paper 1 science bio

Nutrient Breakdown

  • Food is broken down into nutrients by stomach acid; further digestion occurs in the small intestine with bile and enzymes.

  • Bile, produced in the liver and stored in the gallbladder, neutralizes stomach acid and emulsifies fats.

Enzymes

  • Enzymes are biological catalysts that break down larger molecules for absorption.

  • Types of enzymes:

    • Amylase: breaks down starch to glucose.

    • Carbohydrases: convert carbohydrates to simple sugars.

    • Proteases: digest proteins into amino acids.

    • Lipases: degrade lipids into glycerol and fatty acids.

  • Enzymes operate on a lock and key principle (active site and substrate).

  • Enzyme activity increases with temperature until denaturation occurs (active site shape alters).

Practical Experiment

  • Mix amylase with starch at different temperatures or pH levels.

  • Use iodine to test for starch breakdown; color change indicates completion of digestion.

  • Optimum conditions determined between lowest times, following allowed interpolation rules.

Nutrient Tests

  • Iodine: orange turns black in presence of starch.

  • Benedict's solution: blue to brick red for sugars.

  • Biuret reagent: blue to purple for proteins.

  • Ethanol: cloudy with lipids.

Respiration and Circulation

  • Breathing supplies oxygen for cellular respiration; air moves from trachea to alveoli.

  • Alveoli facilitate gas exchange, where oxygen binds hemoglobin and carbon dioxide is exhaled.

  • Heart functions as a double circulatory system:

    • Deoxygenated blood enters right atrium via vena cava, pumped to lungs for oxygenation.

    • Oxygenated blood returns to left atrium, sent to body via aorta.

Heart Structure

  • Right ventricle pumps to lungs; left ventricle thicker for systemic circulation.

  • Heartbeat regulated by electrical pulses; artificial pacemakers can assist.

Blood Vessels

  • Arteries (thicker walls, carry oxygenated blood) vs. veins (thinner walls, valves to prevent backflow).

  • Capillaries: one cell thick for efficient molecule diffusion.

Cardiovascular Health

  • Coronary artery supplies heart with oxygen; blockages may cause heart attacks (coronary heart disease).

  • Stents and statins are treatments for blood vessel blockages.

  • Blood also contains white blood cells (infection defense) and platelets (clotting).

Diseases and Lifestyle

  • Cardiovascular disease (CVD) is non-communicable; influenced by obesity, sugar, smoking, and alcohol consumption.

  • Cancer caused by uncontrolled cell division; carcinogens increase cancer risk.

  • Benign vs malignant tumors: benign remain localized, malignant spread.

Body Mass Index (BMI)

  • BMI indicates weight status relative to height (underweight, healthy, overweight, obese).

Plant Biology

  • Plants also possess organ systems similar to animals, highlighting biological complexity.