Mass transport Flashcards
(21 cards)
Tissue fluid is formed from blood at the arteriole end of a capillary bed.
Explain how water from tissuefluid is returned to the circulatory system.
- Plasma proteins remain
- This creates a water potential gradient as it reduces the water potential of the blood
- Water moves to the blood via osmosis
- This returns to blood via the lymphatic system
Explain how an arteriole can reduce the blood flow into capillaries
- muscle contracts
- this constricts/narrows the arteriole’s lumen
at point Q there is a small increase in pressure and in rate of blood flow in aorta.
Explain how this happens and its importance
- elastic recoil of the aorta wall/tissue
- maintains the rate of blood flow/blood pressure
at point P, the pressure in the left ventricle is increasing. At this time, the rate of blood flow has not yet started to increase in the aorta.
Use evidence from the diagram above to explain why.
- Semi-lunar valves are closed.
- Because pressure in aorta is higher than in ventricle.
describe the advantage of the bohr effect during intense exercise
- increases dissociation of oxygen for aerobic respiration at cells
Describe a physiological change that could cause pCO2 in air breathed out to not show a large increase (normal) during intense exercise
- increase in breathing rate
- similar pCO2 per breath, but more breaths
- increase in breathing rate
- increase in tidal volume
-similar pCO2 per breath, but increased volume per breath
- increase in tidal volume
describe and explain the effect of increasing CO2 concentration on the dissociation of oxyhaemoglobin
- decreases haemoglobin’s affinity for oxygen (increases dissociation)
- by way of decreasing blood pH
explain how the left AV valve maintains a unidirectional flow of blood
- Pressure in the leftatriumis higher than in the ventricle, causing valve to open
- Pressure in the left ventricl is higher than in atrium, cauing valve to close
Describe how the mass flow hypothesis accounts for the movement from leaves to roots
- sugars loaded actively into phloem/sieve tubes
- this lowers water potential
- so that water will enter the phloem
- pressure in the phloem increases. This pressure increase moves the sugars
- sugars converted into insoluble starch in root cells, increasing water potential so water moves out
Flow and pressure is reduced during the hottest part of the day. Use your understanding of transpiration and a mass flow to explain why
- High rate of transpiration/ evaporation
- Water is lost through stomata
- Causes less water movement from xylom to phloem
Explain why water moves up the stalk of the plant
- Water evaporates/ is transpired
- A water potential gradient pulls up water/ osmosis creates tension
- Hydrogen bonds/cohesion maintains the column
Describe the cohesion-tension theory of water transport in the xylem
- water is lost from leaf due to evaporation/transpiration
- lowers the water potential of mesophyll cells
- water is pulled up the xylem, creating tension
- water molecules are cohesive due to hydrogen bonds between molecules
- this forms the column
- adhesion of water molecules to walls of xylem
Explain four ways in which the structure of the aorta is related to its function.
- Thick muscular walls withstand high pressure
- Muscle for contraction/vasoconstriction
- Elastic tissue to allow recoil/maintains pressure
- Elastic tissue stretches when ventricles contract
- Smooth endothelium reduces friction
- Semi-lunar valve prevents backflow
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 are too large to leave capillary
- Higher concentration of blood proteins, so lower water potential
A principle of homeostasis is the maintenance of a constant internal environment. An increase in
the concentration of carbon dioxide would change the internal environment and blood pH.
Explain the importance of maintaining a constant blood pH.
- Haemoglobin in blood is sensitive to pH
- Change in pH leads to a change in tertiary structure of haemoglobin - it denatures
- So less oxygen can bind with haemoglobin
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from
the left atrium to the aorta.
- Atrium has a higher pressure than ventricle causing AV valve to open
- Ventricle has a higher pressure than atrium causing AV valves to close
- Ventricle has higher pressure than aorta causing semi-lunar valve to open
- aorta has higher pressure than ventricle causing semi-lunar valve to close
- muscle contraction causes increase in pressure
Kwashiorkor is a disease caused by a lack of protein in the blood. This leads to a swollen
abdomen due to a build up of tissue fluid.
Explain why a lack of protein in the blood causes a build up of tissue fluid.
- water potential in capillary is higher
- less water moves into capillary
- by osmosis
Explain why the values for the pressure in the xylem are negative.
Inside the xylem there is a lower than atmospheric pressure and the water is under tension
The thickness of the aorta wall changes all the time during each cardiac cycle.
Explain why
- Aorta wall stretches when ventricle contracts
- aorta wall recoils because ventricle relaxes
- maintaining pressure
describe how a hole between the aorta and the pulmonary artery could cause a baby to die within 12 months of its birth
- (Some) oxygenated blood (from the aorta)
flows into pulmonary artery;
OR
Less oxygenated blood flows out through
aorta;
OR
Lower blood pressure in aorta; - Less oxygen delivered to cells / tissues /
organs / named organ / via named blood
vessel; - So less/not enough oxygen for aerobic
respiration (in cell/ tissue/organ); - Tissue/organ doesn’t grow/develop properly
(causing death);
OR
Tissue dies/organ stops working (causing
death);
Explain the importance of the xylem being kept open as a continuous tube by lignin
- allows water to move in a column
- Cohesion between h bonds in water
- transpiration creates tension
