7: Mass transport Flashcards
1
Q
Haemoglobin
A
- quaternary structured protein
- haemoglobin and red blood cells transport oxygen
- each of the 4 polypeptide chain is associated with a haem group
- this haem group each contains a ferrous ion which binds to an oxygen molecule. therefore each haemoglobin molecule can carry four oxygen molecules
- biconcave structure (large sa)
2
Q
to be efficient with transporting oxygen, haemoglobin must;
A
- readily associate with oxygen at the surface where gas exchange takes place
- readily dissociate with oxygen at tissues requiring it
3
Q
How does haemoglobin change its affinity for oxygen under different conditions
A
- the shape changes in the presence of certain substances
- in the presence of carbon dioxide, the shape of hb binds more loosely to oxygen so it releases
- respiring tissues = low conc oxygen, high conc co2, so low affinity for oxygen and dissociates
- gas exchange surfaces = high conc of oxygen, low conc of co2, so high affinity for oxygen and associates
4
Q
Oxygen dissociation curve
A
- shape of hb makes it hard for first oxygen molecule to bind as closely packed together, so at low oxygen concs little oxygen binds
- first binding changes quaternary structure shape which induces other subunits to bind as is easier which is positive cooperativity
- but by the fourth molecule, it is harder to bind due to probability, less likely to find empty site
- there is low affinity to left
5
Q
the bohr effect
A
- lots of carbon dioxide - high carbon dioxide partial pressure
- oxyhaemoglobin curve shifts to the right
- affinity decrease, so more readily unloads oxygen
6
Q
loading and unloading of oxygen from hameoglobin
A
- gas exchange surfaces co2 is removed so low concentrations
- this raises pH, which changes the shape of the hameglobin to load oxygen more readily
- when co2 conc high its acid so lowers the pH which causes the haemoglobin to change shape to have low affinity
7
Q
fetal haemoglobin
A
- curve shifts to the left
- with the same partial pressure there is higher affinity
- the fetus cant inhale or exhale, has to take oxygen from adults haemoglobin
8
Q
llamas, doves and earthworms haemoglobin
A
- llamas live in high altitudes so have a higher affinity for oxygen at lower partial pressures (moves left)
- doves have a fast metabolism so need more oxygen for respiration so lower affinity (unloads more oxygen)
- worm live underground so require haemoglobin with a high affinity (moves left)
9
Q
does a mouse or an elephant have a high surface area to volume ratio
A
- an elephant has a lower surface area to volume, which is why mammals need circulatory system (and they r active)
10
Q
mammalian circulatory systems
A
- closed (blood remains in vessels)
- double circulatory system (the blood passes through the heart twice, 1 to lungs, 2 rest of body)
- its double bc different parts of the body require different pressures. the lungs need a low pressure of blood, the ody needsa high pressure
11
Q
blood vessels
A
- heart (vena cava, aorta, pulmonarey artery, pulmonary vein)
- lungs (pulmonary artery, pulmonary vein)
- kidneys (renal artery, renal vein)
12
Q
structure of the heart
A
- left = oxygenated blood from lungs, pumps to body so thick muscular walls
- right = deoxygenated blood from body, pumps blood to lungs so thin walled
- the atrium is thin walled and elastic so stretches when collects blood
- the ventricle is thick muscular walled as it contracts
both sides of heart pump at same time
- left and right atrioventricular valves to to prevent backflow of blood into atria when ventricule contracts
13
Q
what are vessels called that connect the heart to the lungs
A
pulmonary vessels
14
Q
properties of the cardiac muscle
A
- myogenic (can contract and relax without input from nervous system or hormones)
- never fatigues (aslong as supply of oxygen)
15
Q
2 veins into the heart
A
- vena cava (brings deoxygenated blood from the body back into the right atrium)
- pulmonary vein (oxygenated blood from the lungs into the left atrium)
16
Q
2 arteries away from the heart
A
- aorta (carries oxygenated blood from the left ventrical to the body)
- pulmonary artery (carries deoxygenated blood from the right ventricle to the lungs)
17
Q
where are semi lunar valves found
A
- in aorta and pulmonary artery
18
Q
where are atroventricular valves found
A
- between atrium and ventricles. two types;
- bicuspid (two flaps)
- tricuspid (three flaps)
19
Q
how do valves work
A
- prevent backflow by closing when there is high pressure infront of the valve
20
Q
Septum
A
- cardiac muscle down the middle and seperates left and right side of heart
- so oxygenated blood isnt being diluted by deoxygenated side
21
Q
Myocardial infarction
A
- blockage in arteries (blood clot) makes heart muscle deprived of oxygen
22
Q
Risk factors associated with cardiovascular diease
A
- smoking (nicotine increases adrenaline which increases heart rate and blood pressure)
- high blood pressure (stress, diet, exercise)
- blood cholesterol (high and low density lipoproteins)
- diet
23
Q
Cardiac cycle
A
- diastole
-atrial systole - ventricular systole
24
Q
Diastole
A
- atria and ventricular muscles are relaxed
- blood enters atrium by vena cava and pulmonary vein
- the blood flowing into the atria increases the pressure
25
Q
Atrial systole
A
- atria muscular walls contract, so volume decreases and increasing the pressure further
- this causes atrioventricular valves to open and blood flows into the ventricules (ventricular diastole)
26
Q
Ventricular systole
A
after short delay
- ventricular walls contract, increasing pressure beyond that of the atria and causes the atrioventricular valves to shut
- semi lunar valves open
- blood pushes out ventricles into the arteries
-
27
Q
Cardiac output
A
= heart rate x stroke volume (volume of blood leaves heart each beat)
28
Q
Types of blood vessels
A
- arteries (blood away from heart into arterioles)
- arterioles (to capillaries)
- capillaries (link arterioles to veins)
- veins (carry blood from capillaries back to heart)
29
Q
the layers of blood vessels
A
- fibrous outerlayer
- muscle layer
- elastic layer
- thin inner lining
- lumen
30
Q
Artery structure related to function
A
- thick muscle layer compared to veins (so constriction and dilation can occur)
- thick elastic layer compared to veins (to help maintain blood pressure)
- thicker walls to help prevent walls from bursting
- no valves
31
Q
Vein structure in relation to function
A
- Thinner muscular layer so it cant control flow of blood
- Thinner elastic layer as the pressure is lower
- Wall thickness is thinner as pressures lower so low risk of bursting
- Valves
32
Q
Capillaries
A
- one cell thick
- red blood cells just fit through diameter of the lumen so blood flow slows down so theres more time for diffusion
-no muscle or elastic layer or valves
33
Q
Arterioles
A
- muscle layers thicker than arteries to help restrict blood flow into capillaries
- elastic layers and wall thickness thinner than arteries as lower pressure
- no valves
34
Q
Tissue fluid
A
- bathes the tissues
- watery substance that contains glucose, amino acids, fatty acids, ions in solution and oxygen that supplies these to tissues by bathing them
35
Q
Formation of tissue fluid
A
- blood pumped by heart passes through arteries, arterioles, capillaries, each smaller so creates high hydrostatic pressure.
- this hydrostatic pressure causes ultrafiltration and the tissue fluid to move out of the blood plasma at the arterial end of capillaries
- red blood cells, proteins and platelets are too large to cross the membranes
36
Q
return of tissues fluid back to the circulatory system
A
- the loss of tissue fluid in capillaries lowers the hydrostatic pressure in them
- by the time the blood has reached the venous end of the capillary network, the hydrostatic pressure is lower than off the tissue fluid outsdie it
- therefore tissue fluid is forced back in by high hydrostatic pressure outside
- also the plasma has lost water but still has large proteins so has a lower water potential than the tissue fluid so tissue loses water by osmosis
- eventually with water moving back into capillaries equilbirium will be reached
- the rest of the tissue fluid is absorbed by the lymphatic system (lympth)
- this brings liquid back into blood
37
Q
Transpiration
A
- the loss of water vapour from the stomata by evaporation
- energy is supplied by sun (passive)
38
Q
factors that affect transpiration
A
- humidity (negative correlation. more water vapour in air = water potential more positive on outside of leaf so reduces water potential gradient)
- light (positive correlation, stomata open so large sa)
- temperature (positive correlation. kinetic energy)
- wind (positive correlation, blows away water vapour so maintains conc grad)
39
Q
Movement of water across the cells of a leaf
A
- mesophyll cells lose water in airspcaes by evaporation
- these cells now have a lower water potential and so water enters neighbouring cells by osmosis
- and again
40
Q
Cohesion-tension theory
A
- COHESION water is dipolar (negative O, positive H) so causes hydrogen bonds to form between h and o of water molecules.so stick together and so water travels up the xylem in continous water column
- CAPILLARITY. adhesion. water sticks to the xylem walls, the narrower the xylem the bigger the impact of capillarity.
- ROOT PRESSURE: water moves into root by osmosis so increases volume so increases pressure and forces water above it upwards (positive pressure).
41
Q
Movement of water up the xylem
A
- water vapour evaporates out stomata which lowers water pressure
- when this waters lost by transpiration, more water moves upwards to replace it
- due to hydrogen bonds, waters cohesive so it creates a column of water up the xylem.
- also adhere so stick to walls
- as water moves upwards it creates tension which pulls xylem in to become narrower
42
Q
Phloem tissue is made up of two key cells:
A
- sieve tube elements (living, no nucleus)
- companion cells (provide atp for active transport)
43
Q
Mass flow hypothesis
A
- transports organic substances in plants, mass flow from the source of production (leaves) to the sink (where the organic substances are used in respiring tissues)
44
Q
Translocation process
A
1) transfer of sucrose from photosythesing tissue to the sieve elements
2) mass flow of sucrose through sieve tube elements
45
Q
Transfer of sucrose from photsynthesising tissue to the sieve tube elements
A
- sucrose is manufactured, from products of photosynthesis in chloroplasts of cells
- sucrose diffuses down a concentration gradient by facilitated diffusion from photosynthesising cells to companion cells
- hydrogen ions actively transported from companion cells to spaces in cell wall using ATP
- these hydrogen ions diffuse down a concentration gradient through carrier proteins into sieve tube elements
- sucrose molecules transported along with hydrogen ions through co-transport
46
Q
Mass flow of sucrose through sieve-tube elements
A
- sieve tubes have lower water potential
- water xylem has high water potential so water moves into sieve tubes by osmosis which creates high hydrostatic pressure
- at respiring cells, sucrose either used by respiration or storage
- so they have low sucrose content and so sucrose is acitvely transported in from sieve tube elements lowering the water potential
- this causes water to move into respiring cells too by osmosis
- so hydrostatic pressure in sieve tubes is lowered and is lower at sink and high at source where waters moving in
47
Q
evidence for and against mass flow hypothesis
A
FOR:
pressure in sieve tubes as sap released when cut. concentration of sucrose is higher in leaves than roots. many mitochondria and atp in companion cells.
AGAINST:
- not all solutes move at same pace
- sucrose goes to all regions at same rate, rather than those with lowest concentration
48
Q
investigating transport in plants
A
- ringing experiments; outerlayer (bark) is removed, above swells and build up of organic substances
- tracer experiments; radioactive isotopes traced as they move within the plant using autoradiography
