Mass transport Flashcards
Why do large organisms have a transport system based on two criteria?
Low surface are to volume ration means larger organism and small surface area do a transport system is needed to carry ,etsblic products to cells and waste away.
The more activity an animal does the greater the need for a specialised transport system with a pump.
What is a transport system’s purpose?
Takes material from cells to specialist exchange surfaces and from exchange surfaces to cells.
Key features of transport system named
Suitable medium
Form of mass transport that is more rapid than diffusion
A system of tubes/vessels
A mechanism for moving the medium
Why is a suitable medium needed for transport system
Normally a water based liquid as water dissolved substances can be gas medium like air
To carry metabolic products with ease
Why is a a form of mass transport that is more rapid than diffusion needed for transport system
Medium is moved in bulk over large distances = more efficient
Why is a system of tubes and vessels needed for transport system
Contains medium and forms a branching network to distribute to all parts of an organism
Why is a mechanism for moving medium needed for transport system
Creates pressure differences
Animals use muscular contraction
Mammals use intercostal muscles and diaphragm durijg breathing
Plants mechanism for moving medium?
Plants use natural passive processes like the evaporation of water
A mechanism that maintains mass flow movement in one direction are
Valves
Open circulatory system description and what organisms use it
Heart pumps blood through blood vessels into open cavities, which bathe all organs and tissues throughout the body in blood
Insects
Advantages of the open circulatory system
Good for organisms with a slower metabolism (less active) because the absence of blood vessels mean that blood pressure is low so O2 takes longer to reach cells.hence less energy is needed to make energy O2 is needed
Closed circulatory system description and which organisms
Found in larger and more a five animals (all vertebrates)
Not bathing all tissues in blood but is instead transported to all extremities and remains in blood vessels
Mammals also use a closed system
Advantages of a closed circulatory system
Higher blood pressure in larger organisms hence this system is efficient because uses less blood for higher and faster levels of distribution so O2 reaches the extremities faster, which allows faster movement, digestion and removal of waste.
Single closed circulatory system description and organism
Blood travels from the heart to site of blood oxygenation and then to the rest of the body straight away
(Fish=gills)
Double loop closed system description and organism
Mammals, reptiles birds all have a higher metabolic rate and body te party re and need blood quicker
Blood travels in the first loop from the heart to the lungs to be oxygenated then back to the heart.
Then does second loop from the heart to the rest of the body.
Advantages of a double closed loop circulatory system
Quicker and greater pressure as it is returned to the heart so blood has enough pressure to reach all extremities quickly
Describe flow of blood in humans ( no valves needed jus to show flow of blood in double loop).
From vena cava into RA then into RV then from PA to lungs then go PV into LA into LV into aorta and then branches to the rest of the body.
Describe the electrical conduction system and SAN in heart process
A wave of electrical activity spreads out from the sino - atrial node (pacemaker) across the atria. Non - conducting tissue prevents the spread to the ventricles. Wave enters the second group of cells called the atrio ventricular node (AVN ). There is a short delay to allow blood to flow into the ventricles. Then the wave of excitation continued along specialised muscle fibres beteeen the ventricles (Bundle of His) then branches further.
Wave then passes along the purkinje fibres causing the the ventricles to contract from the base upward and then the pressure increases and nodes shut.
NOT NERVES - SPECIALISED HEART CELLS
ECG full form what can be seen what to look out for
Electrocardiograma shows activity of the electrical conduction system (electrical waves) need to/know starts at SAN -> AVN-> bundle of His -> bundle branches -> purkinje -> ventricles
Work out heart rate by going peak to peak and diving sixty by this number
Diastole
Atria full and pressure rises, pressure exceeds that of ventricle so atrioventricular valves open (bi/mi/tri), blood enters ventricle with aid of gravity, both a and v muscles are relaxed, recoil in v muscles causes pressure to reduce so v pressure is less than aorta/PA so semilunar valves shut creating dub
Order of systole and diastole
Diastole (both) (relaxed) then atrial systole then ventricular systole
Diastole vs systole difference
Diastole is relaxed
Systole is contracts
Atrial systole
Atrial walls contract and the recoil of v muscles pushes remaining blood into ventricle - v muscles are always relaxed here
Ventricular systole
Short delay allows ventricle to fill with blood
Both v muscles contract simultaneously which increases blood pressure of ventricle so atrioventricular valves (bi/mi/tri) shut “lub” then presssure in v increases and excess aorta and PA so ASL and PSL open and v muscle contracts to pump blood through so blood flows around the body
Pressure in the heart two main facts
Blood circulation relies on the pressure gradients
Blood will always move down a pressure gradient - from high to low
Diet and obesity causing CVD
High levels of salt raise BP
High levels of saturated fat increase Low Density Lipoproteins (LDL) level hence increase blood cholesterol
Antioxidants reduce risk of heart disease as does non starch polysaccharide/ dietary fibre
High blood pressure genetic predisposition
Can not change this fact can only manage lifestyle factors
Blood cholesterol and CVD
High density lipoproteins (HDL) remove cholesterol from tissues and transport it to to the liver for excretion protect the artieries against heart disease
LDL transport from liver to tissues including the artery walls which get infiltrated and lead to atheroma which leads to heart disease
Why does higher blood pressure increases risk of CVD
Already high pressure in the arteries, the heart must work harder to pump blood into them, hence is more prone to failure
High blood pressure within the arteries mean they are more likely to develop an anyerusm (wearing of the wall) and burst, causing haemorrhage
To resist the higher pressure within them, the walls of the arteries become thicker and may harden, which could restrict blood flow
Arterioles function
Smaller arteries that control blood flow from arteries to capillaries
Capillaries function
Tiny vessels that link arterioles to veins and are small so permeate tissue to distribute metabolic material
Básica structure of blood vessels
Tough fibrous outer layer to resist both internal and external pressure
Muscle layer to contract and control blood flow
Elastic layer to maintain BP by streacthing and recoiling
Endothelium (inner lining (thin)) is smooth to reduce friction and thin to allow easy diffusion
Lumen is a centavo cavity through which blood flows
Fenestrations are
Fenster = window (German)
Windows for exchange of material like WBC in endothelium
Arterioles have similar proportions to arteries but smaller ——— and larger ——— ——— and lower —— . Why?
Smaller in diameter as it slows blood flow in time for exchange
Larger muscle layer and lumen allows for vasoconstriction and vasodilation to control blood flow
Lower pressure than artery so relatively thinner elastic layer as not much recoil needed to control BP
artery basic structure compare to veins Muscle layer Elastic layer Overall thickness Valves
Thicker muscle layer for constriction and dilation as volume of blood need to be controlled to reach tissues
Thicker elastic layer as BP in artery is high and blood needs to reach extremities - this manages pressure surge es from heater because stretches at systole and recoils when hearts relaxes so diastole
Thicker overall than veins because it needs to resist bursting under pressure
No valves as there is high and constant pressure so unlikely back flow
Vein structure compared to artery Muscle layer Elastic layer Overall thickness Valves
Near muscle layer because carries blood away from tissues so vasoconstriction/vasodilation is unnecessary
Thinner elastic layer because low BP in veins so low risk of bursting, hence no recoils action needed
Overall thickness of wall is small because pressure is low so unlikely to burst also allows flattering by=muscles which aids blood flow
Valves at intervals because low pressure means back flow could occurs
How do muscles aid valves in veins to ensure blood only flows to heart
Muscles contract, which compresses veins, which pressurises the blood flow, hence the valve ensures the pressure only directs blood in one direction
Capillary function
To exchange metabolic materials (O2,CO2,C6H12O6) between blood and the cells of the body
Capillary structure
Mostly inner lining layer (endothelium) = extremely thing so short diffusion distance (Fick’s Law)
Numerous and highly branched so large SA for exchange and slows blood flow so there is more time for exchange to occur
Narrow diameter means the tissue can permeated si no cell is far from a capillary = short diffusion distance
Narrow lumen means RBC can just fit - walls are against side of capillary so there is a short diffusion distance as it is close to cell
Fensters = allow WBC to escape to deal with any tissue infections
What is the final journey of metabolic materials made in?
Every cell can’t be served directly by capillary so tissue fluid bathes cells
The pulmonary circuit is —— and has a lower —— —— than the —— ——
Is circuit of blood vessels to and from and in lungs have a large SA to reduce blood pressure and slows down flow of blood for diffusion to occur (resistance this is called)
Lower pressure than the systemic circuit
The higher the blood pressure the
Faster the flow of blood
Blood is made of
55% plasma which has 90% water and 10% dissolves substances like plasma proteins and glucose
45% cell suspension which has RBC, WBC and platelets
Tissue fluid is the immediate ——— and exception
Environment bathing all cells
Touches tissues directly in liver
Tissue fluid purpose
Means by which substances are exchanges between cells and the blood
Gives glucose and receives CO2 and waste products
What is hydrostatic pressure?
Pressure created by the pumping of the heart
What allows plasma to move out of the capillary into the tissue fluid, but is too small to let proteins/ cells through?
Fenestrations
Tissue fluid routes/ formation
From blood plasma out into tissues by ultra filtration then back into blood plasma by reabsorción or drains into lymph nodded and returns to blood plasma (from heart) by lymph vessels.
Describe pressure and water potential at the arterial end of a capillary
BP is high
Hydrostatic pressure is higher than the water potential into blood so fluid is filtered out
Describe pressure and water potential gradients and what consequently occurs in the venous end of the capillary?
Mention resistance
Blood pressure drops because or the friction/resistance of wall as and reduced blood volume
Water potential in blood becomes lower (more negative) because the proteins become more concentrated
The water potential gradient into the blood is higher than the hydrostatic pressure so tissue fluid is reabsorbed back into capillary.
Lymphedema
Blockage in the lymphatic system causes excess tissue fluid to build up around the cells and in the lymph vessels leading up to the blockage, which can cause severe swelling
What ensures the lymph fluid only travels in one direction - to heart?
Contraction of muscles
Explain primary, secondary, tertiary structures etc of haemoglobin
Primary = sequence of amino acids in four polypeptide chains Secondary = each chain coils into a helix Tertiary = each chain folds into a precise 3D shape Quaternary = all four polypeptide chains link to form an almost spherical molecule. Each polypeptide chain is associated with a haem group (contains Iron II) (four haem groups total on haemoglobin so 4 O2 molecules carried at once)
Can you describe the role of haemoglobin and red blood cells in the transport of oxygen?
Each Fe 2+ can combine with and one O2 molecule each, total of 4 O2 molecules can be carried by one haemoglobin molecule at once. Needed for transport of oxygen from surface of gas exchange to tissues that require O2.
Efficient: readily associate with O2 at site of gas exchange and readily dissociate at respiring tissues
Loading/aAssociating of O2 def and where in human body
Haemoglobin binds with O2
Lungs
Unloading/Disassociating def of O2 and where in the body
Haemoglobin releases O2
Respiring tissues
Affinity definition
The degree to which a substance tends to combine with another
A high affinity of oxygen means
Oxygen binds to haemoglobin easily but is not released as easily
How does haemoglobin change affinity for oxygen?
Under different conditions, shape changes occur in presence of other substances
Affinity of oxygen in low CO2 conc
High affinity (at site of gas exchange)
Affinity of oxygen in low O2 conc
Low (at respiring tissues we want disassociation)
High CO2 conc affinity?
Low affinity (at respiring tissues)
Low CO2 conc affinity?
High affinity (at site of gas exchange)
Bohr Effect and explain the chemistry behind it and effect on graph
CO2 presence Causes tertiary structure change, resulting in a loose binding to O2 and hence O2 released at respiring tissues.
CO2 reacts with H2O to form carbonic acid. Weak acid dissociates partially releasing hydrogen atoms causing a decrease in pH. Changes charges in protein causing change in tertiary structure (shifts graph to right)
Why do different types of haemoglobin exist?
Different sequence of amino acids, resulting in differences (small) to tertiary and quaternary structure and hence changes affinity to oxygen
Lugworm affinity compared to humans and explain
Higher affinity, mostly covered by seawater (O2 diffuses from H2O into lungs) when tide goes out the burrow has less O2 hence high affinity means loaded with oxygen even in low concentration of oxygen
Llama affinity to oxygen compared to human and explain
Higher affinity for oxygen, lives at high altitudes where there is a low partial pressure of O2 hence fully loaded haemoglobin with oxygen even in low partial pressure of oxygen
Legume (bacteria) affinity to oxygen and explain?
Live in root nodules and fix nitrogen into ammonia
Has high affinity with oxygen and keeps oxygen concentration low so increases efficiency of nitrogen fixation
Saturation of haemoglobin at atmospheric pressure is around 97% so normally — released at —; in very — …..
One O2 molecule released at tissue with low respiratory rate
Very active tissues = 3O2 molecules released at once
Describe the cooperative nature of oxygen binding
Binding of first oxygen molecule causes a change in shape to geriatric and quaternary structure of haemoglobin, making it easier for second and third binding. (Positive cooperativity)
Theoretically, fourth binding should be easier, however majority of binding sites are occupies so probability of binding is less likely
Name product that is not hydrogen when carbonic acid dissociates and where did it go
Hydrogen carbonate HCO3 -
Dissolved in plasma and taken to lungs
Sequence of events relating to Bohr Effect when activity of tissue is increased and relate to graph
More active so higher rate of respiration. More CO2 produced . Reacts with water to form carbonic acid - more dissociation so more acidic blood so more O2 unloaded. Graph shifts to the right
Describe loading, transport and unloading of oxygen in relation to the oxyhaemoglobin dissociation curve.
Shape of haemoglobin molecule molecule in low concentration of O2 means hard for first O2 molecule to bind so graph is shallow,
Binding of first O2 molecules causes change in quaternary structure of haemoglobin, which induces other subunits to bind to O2.
Smaller increase in O2 kPa needed for second binding = positive cooperativity - each binding makes it easier for next binding so gradient is steep
After third binding majority of sites are filled hence probability of fourth binding is lower as harder to find an empty site hence gradient reduces and graph plateaus.
Why does curve have a sigmoid shape (short answer)
Positive cooperativity
CO2 binds to haemoglobin true or false
False but CO does
The further to the left the curve is the
Greater the affinity because loads easily but unloading is difficult
The further to the right the curve is
Lower affinity as loading is hard unloaidng is easy
Write out graph if pressure and volume changes with associated valve movements during the cardiac cycle
Write out
Diagram of cross - section of plant has an X in the middle and four teardrops around it - identify what parts of plant it is? (Vascular bundle of roots)
Second diagram key thing to remember
X= xylem
Teardrops on outside = phloem
Inner layer of meristems is known as pericycle
Phloem always on outside
Root Hair Cells adaptations and functions
Active transport of minerals and absorption of water.
Large surface area to volume ratio so via Fick’s law more efficient osmosis
Many carrier proteins for active transport of ions also many mitochondria to produce ATP
Lower (more negative) water potential in cells so water moves into cell
Lignification
Deposits on membrane preventing exchange between cells, hence cells die and nucleus and organelles die - hence hollow tubes formed (xylem)
Xylem adaptations (5 - think key words!)
Lack of organelles - unrestricted flow of continuous stream of water
Lignified walls - prevents collapse under pressure
No end walls on cells - series of continuous, unbroken tubes of xylem
Hollow - space for H2O to pass
Spiral thickening for efficient support
What is transpiration
Passive force (energy supplied from the sun) and is main driving force for drawing water up stem against gravity through xylem
Describe and explain loss of water out of stomata
Humidity of atmosphere is less than air spaces next to stomata, which forms a water potential gradient
High WP (less negative inside) hence water loss from stomata
Water lost by diffusion from air spaces is replaced by water evaporating from mesophyll cell walls
Size of stomata controls rate transpiration - more open = quicker
Describe and explain movement of water across the leaf
Water lost from mesophyll cells via evaporation from cell walls is replaced by water from xylem
Water lost from mesophyll cells via evaporation from cell walls is replaced by water from xylem.
Mesophyll cells lose water to air spaces because of evaporation due to heat from sun
Mesophyll cells have a lower (more neg) WP than neighbouring cells
H2O enters via osmosis into mesophyll cells
Neighbouring cells have a lower WP now across lead so water pulled up from xylem
Movement between cells can be through symplastic pathway (through cytoplasm) or apoplastic pathway (through cell walls) (weird one)
Describe symplastic and apoplastic pathways
Symplastic - osmosis through cytoplasm
Apoplastic- through cell walk (follows line of cell wall till it hits casparin which is a waterproof layer and hence water enters via osmosis into the endodermis where it converges with symplastic pathway)
Describe diagram of cross section of vascular bundle in stem
Phloem outside
Xylem inside
Cambium in middle - meristem cells incokvded in producing new phloem and xylem cells
Describe and explain movement of water up xylem
H2O evaporates from mesophyll cells due to heat from sun leading to transpiration
Due to the polarity of water, hydrogen bonds form between water molecules known as cohesion
This forms an unbroken, continuous column of water across mesophyll calls and xylem
As H2O molecules evaporate into air spaces near stoma, more are pulled up due to cohesion to replace water molecules lost. Hence transpiration pull causes a column of water to be pulled up xylem
Hydrogen bonds also form between water molecules and the xylem walls, which assists in pulling water molecules up xylem.
The transpiration pull creates a negative pressure on the xylem, which pulls xylem walls in together
Hence known as cohesion-tension theory
Evidence that transpiration occurs (3 pieces). State specifically the piece fo evidence that supports the idea of negative pressure.
Smaller diameter of tree trunks at hottest point of day, due to more heat from sun causing a higher rate of evaporation and hence transpiration, more negative pressure is created due to more tension, hence walls of xylem pulled towards each other and trunk shrinks in diameter.
If a xylem vessel is broken and air enters, the CONTINUOUS COLUMN OF WATER is broken, hence the hydrogen bonds break and transpiration does not occur
If xylem vessel were under pressure, than H2O woudl leak out when a xylem vessel is broken. As it does not and air is drawn in the idea of negative pressure is supported.
Transpiration key words for mark scheme
Unbroken, continuous column of water Transpiration pull Cohesion Adhesion Negative pressure Unrestricted flow
Translocation definition
transport of organic molecules and mineral ions from sources (sites of production of sugars from photosynthesis) to sinks (where sugars can be stored or used.) and occurs in the phloem
Why is it not possible that translocation is diffusion
Too fast to be diffusion
How many phases in Mass Flow Hypothesis?
Three
Phase one of mass flow: sucrose
Manufactured from products of photosynthesis in cells containing chloroplasts
Sucrose diffuses down conc gradient by facilitated diffusion from photosynthesising cells to companion cells.
Active transport of hydrogen cells from companion cells into cell wall spaces
Hydrogen ions then (facilitated) diffuse down a conc gradient through carrier proteins into sieve tube elements
Sucrose molecules are the co - transported with hydrogen ions by co - transport proteins. (Hydrogen ions create an electrochemical gradient that pulls in sucrose molecules AGAINST sucrose concentration gradient) into sieve tube elements
Mass Flow Phase Two: Mass Flow
At source:
Active transport of sucrose out of source cells into sieve tubes lowers WP inside sieve tubes so water from xylem flows in via osmosis.
Increases hydrostatic pressure near the source cells
At sink:
Active transport of sucrose from sieve tubes into sink cells increases WP in the phloem.
Hence water leaves sieve tubes via osmosis, so decrease in hydrostatic oressure near the sink
Hence passive mass flow of sucrose down hydrostatic gradient, but due to active transport of sugars is controlled by enzymes and therefore affected by temperature, pH and metabolic poisons etc
Mass Flow Phase Three: Transfer from sieve tube elements into — or sink cells
Storage
Before entering sink cells (in middle of phase two explanation)
Active transport by companion cells out of sieve tubes and into sink cells
Evidence For Mass Flow (6)
Sap is releases when sieve tubes are cut, hence pressure within sieve tubes
Conc of sucrose in leaves is higher than in the roots ( supports source and sink idea)
Downward flow in phloem in daylight, but ceases in shade. less photosynthesis and supports movement to sinks
An increase in sucrose levels at sinks are followed by an increase in sucrose levels in the phloem
Metabolic poisons/ lack of O2 inhibit translocation in the phloem hence enzymes and active transport used.
Companion cells possess many mitochondria and readily produce ATP that can be produced for the active transport of hydrogen ions for example and sucrose
Evidence Against Mass Flow (3)
Sieve plates function isn’t clear as they seem to hinder mass flow - may help prevent bursting under pressure?
Not all solutes move at the same speed, which would occur if movement by mass flow
Sucrose delivered at the same rate to all regions, rather than more quickly at ones with a lower sucrose concentration, as mass flow would suggest
Tracer experiments and do they support or reject mass flow hypothesis
If plant is brown in atmosphere with 14CO2 then 14C isotope will be present in sugars that are produced and can be tracked by radiography as they travel through a plant.
Cross - sections of plant stem placed on X - ray film causes BLACKENING OF FILM where 14C is present and correspond to WHERE PHLOEM IS FOUND in tissues, and other tissues do not cause blackening hence ONLY THE PHLOEM CARRIES SUGARS.
Supports mass flow
Ringing experiments and do they support or reject mass flow hypothesis
Remove section of circumference around stem, whilst attached to plant (removing phloem)
Sugars of phloem will accumulate above the removed section, causing swelling
Tissues will die due to interruption of translocation.
(Samples of accumulation show high in sugars and organic substances)
As xylem is not removed, phloem transports sugars.
Supports mass flow hypothesis
