A2 Human Biology Unit 10

Text questions

P215/Q1		4� structure: aggregation of polypeptide chains into a functional molecule of a protein. Presence of haem group (non-protein prosthetic group);
P216/Q2	a)	pO2 will drop;
	b)	Amount of O2 supplied to the muscle will increase;
P217/Q3		The highest pCO2 & lowest pO2 would be found in a respiring muscle. The substrate for respiration is O2, so pO2 will drop; The by-product is CO2, hence pCO2 will increase;
P219/Q4		Vigorous exercise → lower pO2 → abnormal haemoglobin (abn/H) is less soluble → abn/H sticks together forming long fibres → the shape of RBC altered (: sickle shape);
P221/Q7		More CO2 carried as carbamino-haemoglobin (C-H) in the vein, because in the tissues: oxyhaemoglobin → haemoglobin + oxygen; haemoglobin + CO2 → carbamino-haemoglobin (→lungs);

Assignment

P223/Q1

Animal	Unloading pressure/kPa
Elephant (1)	2.6
Human (2)	4.2
Cat (3)	5.2
Mouse (4)	7.2

P224/Q2

The smaller the animal, the higher the unloading pressure; (the smaller the animal, the more readily/easily its haemoglobin gives up oxygen to the surrounding tissues).

Body mass/kg	Surface area/m2	Heat loss/kJ/h	Relative heat loss
Body mass/kg	Surface area/m2	Heat loss/kJ/h	kJ/h/kg	kJ/h/m2
31.2	1.08	191.1	6.1	176.9
24.0	0.88	171.0	7.1	194.3
18.2	0.77	146.4	8.0	190.1
9.6	0.53	108.9	11.3	205.5
3.2	0.24	49.1	15.3	204.6

P224/Q4

The animal's mass. As the mass of the animal drops, the relative heat loss (RHL) /hr/kg body mass increases more rapidly than RHL/hr/m2 body surface area.

P224/Q5

S.A./V. of small mammals is larger than S.A./V. of big mammals → larger heat transfer/loss to the environment from the body of a small mammal → more heat needs to be generated to maintain the steady body temperature in small mammals → higher respiration rate/kg body mass/hr → (b);

Higher respiration rate → higher oxygen consumption/kg body mass/hr;

Small mammals benefit from haemoglobin that gives up its O2 very readily/easily (i.e. at a high unloading pressure). O2 can be delivered to the tissues to maintain the high rate of aerobic respiration.

P225/Q6

Mitochondria = sites of respiration. More mitochondria in the liver → more ATP produced to maintain a high metabolic rate of the liver cells (e.g. conversion of NH3 to urea in the ornithine cycle).

Cristae are the sites of respiration (electron transport chain). More cristae → larger SA available for the processes of respiration → more ATP/heat produced.

Capillaries are the sites of gas/metabolite exchange between blood & tissues. The denser the capillary network, the better exchange between blood & tissues → higher metabolic rate in the tissues.

Examinations

P225/Q1	a)	(i) High pO2 in lungs → haemoglobin in lungs saturated with O2; (ii) pO2 in tissues low → haemoglobin unloads its O2;
	b)	The Bohr shift. Physical exercise → increased pCO2 in blood → dissociation curve for haemoglobin moves to the right : for the same pO2 saturation of haemoglobin with O2 will drop → O2 released by haemoglobin to the muscle tissue to maintain aerobic respiration;