exchange and transport exam questions

why are valves needed in veins

prevents the back flow of blood due to low pressure

allows for one way blood flow back to the heart

Explain how arterioles are better adapted than arteries to allow the blood to flow into an individual organ.

relaxation of smooth muscle (in arteriole) causes vasodilation (of the lumen) ✓

2 (this) regulates / controls, blood flow to capillaries (in the organ) ✓

3 pressure of blood in artery is higher ✓

4 as blood flows from the artery to the arteriole, the pressure falls ✓

5 (so) capillary (walls) will not rupture

Lymph and tissue fluid are both formed from the blood.

Which statement describes the composition of these fluids?

Lymph contains more protein than tissue fluid because of antibody production.

Which statement describes features of the mammalian heart?

The wall of the left ventricle is thicker because it needs to pump blood around the whole body.

Describe the flow of blood through the left side of the heart during the cardiac cycle and explain the role of valves and pressure differences in this process.

level 3 exemplar

• blood enters the left side of the heart via the pulmonary vein and blood passively fills the left atrium and ventricle during diastole

• this causes the gradual increase in atrial and ventricular pressure

• during atrial systole the left atrium contracts and volume decreases and pressure increases forcing blood into the left ventricle

• as pressure in the atrium is higher than that of the ventricle there is a slight delay in between atrial and ventricular systole

• the bicuspid atrioventricular valve closes before the ventricular systole to prevent backflow of blood into the atrium

• 
  

describe an active mechanism which cold possibly be involved in the transport of sugars from sources to sinks

loading, into companion cell / from transfer cell / into sieve tube /
into phloem – implied;
H ions / protons, pumped out of, companion cell / sieve tube / phloem;
diffuse back in with sucrose;
protein carrier / co-transporter;
possible active unloading by reverse mechanism;