State that chlorophyll is essential for photosynthesis.

Cambridge IGCSE Biology (0610) – Complete Syllabus Notes

Contents

1. 0. Characteristics & Classification of Living Things
2. 1. Cell Structure & Function
3. 2. Organisation of the Organism
4. 3. Movement Into & Out of Cells
5. 4. Biological Molecules
6. 5. Enzymes
7. 6. Plant Nutrition – Photosynthesis & Related Processes
8. 7. Human Nutrition & Digestion
9. 8. Transport in Animals
10. 9. Gas Exchange
11. 10. Cellular Respiration
12. 11. Excretion
13. 12. Coordination & Response
14. 13. Hormones
15. 14. Homeostasis
16. 15. Drugs & Antibiotic Resistance
17. 16. Reproduction – Asexual & Sexual
18. 17. Genetics & Inheritance
19. 18. Ecology & the Environment
20. 19. Biotechnology
21. 20. Practical Skills (AO3)
22. 21. Exam‑Style Checklist

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0. Characteristics & Classification of Living Things

Key Characteristics (7)

• Cellular organisation – all living things are made of cells.
• Metabolism – uptake of materials and release of waste (e.g., respiration).
• Growth & development – increase in size and complexity.
• Reproduction – production of offspring (sexual or asexual).
• Response to stimuli – e.g., tropisms, reflexes.
• Homeostasis – maintenance of a stable internal environment.
• Evolution – change in genetic composition over generations.

Classification Basics

• Binomial nomenclature – genus (capitalised) + species (lower‑case), italicised (e.g., Homo sapiens).
• Five‑kingdom system (as required for IGCSE): Monera, Protista, Fungi, Plantae, Animalia.
• Key features of each kingdom (cell type, nutrition, habitat, etc.).
• Viruses – not classified in the five‑kingdom system; they are acellular and require a host.

Practical Activity

Build a simple dichotomous key for a set of 10 common garden plants. Record the observable characters used at each step.

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1. Cell Structure & Function

• Prokaryotic vs eukaryotic cells – size, presence of nucleus, organelles, examples.
• Major organelles – nucleus, mitochondrion, chloroplast, endoplasmic reticulum, Golgi apparatus, vacuole, cell wall, plasma membrane.
• Microscopy – light microscope (max ≈ 0.2 mm) and electron microscope (max ≈ 0.02 mm); calculation of magnification: Magnification = (size of image on screen) ÷ (actual size of specimen).

Practical: Prepare a wet mount of onion epidermis, identify the cell wall, nucleus and vacuole, and calculate the magnification used.

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2. Organisation of the Organism

Levels of Organisation

1. Cell
2. Tissue (e.g., simple squamous epithelium, vascular tissue)
3. Organ (e.g., leaf, heart)
4. Organ system (e.g., digestive system, transport system)
5. Organism

Plant Organisation (Dicot Leaf)

• Cuticle – waxy layer reducing water loss.
• Epidermis – outer cell layer, contains stomata.
• Palisade mesophyll – columnar cells, high chloroplast density → main site of photosynthesis.
• Spongy mesophyll – loosely packed cells, gas exchange.
• Stomata – pores regulated by guard cells.
• Vascular bundles – xylem (water transport) and phloem (sugar transport).

Diagram suggestion: Labeled cross‑section of a dicot leaf.

Root Organisation

• Root hairs – increase surface area for water/mineral uptake.
• Pericycle – site of lateral root formation.
• Xylem and phloem arrangement.

Practical: Starch test on a leaf (iodine) to locate the site of photosynthesis.

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3. Movement Into & Out of Cells

Diffusion

• Movement of particles from high to low concentration.
• Factors influencing rate (table below).

Osmosis

• Diffusion of water across a semi‑permeable membrane.
• Tonicity: hypotonic, isotonic, hypertonic.

Active Transport

• Requires ATP; moves substances against a concentration gradient (e.g., glucose uptake in intestinal cells).

Factors Influencing Diffusion (and Osmosis)

Factor	Effect on Rate
Concentration gradient	Steeper gradient → faster diffusion
Surface area	Larger area → faster diffusion
Distance (membrane thickness)	Shorter distance → faster diffusion
Temperature	Higher temperature → particles move faster → faster diffusion

Design an Investigation (AO3)

Example: Investigate the effect of temperature on the rate of diffusion of starch into agar blocks.

1. Prepare identical agar blocks containing starch.
2. Place each block in a beaker of iodine solution at different temperatures (5 °C, 20 °C, 35 °C, 50 °C).
3. Record the time taken for the colour change to reach the centre of each block.
4. Analyse how temperature influences diffusion rate.

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4. Biological Molecules

Elements & Polymers

• Carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur – building blocks of biomolecules.
• Polymerisation: monomers → polymers (e.g., glucose → starch).

Major Groups & Functions

Group	Monomer	Polymer (example)	Function
Carbohydrates	Monosaccharide (glucose)	Polysaccharide (starch, glycogen, cellulose)	Energy storage, structural support
Proteins	Amino acid	Polypeptide (e.g., enzymes)	Enzymes, structural, transport, defence
Lipids	Fatty acid + glycerol	Triglyceride, phospholipid	Energy storage, membrane structure, insulation
Nucleic acids	Nucleotides	DNA, RNA	Genetic information, protein synthesis

Qualitative Tests (required for practicals)

Test	Reagent	Positive Result
Iodine (starch)	Iodine solution	Blue‑black colour
Benedict’s (reducing sugars)	Benedict’s solution + heat	Brick‑red precipitate
Biuret (proteins)	Biuret reagent (CuSO₄ + NaOH)	Violet colour
Ethanol emulsion (lipids)	Ethanol then water	Milky/cloudy layer
DCPIP (vitamin C)	DCPIP solution	Colourless (reduced) solution

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5. Enzymes

General Features

• Biological catalysts – lower activation energy, not consumed.
• Specificity – lock‑and‑key model; active site fits only one substrate (or a group of similar substrates).
• Enzyme‑substrate complex → products released, enzyme free to act again.

Factors Affecting Enzyme Activity

Factor	Effect
Temperature	↑ → ↑ rate up to optimum; > optimum → denaturation.
pH	Each enzyme has an optimum pH; extreme pH causes denaturation.
Substrate concentration	↑ → ↑ rate until all active sites are occupied (Vmax).
Enzyme concentration	↑ → ↑ rate (more active sites).
Inhibitors	Competitive (bind active site) or non‑competitive (alter enzyme shape).

Key Example

Amylase (found in saliva) catalyses the hydrolysis of starch → maltose. Practical: test the effect of temperature on amylase activity using the iodine test.

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6. Plant Nutrition – Photosynthesis & Related Processes

Learning Objective

State that chlorophyll is essential for photosynthesis.

Why Chlorophyll Is Essential

1. Light absorption – chlorophyll a (and accessory pigments) absorb photons most efficiently in the blue (≈ 430 nm) and red (≈ 660 nm) regions.
2. Electron donation – absorbed energy excites electrons; these electrons travel through the photosystems, driving the light‑dependent reactions that produce ATP and NADPH.
3. Without chlorophyll, a plant cannot capture light energy, so the light‑dependent reactions – and consequently the Calvin cycle – cannot occur.

Overall Equation

6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂

Photosynthetic Process Overview

Stage	Location	Main Products	Key Role of Chlorophyll
Light‑dependent reactions	Thylakoid membranes (photosystems II & I)	ATP, NADPH, O₂	Absorbs light, excites electrons, powers photolysis of water
Light‑independent reactions (Calvin cycle)	Stroma	Glucose (C₆H₁₂O₆)	Uses ATP & NADPH produced by the light‑dependent reactions

Related Plant Processes

• Leaf structure – palisade mesophyll contains the highest chloroplast density.
• Transpiration – creates a water‑pull that supplies the leaf with the H₂O needed for photosynthesis.
• Phototropism – auxin redistribution causes growth towards light, maximising chlorophyll exposure.

Practical Investigation – Rate of Photosynthesis

Elodea bubbling experiment under coloured lights

1. Place an Elodea sprig in a test tube with water + a pinch of NaHCO₃ (source of CO₂).
2. Seal with a rubber bung fitted with a delivery tube leading to an inverted graduated cylinder over water.
3. Expose the plant to red, blue, green and yellow LEDs (same intensity) for 5 min each.
4. Record the volume of O₂ collected.
5. Interpretation: greatest O₂ evolution under red and blue light confirms chlorophyll’s absorption peaks.

Diagram Suggestion

Labeled cross‑section of a dicot leaf showing chloroplast‑rich palisade mesophyll, stomata, and vascular bundles.

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7. Human Nutrition & Digestion

Digestive System Overview

• Mouth – mechanical breakdown, salivary amylase.
• Esophagus – peristalsis.
• Stomach – gastric juices (pepsin, HCl) – protein digestion.
• Small intestine – duodenum (bile, pancreatic enzymes), jejunum & ileum – absorption via villi & microvilli.
• Large intestine – water re‑absorption, formation of faeces.
• Accessory organs – liver (bile), pancreas (digestive enzymes), gallbladder (bile storage).

Key Enzymes & Where They Act

Enzyme	Substrate	Site
Amylase	Starch	Saliva & pancreatic juice
Protease (pepsin, trypsin)	Proteins	Stomach & duodenum
Lipase	Triglycerides	Duodenum (with bile)

Balanced Diet & Micronutrients

• Food‑group recommendations (e.g., 5‑7 portions of fruit/veg per day).
• Vitamin C deficiency → scurvy; Vitamin D deficiency → rickets; Iron deficiency → anaemia.

Practical: Test a selection of foods for starch (iodine), protein (Biuret) and lipid (ethanol emulsion).

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8. Transport in Animals

Circulatory System Components

• Heart – four chambers (right/left atrium, right/left ventricle); double circulation (pulmonary & systemic).
• Blood vessels – arteries, veins, capillaries.
• Blood – plasma, red blood cells (haemoglobin), white blood cells, platelets.

Functions of Blood

• Transport of gases (O₂, CO₂), nutrients, hormones, waste products.
• Regulation of temperature, pH and osmotic balance.
• Defence – immune cells and clotting.

Practical: Measure resting heart rate, then after 2 min of moderate exercise; plot pulse (bpm) against activity level.

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9. Gas Exchange

Human Lungs

• Structure – trachea → bronchi → bronchioles → alveoli (thin walls, large surface area).
• Diffusion of O₂ into blood and CO₂ out of blood driven by partial pressure gradients.

Plant Stomata

• Guard cells regulate opening (turgor‑driven) in response to light, CO₂, humidity.
• Stomata allow CO₂ entry for photosynthesis and O₂ exit; also the main route for transpiration.

Factors Affecting Diffusion Rate

• Surface area (larger → faster).
• Concentration/partial‑pressure gradient (steeper → faster).
• Membrane thickness (thinner → faster).
• Temperature (higher → faster molecular motion).

Practical: Diffusion of iodine into agar blocks of varying thickness; record time for colour change to centre.

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10. Cellular Respiration

Overall Equation

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + ≈ 38 kJ mol⁻¹ ATP

Three Stages

Stage	Location	Main Products
Glycolysis	Cytoplasm	2 ATP, 2 NADH, 2 pyruvate
Krebs (Citric Acid) Cycle	Mitochondrial matrix	2 ATP, 6 NADH, 2 FADH₂, 4 CO₂
Electron‑Transport Chain (ETC)	Inner mitochondrial membrane	≈ 34 ATP, H₂O (from O₂)

ATP – Energy Currency

• ATP hydrolysis releases ~30 kJ mol⁻¹ for cellular work.
• Used for active transport, muscle contraction, biosynthesis, etc.

Practical: Yeast fermentation – measure CO₂ volume produced from glucose solution at 20 °C, 30 °C and 40 °C.

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11. Excretion

Human Kidneys

• Nephron structure – renal corpuscle (glomerulus + Bowman's capsule) → renal tubule (proximal convoluted, loop of Henle, distal convoluted) → collecting duct.
• Functions – filtration, re‑absorption of glucose, amino acids, ions, water; secretion of waste (urea, creatinine).
• ADH – increases permeability of collecting ducts → water re‑absorption → concentrated urine.

Plant Excretion

• Transpiration – loss of water (and dissolved minerals) via stomata.
• Leaf fall – removal of excess salts and damaged tissue.

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12. Coordination & Response

Nervous System

• Neuron structure – dendrite, cell body, axon, myelin sheath, synaptic terminal.
• Synapse – neurotransmitter release, signal transmission.
• Reflex arc – sensory neuron → spinal cord → motor neuron (quick response).

Endocrine System (basic overview)

• Hormones are chemical messengers released into blood.
• Key glands – pituitary (master gland), thyroid, adrenal.

Plant Responses

• Phototropism – auxin accumulation on the shaded side causes cell elongation.
• Gravitropism – auxin redistribution in roots vs shoots.
• Nastic movements – e.g., Venus flytrap closure (stimulus‑independent of direction).

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13. Hormones

• Insulin – lowers blood glucose; deficiency → diabetes mellitus (type 1).
• Glucagon – raises blood glucose; acts opposite to insulin.
• Adrenaline (epinephrine) – “fight‑or‑flight”; increases heart rate, glycogenolysis.
• Thyroxine (T₄) – regulates basal metabolic rate.
• Growth hormone – stimulates protein synthesis and growth.

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14. Homeostasis

Temperature Regulation

• Vasodilation & vasoconstriction.
• Sweating – evaporative cooling.
• Shivering – heat production.

Blood Glucose Regulation

• Insulin released when blood glucose rises → uptake by cells, glycogen synthesis.
• Glucagon released when blood glucose falls → glycogen breakdown, gluconeogenesis.

Water Balance

• ADH controls permeability of the distal convoluted tubule and collecting duct.
• Thirst mechanism – osmoreceptors in the hypothalamus.

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15. Drugs & Antibiotic Resistance

• Antibiotics – substances that inhibit bacterial growth (e.g., penicillin blocks cell‑wall synthesis).
• Mechanisms of resistance – mutation of target site, production of β‑lactamase, efflux pumps, plasmid‑mediated gene transfer.
• Selective pressure – over‑use of antibiotics favours resistant strains.
• Case study: MRSA – methicillin‑resistant Staphylococcus aureus; multi‑drug resistance and hospital‑acquired infections.

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16. Reproduction – Asexual & Sexual

Asexual Reproduction

• Vegetative propagation (runners, tubers, bulbils).
• Budding (hydra, yeast).
• Fragmentation (starfish).
• Advantages – rapid, no need for mate; disadvantages – no genetic variation.

Sexual Reproduction in Plants

• Flower structure – sepals, petals, stamens (male), carpels (female).
• Pollination (biotic/abiotic) → fertilisation (double fertilisation → zygote + endosperm).
• Seed development and dispersal mechanisms.

Human Reproductive System

• Male – testes, epididymis, vas deferens, seminal vesicles, prostate, penis.
• Female – ovaries, fallopian tubes, uterus, vagina.
• Menstrual cycle – phases (menstrual, proliferative, secretory) with hormone fluctuations (FSH, LH, estrogen, progesterone).

Diagram suggestion: Hormone profile across a 28‑day menstrual cycle.

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17. Genetics & Inheritance

Central Dogma

DNA → RNA (transcription) → Protein (translation).

Chromosomes, Genes & Alleles

• Humans: 46 chromosomes (23 pairs), autosomes + sex chromosomes.
• Gene – unit of inheritance; allele – alternative form.
• Dominant vs recessive; homozygous vs heterozygous.

Mitosis vs Meiosis

Process	Purpose	Location	Resulting Cells
Mitosis	Growth, repair	Somatic tissue	2 diploid cells, genetically identical
Meiosis	Gamete formation	Gonads	4 haploid cells, genetically varied

Monohybrid Cross (Punnett Square)

Example: Tall (T, dominant) × short (t, recessive)

	T	t
T	TT	Tt
t	Tt	tt

Genotype ratio 1 TT : 2 Tt : 1 tt → phenotype ratio 3 tall : 1 short.

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18. Ecology & the Environment

Energy Flow

• Food chains → food webs → ecological pyramids (energy, biomass, numbers).
• 10 % rule – only ~10 % of energy transferred to the next trophic level.

Biogeochemical Cycles

• Carbon cycle – photosynthesis, respiration, decomposition, fossil fuel combustion.
• Nitrogen cycle – nitrogen fixation, nitrification, assimilation, denitrification.
• Water cycle – evaporation, condensation, precipitation, runoff.

Human Impacts

• Deforestation – loss of habitat, reduced CO₂ uptake.
• Greenhouse gases – global warming, climate change.
• Biodiversity loss – ecosystem stability.

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19. Biotechnology

• Cloning (SCNT) – somatic cell nucleus transferred into enucleated egg (e.g., Dolly the sheep).
• Genetically Modified (GM) Crops – traits: pest resistance (Bt toxin), herbicide tolerance, improved nutrition (Golden Rice).
• Ethical considerations – food safety, environmental impact, patenting of life, animal welfare.

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20. Practical Skills (AO3)

Each core topic includes at least one suggested investigation. Summarised below:

Topic	Investigation	Key Variable(s)
Cell structure	Microscope observation of onion epidermis	Magnification, staining
Movement into/out of cells	Iodine diffusion in agar of different thicknesses	Thickness, temperature
Enzymes	Amylase activity at varying temperatures	Temperature, substrate concentration
Photosynthesis	Elodea O₂‑production under coloured lights	Light colour, intensity, CO₂ concentration
Respiration	Yeast fermentation at different temperatures	Temperature, glucose concentration
Excretion	Effect of ADH analogue on urine concentration (simulated using dialysis tubing)	ADH concentration
Homeostasis	Body temperature change after exercise	Exercise intensity, time

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21. Exam‑Style Checklist

• Define all key terms (e.g., chlorophyll, osmosis, allele).
• State and explain the significance of the seven characteristics of life.
• Draw and label a diagram of a dicot leaf, a neuron, and the human heart.
• Write balanced equations for photosynthesis and cellular respiration.
• Explain the role of chlorophyll in the light‑dependent reactions.
• Describe at least two factors that affect the rate of diffusion and give a practical example.
• Compare and contrast aerobic respiration and fermentation.
• Outline the steps of a monohybrid cross and calculate genotype/phenotype ratios.
• Discuss one advantage and one disadvantage of asexual reproduction.
• Evaluate a given investigation (e.g., effect of light colour on photosynthesis) – identify independent, dependent and controlled variables, suggest improvements.

Use this checklist when practising past‑paper questions to ensure full coverage of AO1 (knowledge), AO2 (application) and AO3 (investigation) skills.