Mass Transport Flashcards
Properties of the xylem
- long
- dead cells
- no cell walls
- contain lignin
Cohesion-Tension theory
- Some water in the leaves is used during photosynthesis
- Most leaves through transpiration
- The loss of water causes tension
- Water is pulled up due to the formation of the hydrogen bonds between water molecules and xylem vessel
- Hydrogen bonds also form between just water molecules(cohesion) so they all get pulled up together
- This replaces the lost water
- Due to this the Ψ in the roots is low, so water diffuses via osmosis down the Ψ gradient
Properties of the phloem
- living cells
- sieve tube walls made of cellulose
- Plasmodesmata allows the cytoplasm to be shared between the sieve tube and companion cells
- sieve plates have pores to allow sap to move through. Sugars are transported through
Process of translocation
- Sucrose is actively transported into the sieve tube elements(STE) so Ψ in the tube decreases
- Water in the xylem moves in via osmosis into the STE, increasing the Pa at the top of the phloem
- Sucrose diffuses out of the phloem into the sink cell so Ψ at the bottom increases
- Water moves out via osmosis back into the xylem and the Pa decreases
- A Pa gradient is established so particles move from top to bottom
- Sucrose is then converted back to glucose for respiration + starch
Using ringing to investigate mass transport
- If a ring is cut outside the stem, this halts transport in the phloem but not the xylem as the phloem is located on the outside
- The tissue above will the ring starts to swell and growth below stops as sucrose cannot be transported
Using tracing to investigate mass transport
- The leaves are exposed to radioactive carbon
- The plant is frozen very quickly in liquid nitrogen and placed on photographic film
- The pathway of radioactive sucrose down the phloem can be traced
Evidence for mass flow
- Tracing and ringing provide evidence for mass flow theory
- Both show a casual link between the phloem and sucrose
Evidence against mass flow
- Sap can move up and down the phloem. Hydrostatic Pa gradient is by the movement water from to source to the sink but does not explain the sap’s movement
- Increased hydrostatic Pa is required for water to flow through the pores, so sieve plates should be a problem
- The purpose why the phloem has living cells is unclear
Why is the oxygen dissociation curve S-shaped?
- 1st oxygen binds easily
- 2nd + 3rd bind easily as well due to the 1st one
- 4th binds with difficulty
What does the curve being further right mean?
That they have a higher affinity for oxygen
What happens when the partial pressure of oxygen is high?
The affinity for oxygen increases so oxygen binds to haemoglobin
What happens when the partial pressure of oxygen is low?
The affinity for O₂ decreases so O₂ dissociates from haemoglobin
The properties of haemoglobin at high altitude
- High affinity for O₂ as there is low PO₂
What happens when partial is low?
- Low affinity for oxygen
- Saturation of haemoglobin is low
What happens when partial pressure is high?
- High affinity for oxygen
- Saturation increases quickly
What is the Bohr effect?
- That the increased dissociation of O₂will cause a shift to the right in the oxyhaemoglobin dissociation
- This means that O₂ will dissociate at lower partial pressures than normal
What does a double circulatory system mean?
Blood travels through the heart twice in one circuit
Function of coronary arteries
Supply blood to the heart
Function of pulmonary artery
Pumps deoxygenated blood away from the heart to the lungs
Function of pulmonary vein
Pumps oxygenated blood to the heart
Why is pressure the aorta high?
To ensure that the blood is pumped to all tissues of the body
Function of the vena cava
To pump deoxygenated blood from the body back to the heart
Function of renal artery
To pump oxygenated blood to the kidneys
Function of renal vein
To pump deoxygenated blood out of the kidneys
What occurs in the right atrium?
Deoxygenated blood from body flows into the heart via the vena cava
What occurs in the right ventricle?
- Atrioventricular (AV) valves open
- Deoxygenated blood flows in from the right atrium
- AV valves close
- The walls of the ventricle contract forcing the semi-lunar (SL) valves
- Blood is pumped of the heart into the lungs via the pulmonary artery
What occurs in the left atrium
Oxygenated blood flows into the left atrium via the pulmonary vein from the lungs
What occurs in the left ventricle
- AV valves open
- Oxygenated blood flows into the ventricle from the left atrium
- AV valves close and SL valves open
- Oxygenated blood is pumped out of the heart via the aorta
- SL valves close
Why are the walls of the left ventricle thicker than the right ventricle?
- The left ventricle has to pump blood to the rest of the body whereas the right ventricle only pumps blood to the lungs which is a shorter distance
- It has more muscle
Why are the walls of the ventricles thicker than that of the atria?
- Ventricles pump blood a further distance, so contract with greater force with higher Pa
What happens at atrial contraction?
- Blood from the lungs flows into the left atrium while the blood from the body flows into the right atrium
- The atria contracts, increasing the Pa, vol decreases
- Blood is forced into the ventricles
- Ventricles relax as they fill with blood
- Slight increase in Pa + vol of ventricles
What happens at ventricular contraction?
- Atria relax + ventricles begin to contract
- This causes Pa in the ventricles to increase + vol decreases
- This shuts the AV valves as Pa in the ventricles is higher than the atria
- The blood in the ventricles are forced out through the pulmonary vein or aorta
What happens during relaxation of the cardiac cycle?
- The blood in the pulmonary artery + aorta are at high Pa
- Causing the SL valves to close as there is more Pa in the arteries than the ventricles
- Both the ventricles + artria relax and AV valves open
What are arterioles?
- Smaller vessels that stem from arteries that are connected to organs
What are veins and their properties?
- They transport blood back to the heart
- Wide lumen; allows blood to flow at low pressure
- Thin muscle wall
- Elastic tissue
- Has valves; to prevent back flow
What are arteries and their properties
- Transports blood away from the heart
- Thick muscle wall; to maintain high pressure
- Elastic fibres; to allow arteries to stretch
- Folded endothelium; allows arteries to stretch
What are capillaries and their properties?
- A network of arterioles that surround body cells
- Close to cells; creating a short diffusion pathway
- Large surface area
- 1 cell thick; short diffusion pathway for efficient exchange
Steps of pressure filtration
- High Pa at the capillary end creating a Pa gradient
- Fluid flows down Pa gradient into surrounding space, leaving plasma protein
- Pa inside capillaries reduces, so Pa lower at capillary bed then capillary end
- Plasma proteins reduce the Ψ, so a Ψ gradient is established and water diffuses in via osmosis
- Excess tissue fluid flows into lymphatic system recycling it into the bloodstream
What is atheromas?
- The deposition of materials in the walls of the arteries
What is fibrous plaque?
Deposition of white blood cells and fatty materials over time which harden
Consequences of narrower lumen of the arteries
- Blood flow is restricted
- Increased blood pressure
- Can lead to cardiovascular disease
What is thrombosis?
- When platelets accumulate and form clots
- It can block blood flow
What is an aneurysm
- A swelling
What causes Thrombosis?
- When atheromas damage the artery wall causing it to burst open
What causes aneursyms?
- The damage caused by atheromas increases blood pressure
- This causes the elastic fibres to swell
Risk factors that contribute to cardiovascular disease
- High cholesterol diet
- High blood pressure
- Smoking
How does a diet high in cholesterol cause coronary heart disease(CHD)?
- Narrows the lumen
- Restricting blood flow to cardiac muscle
- Causing myocardial infarction (heart attack)
What is the equation of cardiac output?
CO = SV x HR
What holds the valves in place?
- Cords
- Heart strings
Name an organism with a single circulatory system?
Fish
What does systole mean?
Contract
What does diastole mean?
Relax
What organ are hepatic arteries/veins linked to?
Liver
What organ are renal arteries/veins linked to?
Kidneys
What causes the AV valves to close?
Pressure in ventricles is higher than the pressure in the atria
What causes the SL valves to close?
Pressure in the arteries is higher than the pressure in the ventricles
