Mass transport in animals

• Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. Do not include descriptions of pressure changes in the heart or the role of heart valves in your answer.

  1. Renal vein;

  2. Vena cava to right atrium;

  3. 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.

  1. Plasma proteins remain;

  2. Creates water potential gradient by reducing water potential of blood;

  3. Water moves to blood by osmosis;

  4. Returns to blood by lymphatic system;
• Explain how an arteriole can reduce the blood flow into capillaries.

  1. Muscle contracts;

  2. Constricts arteriole;
• Which blood vessel carries blood at the lowest blood pressure.

  vena cava
• Describe the advantage of the Bohr effect during intense exercise.

  1. Increases dissociation of oxygen;

  2. For aerobic respiration at the muscle tissues
• 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.

  1. EPO causes blood to thicken;

  2. The thickened blood could block the coronary arteries
• The normal haematocrit for human males is 47(±5)%. For professional male cyclists, the maximum haematocrit allowed is 50%. A student suggested that professional male cyclists should be allowed to use EPO until their haematocrit is 50%. Give two reasons why this suggestion is not valid.

  1. Some cyclists will gain a bigger advantage

  2. There are health risks associated with taking EPO;
• Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin.

  1. Increases oxygen dissociation

  2. By decreasing blood pH
• Give two safety precautions that should be followed when dissecting a heart.

  Use a sharp scalpel/scissors

  Wash hands/wear gloves

  Disinfect bench/equipment

  Cover any cuts

  Cut away from self/others/on a hard surface

  Safe disposal
• Name the blood vessels that carry blood to the heart muscle

  Coronary artery
• Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind. Explain why.

  1. Binding of first oxygen changes tertiary structure of haemoglobin;

  2. Uncovers another binding site/haem group to bind to;
• Explain the role of the heart in the formation of tissue fluid

  1. Contraction of ventricles produces high hydrostatic pressure;

  2. This forces water and some dissolved substances 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.

  Excess tissue fluid cannot be reabsorbed and builds up;
• 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.

  1. Allows comparison;

  2. Initial heart rates different between males and females.
• The scientists calculated the cardiac output of the volunteers before and after the exercise programme. In some volunteers, their cardiac output stayed the same, even though their resting heart rate decreased.

  Explain how their cardiac output could stay the same even when their resting heart rate had decreased.

  1. Cardiac output = stroke volume × heart rate

  2. So stroke volume increases
• What is the function of the coronary arteries?

  1. Carry oxygen

  2. To heart muscle
• The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN).

  Describe how

  1. SAN sends wave of electrical activity across atria causing atrial systole;

  2. AVN delays electrical activity;

  3. Allowing ventricles to fill before they contract;

  4. AVN sends wave of electrical activity down Bundle of His;

  5. Causing ventricles to contract
• Blood leaving the kidney eventually returns to the kidney. Describe the pattern of blood circulation in a mammal that causes blood to return to the kidney.

  1. Blood flows from kidney along renal vein to vena cava;

  2. Then along vena cava to RIGHT atrium;

  3. And then along pulmonary artery to lungs;

  4. Then along capillaries to pulmonary vein;

  5. Then along pulmonary vein to RIGHT atrium;

  6. And then along aorta to renal artery to kidney;

  7. Blood may pass through several complete circuits before returning to kidney;
• Describe the mass flow hypothesis for the mechanism of translocation in plants.

  1. Sucrose is actively transported out of the cell

  2. By companion cells

  3. Sucrose moves into the phloem, reducing the water potential and as a result, water from the xylem moves into the phloem by osmosis at a high hydrostatic pressure which causes mass movement

  4. Sucrose moves down the phloem and is actively transported out of the phlome

  5. Sucrose is either used for respiration or storage in sink cell