Intermediate 2 Biology:
Course summary

Unit 1: Living Cells

Cell structure and function

Features of animal cells (e.g. cheek epithelium), plant cells (e.g. leaf mesophyll) and microbial cells (e.g. yeast).

Cell structures: nucleus, cytoplasm, cell membrane, cell wall, chloroplasts, vacuole.

Commercial use of cells to produce bread, alcohol, antibiotics, yoghurts, and fuels (biogas, gasohol).

Diffusion and osmosis in plant and animal cells

Diffusion as the movement of substances down a concentration gradient.

Osmosis as the movement of water across a selectively permeable membrane down a water concentration gradient; hypotonic/hypertonic/isotonic solutions; turgid/flaccid/plasmolysed cells.

Enzyme action

Enzymes as protein catalysts; specificity due to shape of active site; enzymes involved in degradation (e.g. amylase, catalase) and synthesis (e.g. phosphorylase).

Factors affecting enzyme activity: temperature and pH; denaturation due to change in shape.

Aerobic and anaerobic respiration

Glucose as an energy source for cellular processes; used to synthesise ATP from ADP and Pi;

Aerobic respiration: breakdown of glucose to pyruvic acid by glycolysis; further breakdown of pyruvic acid to CO2 and water in presence of oxygen; yield of 38 ATP molecules.

Anaerobic respiration: reversible conversion of pyruvic acid to lactic acid in animals; yield of 2 ATP molecules; muscle fatigue and oxygen debt; irreversible conversion of pyruvic acid to ethanol and CO2 in plants and yeast.


Chloroplasts trapping light energy as ATP; photolysis producing hydrogen (bound to a hydrogen carrier) and oxygen; carbon fixation using hydrogen, ATP and CO2 to produce glucose; conversion of glucose to other carbohydrates (starch, cellulose);

Limiting factors: temperature, light intensity, CO2 concentration; supplementing these in horticulture.

Unit 2: Environmental Biology and Genetics


Components of an ecosystem: habitats, populations, communities; ecological niches.

Food chains and food webs: producers, primary and secondary consumers, herbivores, carnivores, omnivores, predators, prey, decomposers; pyramids of energy, numbers and biomass.

Biodiversity defined as the range of species in an ecosystem; reduction in biodiversity caused by very high/low grazing pressure, pollution or habitat destruction; competition in plants and animals.

Adaptations to habitat/niche (in Darwin's finches and desert plants); behavioural adaptations (in woodlice).

Factors affecting variation in a species

Continuous/discontinuous variation in animals and plants.

Gamete production in mammals (in ovaries and testes) and flowering plants (in ovaries and anthers) involving halving of chromosome number; matching chromosomes pair and separate at meiosis, with independent assortment producing variation; fusion of gametes to produce a zygote at fertilisation restoring chromosome number.

Chromosomes as chains of DNA bases encoding proteins; 23 pairs in humans; sex chromosomes;

Chromosomes contain genes with different alleles; homozygous/heterozygous; dominant/recessive; genotype and phenotype; monohybrid crosses between true breeding parents; parental, F1 and F2 generations; codominance; polygenic inheritance;

Natural selection illustrated by peppered moth; selective breeding; genetically engineering bacteria to produce foreign proteins (e.g. human hormones) by inserting plasmid containing appropriate gene.

Unit 3: Animal Physiology

Mammalian nutrition

Food groups: carbohydrates (based on sugars), fats (made from fatty acids and glycerol), proteins (made from amino acids), vitamins, minerals; food tests; energy content of foods;

Digestion: mechanical breakdown of food in mouth and mixing with saliva containing mucus and amylase (digesting starch into maltose); peristalsis in oesophagus; churning of food by longitudinal and circular muscles of stomach and mixing with gastric secretions containing mucus, acid, and pepsin (breaking down protein); further digestion in small intestine including breakdown of fat by lipase and protein by trypsin; water absorption in large intestine prior to elimination of faeces.

Absorption by villi containing capillaries and lacteals; use of absorbed substances as source of energy and raw materials.

Pancreas produces enzymes including lipase, amylase and trypsin; liver stores glucose as glycogen; gall bladder stores bile which assists fat breakdown.

Control of internal environment

Human urinary system: kidney, renal artery and vein, ureter, bladder and urethra.

Osmoregulation by kidneys; water gain (drinking, food and metabolism) and loss (sweat, breath, faeces and urine).

Urea as nitrogenous waste, produced by deamination of excess amino acids in liver, and excreted by kidneys.

Kidney nephron: filtration in Bowman's capsule/glomerulus, reabsorption from tubules and collecting ducts into capillaries, permeability of collecting ducts increased by ADH from hypothalamus; osmoregulation in saltwater/freshwater fish.

Circulation and gas exchange

Heart: four chambers, bicuspid/tricuspid/semi-lunar valves; difference in thickness of ventricle walls; coronary arteries and the consequence of their blockage; pulse;

Structure and function of arteries, veins and capillaries; location of aorta/vena cava, pulmonary artery/vein, hepatic artery/vein, mesenteric artery, hepatic portal vein, renal arteries/veins.

Lungs: trachea, bronchi, bronchioles, and alveoli (with large surface area, thin walls, moist surfaces and good blood supply for efficient diffusion of oxygen and CO2);

Oxygen carried as oxyhaemoglobin in red blood cells; CO2 carried in red blood cells and dissolved in plasma, causing acidity; nutrients carried dissolved in plasma;

Phagocytosis (engulfing then digestion) of foreign bodies by macrophages; production of specific antibodies in defence.

Sensory mechanisms and processing of information

Brain: cerebrum (for conscious responses and higher functions, containing localised sensory/motor areas), cerebellum (for balance and co-ordination), medulla (for involuntary processes); hypothalamus (for osmoregulation and temperature control).

Nerves carrying sensory information to CNS, which sorts information, and carrying impulses from CNS to muscles;

Reflex arcs for rapid protective responses: containing receptor, sensory neurone, relay fibre, motor neurone and effector;

Temperature regulation: motor responses, constriction and dilation of blood vessels, alterations in blood flow to skin, shivering, sweating.


Disclaimer: I cannot guarantee the accuracy of the information given here, and the syllabus may change in the future. For authoritative information about this course, see the Scottish Qualifications Authority web site.

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© Andrew Gray, 2005