Section 3: Mass Transport Flashcards
Why is mass transport systems required?
- Most cells too far away from exchange surfaces for diffusion alone to maintain composition of tissue fluid
- Mass transport maintains final diffusion gradients bringing substances to and from cells
- Mass transport helps maintain relatively stable immediate environment of cells
What is the double circulatory system?
- Pulmonary circulation: Deoxygenated blood in right side of heart pumped to lungs - oxygenated blood returns to side of heart - left side
- Systemic circulation: Oxygenated blood in left side pumped to tissues/ deoxygenated blood returns on right side
Why is the double circulatory system important to animals?
- Prevents mixing of oxygenated and deoxygenated blood - so blood is saturated with oxygen - efficient delivery of oxygen and glucose for respiration
- Blood can be pumped at a higher pressure - substances taken to and removed from cells quicker and more efficient.
What are the coronary arteries?
- Deliver oxygenated blood to cardiac muscle (heart)
What are the names if the blood vessels entering and leaving the heart?
- Aorta - takes oxygenated blood from heart - respiring tissue
- Vena cava - takes deoxygenated blood from respiring tissue to heart
- Pulmonary artery - takes deoxygenated blood from heart to lungs
- Pulmonary vein - takes oxygenated blood from lungs to heart
What are the names of the blood vessels entering and leaving the lungs?
- Pulmonary artery
- Pulmonary vein
What are the names of the blood vessels entering and leaving the kidney?
- Renal artery - Takes oxygenated blood - kidneys
- Renal veins - take deoxygenated blood to the vena cava from the kidneys
What are the different valves?
- Atrioventricular valves - prevent backflow of blood to ventricles from atria
- Semi-lunar valves - prevent backflow of blood from arteries to ventricles
What is the adaptation of the left ventricle
- Has thicker muscular walls
- Generates high blood pressure
- For oxygenated blood has to travel greater distance around the body
What is the structure of arteries related to their function?
- Thick smooth muscle layer - Contract pushing blood along and control blood flow/pressure
- Elastic tissue layer - stretch as ventricles contract and recoil as ventricle relaxes. Even out blood pressure and maintain high pressure
- Thick wall - Withstands high pressure and prevents artery bursting
- Smooth endothelium - reduces friction
- Narrow lumen - Increases and maintains high blood pressure
What are arterioles and what is their structure related to their function?
- Division of arteries to smaller vessels directing blood to capillaries. Structure similar to arteries BUT…
- Thicker muscle layer - constricts to reduce blood flow and dilates to increase blood flow
- Thinner elastic layer as lower pressure
What is the structure of veins related to its function?
- Wider lumen than arteries
- Very little elastic and muscle tissue
- Valves - prevents the backflow of blood
Exam Question: The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why.(3)
- Aorta is close/directly linked to the heart/ventricle/ pressure is higher
- Aorta has elastic tissue
- Aorta has stretch and recoil
Structure of capillaries related to its function
- Capillary wall is a thin layer (1 cell thick) - short diffusion pathway - rapid diffusion
- Capillary bed is made of a large network of capillaries - large SA - rapid diffusion
- Narrow lumen - reduces flow rate so more time for diffusion
- Capillaries permeate tissues - short diffusion pathway
- Pores - allows substances to escape
What is tissue fluid?
- The fluid surrounding cells/tissues
- Provides respiring cells with water, oxygen, glucose, amino acids
- Enables waste substances to move back into blood e.g urea, lactic acid
What is the formation of tissue fluid?
- Higher blood/ hydrostatic pressure inside capillaries than tissue fluid
- Forces fluid/ water out of capillaries
- Large plasm proteins remain in capillary
What is the return of tissue fluid to the circulatory system?
- Hydrostatic pressure reduces as fluid leaves
- An increasing conc of proteins lowers the WP in the capillary below the tissue fluid
- Water re-enters the capillaries from the tissue fluid by osmosis - down WP gradient
- Excess water taken up by lymph system and returned to circulatory system
How does a low concentration of plasma proteins cause the accumulation of tissue fluid?
- Water potential in capillary not as low so WP potential gradient is reduced
- More tissue fluid formed at arteriole end
- Less/ no water absorbed into blood capillary by osmosis
How does high blood pressure lead to the accumulation of tissue fluid?
- High blood pressure = high hydrostatic pressure
- Increases outward pressure from arterial end
- So more tissue fluid formed/ less reabsorbed
- Lymph cant drain fast enough
What are the different stages of the cardiac cycle?
- Atrial systole
- Ventricular systole
- Diastole
What is atrial systole?
- Atria contract - decreasing volume and increasing pressure inside atria
- AV forced open, semi lunar closed
- Blood pushed into ventricles
What is ventricular systole?
- Ventricles contract from the bottom up - decreasing the volume and increasing pressure in ventricles
- Semi lunar valves are open
- AV valves shut
- Blood pushed out of heart through arteries
What is diastole?
- Atria and ventricles relax - increasing volume and decreasing pressure inside chambers
- Blood from veins fill atria (increasing pressure slightly) and flows passively into ventricles
- AV valves open, SL valves closed
How do you calculate cardiac output and what do the different parts of the equation mean?
- Cardiac output = stroke volume x heart rate
- Cardiac output = amount of blood pumped out of the heart per minute
- Stroke volume = volume of blood pumped by the ventricles in each heart beat
- Heart rate = number of beats per minute
How do you calculate heart rate from cardiac cycle data?
- 1 beat = 1 cardiac cycle
- Find the length of 1 cardiac cycle
- Heart rate in beats per minute = 60 seconds
What is cardiovascular disease and name an example of one?
- Conditions affecting structure or functions of the heart
- Coronary heart disease
How can an atheroma result in a heart attack
- Atheroma causes narrowing of coronary arteries
- Restricts blood flow to heart muscle supplying glucose or oxygen
- Heart anaerobically respires - less ATP produced - not enough energy for heart to contract - lactate produced - damages heart tissue
What are the common risk factors of cardiovascular disease (increase probability of getting disease)
- Age
- Diet - high in salt or saturated fat
- High consumption of alcohol
- Stress
- Smoking
- Genetic
Exam Question: Studies of CVD patterns between different countries suggest there is a link between CBD and diet. Suggest why such studies may not prove the link between CVD and diet (2)
- Other variables/ uncontrolled variables affect CVD
- Genetic differences
- Different countries have different lifestyles
- Data does not provide a causal link
What is haemoglobin?
- Is a group of chemically similar molecules found in many different organisms
- This structure may differ between organisms
Where is Haemoglobin found?
- In red blood cells
What is the structure of haemoglobin?
- No nucleus - contain more haemoglobin
- Biconcave shape - increase surface area for rapid diffusion
- Quaternary structure - 4 polypeptide chains
- Each polypeptide chain contains a haem group of Fe2+ which combines with oxygen
What is the structure of haemoglobin?
- No nucleus - contain more haemoglobin
- Biconcave shape - increase surface area for rapid diffusion
- Quaternary structure - 4 polypeptide chains
- Each polypeptide chain contains a haem group of Fe2+ which combines with oxygen
Where in the body does haemoglobin have a high and low affinity to oxygen?
- In lungs there is a high pO2, haemoglobin has a high affinity for oxygen - readily loads
- At respiring tissues, a low pO2 oxygen readily unloads. CO2 conc high increasing unloading
Explain the shape of the oxyhaemoglobin dissociation curve?
- Haemoglobin has a low affinity for oxygen as first oxygen binds
- After first binds the shape changes that makes 2nd and 3rd easier to bind
- After 3rd, haemoglobin starts to become saturated, shape changes and it is hard to bind
What is the effect of CO2 (bohr effect)
- Lowers the pH and reduces haemoglobin’s affinity for oxygen as haemoglobin changes shape
- Oxygen rapidly unloads
- Advantageous - provides more oxygen for muscles for aerobic respiration. Curve shifts to the right
What is the effect of the curve being shifted to the left?
- Haemoglobin has a higher affinity for oxygen
- More oxygen associates with haemoglobin more readily at low pO2 and dissociates less readily
- Advantageous - for those living in high altitudes, underground
What is the effect of the curve being shifted to the right?
- Oxygen dissociates from haemoglobin more readily to respiring cells
- Advantageous to organisms with a high rate of respiration
What is the function of the xylem?
- Is the tissue that transports water in the stem and leaves of plants
What is the cohesion tension theory?
- How water moves up the xylem against transpiration via transpiration stream
What is the process of the cohesion tension theory?
- Water evaporates from the leaves via the stomata due to transpiration
- Reducing WP in the cell and increasing WP gradient
- Water drawn out of xylem
- Creating tension
- Cohesive forces between water molecules pull water up as a column
What are some adaptations of the xylem?
- Elongated cells arranged end to end to form a continuous column
- Hollow
- End walls break down for flow
- Thick cell walls
- Rigid - less likely to collapse under low pressure
- Waterproof
What is the process of transloaction?
- Movement of solutes from source to sink
What is the mass flow hypothesis at the source?
- High conc of solute
- Active transport loads solutes from companion cells to sieve tubes of the phloem
- Lowering WP inside sieve tubes
- Water enters sieve tubes by osmosis from xylem and companion cells
- Increasing pressure inside sieve tubes at the source end
What is the mass flow hypothesis at the sink?
- Low conc of solute
- Solutes removed to be used up
- Increasing WP inside sieve tubes
- Water leaves by osmosis
- Lowering pressure inside sieve tubes
What is the mass flow in the mass flow hypothesis?
- Pressure gradient from source to sink
- Pushes solutes from source to sink
- Solutes used/stored at sink
What are the adaptations of the phloem?
- Sieve tubes have no nucleus and few organelles
- Companion cell for each sieve tube carry out important functions - provide ATP
What are some of the ways to investigate transport in plants?
- Use of tracers and ringing experiments
- Aphid
- Metabolic inhibitor
How do you use tracers to investigate transport in plants?
- Supply plant with C14
- This is incorporated into organic substances produced by the leaf and undergo translocation
- Plant killed and placed in autoradiography and turns black when radioactive substance is present
How do you use aphids to investigate transport in plants?
- Aphids pierce the phloem using mouthpiece
- Releasing sap from plants
- Flow of sap higher at leaves than at sink
- Evidence of pressure gradient - higher near source
How do you use of metabolic inhibitors to investigate transport in plants?
- Add a metabolic inhibitor to phloem
- Translocation stops
- Proves active transport is involved - as it requires ATP against conc gradient
What does a potometer do?
- Estimates the transpiration rate by measuring water uptake
What is the method of using a potometer?
- Cut shoot underwater - prevent air entering
- Assemble potometer and insert shoot underwater
- Dry leaves and allow time to acclimatise
- Shut off tap reservoir
- Remove the end of the capillary tube from water beaker until 1 bubble has formed
- Record position of air bubble and record time
- Rate of air movement = estimate transpiration rate can change variables
How does light affect the rate of transpiration?
- Higher light intensity - faster transpiration
- Because stomata open in light to let CO2 in for photosynthesis
- Allowing more water to evaporate faster
- Stomata close when it is dark - low transpiration rate
How does temperature affect the rate of transpiration?
- Higher temperature = faster transpiration rate
- Water molecules gain K.E and move faster
- Water evaporates faster
How does humidity affect the rate of transpiration?
- Lower humidity - faster transpiration rate
- Because as humidity increases, more water is in the air so has a higher WP potential
- Decreasing WP gradient - water evaporates more slower
How does wind affect the rate of transpiration?
- Windier = faster transpiration rate
- Wind blows away water molecules from around stomata
- Decreasing WP of air around stomata
- Increasing WP gradient
- Water evaporates faster
