Exam q mistake topic three

• explain why the mammal needs such a complex system for gas exchange when single celled organism doesn’t

  1. Single cells have a larger surface area to volume ratios
  2. for diffusion
  3. So exchange across this surface membrane as it has a shorter diffusion pathway
  4. oxygen and carbon dioxide diffuses in and out down the diffusion gradient
  5. Mammals are larger giving a smaller surface area to volume ratio
  6. don’t diffuse across the cell surface membrane as the diffusion pathway is too long
  7. Also, the skins, waterproof and gas tight
  8. need internal gas exchange surface like lungs
  9. with larger surface area
• Explain why counter current flow is more effective than parallel flow

  • steady concentration gradient to be maintained across entire length of lamellae
  • As it ensures that water with higher oxygen concentration continuously moves
  • So more oxygen can diffuse from water to the blood so constant diffusion can occur
• Mackerel are active fast swimming fish whilst place spent most of the times moving slowly there are differences in the girls of these two type types of fish suggest what these differences might be

  • Mackerel have more lamellae
  • Mackerel have longer gill filaments ( to give higher surface areas )
  • As they move more they need more atp so need increased respiration so need more oxygen
• Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish (3)

  1. water and blood flow across gills in opposite directions
  2. Maintains the oxygen concentration in the blood so it never reaches equilibrium
  3. This diffusion gradient is maintained across entire length of lamellae
• Describe one way in which transport of oxygen to a muscle in an insect is different from that in a fish

  Fish need a mass transport system the blood so oxygen can be obtained at an efficient rate but insects don’t need blood to transport respiratory gases as there tracheal system is sufficient In supplying oxygen
• Suggest an advantage of spiracle movement in a terrestrial insect

  It helps to conserve water as spiracles aren’t opened continuously therefore water doesn’t diffuse out continuously
• Fossil insects have been discovered that are larger than insects that occur on Earth today. What does this suggest about the composition of the atmosphere at the time when these fossil insects lived.

  Higher concentration of oxygen in the atmosphere giving steeper gradient so compensates for the longer pathway
• Explain how to features of gills allows efficient gas exchange

  1. Many gill filaments / lamellae that give a larger surface area
  2. Counter current flow maintain a concentration gradient
  3. Thin epithelium so short diffusion pathway from water to blood
• Explain why a logarithmic scale was used to plot body mass (1)

  Large data range of values can fit on a graph
• Explain three ways in which tracheal systems adapt are for efficient gas exchange

  1. Tracheoles have thin walls so short diffusion pathway
  2. large number of tracheoles so short diffusion distance to cell / increased surface area for gas exchange
  3. body can be moved by muscles to move air so it maintains the concentration gradient for oxygen
  4. Tracheae provide tubes full of air so faster diffusion into insect tissue
  5. Fluid in end of tracheoles that moves out during exercise so larger surface area for gas exchange
• Abdominal pumping increases the efficiency of gas exchange between tracheal and muscle tissue of the insect explain why

  1. More oxygen enters tracheoles
  2. Maintain the oxygen concentration gradient for faster diffusion
• The removal of water from the increases the rate of diffusion of oxygen between tracheal and muscle tissues explain why (1)

  1. more surface area exposed to air
  2. Increases the volume of
  3. Oxygen diffuses faster in air than water
• Adaptations of insects in hot climates

  1. Waterproof exoskeleton doenst allow the diffusion of water
  2. closes spiracles periodically
  3. hairs in the spiracles to trap moisture air and lower water potential gradient
  4. small surface area to volume ratio to minimise area over which waters lost
• What does standard deviation show (2)

  Variation in data

  Around the mean
• Suggest an explain why reduced title volume affects exchange of carbon dioxide between the blood and the alveoli

  1. Less carbon dioxide breathe out / exhaled
  2. Reduces the concentration gradient
  3. less diffusion of carbon dioxide form blood to alveoli
• Describe method used to get surface area of a leaf (3)

  Place leaf on graph paper trace around it

  Count the squares

  Multiply by two to get lower and upper surface
• Describe how oxygen in the air reaches capillary surrounding the alveoli in the lungs (4)

  1. Air goes through trachea bronchi bronchioles
  2. Down a pressure gradient
  3. Diffuses Down a concentration gradient
  4. across alveoli epithelium
  5. across capillary endothelium
• Suggest and explain one way leaf growth of xerophytic plants would be different from sunflower

  1. Slower growth
  2. Due to smaller number of stomata
• Haematoxylin solution stains DNA a blue colour.

  • lodine solution stains starch a blue-black colour.

  The scientist used haematoxylin solution and/not iodine solution to stain the lung tissue.

  (Suggest why.

  1. Lung tissue doesn’t contain starch
  2. Makes nucleus visible as nucleus contains dna
• Identify k and l

  K is bronchioles

  L is an artery / arterioles / veins / venule

  
• Describe the role played by rough endoplasmic reticulum in the formation oh chylomicrons (2)

  1. synthesis proteins
  2. Involvement of ribosomes
  3. Protein isolation
  4. Vesicle formation
• Suggest how chylomicrons leave the epithelial cell and give a reason for your answer (2)

  1. exocytosis
  2. Because of size / too large to leave by other methods
• Explain the advantage of the curve for fetal hawmoglobin being different from the curve for adult hawmoglobin (2)

  Fetal hb has higher affinity for oxygen at lower partial pressures

  At partial pressures when adult hb disassociates foetal hb takes up oxygen
• Explain how aerobic respiration in cells leads to a change in ph of blood plasma (2)

  1. Aerobic respiration produces carbon dioxide
  2. It then dissolved in blood Releasing H plus ions / forms carbonic acid
• What is the advantage to tissue cells of a reduction in the affinity of hb for oxygen when plasma ph decreases (2)

  1. Low ph because of high rate of respiration
  2. Cells need more oxygen
  3. More oxygen released ( unload more readily )
• Explain the advantage for mice Living at high altitudes having a disassociation curve which is to the left of the curve for mice at low altitudes 2

  1. High altitudes have a lower partial pressure for oxygen
  2. So mice will have higher affinity for oxygen at lower partial pressures
  3. So enough oxygen can be supplied to cells
• Suggest why it would be a disadvantage for the curve to be much further to the left

  Difficult to unload
• Describe and explain four ways in which the structure of a capillary adapts for the exchange of substances between the blood and surrounding tissue (4)

         1.      permeable capillary wall / membrane;

  2.      single cell thick / thin walls, reduces diffusion distance;

  3.      flattened (endothelial) cells, reduces diffusion distance;

  4.      fenestrations, allows large molecules through;

  5.      small diameter / narrow, gives a large surface area to volume / short diffusion distance;

  6.      narrow lumen, reduces flow rate giving more time for diffusion;

  7.      red blood cells in contact with wall / pass singly, gives short diffusion distance / more time for diffusion;
• Explain how tissue fluid is formed and how it may be returned to the circulatory system. 6

  1.      (hydrostatic) pressure of blood high at arterial end;

  2.      fluid / water / soluble molecules pass out (reject plasma);

  3.      proteins / large molecules remain;

  4.      this lowers the water potential / water potential becomes more negative;

  5.      water moves back into venous end of capillary by osmosis / diffusion;

  6.      lymph system collects any excess tissue fluid which returns to blood / circulatory system / link with vena cava / returns tissue fluid to vein;
• Explain what causes pressure of blood in aorta to decrease during each heartbeat

  Ventricle diastole
• Explain what causes pressure of blood in aorta to stay above 10 kpa (2)

  1. Elastic wall
  2. Recoils to maintain high pressure

  
• Suggest how the structures labelled Y help to maintain the flow of blood in one direction through the heart. (2)


  1. Valve closes due to high blood pressure / ventricles contracting
  2. Tendons prevent valves from being inverted

  
• If a photometer is used to compare transpiration rates of two different species suggest one feature of both plants that should be kept as same as possible

  Same surface area of leaves
• Suggest reasons why the results obtained from a laboratory potometer experiment may not be representative of transpiration rates of same plant in the wild

  1. Isolated shoot is a lot more smaller than the whole plant
  2. Also cutting could damage the plant shoot
  3. May not be representative of the whole plant
  4. Conditions in lab may be different form those in the wild like light and humidity
• What’s affinity

  The tendency of a molecule to bind with oxygen
• at q theirs a small increase in pressure and in rate of blood flow in the aorta explain how his happens and the importance

  1. elastic fibres allow artery walls to stretch to accomodate surges in pressure
  2. elastic recoil of arteries helps to smooth out blood flow and keeps blood under pressure during diastole
• explain the importance of elastic fibres in te wall of aorta ? (2)

  1. stretches when ventricle is systole (contracted) and recoils when the ventricles diastole under low pressure
  2. smooth blood flow / maintains blood pressure / reduces blood pressure surges
• explain the importance of muscle fibres in the wall of an arteriole (2)

  1. muscle contracts
  2. arteriole constricts / narrow / regulates blood flow to capillaries
• efficient exchange of substances in the capillaries is linked to the rate of blood flow explain how (1)

  more time for exchange of substances
• explain the role of heart in the formation of tissue fluid (2)

  1. ventricle contracts producing high hydrostatic pressure
  2. forces out water from capillaries