mass transport

Question 1

structure of haemoglobin

Answer 1

globular
water soluble
4 polypeptide chains (quaternary)

Question 2

role of haemoglobin

Answer 2

in RBC
o2 molecules bind to haem groups and are carried around body to respiring tissues

Question 3

3 factors affecting o2-haemoglobin binding

Answer 3

pp/conc of o2
pp/conc of co2
saturation of haemoglobin with o2

Question 4

how does pp of oxygen affect o2-haemoglobin binding

Answer 4

as pp of o2 increases, the affinity of haemoglobin for o2 also increases, so o2 binds tightly to haemoglobin. when pp is low, o2 is released from haemoglobin

Question 5

how does pp of co2 affect o2-haemoglobin binding

Answer 5

as pp of co2 increases, the conditions become acidic causing haemoglobin to change shape. the affinity of haemoglobin for oxygen decreases, so oxygen is released from haemoglobin (BOHR EFFECT)

Question 6

how does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding

Answer 6

its hard for 1st o2 molecule to bind. once it does, it changes the shape to make it easier for the 2nd and 3rd molecules to bind (+VE COOPERATIVITY) then harder for 4th to bind because low chance of finding a binding site

Question 7

why does o2 bind to haemoglobin in the lungs

Answer 7

-pp of o2 is high
-low co2 conc in lungs, high affinity
-+ve cooperativity

Question 8

why is 02 released from haemoglobin in respiring tissues

Answer 8

-low pp of o2
-high co2 conc in respiring cells, affinity decreases

Question 9

what do oxyheamoglobin dissociation curves show

Answer 9

saturation of haemoglobin with o2 (in %), plotted against pp of o2 (in kPa). curves further to the left show the haemoglobin has a higher affinity for o2

Question 10

how does co2 affect the position of an oxyhaemoglobin dissociation curve

Answer 10

curve shifts right beacause haemoglobins affinity for o2 has decreased

Question 11

name the common features of a mammalian circulatory system

Answer 11

1) suitable transport medium, water soluble to allow substances to dissolve
2) means of moving the medium and maintaining pressure throughout body e.g. heart
3) means of controlling flow, so it remains unidirectional e.g. valves

Question 12

features of right side of heart

Answer 12

pulmonary artery
vena cava
right atrium
tricuspid valve
right ventricle

Question 13

features of left side of heart

Answer 13

aorta
pulmonary vein
left atrium
semilunar valves
bicuspid valves
left ventricle

Question 14

relate the structure of the chambers to their function

Answer 14

ATRIA:
thin walled and elastic- stretch when filled with blood
VENTRICLES:
thick muscular walls- pump blood under high pressure
left thicker than right- has to pump blood all the way around the body

Question 15

relate the structure of the vessels to their function

Answer 15

ARTERIES:
thick walls- handle high pressure without tearing
muscular and elastic- control blood flow
VEINS:
thin walls - lower pressure
valves - prevent backflow
less muscular and elastic - don’t control blood flow

Question 16

why are 2 pumps (left and right) needed instead of 1

Answer 16

to maintain BP around whole body. when blood passes through narrow capillaries of lungs, pressure drops sharply and therefore would not be flowing strongly enough to continue around whole body, It’s returned to heart to increase pressure

Question 17

cardiac diastole

Answer 17

-heart is relaxed
-blood enters atria, pressure increases
-atrioventricular valves open, allowing blood to flow into ventricles
-pressure in heart lower than in arteries so semilunar valves stay closed

Question 18

atrial systole

Answer 18

atria contract, pushing any remaining blood into ventricles

Question 19

ventricular systole

Answer 19

-ventricles contract, pressure increases
-atrioventricular valves close to prevent backflow
-semilunar valves open
-blood flows into arteries

Question 20

name the nodes involved in heart contraction and where they’re situated

Answer 20

sinoatrial node (SAN) = wall of right atrium
atrioventricular node (AVN)= in between 2 atria

Question 21

myogenic

Answer 21

heart’s contraction initiated from within muscle itself, rather than by nerve impulses

Question 22

how is the structure of capillaries suited to their function

Answer 22

one cell thick- short diffusion pathway
very narrow- can permeate tissues + RBC can lie flat against the wall, effectively delivering o2 to tissues
numerous and highly branched- large SA

Question 23

tissue fluid

Answer 23

watery substance containing glucose, AA, oxygen, and other nutrients. It supplies these to the cells , while also removing waste materials

Question 25

how is tissue fluid formed

Answer 25

hydrostatic pressure created as blood is pumped through increasingly small vessels; fluid forced out of capillaries- it bathes the cells and then returns to the capillaries when the hydrostatic pressure is low enough

Question 26

how is water transported in plants

Answer 26

xylem vessels; long, continuous columns that also provide structural support to the stem

Question 27

cohesion-tension theory

Answer 27

water molecules form H bonds, causing them to stick together (cohesion). The surface tension of the water also creates this sticking effect
- as water is lost by transpiration,more can be drawn up the stem

Question 28

3 components of phloem vessles

Answer 28

sieve tube elements- form a tube to transport sucrose in the dissolved form of sap
companion cells- involved in ATP production for active loading of sucrose into sieve tubes
plasmodesmata- gaps between cell walls where the cytoplasm links, allowing substances to flow

Question 29

process whereby oragnic materials are transported around plant

Answer 29

translocation

Question 30

how does sucrose in leaf move into phloem

Answer 30

sucrose enters companion cells of phloem vessels by active loading, using ATP + diffusion gradient of H+ ions

sucrose then diffuses from companion cells into sieve tube elements through plasmodesmata

Question 31

how do phloem vessels transport sucrose around the plant

Answer 31

as sucrose moves into the tube elements, water potential inside pholem reduced- causes water to enter via osmosis from xylem and increases hydrostatic pressure

water moves along sieve tube towards areas of lower hydrostatic pressure - sucrose diffuses into surrounding cells where needed

Question 32

evidence FOR mass flow hypothesis of translocation

Answer 32

-sap released when stem cut, there must be pressure in the phloem
-higher sucrose conc in the leaves than roots
-increasing sucrose levels in the leaves results in increased sucroses in phloem

Question 33

evidence AGAINST mass flow hypothesis of translocation

Answer 33

-structure of sieve tubes seems to hinder mass flow
-not all solutes move at same speed, as they would in mass flow
-sucrose delivered at same rate throughout plant, rather than to areas with lowest conc first

Question 34

how can ringing experiments be used to investigate transport in plants

Answer 34

bark and phloem of tree removed in a ring, leaving xylem behind

evenrtually, tissues above the missing ring swells due to accumulation of sucrose as the tissue below begins to die - therefore sucrose must be transported in the phloem

Question 35

how can tracing experiments be used to investigate transport in plants

Answer 35

plants grown in presence of radioactive co2, which is incorporated into plant’s sugars

using autoradiography, we can see that the areas exposed to radiation correspond to where the phloem is