Biology unit 2

Stretches/’expands’ under high pressure/when ventricle 

contracts / systole;

Recoils/’springs back’ under low pressure/when ventricle 

relaxes / diastole;

Smooths blood flow / maintains blood pressure / reduces

pressure surges;

(Muscle) contracts;

(Arteriole) constricts / narrows/alters size of lumen / 

reduces/regulates blood flow (to capillaries);

(More) time for exchange of substance

Interphase/ S/synthesis (phase);

(explanation : DNA/gene replication/synthesis occurs / longest stage;)

(Different) form/type/version of a gene / different base 

sequence of a gene

Loading/uptake/association of oxygen at high p.O2;

In lungs (haemoglobin) is (almost) fully saturated / in lungs 

haemoglobin has a high affinity for oxygen; 

Unloads/releases/dissociates oxygen at low p.O2;

Unloading linked to higher carbon dioxide concentration; 

Smaller mammal has greater surface area to volume ratio;

Smaller mammal/larger SA:Vol ratio more heat lost (per unit 

body mass);

Smaller mammal/larger SA:Vol ratio has greater rate of 

respiration/metabolism;

Oxygen required for respiration;

(Haemoglobin) releases more oxygen / oxygen released more 

readily / haemoglobin has lower affinity;

Isolation / quarantine / ‘kept separate’;

Screening/testing (of patients/doctors etc);

Sterilisation of wards/equipment / method to improve hygiene;

Prevents bias;

Vested interest (of scientists);

Prevents ‘placebo’/positive/negative/psychological 

effects/’demand characteristics’ (in volunteers); 

More than one polypeptide chain;

1. Mark for general principle of - reduced variety/number of   

    different alleles/DNA / reduced gene pool 

2. Founder effect;

3. A few individuals from a population become isolated/form   

    colonies:

4. (Genetic) bottlenecks;

5. (Significant) fall in size of population

6. Selective breeding / artificial selection;

7. Using organisms with particular 

    alleles/traits/phenotypes/characteristics;

Change in (sequence of) amino acids/primary structure; 

Change in hydrogen/ionic/disulfide bonds; 

Alters tertiary structure/active site (of enzyme); 

Substrate cannot bind / no enzyme-substrate complexes form;