Chapter 2 Biology: Organisation

1. Parts of Blood and Their Functions

Blood is a tissue composed of different components, each with a unique role. These include red blood cells, white blood cells, plasma, and platelets.

Red Blood Cells (RBCs)

• Main Function: Transport oxygen from the lungs to tissues and carbon dioxide back to the lungs.

• Structure: Adaptations for their function:

  1. Biconcave Disc Shape: Increases surface area-to-volume ratio for faster oxygen diffusion.

  2. No Nucleus: Maximizes space for hemoglobin, the protein that carries oxygen.

  3. Hemoglobin:

     • Binds to oxygen to form oxyhemoglobin in high oxygen areas (e.g., lungs).

     • Releases oxygen in low oxygen areas (e.g., tissues).

White Blood Cells (WBCs)

• Main Function: Part of the immune system, protecting the body from infections.

• Types:

  1. Phagocytes:

     • Ingest and destroy pathogens through phagocytosis.

     • Release digestive enzymes to break down the pathogen.

  2. Lymphocytes:

     • Produce antibodies that bind to specific antigens on pathogens to neutralize them.

     • Produce antitoxins to counteract toxins released by bacteria.

Plasma

• Main Function: A pale yellow liquid that transports substances around the body.

• Substances Transported:

  1. Nutrients: Glucose and amino acids from digestion.

  2. Hormones: Chemical messengers (e.g., insulin).

  3. Waste Products:

     • Carbon dioxide to the lungs.

     • Urea to the kidneys for excretion.

  4. Heat: Helps regulate body temperature.

Platelets

• Main Function: Blood clotting and preventing bleeding.

• Mechanism: When there is a wound:

  1. Platelets stick to the wound and release clotting factors.

  2. These activate a chain reaction, converting fibrinogen (a soluble protein) into fibrin (insoluble threads).

  3. Fibrin forms a mesh that traps red blood cells, forming a clot.

2. Symbol Equation for Respiration

Respiration is the process of releasing energy from glucose. There are two types: aerobic and anaerobic.

Aerobic Respiration

• Definition: Complete breakdown of glucose with oxygen to release energy.

• Equation: C6H12O6+6O2→6CO2+6H2O+Energy (ATP)C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}C6​H12​O6​+6O2​→6CO2​+6H2​O+Energy (ATP)

• Key Points:

  • Produces 38 ATP molecules per glucose molecule.

  • Occurs in the mitochondria (the powerhouse of the cell).

  • Byproducts: Carbon dioxide (exhaled) and water.

Anaerobic Respiration

• Definition: Incomplete breakdown of glucose without oxygen.

• Equation (Animals): Glucose→Lactic Acid+Energy\text{Glucose} \rightarrow \text{Lactic Acid} + \text{Energy}Glucose→Lactic Acid+Energy

• Key Points:

  • Produces only 2 ATP molecules per glucose molecule.

  • Lactic acid builds up, causing muscle fatigue.

  • Oxygen debt: Lactic acid is broken down in the liver after exercise using oxygen.

3. Alveoli and Their Adaptations

Structure:

• Alveoli are tiny air sacs in the lungs, where gas exchange occurs.

• Found in clusters at the ends of bronchioles in the respiratory system.

• Each alveolus is surrounded by a dense network of capillaries.

Adaptations for Gas Exchange:

1. Large Surface Area:

   • The lungs contain millions of alveoli, increasing the surface area for diffusion.

2. Thin Walls:

   • Alveoli and capillaries are one cell thick, reducing the diffusion distance.

3. Moist Surface:

   • Gases dissolve in the moisture, making diffusion easier.

4. Good Blood Supply:

   • Capillaries maintain a steep concentration gradient by constantly removing oxygen and bringing in carbon dioxide.

5. Ventilation:

   • Breathing ensures fresh air enters and stale air leaves, maintaining the gradient.

Process of Gas Exchange:

1. Oxygen:

   • Diffuses from alveoli into the blood (high to low concentration).

2. Carbon Dioxide:

   • Diffuses from the blood into alveoli to be exhaled.

4. Process of Aerobic Respiration

Stage 1: Glycolysis

• Location: Cytoplasm.

• Process: Glucose is broken into two molecules of pyruvate.

• ATP Produced: 2 molecules.

Stage 2: Krebs Cycle

• Location: Mitochondria.

• Process: Pyruvate is further broken down, releasing carbon dioxide.

• ATP Produced: 2 molecules.

Stage 3: Electron Transport Chain

• Location: Inner mitochondrial membrane.

• Process: High-energy electrons move through proteins, producing ATP.

• Oxygen is the final electron acceptor, forming water.

• ATP Produced: ~34 molecules.

5. Label a Heart

Key Parts to Label:

1. Chambers:

   • Right atrium, left atrium.

   • Right ventricle, left ventricle (left is thicker for pumping blood to the body).

2. Valves:

   • Tricuspid (right atrium to ventricle).

   • Bicuspid/Mitral (left atrium to ventricle).

   • Pulmonary and aortic valves (prevent backflow).

3. Major Vessels:

   • Pulmonary artery (to lungs).

   • Pulmonary vein (from lungs).

   • Aorta (to body).

   • Vena cava (from body).

6. Treatment of Heart Disease

Lifestyle Changes:

• Balanced diet (low fat and salt).

• Regular exercise.

• Avoid smoking and alcohol.

Medical Treatments:

1. Statins: Reduce cholesterol levels, preventing plaque build-up.

2. Anticoagulants: Prevent blood clots.

3. Beta-blockers: Lower blood pressure and heart strain.

Surgical Treatments:

1. Stents: Small mesh tubes to open narrowed arteries.

2. Bypass Surgery: Using a vein to reroute blood around a blockage.

3. Heart Transplant: For severe cases.

7. Role of Stomata

• Structure: Small pores on leaf surfaces, controlled by guard cells.

• Function:

  1. Gas exchange for photosynthesis (CO₂ in, O₂ out).

  2. Water loss through transpiration.

• Mechanism:

  • Open Stomata: When guard cells take in water, they swell and curve outward.

  • Closed Stomata: When guard cells lose water, they shrink, closing the pore.

8. Osmosis and Impact on Plant Cells

Osmosis:

• Movement of water across a semi-permeable membrane from high water potential to low water potential.

Effects on Plant Cells:

1. Turgid (Normal): Water enters, cell swells, and cytoplasm presses against the cell wall, providing structure.

2. Flaccid: Water leaves, causing the cell to become soft.

3. Plasmolysis: Extreme water loss, membrane pulls away from the wall.

9. Enzymes

• Definition: Proteins that act as biological catalysts.

• Active Site: Where the substrate binds.

• Lock-and-Key Model: Substrate fits into the enzyme’s active site perfectly.

• Factors:

  • Temperature: Optimal at ~37°C. Too high causes denaturation.

  • pH: Each enzyme has an optimum (e.g., amylase: pH 7, pepsin: pH 2).

  • Substrate Concentration: Higher concentration increases rate until saturation.