Molecules, Transport and Health flashcards

Topic 1: Molecules, Transport and Health

Condensation vs hydrolysis

Condensation joins monomers and releases water. Hydrolysis breaks the bond using water.

Monomer, bond and polymer for carbohydrates, proteins and nucleic acids

Monosaccharide → glycosidic bond → polysaccharide. Amino acid → peptide bond → polypeptide. Nucleotide → phosphodiester bond → nucleic acid.

Starch and glycogen vs cellulose

Starch and glycogen: α-glucose, coiled or branched, for storage. Cellulose: β-glucose with alternate molecules inverted, giving straight chains that hydrogen-bond into microfibrils of high tensile strength.

Why are oils liquid at room temperature?

They contain unsaturated fatty acids, whose C=C double bonds produce kinks that stop the chains packing closely.

Properties of water and their importance

Polar: solvent for ions and polar molecules. High specific heat capacity: buffers temperature change. High latent heat of vaporisation: cooling by evaporation. Cohesion: continuous column in xylem. Ice floats and insulates. All due to hydrogen bonding.

Why do large organisms need a mass transport system?

Their surface area to volume ratio is too small for diffusion alone to supply their needs quickly enough over the distances involved.

Advantage of a double circulation

Blood passes through the heart twice per circuit, keeping oxygenated and deoxygenated blood separate and allowing the systemic circuit to run at a higher pressure.

Arteries vs veins vs capillaries

Artery: thick muscular wall, elastic fibres, narrow lumen; withstands high pressure, recoil smooths flow. Vein: thin wall, wide lumen, valves; low pressure. Capillary: one cell thick; short diffusion distance.

The cardiac cycle

Atrial systole: atria contract, forcing blood into the ventricles. Ventricular systole: ventricles contract; AV valves close, semilunar valves open. Diastole: all chambers relax; semilunar valves close; atria refill.

What opens and closes the heart valves?

Pressure differences alone. A valve opens when the pressure behind it exceeds the pressure in front, and closes when the reverse is true. Valves are passive flaps, not muscles.

Sequence of events in atherosclerosis

Endothelium damaged (high blood pressure, smoking) → inflammatory response, white blood cells gather → cholesterol and lipids deposit, forming an atheroma → calcium salts and fibrous tissue harden it, narrowing the lumen → higher pressure causes more damage.

How can an atheroma cause a heart attack or stroke?

A plaque may rupture and trigger a thrombus (blood clot) that blocks the artery. A blocked coronary artery causes a myocardial infarction; a blockage in the brain causes a stroke.

HDL vs LDL

HDL transports cholesterol to the liver for disposal and is protective. LDL transports cholesterol to the tissues and is associated with plaque formation.

Modifiable and non-modifiable risk factors for CVD

Modifiable: diet high in saturated fat and salt, smoking, inactivity, obesity, high alcohol intake. Non-modifiable: age, sex, genetics.

Statins and anticoagulants: benefit and risk

Statins lower LDL cholesterol by inhibiting a liver enzyme in cholesterol synthesis; side effects include muscle pain. Anticoagulants (such as warfarin) reduce clotting, lowering thrombus risk, but raise the risk of serious bleeding.

How should a study of a CVD risk factor be evaluated?

Check sample size and whether it was representative, whether it was controlled, how long it ran, whether other variables were accounted for, and who funded it. Correlation does not establish causation.