3 Organisms exchange substances with their environment EQs Flashcards
How is the pressure in the ventricle related to the thickness of the ventricle wall? (2 marks)
- Thickness of wall increases because ventricle wall contracts
- Contraction causes the increase in pressure
The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why. (1 mark)
Loss of water
High blood pressure leads to an accumulation of tissue fluid. Explain how. (3 marks)
- High blood pressure = high hydrostatic pressure
- Increases outward pressure from arterial end of capillary
- So more tissue fluid formed
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. (3 marks)
- Water has left the capillary;
- Proteins in blood too large to leave capillary;
- Higher concentration of blood proteins and so 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. (3 marks)
- Haemoglobin affected by change in pH
- Change of tertiary structure;
- Increases dissociation
e.g. less oxygen binds with haemoglobin
Although the speed of blood flow in an arteriole is greater than speed of blood flow in a capillary, blood does not accumulate in the arterioles.
Explain why. (1 mark)
- More capillaries than arterioles
- Cross-sectional area of capillaries much greater than of arterioles
Other than causing slow blood flow, explain one advantage of capillaries being narrow. (2 marks)
- Short distance between blood and outside of capillary
- Fast exchange
What factor limits the minimum internal diameter of the lumen of a capillary? (1 mark)
Size of blood cell.
The volume of blood leaving the capillary network into the veins is less than the volume of blood entering from the arteries.
Explain why. (1 mark)
Fluid in tissue fluid
What is the function of the coronary arteries? (2 marks)
- Carry oxygen
- To heart muscle
The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why. (3 mark)
- Aorta is directly linked to the heart
- Aorta has elastic tissue;
- Aorta has stretch / recoil.
The scientists used the percentage change in the mean resting heart rate after the
exercise programme to compare the results for males and females.
Explain why they used percentage change in the resting heart rate. (2 marks)
- Allows comparison
- Initial heart rates different between males and females
Explain how their cardiac output could stay the same even when their resting heart
rate had decreased in an exercise programme? (2 marks)
- Cardiac output = stroke volume × heart rate
- So stroke volume increases
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. (3 marks)
- Renal vein;
- Vena cava to right atrium;
- Right ventricle to pulmonary artery;
Tissue fluid is formed from blood at the arteriole end of a capillary bed. Explain how water from tissue fluid is returned to the circulatory system. ( 4 marks)
- Plasma proteins remain;
- Creates water potential gradient
- Water moves to blood by osmosis;
- Returns to blood by lymphatic system;
Explain how an arteriole can reduce the blood flow into capillaries. (2 marks)
- Muscle contracts;
- Narrows lumen;
What blood vessel carries blood at the lowest
blood pressure? (1 mark)
Vena Cava
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. Explain why (2 marks)
- Semi-lunar valves is closed;
- Because pressure in aorta higher than in ventricle;
There is a small increase in pressure and in rate of blood flow in the aorta.
Explain how this happens and its importance. (2 marks)
- Elastic recoil of the aorta wall
- Maintains rate of blood flow
Maintains blood pressure
EPO is another performance-enhancing drug. It can increase the haematocrit (the percentage of red blood cells in blood). A heart attack is caused by a lack of glucose and oxygen being delivered to cardiac muscle via the coronary arteries. The overuse of EPO can increase the risk of a heart attack.
Suggest how. (2 marks)
- EPO causes blood to thicken;
- The thickened blood could block the coronary arteries
Describe and explain the effect of increasing carbon dioxide concentration
on the dissociation of oxyhaemoglobin. (2 marks)
- More oxygen dissociation
- By decreasing blood pH
Give two safety precautions that should be followed when dissecting a
heart. (1 mark)
- Wash hands/wear gloves
- Disinfect bench/equipment
Explain how left atrioventricular valve maintains a unidirectional flow of blood. (2 marks)
- Pressure in left atrium is higher than in ventricle causing valve to open;
- Pressure in left ventricle is higher than in atrium causing valve to close;
Explain the role of the heart in the formation of tissue fluid. (2 marks)
- Contraction of ventricle produces high hydrostatic pressure;
- This forces water out of blood capillaries
Lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system.
Suggest how a blockage in the lymphatic system could cause
lymphoedema. (1 mark)
Excess tissue fluid builds up
Why is putting a replacement organ in an isotonic solution important? (2 marks)
- Because same water potential;
- So prevents loss or gain of water by osmosis
- So cells aren’t damaged;
Why is putting a replacement organ in an antibiotic important? (1 mark)
Kills bacteria that could cause infection/disease
Describe the mass flow hypothesis for the mechanism of translocation in plants. (4 marks)
- In source sugars actively transported into phloem;
- By companion cells;
- Lowers water potential of sieve cell and water enters by osmosis;
- Increase in pressure causes mass movement towards sink
- Sugars used in root for respiration for storage.
What other information is required in order to calculate the mean rate of movement down a trunk of a tree? (1 mark)
Length of trunk
Describe how a high pressure is produced in the leaves. (3 marks)
- Water potential becomes lower as sugar enters phloem
- Water enters phloem by osmosis
- Increased volume of water causes increased pressure.
Suggest and explain one other way in which sieve cells are
adapted for mass transport. (2 marks)
- Few organelles
- So more flow
Suggest and explain one other way in which companion
cells are adapted for the transport of sugars between cells. (2 marks)
- Mitochondria release energy
- For active transport
The mass flow hypothesis is used to explain the movement of substances through phloem.
Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube. (3 marks)
- Sucrose actively transported into phloem
- Lowering water potential
- Water moves into phloem by osmosis from xylem
Phloem pressure is reduced during the hottest part of the day. Use your understanding of
transpiration and mass flow to explain why. (3 marks)
- High rate of transpiration/evaporation;
- Water lost through stomata
- Causes less water movement from xylem to phloem
Suggest how a plant is able to survive without xylem tissue. (1 mark)
It has a surface permeable to water
The student wanted to determine the rate of water loss per mm2 of surface area of the leaves of a shoot. Outline a method she could have used to find this rate. You should assume that all water loss from the shoot is from the leaves. (3 marks)
- Method for measuring area;
e.g. draw round each leaf on graph paper and count squares; - Of both sides of each leaf;
- Divide rate by total surface area of leaves
The rate of water movement through a shoot in a potometer may not be the same as the rate of water movement through the shoot of a whole plant.
Suggest one reason why. (1 mark)
Plant has roots
Describe the mechanism for the absorption of amino acids in the ileum (4 marks)
- Co-transport;
- Sodium ions actively transported from cell to blood
- Creating sodium ion concentration gradient;
- Facilitated diffusion of amino acid into blood
High concentration of salt can lead to a build-up of tissue fluid.
Explain how. (2 marks)
- Higher salt results in lower water potential of
tissue fluid - So less water returns to capillary by osmosis at venule end
Suggest one advantage to a bacterium secreting a protein (2 marks)
- To digest protein;
- So they can absorb amino acids for growth
Describe the action of membrane-bound dipeptidases and explain their importance. (2 marks)
- Hydrolyse peptide bonds to release amino acids;
- Amino acids can cross cell membrane and dipeptidases cannot
Explain three ways in which an insect’s tracheal system is adapted for efficient gas
exchange. (3 marks)
- Tracheoles have thin walls so short diffusion distance to cells
- Highly branched tracheoles so short diffusion distance to
cells; - Body can be moved by muscles to move air so maintains concentration gradient
Why are gills useful for actively seeking prey underwater? (2 marks)
- higher respiratory rate
- so uses more oxygen
In large cells of U. marinum, most mitochondria are found close to the cell-surface membrane. Mitochondria use oxygen during aerobic
respiration. Suggest an explanation for the position of mitochondria in large U.
marinum cells. (2 marks)
- Larger cells have smaller surface area to volume ratio;
- Takes longer for oxygen to diffuse to mitochondria
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake. (2 marks)
- Larger cells have smaller surface area to volume ratio;
- Faster diffusion
Mammals such as a mouse and a horse are able to maintain a constant body temperature.
Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse. (3 marks)
- Smaller so larger surface area to volume ratio;
- More heat loss per gram
- Faster rate of respiration/metabolism releases heat;
Suggest one practical advantage of measuring the masses of frog eggs,
tadpoles and adults, compared with measuring their volumes. (1 mark)
More accurate
Explain why oxygen uptake is a measure of metabolic rate in organisms. (1 mark)
Oxygen is used in respiration, which is a metabolic process
Describe and explain one feature of the alveolar epithelium that makes the
epithelium well adapted as a surface for gas exchange. (2 marks)
- Single layer of cells
- Reduces diffusion distance
Suggest and explain how a reduced tidal volume affects the exchange of
carbon dioxide between the blood and the alveoli. (3 marks)
- Less carbon dioxide exhaled
- So reduced diffusion (between blood and alveoli);
- Less movement of carbon dioxide out of blood
Describe and explain the mechanism that causes lungs to fill with air. (3 marks)
- Diaphragm muscle contracts and external intercostal muscles
contract; - Causes volume increase and pressure decrease;
- Air moves down a pressure gradient
Explain why death of alveolar epithelium cells reduces gas exchange in
human lungs. (3 marks)
- Reduced surface area;
- Increased distance for diffusion;
- Reduced rate of gas exchange;
Suggest and explain one way the leaf growth of xerophytic plants would be
different from the leaf growth of sunflowers (2 marks)
- Low growth;
- Due to smaller number of stomata for gas exchange
Explain why plants
grown in soil with very little water grow only slowly. (2 marks)
- Stomata close;
- Less carbon dioxide uptake for less photosynthesis
Describe the pathway taken by an oxygen molecule from an alveolus to the blood. (2 marks)
- Across alveolar epithelium;
- Endothelium / epithelium of capillary;
Explain how one feature of an alveolus allows efficient gas exchange to occur. (2 marks)
- The alveolar epithelium is one cell thick
- Creating a short diffusion pathway
A student correctly plotted the right ventricle pressure on the same grid as the left ventricle pressure. Explain one way they would be similar and different. (2 marks)
- Peaks at same time
- Lower pressure;
Explain how changes in the shape of haemoglobin result in the S-shaped oxyhaemoglobin dissociation curve (2 marks)
- First oxygen binds to haemoglobin causing change in shape
- Shape change of Hb allows more O2 to bind easier
Give three measurements to calculate rate of water movement? (3 marks)
- Initial and final mass
- Number of xylem vessels
- Time taken for water movement
Explain why water moves up the stalks of plants? (3 marks)
- Water evaporates from leaves
- Lowers water potential and creates tension
- Hydrogen bonds create tension
Describe how to handle a scalpel safely during this procedure. (2 marks)
- Cut away from body
- Against flat surface
Describe the role of micelles in the absorption of fats into the cells lining the ileum. (3 marks)
- Micelles include bile salts and fatty acids
- Make the fatty acids more soluble in water
- Carries fatty acids to the lining of the ileum
- Maintain higher concentration of fatty acids to the lining of the ileum
- Fatty acids absorbed by diffusion;
Describe one way this uncontrolled cell division changes the gills (3 marks)
- thicker filament =
- increase diffusion distance,
- so gas exchange would slow down
Give two differences between circulation of blood in fish and circulation of blood in a mammal (2 marks)
- single circulatory system in fish, double in mammal
- 2 chambers in fish, 4 chambers in mammal
In healthy lungs, a gradient is maintained between the concentration of oxygen in the
alveoli and the concentration of oxygen in the lung capillaries.
Describe how ventilation helps to maintain this difference in oxygen concentration. (2 marks)
(In alveolus)
1. Brings in air containing a high(er) oxygen concentration;
2. Removes air with a low(er) oxygen concentration;
Name one thing that helps maintain difference in oxygen concentration? (1 mark)
Circulation of blood
How do mitochondria help digestion? (2 marks)
- (Site of aerobic) respiration / ATP production
- Active transport
What is the advantage of giving the results as a ratio? (2 marks)
- Allows comparison
- Different starting masses / weights;
An increase in respiration in the tissues of a mammal affects the oxygen dissociation
curve of haemoglobin. Describe and explain how (2 marks)
- Increase in carbon dioxide;
- Curve moves to the right
Give one way that blood is different from tissue fluid (1 mark)
more proteins
The blood pressure decreases along the length of the capillary. What causes this
decrease in pressure? (1 mark)
loss of fluid
The demand for increased food production has led to areas of heath being used to grow
wheat. Explain the effect of this on the species diversity of plants (2 marks)
- Reduced as one crop grown / other species removed;
- Use of herbicides/weeding/ploughing;
The demand for increased food production has led to areas of heath being used to grow
wheat. Explain the effect of this on the species diversity of animals (2 marks)
- (Reduced) as less variety of food sources;
- (Reduced) as fewer habitats/niches;
The zoologist measured oxygen uptake per gram of body mass. Explain why he
measured oxygen uptake per gram of body mass. (2 marks)
- Enables comparison;
- As animals differ in size/mass;
When a wave of electrical activity reaches the atrioventricular valve, there is a short delay before a
new wave leaves the atrioventricular valve. Explain the importance of this short delay. (2 marks)
- Allow atria to empty / contract / ventricles to fill;
- Before ventricles contract;
How does training has caused the resting heart
rate of this athlete to be lower. (2 marks)
- Increase in size or volume of heart
- Cardiac output is the same (before and after training);
- Increase in stroke volume
The haemoglobin in one organism may have a different chemical structure from the
haemoglobin in another organism. Describe how. (1 mark)
different primary structure
The maximum pressure in the ventricle is much higher than that in the atrium.
Explain what causes this. (2 marks)
- (Ventricle has) thick wall
- So contractions are stronger
Name two structural features of the gills of a fish that increase their surface area? (1 mark)
- lots of gill filaments
- gill filaments covered in lamellae
