mass transport

Question 1

describe the structure of haemoglobin

Answer 1

globular protein made of 4 polypeptide chains

each associated with a haem group which contains an Fe+ ion

each Fe+ can combine with one molecule of O2

Question 2

what is the role of haemoglobin in the transport of oxygen?

Answer 2

readily associate with O2 at gas exchange surfaces

readily dissociate from O2 at tissues

Question 3

explain the shape of the oxygen dissociation curve (S shape)(3)

Answer 3

shape of haemoglobin makes it difficult for first oxygen bind bc they are closely packed

binding of first oxygen changes quaternary structure so shape changes, making it easier for other O2 molecules to bind

the last molecule has lower probability of binding as there are less empty sites

Question 4

what is positive cooperativity?

Answer 4

when the binding of the first oxygen molecule increase the chance of the second binding

Question 5

what is the Bohr effect?

Answer 5

the greater the concentration of carbon dioxide, the more readily the haemoglobin releases the oxygen molecule

Question 6

what does it mean if the oxygen dissociation curve is further to the left?

Answer 6

there is a greater affinity for oxygen

Question 7

what does it mean if the oxygen dissociation cure is further to the right?

Answer 7

there is a lower affinity for oxygen

Question 8

Describe the advantage of the Bohr effect during intense exercise.(2)

Answer 8

more CO2 at cells so increased dissociation of oxygen for aerobic respiration.

Question 9

why do large organisms require a transport system

Answer 9

small SA:V
more active

Question 10

what type of circulatory system do mammals have?(2)

Answer 10

closed-blood is confined to blood vessels
double circulatory-passes through the heart twice

Question 11

what are the 4 chambers of a heart?

Answer 11

right atrium
right ventricle
left atrium
left ventricle

Question 12

what are the 4 vessels connected to the chambers of the heart?

Answer 12

aorta
vena cava
pulmonary artery
pulmonary vein

Question 13

describe the flow of blood starting at the vena cava

Answer 13

unoxygenated blood enters right atrium -> right ventricle -> pulmonary artery -> lungs -> oxygenated blood enters left atrium -> left ventricle -> aorta -> body

Question 14

what prevents backflow of blood into the atria and where are these located?

Answer 14

bicuspid valve (left)
tricuspid valve (right)

these are between the atria and the ventricles

Question 15

what blood vessels supply the heart with oxygen?

Answer 15

coronary arteries

Question 16

what happens when coronary arteries become blocked?

Answer 16

myocardial infarction(heart attack)

Question 17

describe diastole(3)

Answer 17

relaxation of the heart
blood enters atria, increasing pressure

when pressure in atria greater than ventricles, atrioventricular valves open

pressure in ventricles is reduced as walls are relaxed, this means it is lower than in the arteries so semi lunar valves close

Question 18

describe atrial systole(2)

Answer 18

contraction of the atrial walls along with the recoil of the relaxed ventricle walls

this forces remaining blood into ventricles

Question 19

describe ventricular systole(3)

Answer 19

ventricle walls contract after a short delay

this increases pressure in ventricles so that it is higher than that in the atria, forcing atrioventricular valves shut.

this causes pressure to rise further so that it is higher than arteries, opening semi lunar valves

Question 20

what valves are found in veins?

Answer 20

pocket valves

Question 21

what is the equation for cardiac output?

Answer 21

cardiac output = heart rate x stroke volume

Question 22

what are the 5 general layers of a blood vessel?

Answer 22

tough fibrous outer layer
muscle layer
elastic layer
thin inner lining
lumen

Question 23

how is the structure of an artery related to its function?(4)

Answer 23

muscle layer is thicker than veins-can be constricted and dilated to control volume of blood

elastic layer is relatively thicker than veins-keep high blood pressure so that it can travel to extremities of the body

overall thickness of wall is great-resists vessel bursting under pressure

no valves-constant high pressure so blood tends not to backflow

Question 24

how is the structure of a vein related to its function?(4)

Answer 24

muscle layer is thin-their constriction and dilation can not control the flow of blood to the tissues

elastic layer is thin-low pressure of blood will not cause them to burst

overall thickness is small- no need for a thick wall as pressure is too low to risk bursting

contains valves-ensures blood does not flow backwards

Question 25

how is the structure of a capillary related to its function?

Answer 25

walls consist mostly of lining layer-makes them extremely thin so diffusion distance is small numerous and highly branched-provides large surface area for exchange narrow diameter- permeate tissues so no cell is far from a capillary spaces between the lining-allows white blood cells to escape to deal with infections in tissues

Question 26

describe how tissue fluid is formed(3)

Answer 26

1. blood is pumped from arteries to arterioles then capillaries, creating high hydrostatic pressure at start of the capillary bed 2. pressure forces tissue fluid out of capillary 3. only small molecules are forced out, molecules like proteins and blood cells remain as they are too large to leave

Question 27

describe how tissue fluid is returned to the circulatory system(5)

Answer 27

1. loss of water reduces hydrostatic pressure in capillary 2. pressure gradient is created at venous end, forcing some tissue fluid back in 3. in addition, the proteins that remained creates a water potential gradient where it is higher inside 4. this means water moves to the blood via osmosis 5. remainder of tissue fluid is carried back via the lymphatic system

Question 28

Describe the cohesion-tension theory of water transport in the xylem(6)

Answer 28

Water lost from leaf because of transpiration / evaporation of water Lowers water potential of mesophyll Water pulled up xylem creating tension Water molecules stick together by hydrogen bonds which is cohesion forming continuous water column Adhesion of water molecules to walls of xylem

Question 29

describe how sucrose is transferred into sieve elements(5)

Answer 29

1. sucrose is produced from photosynthesis in chloroplasts in the leaf 2. sucrose diffuses down conc gradient via facilitated diffusion to companion cells 3.H+ ions actively transported from companion cells into spaces within cell walls using ATP 4. H+ ions diffuse down conc gradient into sieve tube elements via facilitated diffusion 5.sucrose is co transported along with H+

Question 30

Describe the mass flow hypothesis for the mechanism of translocation in plants(4)

Answer 30

In source sugars actively transported into sieve elements by companion cells this lowers water potential of sieve cell and water enters by osmosis from xylem Increase in hydrostatic pressure causes mass movement of sucrose solution towards sink as pressure is lower at the sink Sugars used / converted in root for storage