Biology, Comp 3 need practice

Describe two ways that an oxygen concentration gradient is maintained between alveolar air and blood.

circulatory system/ flow of blood/ {deoxygenated blood brought to/ oxygen(ated blood) removed from } lungs (1)

ventilation/ breathing/ exchanges air in the lungs/ inhale and exhale (1)

State the different forms in which carbon dioxide is transported to the lungs for excretion.

hydrogen carbonate (ions) / bicarbonate (ions)

Carbaminohaemoglobin

carbonic acid/ carbon dioxide dissolved in plasma

Explain why a low protein diet would result in fluid retention in the tissues.

A low protein diet reduces plasma protein/albumin levels

Plasma proteins/albumin reduce water potential of blood

Lack of protein means water potential of plasma becomes higher

This decreases water potential gradient so less water is reabsorbed/ more water remains in tissue fluid

State features of a successful vaccine

Must be safe/ not have side effects

Must be effective/ trigger an immune response

Explain why leaves and chloroplasts change their orientation during the day

to maximise their absorption of light

OR

so that a greater surface area of leaves face the sun

Explain how ATP is used at a synapse

Synthesis of neurotransmitter

Movement of vesicles/exocytosis

Active transport of Calcium ions out (of knob)

Synthesis of neurotransmitter receptors

Energy to package neurotransmitters into synaptic vesicles

Suggest why terrestrial insects do not require haemoglobin.

Oxygen diffuses directly into {cells/ tissue} from tracheoles

Define the term holozoic.

Internal digestion of food substances

Describe what is meant by the term autosomal dominant allele.

a chromosome that is not a sex chromosome/ not sex linked

Only 1 copy of the allele is needed to inherit disease

State the meaning of the term endemic

A disease which is present at low levels in an area

State the function of the Casparian strip.

Forces / moves water / (dissolved) ions from the apoplast pathway into the symplast pathway

Define what an organ is

A group of tissues working together to perform a similar/specific function

When should the null hypothesis be accepted

If your calculated value is lower than the critical value, you should accept the null hypothesis- there’s no significant difference.

Suggest why an increase in carbon dioxide conc. may result in reduced stomatal density

The carbon dioxide is used for photosynthesis. An increased conc of carbon dioxide means that photosynthesis happens at an increased rate.

This higher conc of carbo dioxide creates a higher conc gradient and so there’s a faster rate of diffusion.

This means there’s a reduced need for the stomata and so their density decreases.

The foetal heart has a hole between the left and right sides. Explain why this hole is open during foetal development.

In an adult, the right atrium pumps blood into the right ventricle and to the lungs.

However, in a foetus, the lungs aren’t yet functional and so there’s no need for this pulmonary circulation.

Therefore, this open hole allows blood to pass directly from the right atrium to the left atrium (and left ventricle), missing out the lungs.