7. Mass transport Flashcards
outline the bohr effect
as partial pressure of carbon dioxide increases, oxygen affinity decreases
how do high-altitude animals adapt to the low oxygen environment?
they naturally produce haemoglobin that has a higher affinity for oxygen
name the blood vessels entering and leaving the heart
vena cava
aorta
name the blood vessels entering and leaving the lungs
pulmonary artery
pulmonary vein
name the blood vessels entering and leaving the kidneys
renal artery
renal vein
what is the function of the kidneys?
to filter the blood
how do valves aid in heart function?
prevent the backflow of blood and help maintain pressure
what connects the valves to the walls of the heart?
chords (valve tendons)
what is an atheroma and how does it affect the artery?
build up of fat, dead cells, white blood cells and connective tissue. Increases pressure as it lowers the size of the lumen
Describe the structure of the arteries and how it relates to its function.
thick muscle layer to control blood flow.
thin elastic layer to maintain high blood pressure
overall thick wall to prevent bursting
no valves as high pressure prevents backflow
describe the structure of the arterioles and how it relates to its function.
thicker muscle than arteries.
able to control movement of blood into capillaries.
lower blood pressure than arteries so thinner elastic layer.
describe the function of the veins and how it relates to its function.
thin muscle as they do not control blood flow to tissues.
thin elastic as low blood pressure
thin wall as low blood pressure
valves prevent backflow
what feature of capillaries, relating to red blood cells, is important for their role as exchange surfaces?
they are small/thin/narrow. This pushes red blood cells right up against the capillary wall to shorten diffusion pathway.
why is fluid forced out of the capillaries at the start of capillary bed?
large hydrostatic pressure in capillary
where is hydrostatic pressure lower. The venule end or the arteriole end?
venule end
How does water potential of the blood change across the capillary bed?
it gets lower/decreases
what system is responsible for draining the excess fluid away from the tissues and back into the circulatory system?
the lymphatic system
what dead tissue in plants transports water?
xylem
outline the 4 steps of the cohesion tension theory, starting at the leaves of a plant
water evaporates from leaves.
Tension created, so water is pulled into the leaves from the xylem.
cohesive water molecules pulled up the xylem.
water enters xylem through roots.
what living plant tissue transports organic substances?
phloem
does translocation require energy?
yes
where do solutes move from and to in translocation?
source cells to the sink cells
how do enzymes maintain a concentration gradient in translocation?
they use up solutes at the sink, converting them to a different product to maintain diffusion gradient
what is the name for the best supported theory how translocation occurs?
mass flow
how does ringing allow scientists to investigate transport in plants?
remove a ring of bark from a stem.
accumulation of sugars above the ring causes the bark to bulge, which indicates it is the phloem in the bark which is responsible for transporting sugars.
The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why.
Loss of water / loss of fluid / friction (against capillary lining)
High blood pressure leads to an accumulation of tissue fluid. Explain how.
- High blood pressure = high hydrostatic pressure;
- Increases outward pressure from (arterial) end of capillary / reduces inward pressure at (venule) end of capillary;
- (So) more tissue fluid formed / less tissue fluid is reabsorbed
The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why.
- Water has left the capillary;
- Proteins (in blood) too large to leave capillary;
- Increasing / giving higher concentration of blood proteins (and thus reducing wp)
An arteriole is described as an organ. Explain why.
Made of (different) tissues / more than one tissue
An arteriole contains muscle fibres. Explain how these muscle fibres reduce blood flow to capillaries.
- (Muscle) contracts;
2. (Arteriole) narrows / constricts / reduces size of lumen / vessel / vasoconstriction
A capillary has a thin wall. This leads to rapid exchange of substances between the blood and tissue fluid. Explain why.
Short diffusion distance / pathway
Blood flow in capillaries is slow. Give the advantage of this.
More) time for exchange / diffusion (of substances)
Explain why a lack of protein in the blood causes a build up of tissue fluid.
- Water potential (in capillary) not as low / is higher / less negative / water potential gradient is reduced;
- Less / no water removed (into capillary);
- By osmosis (into capillary)
Explain how the structures of the walls of arteries and arterioles are related to their functions.
Elastic tissue
1. Elastic tissue stretches under pressure / when heart beats then recoils / springs back;
2. Evens out pressure / flow;
Muscle
3. Muscle contracts to reduce diameter of lumen / vasoconstriction / constricts vessel;
4. Changes flow / pressure;
Epithelium
5. Epithelium smooth;
6. Reduces friction / blood clots / less resistance;
what can cardiac contraction and relaxation also be called?
systole and diastole
define the cardiac cycle
an ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating round the body
the volume of the atria and ventricles changes as they contract and relax. what effect does this have on the pressure of the chambres?
decrease in volume increases the pressure
increases in volume decreases pressure
how many stages can the cardiac cycle be simplified into?
3
The cycle can start or end anywhere because it’s a continual cycle
what determines when a valve opens/closes?
higher pressure in front of the valve causes it to close
higher pressure behind a valve forces it open
what happens during ‘ventricular diastole / atrial systole’
The ventricles are relaxed.
The atria contract, decreasing the volume of the chambers and increasing the pressure inside the chambers.
This pushes the blood into the ventricles.
There’s a slight increase in ventricular pressure and chamber volume as the ventricles receive the ejected blood from the contracting atria.
What happens during ‘ventricular systole / atrial diastole’
The atria relax.
The ventricles contract, volume decreases and pressure increases.
The pressure inside the ventricles becomes higher than that of the of the atria.
This forces the atrioventricular (AV) valves shut to prevent back flow.
The pressure in the ventricles is also higher than the aorta and pulmonary artery, which forces open the semi-lunar(SL) valves and blood is forced into these arteries.
what happens during ‘ventricular diastole / atrial diastole’
The ventricles and the atria both relax.
The higher pressure in the pulmonary artery and the aorta closes the SL valve to prevent back flow into the ventricles.
Blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and pulmonary vein.
This increases the pressure of the atria.
As the ventricles continue to relax, their pressure falls below the pressure of the atria and so the AV valve opens.
This allows blood to flow passively (without being pushed by atrial contraction) into the ventricles from the atria.
The atria contract, and the whole process begins again.
Define the Bohr effect?
oxygen dissociation curves will shift to the right in a co2 rich environment.
more oxygen dissociates from oxyhaemoglobin
what are the two labeled axis that must be considered considering oxygen dissociation curves>
% saturation of haemoglobin
partial pressure of oxygen (Kpa)
what is positive cooperativity?
occurs after the binding of the first o2 molecules.
This alters the shape of the haemoglobin to allow further o2 molecules to bind with greater ease.
what happens to an oxygen dissociation curve when in an environment with low o2 levels.
it shifts to the left
what percentage of tissue fluid is returned into the circulatory system?
95%
explain the purpose of tissue fluid.
the means by which materials are exchanged between blood and cells
define ultrafiltration, give an example
The filtration of molecules under pressure, where the pressure is only enough to push certain molecules of size across a membrane.
e.g the ultrafiltration of tissue fluid causes substances such as plasma, o2, glucose, amino acids, fatty acids and ions to pass through the capillary wall but all cells and proteins remain in the blood due to their size.
What substances are transferred into surrounding tissue during ultrafiltration, what substances pass back into the capillary?
plasma, o2, glucose, amino acids, fatty acids and ions
tissue fluid, co2, urea
list the two ways to investigate transport in plants.
Ringing experiments
Tracer experiments
explain how to carry out a ringing experiment when investigating transport in plants.
phloem vessels can be selectively removed by cutting a ring in a stem deep enough to cut the phloem but not the xylem
after a week there is swelling above the ring, reduced growth below the ring. The leaves remain unaffected
This is early evidence that sugars are transported downwards in the phloem
explain how to carry out a tracer experiment when investigating transport in plants
a plant is grown in a lab and one leaf is exposed for a short time to carbon dioxide containing the radioactive isotope 14c
this 14co2 will be taken up by photosynthesis and the 14c incorporated into glucose and then sucrose.
the plant is then placed onto photographic film in the dark
the resulting autoradiograph shows the location of compounds containing 14c
what are diseases associated with your heart and blood vessels called?
cardiovascular diseases
Describe the process of Atheroma formation in cardiovascular disease
the wall of an artery is made up of several layers
the endothelium is usually smooth and unbroken.
if damage occurs to the endothelium (e.g by high blood pressure) white blood cells (mostly macrophages) and lipids (fat) from the blood, clump together under the lining to form fatty streaks
Over time, more white blood cells, lipids and connective tissue build up and harden to form a fibrous plaque called an atheroma.
this plaque partially blocks the lumen of the artery and restricts blood flow, which causes blood pressure to increase
What is CHD and how does it occur?
Coronary heart disease
Type of cardiovascular disease that occurs when the coronary arteries have lots of atheromas in them, which restricts blood flow to the heart muscle. It can lead to myocardial infarction
What two types of disease affect the arteries?
Aneurysm
Thrombosis
What is an aneurysm?
a balloon like swelling of the artery
atheroma plaques damage and weaken arteries, they also narrow arteries, increasing blood pressure
when blood travels through a weakened artery at high pressure, it may push the inner layers of the artery through the outer elastic layer to form a balloon-like swelling.
What is thrombosis?
formation of a blood clot
an atheroma plaque can rupture the endothelium of an artery
this damages the artery wall and leaves a rough surface
platelets and fibrin (a protein) accumulate at the site of damage and form a blood clot (a thrombus)
this blood clot can cause a complete blockage of the artery, or it can become dislodged and block a blood vessel elsewhere in the body
debris from the rupture can cause another blood clot to form further down the artery.
What is the name for when an aneurysm bursts?
a haemorrhage
What can cause myocardial infarction?
Interrupted blood flow to the heart
What is myocardial infarction more commonly known as?
a heart attack
Explain the process of a myocardial infarction
The heart muscle is supplied with blood by the coronary arteries
this blood contains the oxygen needed by the heart muscle cells to carry out respiration
if a coronary artery becomes completely blocked an area of the heart muscle will be totally cut off from its blood supply, receiving no oxygen
this causes a myocardial infarction
what effect can a myocardial infarction have on the heart?
can cause damage and death of the heart muscle
symptoms include pain in the chest and upper body, shortness of breath and sweating
if large areas of the heart are affected complete heart failure can occur, which is often fatal
What are the most common risk factors for cardiovascular disease?
high blood cholesterol and poor diet cigarette smoking high blood pressure age (risk increases with age) sex (men are more at risk than women)
Why is high blood cholesterol and poor diet a risk for myocardial infarction?
cholesterol is one of the main constituents of fatty deposits that form atheromas
atheromas can lead to increased blood pressure and blood clots
this could block the flow of blood to coronary arteries, which could cause a myocardial infarction
a diet high in saturated fat is associated with high blood cholesterol levels
a diet high in salt also increases the risk of cardiovascular disease because it increases the risk of high blood pressure
why is cigarette smoking a risk for myocardial infarction
both nicotine and carbon monoxide, found in cigarette smoke increase the risk of cardiovascular disease
nicotine increases the risk of high blood pressure
carbon monoxide combines with haemoglobin and reduces the amount of oxygen transported in the blood, and so reduces the amount of oxygen available to tissues , if heart muscles don’t receive enough oxygen it can lead to a heart attack
smoking also increases the amount of antioxidants in the blood - these are important for protecting cells from damage. Fewer antioxidants means cell damage in the coronary artery walls is more likely, and this can lead to atheroma formation
why is high blood pressure a risk for myocardial infarction?
high blood pressure increases the risk of damage to the artery walls
damaged walls have an increased risk of atheroma formation, causing a further increase in blood pressure
atheromas can also cause blood clots to form
a blood clot could block flow of blood to the heart muscle, possibly resulting in myocardial infarction
so anything that increases blood pressure also increases the risk of cardiovascular disease, e.g. being overweight, not exercising and excessive alcohol consumption
describe the structure of the xylem.
narrow tubes made of dead cells, so there is little resistance/obstacles to water movement
strong walls made of lignin to stop the xylem collapsing
define transpiration
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers
describe transpiration
water potential gradient from the air spaces in the leaf, through the stomata and to the air
mesophyll cells in leaf lose water through evaporation
cells now have lower water potential so water enters by osmosis from surrounding cells
water potential gradient is established which pulls water up xylem
what causes hydrogen to be ‘sticky’?
hydrogen bonds
define cohesion, give an example from transpiration
a force resulting from attraction between molecules of the same substance.
water molecules ‘stick’ to each other by cohesion
define adhesion, give an example from transpiration
a force resulting from attraction between molecules of different substances.
water molecules ‘stick’ to the side of the xylem
describe the cohesion-tension mechanism (theory)
water evaporates from the leaf cell walls and diffuses out of the stomata (aka transpiration)
this creates a tension (pulling) on the water in the xylem
the cohesion of the ater (due to hydrogen bonding) transmits the pulling force all the way down the roots
this is called the transpiration pull
adhesion of water to the xylem vessels also aids in resisting gravity.
evidence to support cohesion-tension theory?
change in the diameter of tree trunks during the day due to transpiration (more transpiration during the day, more tension so xylem vessels shrink)
if a xylem vessel is broken and air enters, the tree can not draw up water due to the column being broken so cohesion can not occur.
when you break a xylem, water does not leak out but air is drawn in due to the tension
Name the types of blood vessels.
arteries
arterioles
capillaries
veins
what is the function of arteries?
carry blood away from the heart and into the arterioles
transport blood rapidly under high pressure from the heart to the tissues
what is the function of arterioles?
smaller arteries that control blood flow from arteries to capillaries
carry blood under lower pressure than arteries, from the arteries to the capillaries. they also control the flow of blood between the two
what are capillaries?
tiny vessels that link arterioles to veins
what is the function of veins?
carry blood from capillaries back to the heart
transport blood slowly, under low pressure, from the capillaries in tissues to the heart
arteries, arterioles and veins all have the same basic layered structure, from the outward in name and describe these layers
tough fibrous outer layer - resists pressure changes from both within and outside
muscle layer - can contract and so control the flow of blood
elastic layer - that helps to maintain blood pressure by stretching and springing back (recoiling)
thin inner lining (endothelium) - that is smooth to reduce friction and thin to allow diffusion
lumen - is not actually a layer but the central cavity of the blood vessel through which the blood flows
What differs between each type of blood vessel?
the relative proportions of the 5 layers that make up blood vessels
the differences in thickness and structure are related to the differences in the function that each type of vessel performs
How is the structure of the arteries adapted to help them perform their function?
the muscle layer is thick compared to veins - this means smaller arteries can be constricted and dilated in order to control the volume of blood passing through them
the elastic layer is relatively thick compared to veins - because it is important that blood pressure in the arteries is kept high if blood is to reach the extremities of the body. the elastic wall is stretched at each beat of the heart (systole). it then springs back when the heart relaxes (diastole) in the same way as a stretched elastic band. thus stretching and recoil action helps to maintain high pressure and smooth pressure surges created by the beating of the heart
the overall thickness of the wall is great - this also resists the vessels bursting under pressure
there are no valves - (except in the arteries leaving the heart) because blood is under constant high pressure due to the heart pumping blood into the arteries, it therefore tends not to flow backwards
How is the structure of the arterioles related to their function?
the muscle layer is relatively thicker than in the arteries - the contraction of this muscle layer allows constriction of the lumen of the arteriole. this restricts the flow of blood and so controls it’s movement into the capillaries that supply the tissues with blood.
the elastic layer is relatively thinner than in the arteries - because blood pressure is low
How is the structure of the veins related to their function?
the muscle layer is relatively thin - compared to arteries because veins carry blood away from tissues and therefore their constriction and dilation cannot control the flow of blood to the tissues
the elastic layer is relatively thin - compared to arteries because the low pressure of blood within the veins will not cause them to burst and the pressure is too low to create a recoil action
the overall thickness of the wall is small - because there is no need for a thick wall as the pressure within the veins is too low to create any risk of bursting. it also allows them to be flattened easily, aiding the flow of blood within them
there are valves at intervals throughout - to ensure that blood does not flow backwards, which it might otherwise do because the pressure is so low. when body muscles contract, veins are compressed, pressurising the blood within them. the valves ensure that this pressure directs the blood in one direction only; towards the heart
what is the function of capillaries, what do they do that allows them to perform this?
to exchange metabolic materials such as oxygen, carbon dioxide and glucose between the blood and the cells of the body.
the flow of blood in capillaries is much slower, this allows more time for the exchange of materials
how does the structure of the capillaries allow them to perform their function?
their walls consist mostly of the lining layer - making them extremely thin, so the distance over which diffusion takes place is short. this allows for rapid diffusion of materials between the blood and the cells
they are numerous and highly branched - thus providing a large surface area for exchange
they have a narrow diameter - and so permeate tissues, which means that no cell is far from a capillary and there is a short diffusion pathway
their lumen is so narrow - that red blood cells are squeezed flat against the side of a capillary. this brings them even closer to the cells to which they supply oxygen. this again reduces the diffusion distance
there are spaces between the lining (endothelial) cells that allow white blood cells to escape in order to deal with infections within the tissues
what is tissue fluid?
a watery liquid that contains glucose, amino acids, fatty acids, ions in solution and oxygen.
tissue fluid is formed from blood plasma
what is the purpose of tissue fluid?
supplies numerous substances to the tissues.
in return, it receives carbon dioxide and other waste materials from the tissues
tissue fluid is therefore the means by which materials are exchanged between blood and cells and, as such, it bathes all the cells of the body.
how is tissue fluid formed?
blood pumped by the heart passes along the arteries, then the narrower arterioles and, finally, the even narrower capillaries.
pumping by the heart creates a pressure, called hydrostatic pressure, at the arterial end of the capillaries.
the hydrostatic pressure causes tissue fluid to move out of the blood plasma, the outward pressure is however opposed by two other forces
- hydrostatic pressure of the tissue fluid outside the capillaries, which resists outward movement of liquid
- the lower water potential of the blood, due to the plasma proteins, causes water to move back in to the blood within the capillaries
however the combined effect of all these forces is to create an overall pressure that pushes tissue fluid out of the capillaries at the arterial
describe the structure of the phloem in plants
sieve tube elements
are alive but have few organelles
have ends that form structures called sieve plates, through which cytoplasm can pass
sieve tube elements cannot keep themselves alive so have to be aided by companion cells which respire on the elements behalf
describe the process of transport in the phloem
phloem tissue transports solutes made in sources to parts of the plant that needs them, called sinks
this transport is called translocation
there is always a high concentration of the solute in the source cells, and a low concentration in the sink cells
what does the phloem transport?
sucrose (soluble carbohydrates)
hormones
describe the process of translocation?
solutes are actively transported (by co-transport) from source cells –> companion cells –> sieve tubes
this lowers the water potential, so water also moves by osmosis into the sieve tubes
this creates a high pressure in the sieve tubes near the source cells
since solutes are used up or stored in sink cells, the opposite happens near the sink cells
this results in a pressure gradient between the two sites
water and solutes moved down the pressure gradient
what material are the xylem made from?
‘dead cells’
lignin
