Mass Transport Systems Flashcards
Why do humans require transport system?
-low surface area to volume ratio to diffuse substance and remove waste such as urea and carbon dioxide
-the transport system can carry raw materials from specialised organs to body cells and carry waste away
What is mass transport?
The bulk movement of substances in a fluid involving a mechanism of moving the fluid around the body
What does mass transport help to do?
-move substances quickly from in exchange surface to another
-maintain diffusion distance/gradients at a surface
-ensure effective cell activity by keeping the immediate fluid environment of cells within a metabolic range
Name the features within a circulatory system
-liquid transport medium which can readily dissolve substances due to presence of water
-vessels to carry transport medium
-pumping mechanism to move the medium around the body
What are the features of a closed circulatory system?
-transport medium enclosed in vessels
-blood pigments
-heart pumps blood under pressure
-blood pumped into small vessels until it can diffuse out
-volume of blood can be adjusted
What is the difference between a single and double circulatory system?
-singles have a heart with 2 chambers and so blood flows through heart once
-doubles have a heart with 4 chambers so blood flows through heat twice
What are the advantages of a double circulatory system?
-maintain body temperature
-increases pressure and speed of oxygenated blood to tissues
-as blood travels through lungs pressure decreases
-one capillary network so high pressure
Types of capillary networks from the aorta are called…..
Hepatic artery to the liver
Renal artery to the kidneys
What is transported in the blood?
Glucose,ions,amino acids,oxygen,albumin,platelets,fibrinogen
What are the 3 main components of the structure of a blood vessel and their jobs?
Smooth muscle layer- contracts to control the flow of blood in arteries,arterioles and veins
Elastic layer- vessel can stretch and recoil in arteries,arterioles and veins
Endothelium- thin inner lining which is smooth to reduce friction in all types of blood vessel
Describe the flow of blood through the different types of blood vessels.
First in the arteries then into the arterioles which branch of forming a network contracting and restricting controlling blood flow depending on the demand into the capillaries where after exchange deoxygenated blood flows into the venules joining the veins back to the heart
Describe the structure and function of an artery
-carries oxygenated blood
-small lumen so has high pressure
-pulse can be felt
Describe the structure of an arterioles
-less elastin and more smooth muscle
-vasoconstriction of arterioles reduce blood entering the capillaries
Describe the structure and adaptations of a vein
-carry deoxygenated blood under pressure
-no pulse felt
-medium size
Adaptations:
-valves maintain flow
-larger near active muscles for contractions to push the blood
-breathing movements move blood in chest and abdomen
-when skeletal muscles contract they compress veins helping to increase pressure and push blood against gravity
Describe the structure of a capillary
-diameter of a red blood cell
-site of substance exchange
-short diffusion pathway close to cell which is one cell thick
-gaps called fenestrations between endothelial cells allow for diffusion
-large number increases SA
-larger cross section than arterioles to decrease flow rate for more diffusion time
comparison of veins to arteries
-veins blood towards in arteries away from heart
-narrow lumen with high pressure in artery
-wider lumen and lower pressure in vein
-thick walls in artery but thinner walls in veins
-folded endothelium in artery so it can stretch and recoil
-valves in veins
describe the pressure changes of blood flow throughout the body
-flows from high to low pressure
-vena cava has the lowest pressure
-highest pressure is in the aorta after ventricular contraction
-blood looses pressure as it moves along vessels from aorta due to branching increasing lumen and friction
Why does the blood pressure fluctuate in the arteries?
elastic fibres stretches when flow is at high pressure and recoils at lower pressure helping to even out the change
what is tissue fluid?
-formed by blood plasma which leaks from capillaries
-surrounds cells in tissue providing them with oxygen and nutrients
How is tissue fluid moved around?
- via mass flow down a pressure gradient
-there is a net outflow at the arterial end of capillary due to higher bp creating hydrostatic pressure
What is the lymph?
-colourless fluid containing high amounts of lipids that passes through lymphatic system passing into blood at the vena cava.
-composition similar to blood plasma but more lipids and less oxygen and nutrients
What are the semi lunar valves
Found between aorta and pulmonary artery to prevent backflow
Name 4 features of the heart specific to its function
-mainly cardiac muscle which contracts in voluntary
-myogenic
-muscle made of cells that are connected by cytoplasmic bridges which enables electrical impulses to pass through the tissue
-large no. of mitochondria and myoglobin and oxygen binding protein molecule
What are the 3 stages of the cardiac cycle?
1- Arterial systole
2- Ventricular systole
3- Diastole
What are the function of the valves in the heart?
-prevent back flow of blood
-controlled via changes in pressure
-high pressure causes opening
Describe atrial systole
-ventricles relax and atria contract
-increased pressure due a decreased volume which causes valve to open
-blood flows into ventricles
Describe ventricular systole
-atria relax and ventricles contract
-increased pressure due to decreased volume which causes AV valves to close
-SL valves open and blood enters pulmonary artery
Describe diastole
-both atria and ventricles relax
-increased pressure in arteries so SL valves relax
-blood enters atria and pressure increases causing AV valves to open and blood flows into ventricle
Describe atrial pressure during the cardiac cycle
-Always relatively low as the thin walls of the atria cannot
create much force
-Pressure is highest when they are contracting (around 1.5 kPa)
-Pressure drops when the left AV valve closes and its wall
relaxes (<0 kPa)
-Pressure increases gradually as the atria fills with blood
(around 1 kPa)
-Slight drop in pressure as the AV valve opens as some blood
moves into the ventricle
Describe ventricular pressure during the cardiac cycle
-Low at first and gradually increases as the ventricles fill with blood as the atria contracts
• Left AV valve closes and pressure rises dramatically as the thick walls of the ventricle contracts (›15 kPa)
• When the pressure rises above aortic pressure blood is forced into the aorta past the semilunar valves
• Pressure falls as the ventricles empty («0 kPa)
Describe aortic pressure throughout the cardiac cycle
-Rises when the muscle in the wall of the ventricles contract as blood is forced through the aorta (›15 kPa)
-This recoil produces a temporary rise in pressure at the start of the relaxation phase
-Gradually falls (never below 12 kPA as the elasticity of the walls creates a recoil action to constantly deliver blood)
What is haemoglobin?
-globular quaternary protein
-4 polypeptide chains each with a haem group which contains an Fe+ ion making the pigment red
-can bind on up to 4 oxygens
State the adaptations of red blood cells
-biconcave shape gives large surface area to volume ratio
-flat and thin so short diffusion pathway
-no nucleus so can store increased amounts of haemoglobin
Explain oxygen loading and unloading
Oxygen loading is the process of which oxygen assosiates to the haemoglobin forming oxyhaemoglobin (usually in the lungs)
Oxygen unloading is the process of which oxygen disassociates forming haemoglobin (usually in respiring cells)
What 3 conditions does haemoglobins oxygen affinity depend on?
-partial pressure of oxygen
-haemoglobin saturation
-partial pressure of carbon dioxide
How does the partial pressure of oxygen affect its affinity to haemoglobin?
the higher the concentration of oxygen the higher the pO,and as pO increases haemoglobins affinity increases.
This means:
haemoglobin will have a higher affinity for O, in oxygen-rich areas (e.g lungs) where there is a high po., promoting oxygen loading.
haemoglobin will have a lower affinity for O, in oxygen-starved areas (e.g respiring tissues) where there is a low po., promoting oxygen unloading.
This ensures oxygen is always picked up by red blood cells in the lungs and released in respiring cells where it is needed
How does haemoglobin saturation affect oxygens affinity?
- as each oxygen molecule binds it changes the shape of the haemoglobin in a way that makes it easier for further oxygen molecules to bind (this is known as co-operative binding)
-However, as the saturation of haemoglobin increases it becomes harder for the final oxygen molecules to bind
How does the partial pressure of carbon dioxide affect hemoglobins affinity for oxygen?
-When pCO,is high (e.g in respiring tissues) oxygen dissociates from haemoglobin more easily, this allows more oxygen to be unloaded to cells during intense activity,
- an increase in carbon dioxide production leads to a decrease in blood pH as it reacts with water to form carbonic acid.
-The low pH causes the tertiary structure of the haemoglobin to be altered, decreasing its affinity for oxygen so increasing the dissociation of oxygen.
-This ensures that where there is the most respiration occurring (more CO, produced) more oxygen will be released to help maintain the level of metabolic activity.
How is the Bohr effect shown on the disassociation graph?
-an increase in CO, or a decrease in pH shits the normal oxygen dissociation curve to the right.
-It stays the same shape, but it shows that for the same po, the saturation of blood with oxygen is lower as more oxygen is being released from the haemoglobin.
Describe how the haemoglobin in the foetus has different affinity to oxygen
-higher affinity so the curve is shifted to the left
-Oxygen binds to foetal haemogiobin more easily and is more reluctant to dissociate.
-This is important, as foetal haemoglobin needs to “steal” oxygen away from the mother’s haemoglobin when they pass in the placenta.
-If the foetal and maternal haemoglobin had the same affinity for oxygen, there would be no incentive for the oxygen to switch from the maternal blood to foetal blood.
Describe how haemoglobins affinity for oxygen is changed in organisms living in low oxygen environments
-higher affinity so graphic shifts to the left
-Organisms can live at high altitudes where there Is lower atmospheric pressure so low po,
-This means there is less oxygen available so need to be able to load more oxygen at lower po, to make sure it is absorbed
Describe how haemoglobins affinity to oxygen is changed in organisms with a high surface area to volume ratio or metabollic rate
-Small mammals that have a higher SA than larger mammals so will lose heat more quickly so they have a higher metabolic rate to help maintain their body temperature. Other high activity organisms will also have a higher metabolic rate.
-Higher metabolic rate = more respiration =
greater oxygen demand. This means the organisms need haemoglobin with a lower affinity for oxygen as they need it to easily unload oxygen to meet their high oxygen demand and allow a faster respiration rate.
Describe the features of the lymphatic system
-use muscle contractions to help flow
-valves
-lymphnodes produce lymphocytes and contain phagocytes to remove bacteria from lymph
-subclavian glands to enter the blood at
What is the hydrostatic pressure at the arterial and ventless end of the capillary?
Arterial end- high hydrostatic pressure so lower oncotic pressure so fluid moves out of capillary
Venule end- lower hydrostatic pressure so higher oncotic pressures so fluid absorbed in capillary
What is the equation for filtration pressure?
Higher pressure - lower pressure
Describe the steps for the formation of tissue fluid
1) at the arteriole end the hydrostatic pressure inside the capillary is greater than the tissue fluid and greater than osmotic pressure
2)the difference in hydrostatic pressure forces the fluid contains small molecules through fenestrations causing tissue fluid to form
3)red blood cells platelets and plasma proteins remain in blood as they are too large to leave
4)exchange occurs between tissue fluid and cells via diffusion, facilitated and active transport of oxygen and nutrients and waste leaves cells entering the tissue fluid
5)as fluid leaves capillary at arteriole end it reduces hydrostatic pressure and bp at the venule ends of the capillary is greater
6)as water leaves capillary but plasma remains this lowers the wp of the blood so it is lower than the wp in the tissue fluid and venule ends of capillary
7)osmotic pressure is higher than hydrostatic pressure at venule ends of capillary so water moves in via osmosis carrying carbon dioxide and waste
8)any excess tissue fluid that is not reabsorbed is returned and collected into the lymphatic system to be transported to circulatory system
What is cardiac muscle?
muscle made up of cardiomyotypes which are specialised myogenic cells meaning they contract without a nervous system
What are atrioventricular valves?
Found between atrium and ventricle and only open one way to prevent the back flow of blood when vessels contract
They allow pressure to build in ventricles as they shut when pressure exceeds atrium pressure
Why do plants need water?
-photosynthesis
-transport minerals
-maintain structure by keeping cells turgid
-regulate tempreture
Why do plants need nitrates and phosphates?
nitrates- for DNA, amino acids, chlorophyll
phosphates- DNA, ATP
State the 4 steps in the water transport in plants
- absorption in roots
- movement of water from root to xylem
- movement into xylem
4.cohesion tension theory
Explain the absorption of water into the roots
-water is absorbed via osmosis into the root hair cell
-mineral ions are absorbed via active transport and dissolved in water
How are root hair cells adapted?
-large surface area
-short diffusion distances
-many carrier protiens
-minerals to maintain low wp
State the 3 pathways of which water can move from the root to the xylem
symplast pathway
vacuolar pathway
apoplast pathway
Explain the symplast pathway
-through cytoplasm
-flows via plasmodesmata
-each cell further away from the root as lower wp so water drawn up
-slower pathway
Explain the vacuolar pathway
-moves through cytoplasm and vacuole
Explain the apoplast pathway
-through cell wall and intracellular spaces (non living) between cellulose fibres
-pulled up plant due to cohesion and tension
-faster route
Explain the movement of water into the xylem
-water via apoplast pathway reaches endodermal cells and is blocked by waxy caspirian strip
-water forced in to cytoplasm by cell membrane
-means all water passes through partially permeable membrane removing any toxins before entering living part of plant
Describe the xylem structure
-elongated tubes of dead cells
-no end walls and hollow lumen allowing for continuous flow
-lignin that forms walls is strong preventing collapse and is waterproof preventing adhesion
-gaps in lignin allow for water to leave/enter vessel
-no cytoplasm
Define cohesion
attraction between like molecules
Define adhesion
attraction between non-like molecules
Explain how water potential effects transpiration
-movement of water increases and transpiration increases
-water evaporates through stomata moving down a wp gradient as there is less water than atmosphere than in leaf
State and explain the 4 steps to the cohesion tension theory
- water evaporates from mesophyll due to heat from the sun and leaves cells with a negative water potential causing more water to enter via osmosis
2.this increase in water tension pulls more water into the leaf known as transpiration pull
3.water is cohesive so as they form hydrogen bonds they undergo adhesion this pulls the whole column of water in the xylem up from mesophyll tissues in the leaves
4.water enters stem through roots
Evidence for the transport in water in plants
- day time transpiration is at its greatest and the adhesion of water to xylem causes tension narrowing the xylem
- night time transpiration is at its lowest and less tension so diameter increases
3.Trunk damage and broken xylem water does not leak prooving it is not due to pressure and when air enters tree it cannot draw water up as column has broken
Describe the heart.
A muscular organ that lies in the thoracic clarity behind the sternum.
Explain why the ventricles have much thicker muscle wall compared to atrium
Has two contract strongly to pump blood some distance to the rest of the body and right side of the lungs.
What is translocation?
-process where assimilates are transported from source to sink via the phloem in a bidirectional way which is an active process
Why is glucose converted to sucrose for transport?
less likely to be metabolised or oxidised as it is much less reactive
Describe the structure of the phloem
-elongated sieve tubes with no nuclei or organelles just as small amount of cytoplasm to maximise space
-each tube has a companion cell with organelles and mitochondria for ATP
-end walls with holes called sieve plates let solutes pass through
Give some examples of sources
-roots
-meristems
-storage locations
Explain what happens at the source during mass flow
-high sucrose concentration so sucrose is moved into sieve cells via active loading decreasing the water potential of the phloem so water moves in from the xylem via osmosis. This causes an increased volume of water and therefore increased hydrostatic pressure.
Explain what happens at the sink during mass flow
-low sucrose concentration as sucrose moves out of the sieve tubes down a concentration gradient as cells convert it to glucose this increases the water potential of the phloem so water moves back into the xylem via osmosis causing a reduction in pressure due to a decrease in volume
Describe the overall mass flow of solutes around the plant
hydrostatic pressure gradient between source and sink causes a continuous flow and the concentration gradient of sucrose in created due to the constant need for glucose in respiring cells and storage.
Explain the process of active loading
-H+ ions actively pumped out of the companion cells using ATP into the source creating a concentration gradient
-H+ ions can diffuse back down a concentration gradient through transport proteins which require sucrose molecules to be transported
-this increases the concentration of sucrose in the companion cells which then diffuse into the sieve tubes
Explain one advantage of the capilliaries being narrow
-short diffusion distance of blood
-large surface area
-increases the rate of diffusion
What factor limits the minimum internal diameter of a capillary lumen?
thickness/width of blood cell wall
Explain why the pressure in a dogs ventricle is related to the thickness of the wall
-the thicker wall enables the ventricle to contract
-the thicker the muscle the grater the pressure as internal volume is decreased
Explain how the pressure in a dogs ventricle is related to the blood flow in the aorta
-as pressure in ventricle increases blood flow to aorta increases
-semi lunar valves open due to the increased pressure
Explain how the changes in shape of haemoglobin result in the s-shaped graph
The first oxygen is difficult to initially bind however this causes the later oxygen molecules to bind much more easily due to cooperative binding which makes it easier to bind except for the last oxygen
State how the change in a babies haemoglobin from fetal to adult is an advantage for the baby.
-adult haemoglobin has a lower affinity for oxygen at low partial pressures so the oxygen unloads more easily at respiring cells
Explain how cardiac output can remain the same even when resting heart rate decreases
increase in ventricular volume
Why is the water potential of the blood plasma more negative at venule end than arteriole end?
water has left the capillary meaning many blood proteins are present as they cannot leave the blood vessel creating a negative water potential
Explain why people with higher ventricular blood pressure have a higher buildup of tissue fluid
the increase in pressure forces more fluid out of the blood however not all the fluid can be returned due to pressure and the lymphatic system cannot drain all the fluid away
What is the equation for the percentage saturation of haemoglobin with oxygen equation?
oxygenated Hb / maximum saturation X 100
State the way in which the structure of the aorta is related to its function
Elastic tissue to allow stretching / recoil / smooths out flow of blood / maintains pressure;
2. Elastic tissue stretches when ventricles contract
OR
Recoils when ventricle relaxes;
3. Muscle for contraction / vasoconstriction;
4. Thick wall withstands pressure OR stop bursting;
5.Smooth endothelium reduces friction;
6.Aortic valve / semi-lunar valve prevents backflow.
Explain why a small increase in and rate of flow in the aorta occurs and its importance
occurs due to the elastic recoil of the aortic wall which allows for blood flow and pressure to be maintained
Evidence towards mass flow
-when sieve tubes are cut sap is released due to being under pressure
-excretion of sap from an aphid when it goes to the phloem to feed as sap flows into the body demonstrating pressure as it flows faster at the top of the plant due to a pressure gradient
-electrical potential difference between companion and source cells
-downward flow mostly in the day due to photosynthesis
-
Evidence against mass flow
-sugar travels to many different sinks but not always the first or fastest to one with a higher water potential
-sieve plates create a barrier to mass flow
Ringing experiment
Remove bark including the phloem
-stem above the ring swells with liquid containing a high concentration of sugars
and organic substances suggesting an accumulation of sugars in the phloem
-some non-photosynthetic tissues below the ring wither and die
Tracer experiment
1) grow a plant in radioactive carbon
2)the carbon is incorporated into glucose via photosynthesis
3)traced as it travels through the phloem
4)done by taking cross sections of the plant and x-raying them as film blackens if exposed to radiation
Explain the use of a potometer
can be used to measure the rate of transpiration via the uptake of water from a plant and several environmental factors can be changed.
Explain how environmental factors effect the rate of transpiration
light- increases the rate as stomata remain open
temperature increases so does kinetic energy so therefore transpiration rate increases
if less humid the rate increases
low carbon dioxide means stomata are open for longer and wider so increases rate
wind increases rate as it steepens the gradient
