Organisation

Principles of Organisation (2.1)

• Cells constitute all living organisms.

• Tissues: Groups of specialized cells with similar structure/function (e.g., muscular tissue, epithelial tissue).

• Organs: Composed of various tissues working together for a specific function (e.g., stomach).

• Organ systems: Groups of organs collaborating to perform a function (e.g., digestive system).

The Human Digestive System (2.2.1)

• Breaks down large, insoluble food into absorbable forms.

• Composed of:

  1. Glands (salivary glands, pancreas): Produce digestive enzymes.

  2. Stomach: Produces hydrochloric acid; optimum pH for protease.

  3. Small intestine: Absorbs soluble molecules.

  4. Liver: Produces bile for lipid digestion.

  5. Large intestine: Absorbs water and forms faeces.

Enzymes

• Biological catalysts that increase reaction rates without being consumed.

• Shape of enzyme/catalysts critical; active sites must match substrate (Lock and Key Hypothesis).

• Require optimum pH (7 for most, lower for stomach enzymes) and temperature (around 37°C).

• Types of enzymes:

  1. Carbohydrases: Convert carbohydrates to sugars (e.g., amylase).

  2. Proteases: Convert proteins to amino acids (e.g., pepsin).

  3. Lipases: Convert lipids to fatty acids and glycerol.

Tests for Biological Molecules

• Benedict’s test: Detects sugars (turns brick red).

• Iodine test: Detects starch (turns blue-black).

• Biuret test: Detects proteins (turns purple).

• Emulsion test: Detects lipids (cloudy layer forms).

Rate of Enzymatic Reactions

• Controlled by factors including pH and temperature.

• Calculation: rate = change/time.

The Heart and Blood Vessels (2.2.2)

• Double circulatory system:

  • Deoxygenated blood to lungs, oxygenated blood to body.

• Structure:

  • Muscular walls, 4 chambers, valves to prevent backflow, coronary arteries for heart's oxygen supply.

• Heart rate: Controlled by pacemaker cells in the right atrium (70 bpm).

Blood Vessels

• Arteries: Carry blood away from heart; strong and elastic.

• Veins: Carry blood to heart; wider lumen and valves.

• Capillaries: Thin walls for efficient substance exchange.

Lungs and Gas Exchange

• Components: Trachea, bronchi, bronchioles, alveoli, diaphragm.

• Gas exchange occurs in alveoli: oxygen in, carbon dioxide out.

• Rate of breathing: breaths per minute.

Blood Composition (2.2.3)

• Plasma: Liquid carrying blood components and substances.

• Red blood cells: Carry oxygen (biconcave shape, no nucleus).

• White blood cells: Part of immune defense (multiple types).

• Platelets: Aid blood clotting.

Coronary Heart Disease (2.2.4)

• Blocked coronary arteries lead to less oxygen, potentially causing heart attack.

• Solutions: Stents, statins, valve replacements, heart transplants, artificial blood.

Health Issues (2.2.5)

• Health: Physical, mental, and social well-being.

• Types of diseases:

  1. Communicable (infectious).

  2. Non-communicable (e.g., heart disease).

• Factors influencing health: Diet, stress, life situations.

Lifestyle Effects on Non-Communicable Diseases (2.2.6)

• Non-communicable diseases linked to lifestyle factors (e.g., diet, smoking).

• Causal mechanisms required for correlation proof.

Cancer (2.2.7)

• Tumours: Benign (non-cancerous) or malignant (cancerous, spread).

• Lifestyle and genetic risk factors influence cancer risk.

Plant Tissues, Organs, and Systems (2.3)

• Plant tissues include epidermal, palisade mesophyll, spongy mesophyll, xylem, and phloem.

• Main organ systems include roots, stems, and leaves for transport.

• Transpiration stream driven by evaporation from leaves.

• Guard cells control stomata for gas exchange and minimize water loss.