WBI11 Molecules, Diet, Transport and Health

Lessons in WBI11

1. Carbohydrates: from sugars to starch
   Condensation forms glycosidic bonds and releases water; hydrolysis breaks them. Amylose is helical (1,4), amylopectin and glycogen are branched (1,4 and 1,6).
2. Water: a polar solvent for transport
   Water is polar (δ- O, δ+ H) and forms hydrogen bonds. Ions and polar molecules dissolve in it, so it is the transport medium; non-polar lipids need carrier lipo
3. Lipids: triglycerides, saturated and unsaturated
   Triglyceride = glycerol + 3 fatty acids joined by 3 ester bonds in condensation reactions. Saturated: no C=C; unsaturated: one or more C=C (kinked chains).
4. Core practical 1: estimating reducing sugar and starch
   Make standards of known concentration, treat them and the unknown identically, and match colours. It is semi-quantitative; a colorimeter and calibration curve m
5. Why animals need circulation, and blood vessels
   Large animals have a small SA:V ratio and long diffusion distances, so need mass transport. Arteries: thick elastic walls; veins: wide lumen, valves; capillarie
6. The heart and the cardiac cycle
   Atrial systole, ventricular systole, diastole. Valves open and close because of pressure differences: AV valves shut as ventricles contract; semilunar valves sh
7. Haemoglobin and the oxygen dissociation curve
   S-shaped curve: loads O2 at high pO2, unloads at low pO2. More CO2 shifts the curve right (Bohr effect). Fetal haemoglobin has higher affinity (curve to the lef
8. Atherosclerosis and blood clotting
   Endothelial damage, inflammation, lipid build-up and plaque formation narrow arteries. Thromboplastin turns prothrombin to thrombin, which turns fibrinogen to f
9. CVD risk factors, antioxidants and cholesterol
   Fixed risks: genes, age, sex. Changeable: blood pressure, smoking, inactivity, diet. High LDL raises risk, high HDL lowers it. Antioxidants neutralise free radi
10. Core practical 2: vitamin C content of food and drink
    Vitamin C decolourises blue DCPIP. Less juice needed means more vitamin C. Juice concentration = standard concentration x (volume of standard / volume of juice)
11. Health data, study design and perceived risk
    Correlation does not prove causation: look for mechanism, consistency, dose-response and trials. Large, representative, well-controlled samples give valid, reli
12. Diet, obesity and reducing heart disease risk
    BMI = mass / height² (25 to 29.9 overweight, 30+ obese). Waist-to-hip ratio shows abdominal fat. Energy in greater than energy out leads to weight gain.
13. Treating CVD: benefits and risks of drugs
    Antihypertensives lower blood pressure; statins lower LDL; anticoagulants and platelet inhibitors reduce clotting. The main risk of clotting drugs is bleeding.
14. Gas exchange surfaces and Fick's law
    Rate of diffusion is proportional to (surface area x concentration difference) / thickness. Lungs: many alveoli, thin walls, ventilation and blood flow keep gra
15. Cell membranes: the fluid mosaic model
    Phospholipid bilayer with hydrophilic heads out and hydrophobic tails in. Fluid mosaic: proteins move in a fluid bilayer; cholesterol regulates fluidity; glycop
16. Core practical 3: membrane permeability
    Higher temperature increases fluidity, then denatures membrane proteins; alcohol dissolves lipids. Both let more pigment leak, measured as higher absorbance.
17. Osmosis and transport across membranes
    Osmosis: water moves from higher to lower water potential across a partially permeable membrane. Facilitated diffusion uses channels or carriers without ATP; ac
18. Proteins: structure and function
    Amino acids join by peptide bonds (condensation). Primary = sequence; secondary = α-helix or β-sheet (hydrogen bonds); tertiary = 3D shape (hydrogen, ionic, dis
19. Enzymes: how they work
    The active site is complementary to the substrate, forming an enzyme-substrate complex. Enzymes lower activation energy and are not used up. Intracellular enzym
20. Core practical 4: factors affecting enzyme activity
    Measure the initial rate (tangent at t = 0). Rate rises with temperature to an optimum then falls as the enzyme denatures; pH has an optimum; substrate concentr
21. DNA, RNA and DNA replication
    Nucleotide = pentose + phosphate + base, joined by phosphodiester bonds. A-T, C-G pairing. Helicase separates strands; DNA polymerase joins new nucleotides. Mes
22. The genetic code and mutations
    Triplet, non-overlapping, degenerate code with start and stop codons. Substitutions may be silent because of degeneracy; insertions and deletions cause frameshi
23. Protein synthesis: transcription and translation
    Transcription: RNA polymerase makes mRNA from the template strand in the nucleus. Translation: tRNA anticodons pair with mRNA codons at the ribosome; peptide bo
24. Monohybrid inheritance and sex linkage
    Ff x Ff gives 3 : 1 phenotypes (1 in 4 recessive). X-linked recessive traits such as red-green colour blindness appear more in males, who have one X.
25. Cystic fibrosis and genetic screening
    Faulty CFTR chloride channels make mucus thick: blocked airways and infections, blocked pancreatic duct, reduced fertility. Screening: carrier tests, PGD, amnio

Next exams for WBI11

• January 2027: Fri 8 Jan 2027, afternoon, 1h 30m
• Summer 2027: Tue 4 May 2027, afternoon, 1h 30m

From Pearson's final timetables. All exam dates. Always confirm your entries with your exams officer.