7 - Mass Transport

Question 1

structure of haemoglobin molecules

Answer 1

protein with a quaternary struture evolved to make it effective at carrying oxygen
consists of 4 polypeptide chains linked to form an almost spherical molecule
each polypeptide chain is associated with a haem group

Question 2

haem group

Answer 2

contains an Fe (II) ion
each Fe (II) ion can combine with an oxygen molecule

Question 3

process by which haemoglobin binds with oxygen molecules

Answer 3

associating / loading

Question 4

process by which haemoglobin releases oxygen molecules

Answer 4

dissociating / unloading

Question 5

effect of carbon dioxide on haemoglobin

Answer 5

carbon dioxide causes haemoglobin to change shape, reducing haemoglobin affinity for oxygen

Question 6

myoglobin

Answer 6

a quaternary protein with just one haem group
has high affinity for oxygen even at low partial pressures
found in muscle cells

Question 7

double circulatory system in humans

Answer 7

one sytem to lungs, one system to the body

maintains pressure

Question 8

hepatic arteries/veins

Answer 8

to/from liver

Question 9

renal arteries/veins

Answer 9

to/from kidneys

Question 10

arteries

Answer 10

away from the heart
high pressure
thick outer wall of collagen and connective tissue
smooth muscle and elastic tissue can stretch and recoil

Question 11

veins

Answer 11

thin outer wall of collagen and connective tissue
smooth inner layer of muscle and elastic tissue
large lumen
semi-lunar pocket valves to prevent backflow

Question 12

aorta

Answer 12

carries oxygenated blood to the body

Question 13

vena cava

Answer 13

carries deoxygenated blood from the body to the heart

Question 14

pulmonary artery

Answer 14

carries deoxygenated blood to the lungs

Question 15

pulmonary vein

Answer 15

carries oxygenated blood from the lungs to the heart

Question 16

cardiac cycle

Answer 16

diastole, atrial systole, ventricular systole

Question 17

diastole

Answer 17

ventricles and atria relax
semilunar valves closed
atrioventricular valves open
atria fill with blood from veins

Question 18

atria systole

Answer 18

atria contract
blood forced into ventricles
semilunar valves closed
atrioventricular valves open

Question 19

ventricular systole

Answer 19

atria relax and ventricles contract
blood forced into arteries
atrioventricular valves closed
semilunar valves open

Question 20

formation of tissue fluid

Answer 20

1. high hydrostatic pressure in capillaries at arterial end forces water and small molecules out
2. this is tissue fluid and moves into spaces between the cells
3. it is similar to blood but doesn’t contain plasma proteins
4. at arterial end, blood pressure > osmotic pressure
5. at venous end, greater osmotic pressure due to plasma proteins draws tissue fluid back in
6. some fluid is drained into lymphatic vessels

Question 21

xylem

Answer 21

tissue that transports water in plants

consist of dead cells which produce lignin

Question 22

lignin

Answer 22

provides mechanical strength and waterproofing for the xylem tissue

Question 23

transpiration

Answer 23

water evaporates from mesophyll cells in the leaf
as water evaporates, more molecules are drawn up behind it due to cohesion
a column of water is therefore pulled up the xylem due to transpiration
this creates negative pressure in the xylem - COHESION TENSION THEORY

Question 24

translocation

Answer 24

transport of soluble organic substnaces and some mineral ions in the phloem

Question 25

source

Answer 25

any area where sucrose is produced (usually leaves)

Question 26

sink

Answer 26

where sucrose is delivered to and used

Question 27

mass flow hypothesis

Answer 27

sucrose moves into companion cells by facilitated diffusion
sucrose co-transported with protons into sieve tubes from companion cells
water potential therefore lowered in sieve tubes
water enters tubes from xylem by osmosis
high pressure at source and low pressure at sink creates pressure gradient
causes organic substances to translocate