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A-LEVEL BIOLOGY – COMPREHENSIVE Q&A NOTES

Based on the Cameroon GCE A-Level Syllabus

1. CELL STRUCTURE & FUNCTION

Q1. What is a cell?

A cell is the basic structural, functional, and genetic unit of all living organisms. It is the smallest unit capable of independent life.

Q2. Distinguish between prokaryotic and eukaryotic cells.

Q3. What are the functions of major cell organelles?

• Nucleus: Stores genetic information, controls cell activities.

• Mitochondria: Site of aerobic respiration and ATP production.

• Ribosomes: Protein synthesis.

• Golgi body: Packaging and secretion of proteins.

• Endoplasmic reticulum:
  • Rough ER – protein transport.

  • Smooth ER – lipid synthesis.

• Chloroplast: Photosynthesis in plants.

• Lysosomes: Intracellular digestion.

Q4. What is the fluid mosaic model?

It describes the structure of the cell membrane as a phospholipid bilayer with proteins embedded and moving freely, resembling a “mosaic.”
It explains membrane properties like:

• Selective permeability

• Flexibility

• Transport mechanisms

2. BIOLOGICAL MOLECULES

Q1. What are the major biological molecules?

• Carbohydrates

• Proteins

• Lipids

• Nucleic acids

Q2. Distinguish between monosaccharides, disaccharides, and polysaccharides.

• Monosaccharides: Simple sugars (glucose).

• Disaccharides: Two monosaccharides (sucrose, lactose).

• Polysaccharides: Many units (starch, cellulose, glycogen).

Q3. What are enzymes?

Biological catalysts made of proteins that speed up reactions without being used up.

Q4. How do enzymes work?

They lower activation energy through:

• Lock-and-key mechanism

• Induced fit model

Q5. What factors affect enzyme activity?

• Temperature

• pH

• Substrate concentration

• Enzyme concentration

• Inhibitors (competitive & non-competitive)

3. GENETICS AND MOLECULAR BIOLOGY

Q1. What is DNA?

DNA (deoxyribonucleic acid) is the hereditary material made of nucleotides arranged in a double helix.

Q2. Describe DNA replication.

• Semi-conservative

• DNA helicase unzips strands

• DNA polymerase adds complementary bases

• Two identical DNA strands form

Q3. What is a gene?

A sequence of DNA coding for a polypeptide or RNA molecule.

Q4. Explain transcription and translation.

• Transcription: DNA → mRNA (in nucleus)

• Translation: mRNA → protein (on ribosomes)

Q5. What is Mendel’s first law?

Law of segregation: allele pairs separate during gamete formation.

Q6. What is a test cross?

Crossing an organism showing a dominant trait with a homozygous recessive to determine its genotype.

4. EVOLUTION

Q1. Define evolution.

The gradual change in populations over generations due to genetic variation and natural selection.

Q2. What is natural selection?

The process by which individuals with favorable traits survive and reproduce, passing traits to offspring.

Q3. Give evidence for evolution.

• Fossil record

• Comparative anatomy

• Molecular biology

• Embryology

• Biogeography

5. ECOLOGY

Q1. What is an ecosystem?

A community of organisms interacting with each other and their physical environment.

Q2. Define the following terms:

• Habitat: Where an organism lives.

• Niche: Role an organism plays in its environment.

• Population: Members of the same species living in an area.

• Community: All species living together.

Q3. Distinguish between food chains and food webs.

• Food chain: Single pathway of energy flow.

• Food web: Interconnecting food chains.

Q4. What causes ecological succession?

• Disturbances (fire, floods, farming)

• New substrates (volcanic rock)

6. HUMAN PHYSIOLOGY

A. Transport System

Q1. What is the function of blood?

• Transport of gases

• Transport of nutrients

• Protection (white blood cells)

• Temperature regulation

Q2. Distinguish between arteries, veins, and capillaries.

Q3. What is the cardiac cycle?

Sequence of events in one heartbeat:

• Atrial systole

• Ventricular systole

• Diastole

B. Respiration

Q1. What is respiration?

The release of energy from food substances.

Q2. Distinguish between aerobic and anaerobic respiration.

• Aerobic: Uses oxygen, releases more energy.

• Anaerobic: No oxygen, produces lactic acid or ethanol.

C. Reproduction

Q1. What is fertilization?

Fusion of male and female gametes to form a zygote.

Q2. What are the main parts of the male reproductive system?

• Testes

• Epididymis

• Vas deferens

• Prostate gland

• Penis

Q3. What are the stages of the menstrual cycle?

• Menstruation

• Follicular phase

• Ovulation

• Luteal phase

7. PLANT PHYSIOLOGY

Q1. What is photosynthesis?

The process by which green plants convert light energy into chemical energy using CO₂ and water.

Q2. What factors affect photosynthesis?

• Light intensity

• CO₂ concentration

• Temperature

• Chlorophyll amount

Q3. What is transpiration?

Loss of water vapour from plant leaves through stomata.

Q4. What factors affect transpiration?

• Humidity

• Wind

• Temperature

• Light

8. MICROBIOLOGY & BIOTECHNOLOGY

Q1. What are microorganisms?

Microscopic organisms such as bacteria, fungi, protozoa, and viruses.

Q2. What is genetic engineering?

Manipulation of DNA to produce desired traits (e.g., insulin production).

Q3. What is fermentation?

Anaerobic breakdown of sugars by microorganisms (e.g., yeast).

9. PRACTICAL SKILLS (PAPER 3)

Q1. How do you calculate magnification of a microscope image?

Magnification = Image size / Actual size

Q2. What precautions ensure accurate experiments?

• Use of control

• Replicates

• Proper calibration

• Avoiding parallax errors

Q3. What is a hypothesis?

A testable statement predicting the relationship between variables.