mass transport pmt flashcards
describe the structure of haemoglobin
globular,water soluble. consists of four polypeptides chains, each carrying a ham group(quaternary structure)
describe the role of haemoglobin
present in red blood cells. Oxygen molecules bind to the harm groups and are carried around the body to where they are needed in respiring tissues
name three factors affecting oxygen haemoglobin binding
1)partial pressure/concentration of oxygen
2)partial pressure/concentration of CO2
3)saturation of haemoglobin with. oxygen
how does partial pressure of oxygen affect oxygen haemoglobin binding
as partial pressure of oxygen increases the affinity of haemoglobin for oxygen also increases , so oxygen binds tightly to haemoglobin.When partial pressure is low , oxygen Is released from haemoglobin
how does partial pressure of carbon dioxide affect oxygen haemoglobin binding
as partial pressure of CO2 increases, the conditions become more acidic causing haemoglobin to change shape.The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin.This is known as the Bohr effect.
how does the saturation of haemoglobin with oxygen affect oxygen haemoglobin binding
it is hard for the first oxygen molecule to bind.Once it does , it changes the shape to make it easier for the second and third molecules to bind, known as positive cooperatively. It is then slightly harder for the fourth oxygen molecule to bind because there is a low chance of finding a binding site
explain why oxygen binds to haemoglobin in the lungs
-partial pressure of oxygen is high
-low concentration of C02 in the lungs, so affinity is high
-positive cooperatively(after the first oxygen molecule binds binding of subsequent molecules is easier)
explain why oxygen is released from haemoglobin in respiring tissues
partial pressure of oxygen is low, high concentration of CO2 in respiring tissues, so affinity decreases
what do oxyhemoglobin dissociation curves show
saturation of haemoglobin with oxygen (in %)plotted against partial pressure of oxygen (in kPa),
Curves further to the left show the haemoglobin has a higher affinity for oxygen
how does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve
curve shifts to the right because haemoglobin affinity for oxygen has decreased
name three common features of a mammalian circulatory system
1)suitable medium for transport ,water based to allow substances to dissolve.
2)means of moving the medium and maintaining pressure throughout the body , such as the heart
3)means of controlling flow so it remains unidirectional , such as valves
relate the structure of the chambers to their functions
atria=thin walled and elastic, so they can stretch when filled with blood
ventricles= thick muscular walls pump blood under high pressure.The left ventricle is thicker than the right because it has to pump blood all the way around the body
relate the structure of the vessels to their function
arteries have thick walls to handle high pressure without tearing, and are muscular and elastic to control blood flow.
veins have thin walls due to lower pressure , therefore requiring valves to ensure blood doesn’t flow backwards.Have less muscular and elastic tissues as they don’t have to control blood flow
why are two pumps (left and right) needed instead of one
to maintain blood pressure around the whole body. When blood passes through the narrow capillaries of the lungs, the pressure drops sharply enough to continue around the whole body.Therefore it is returned to the heart to increase the pressure
describe what happens during cardiac diastole
the heart is relaxed.Blood enters the atria increasing the pressure and pushing open the atrioventricular valves.This allows blood to flow into the ventricles.Presssure in the heart is lower than in the arteries, so semilunar valves remain closed
describe what happens during atrial systole
the atria contract, pushing any remaining blood into the ventricles
describe what happens during ventricular systole
the ventricles contract.The pressure increases, closing the atrioventricular valves to prevent back flow,and opening the semilunar valves.Blood flows into the arteries
name the nodes involved in heart contraction and where they are situated
sinoatrial node(SAN)=wall of right atrium
atrioventricular node(AVN)=in between the two atria
what does myogenic mean
the hearts contraction is initiated from within the muscles itself, rather then by never impulses
explain how the heart contracts
SAN initiates and spreads impulse across the atria, so they contract
-AVN receives ,delays and then conveys the impulse down the bundle of his
-impulse travels into the purine fibres which branch across the ventricles,so. they contract from the bottom up
why does the impulse need to be delayed
if the impulse spread straight from the atria into the ventricles, there would not be enough time for all the blood to pass through and for the valves to close
how is the structure o capillaries suited to their function
-walls are only one cell thick, short diffusion pathway
-very narrows can permeate tissues and red blood cells can lie flat against the wall , effectively delivering oxygen to tissues
-numerous and highly branched, providing a large SA
what is tissue fluid
a watery substance containing glucose, amino acids ,oxygen, and other nutrients.
It supplies these to the cells while also removing any waste materials
how is tissue fluid formed
as blood is pumped through increasingly small vessels , this creates hydrostatic pressure which forces fluid out of the capillaries.It bathes the cells and then returns to the capillaries when the hydrostatic pressure is low enough
how is water transported in plants
through xylem vessels . long continuous columns that also provide structural support to the stem
explain the cohesion tension theory
water molecules form hydrogen bonds with each other,causing them to stick together .The surface tension of the water also creates this sticking effect.Therefore as water is lost through transpiration more cab be drawn up the stem
what are the three components of phloem vessels
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
name the process whereby organic materials are transported around the plant
translocation
how does sucrose in the leaf move into the phloem
sucrose enters companion cells of the phloem vessels by active by active loading, which uses ATP and a diffusion gradient of hydrogen ions.Sucrose then diffuses from companion cells into the sieve tube elements through the plasmodesmata
give evidence for the mass flow hypothesis of translocation
sap is released when a stem is cut,therefore there must be pressure in the phloem.
-there is a higher sucrose concentration in the leaves than the roots
-increasing sucrose levels in the leaves results in increased sucroses in the phloem
how do phloem vessels transport sucrose around the plant
as sucrose moves into the tube elements, water potential inside the phloem is reduced.This causes water to enter via osmosis from the xylem and increased hydrostatic pressure.Water moves along the sieve tube towards areas of lower hydrostatic pressure.Sucrose diffuses into surrounding cells where it is needed.
how can ringing experiments be used to investigate transport in plants
the bark and phloem of a tree are removed in a ring, leaving behind the xylem.Eventually the 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
give evidence against the mass flow hypothesis of translocation
the structure of sieve tubes seems to hinder mass flow , not all solutes move at the same speeds that would in mass flow
-sucrose is delivered at the same rate throughout the plant, rather than to areas with the lowest sucrose concentration first
how can tracing experiments be used to investigate transport in plants
plants are grown in the presence of radioactive CO2,which can be incorporated into the plants sugars.Using autoradiography we can see that the areas exposed to radiation correspond to where the phloem is
