • Type 1 diabetes involves the pancreas failing to produce insulin and requires insulin injections.
  • Type 2 diabetes results from insufficient insulin production or insulin resistance and can be managed with diet and exercise.
  • Complications from diabetes include blindness, amputation, kidney disease, slow wound healing, and cardiovascular disease.
• Hypertension (High Blood Pressure):
  • Can lead to heart attacks and strokes.
  • Normal blood pressure is 120/80 mmHg.
  • Weight gain increases blood pressure.
• Heart Attack and Stroke:
  • Heart attack occurs when a portion of heart muscle dies due to blocked or ruptured blood vessels.
  • Stroke occurs when a portion of the brain dies due to blocked or ruptured blood vessels.
  • Atherosclerosis, the buildup of fat and cholesterol deposits in arteries, contributes to heart attacks and strokes.

Eating Disorders

• Anorexia:
  • An irrational fear of gaining weight leading to self-imposed starvation.
  • Can cause organ failure, death, and amenorrhea (loss of menstrual cycle).
• Bulimia:
  • Characterized by binge eating followed by purging.
  • Leads to dental problems, dehydration, and electrolyte imbalances.

A Healthy Diet

• Dietary guidelines include:
  • Moderate fat intake, with low saturated fats and trans fats.
  • Consuming complex carbohydrates from whole grains, vegetables, and legumes.
  • Avoiding refined carbohydrates (sugars and starches).
  • Low salt intake.
  • Adequate protein from poultry, fish, and plants, as well as vitamins and minerals.
  • Moderate alcohol consumption.
  • Avoiding fad diets.

Energy in Cells

• Energy is the capacity to do work.
• Potential energy is stored energy, while kinetic energy is the energy of motion.
• ATP (Adenosine Triphosphate) is the energy currency of the cell.
• ATP is composed of adenine, ribose, and three phosphate groups.
• The ATP cycle involves the release of energy when a phosphate group is removed from ATP (ATP → ADP) and the rebuilding of ATP by adding energy (ADP + P → ATP).
• Energy flows from solar energy to glucose through photosynthesis and from glucose to ATP through cellular respiration.

Metabolism

• Metabolism encompasses all chemical reactions in the body.
• Catabolism breaks down molecules, releasing energy.
• Anabolism builds up molecules, requiring energy.
• Enzymes are proteins that act as catalysts, speeding up reactions without being consumed.
• Activation energy is the energy required for a reaction to occur.
• Enzymes function by binding to a specific substrate at their active site.
• Enzyme-related problems include lactose intolerance (missing lactase enzyme), albinism (missing enzyme to produce melanin), and Tay-Sachs disease (missing enzyme to break down toxic brain waste).

Cellular Transport

• The plasma membrane controls the movement of molecules in and out of the cell.
• The plasma membrane is composed of a phospholipid bilayer with protein passageways and is selectively permeable.
• Types of Cellular Transport:
  • Passive Transport: Movement from high to low concentration requiring no energy.
    • Simple Diffusion: Movement of small, nonpolar molecules like oxygen and carbon dioxide.
    • Facilitated Diffusion: Movement of ionic/polar molecules using protein passageways.
    • Osmosis: Water movement across a membrane.
      • Isotonic: Equal solute concentration.
      • Hypertonic: More solute outside, causing the cell to shrink.
      • Hypotonic: Less solute outside, causing the cell to burst.
  • Active Transport: Movement from low to high concentration requiring energy.
    • Example: Sodium/Potassium pump (Na/K pump).
  • Bulk Transport: Moving macromolecules in and out of the cell.
    • Exocytosis: Moving substances out of the cell.
    • Endocytosis: Engulfing substances into the cell.
    • Phagocytosis: "Cell eating" - Engulfs solids.
    • Pinocytosis: "Cell drinking" - Engulfs liquids.
    • Receptor-Mediated Endocytosis: Engulfs specific molecules, like cholesterol.

Importance of Photosynthesis

• Photosynthesis transforms solar energy into chemical energy (glucose).
• Autotrophs: Organisms that produce their own food (e.g., plants, cyanobacteria, algae).
• Heterotrophs: Organisms that acquire food from other sources (e.g., herbivores, carnivores).
• Photosynthesizers form the base of the food chain by producing energy-rich carbohydrates.

Structures Involved in Photosynthesis

• Leaves are the primary site of photosynthesis.
• Stomata: Tiny pores on the underside of leaves that allow for gas exchange (CO₂ in, O₂ and H₂O out).
• Chloroplasts: Organelles within leaf cells where photosynthesis occurs.
  • Stroma: Fluid inside the chloroplast.
  • Thylakoids: Membrane sacs inside the chloroplast, stacked into grana.
• Chlorophyll: The primary pigment that absorbs light energy for photosynthesis, located in the thylakoids.

The Process of Photosynthesis

• Photosynthesis produces carbohydrates, primarily glucose (C₆H₁₂O₆).
• Electron transfer involves removing electrons from H₂O and transferring them to CO₂ through redox reactions.
  • Reduction: Gains electrons and energy.
  • Oxidation: Loses electrons and energy.
• Two Stages of Photosynthesis:
  • Light Reactions:
    • Chlorophyll absorbs solar energy, exciting electrons.
    • Water is oxidized, releasing electrons and H⁺.
    • ATP is produced, and NADP⁺ becomes NADPH after accepting electrons.
  • Calvin Cycle:
    • CO₂ is absorbed and, using ATP and NADPH, reduced to a carbohydrate (glucose).

Harvesting Light Energy

• Radiant energy (solar energy) exists in different wavelengths, with visible light being a small portion of the spectrum.
  • Colors of Light: ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet).
  • Energy Content: Highest for violet, lowest for red.
• Photosynthetic Pigments:
  • Chlorophyll a: The main pigment responsible for photosynthesis, absorbing blue and red light, and reflecting green (the color seen by our eyes).
  • Accessory Pigments:
    • Chlorophyll b: Yellow-green.
    • Carotenes: Orange.
    • Xanthophylls: Yellow.

Overview of Cellular Respiration

• Cellular respiration produces ATP, the energy currency of the cell.
• Equation: C₆H₁₂O₆ (glucose) + O₂ → CO₂ + H₂O + ATP.
• ATP powers all cellular activities.
• Cellular respiration occurs in the mitochondria.
• Energy release: Glucose is broken down to produce 38 ATP per glucose molecule.
• Coenzymes (Electron carriers):
  • NAD⁺ becomes NADH.
  • FAD becomes FADH₂.
• Four Phases of Cellular Respiration:
  1. Glycolysis.
  2. Prep Reaction.
  3. Citric Acid Cycle (Krebs Cycle).
  4. Electron Transport Chain (ETC).

Phases of Cellular Respiration

• A. Glycolysis:
  • Location: Cytoplasm.
  • Requires 2 ATP to start.
  • Breaks glucose into 2 pyruvate molecules.
  • Yield: 2 pyruvate, 2 ATP, 2 NADH.
• B. Prep Reaction:
  • Location: Mitochondria.
  • Prepares 2 pyruvates for the Citric Acid Cycle.
  • Yield: 2 acetyl CoA, 2 NADH, 2 CO₂.
• C. Citric Acid Cycle (Krebs Cycle):
  • Location: Mitochondria.
  • Two turns of the cycle occur for each glucose molecule.
  • Yield (per glucose molecule): 4 CO₂, 6 NADH, 2 FADH₂, 2 ATP.
• D. Electron Transport Chain (ETC):
  • Location: Inner mitochondrial membrane.
  • Electrons from NADH and FADH₂ are passed down a chain of proteins, releasing energy.
  • This energy is used to pump H⁺ ions across the membrane, creating a proton gradient.
  • The flow of H⁺ ions back across the membrane powers ATP synthesis.
  • The ETC uses O₂ as the final electron acceptor, producing H₂O as a byproduct.
  • Yield: Approximately 34 ATP per glucose molecule.