bilogy paper1

Cell Biology

Cell Types

- Prokaryotic cells (bacteria): No nucleus, plasmids, smaller.

- Eukaryotic cells: Animal and plant cells, have a nucleus, more complex organelles.

Cell Structures

- Common: nucleus (contains DNA), cytoplasm, cell membrane (controls entry/exit), mitochondria (energy production), ribosomes (protein synthesis).

- Plant cells also have: cell wall (provides support), chloroplasts (photosynthesis), vacuole (storage).

Microscopy

- Light vs electron microscopes: Light microscopes use light and lenses, lower magnification. Electron microscopes use electrons, higher magnification and resolution.

- Magnification = Image size ÷ Actual size

Cell Division

- Mitosis: For growth & repair, produces 2 identical cells. Stages include prophase, metaphase, anaphase, telophase.

- Cell cycle includes DNA replication (S phase). G1 and G2 phases for growth and preparation.

- Stem Cells:

- Embryonic (any type), can differentiate into any cell type.

- Adult (limited types), specific to certain tissues.

- Used in medicine (e.g. treating paralysis, bone marrow transplants).

- Transport in Cells

- Diffusion: Passive movement from high to low concentration, no energy required.

- Osmosis: Movement of water across a semi-permeable membrane, from high water potential to low water potential.

- Active Transport: Requires energy (ATP), movement against concentration gradient (low to high), e.g., root hair cells absorbing mineral ions.

Required Practical: Investigating osmosis in potatoes. Measure mass change in different sucrose concentrations.

2. Organisation

Levels of Organisation

- Cells → Tissues → Organs → Organ systems → Organism

Digestive System

- Organs: mouth, oesophagus, stomach, small/large intestines, liver, pancreas, gall bladder.

- Enzymes:

- Amylase: Starch → sugars, produced in salivary glands and pancreas.

- Protease: Proteins → amino acids, produced in stomach, pancreas, and small intestine.

- Lipase: Lipids → fatty acids + glycerol, produced in pancreas and small intestine.

- - Bile: Made in liver, stored in gall bladder, neutralises stomach acid, emulsifies fats for larger surface area.

Heart and Circulation

- Double circulatory system: Right side pumps to lungs (pulmonary circulation); left to body (systemic circulation).

- Blood flow: vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta

- Pacemaker: Controls heartbeat rhythm, located in right atrium (SAN). Artificial pacemakers can be used.

- Coronary Heart Disease: Caused by fatty deposits (atheroma) in coronary arteries, reduces blood flow to heart.

- Treatments: stents (expand arteries), statins (reduce cholesterol).

- Blood Vessels

- Arteries: Thick walls, high pressure, carry blood away from the heart.

- Veins: Valves, carry blood back to heart, lower pressure.

- Capillaries: One cell thick for exchange of substances between blood and tissues.

Blood

- Components: red cells (erythrocytes), white cells (leukocytes), platelets, plasma.

- Red blood cells: carry oxygen (contain haemoglobin), no nucleus, biconcave shape.

Plant Tissues

- Xylem: Water & mineral transport (transpiration), dead cells, one-way flow.

- Phloem: Sugar transport (translocation), living cells, two-way flow.

- Transpiration affected by temperature, humidity, wind, light. Measured using a potometer.

3. Infection and Response

Pathogens

- Types: bacteria, viruses, fungi, protists.

Diseases to Know

- Bacterial: Salmonella (food poisoning), gonorrhoea (STD)

- Viral: Measles, HIV (AIDS), TMV (in plants)

- Fungal: Rose black spot (plant disease)

- Protist: Malaria (spread by mosquitoes)

Body Defences

- Skin, nose hairs, stomach acid (HCl).

- White blood cells: phagocytosis (engulfing pathogens), antibody production (specific to antigens), antitoxins (neutralise toxins).

Vaccination

- Dead/inactive pathogen triggers antibody production, memory cells produced.

- Leads to immunity and herd protection.

Drugs

- Antibiotics kill bacteria, not viruses.

- Antibiotic resistance from overuse/misuse: MRSA.

- Drug Development stages:

- Preclinical (cells/animals): testing for efficacy and toxicity.

- Clinical trials (low dose → larger groups → double-blind testing): testing on humans, placebo groups used.

- 4. Bioenergetics

Photosynthesis

- Equation: CO₂ + H₂O → glucose + O₂

- Needs light, chlorophyll, water, CO₂.

- Limiting factors: light intensity, CO₂ concentration, temperature.

- Glucose used for respiration, storage (as starch), making cellulose/amino acids.

Required Practical: Effect of light intensity on photosynthesis (using pondweed). Measure oxygen production.

Respiration

- Aerobic (with O₂): Glucose + O₂ → CO₂ + H₂O + energy (ATP)

- Anaerobic (in muscles): Glucose → lactic acid