animals

• What conditions in respiring muscles help haemoglobin to dissociate with O$_2$ molecules?


  Low pH, higher temperature, high pCO$_2$, and low pO$_2$
• What is the innermost layer of a blood vessel called?

  Endothelium
• Explain the importance of muscle fibres in the wall of an arteriole.

  They control the flow of blood by decreasing the diameter of the lumen when they contract.
• Why can't you assume that water uptake in a potometer is equivalent to the actual rate of transpiration?

  Some water is used for photosynthesis and to keep cells turgid.
• Why do all tree trunks decrease in diameter during the middle of the day?

  Transpiration is at its fastest rate, creating tension that pulls water up the trunk.
• How many polypeptide chains does haemoglobin have?

  Four polypeptide chains
• What happens when haemoglobin binds with oxygen?

  This process is called loading or associating.
• Where does haemoglobin release oxygen in humans?

  In the tissues
• How does the affinity of haemoglobin for oxygen change depending on conditions?


  Haemoglobin with a high affinity takes up oxygen more easily, while low affinity releases it more easily.
• What is positive cooperativity in the context of oxygen binding to haemoglobin?

  When the first O$_2$ binds, it changes the shape of haemoglobin, making it easier for subsequent O$_2$ molecules to bind.
• What does it mean if the oxygen dissociation curve is further to the left?

  It means haemoglobin loads oxygen more easily.
• What does it mean if the oxygen dissociation curve is further to the right?


  It means haemoglobin unloads oxygen more easily.
• Why is the change from HbF to HbA advantageous for a baby?

  HbA has a lower affinity for O$_2$ at low partial pressures, making it easier to unload O$_2$ for aerobic respiration.
• How does the haemoglobin of a more active species allow a greater level of activity?

  The curve shifts to the right, indicating lower affinity and easier unloading of oxygen for greater respiration.
• What type of circulatory system do mammals have?

  A closed, double circulatory system
• Where does exchange (diffusion) take place in mammals?

  At the capillaries
• What is the formula for cardiac output?

  Cardiac output = stroke volume x heart rate
• If the stroke volume is 70 mL and the heart rate is 60 beats per minute, what is the cardiac output?

  Cardiac output = $70 \text{ mL} \times 60 \text{ bpm} =$$4200 \text{ mL/min}$
• Why is the maximum pressure in the ventricle much higher than that in the atrium?

  The ventricle has a thick wall with more muscle, allowing for stronger contractions.
• How do you calculate the heart rate in beats per minute from the given data?

  Heart rate = $85.7 \text{ bpm}$
• How do you calculate cardiac output using the heart rate and stroke volume?

  Cardiac output = heart rate x stroke volume
• What are the four ways in which the structure of the aorta is related to its function?

  • Elastic tissue allows stretching and recoil.
  • Thick walls withstand pressure.
  • Smooth endothelium reduces friction.
  • Muscle allows for contraction and vasoconstriction.
• What does tissue fluid supply to the cells?

  Water, glucose, amino acids, fatty acids, and O$_2$
• How is tissue fluid formed?

  It is formed when water and solutes are forced out of the capillary by high hydrostatic pressure.
• Why do soluble proteins remain in the capillary during the formation of tissue fluid?

  They are too large to move out of the capillary.
• What happens to excess tissue fluid?

  It drains into lymph vessels.
• What causes hydrostatic pressure to fall as blood moves along the capillary?

  Water is lost and friction decreases the rate of blood flow.
• What is the main force that pulls water through the xylem in plants?

  Evaporation of water from the leaves, known as transpiration.
• How does temperature affect transpiration?

  High temperature increases transpiration due to increased kinetic energy of water molecules.
• How does humidity affect transpiration?

  High humidity decreases transpiration due to a reduced water potential gradient.
• How does air movement affect transpiration?

  Rapid air movement increases transpiration by maintaining the water potential gradient across the leaf.
• What is the process of tissue fluid formation and reabsorption?

  • Tissue fluid supplies cells with nutrients and oxygen.
  • Formed by high hydrostatic pressure forcing water and solutes out of capillaries.
  • Soluble proteins remain in capillaries, lowering water potential.
  • Water returns by osmosis at the venous end.
  • Excess fluid drains into lymph vessels.
• What are the factors affecting transpiration in plants?

  • Temperature: High increases transpiration.
  • Humidity: High decreases transpiration.
  • Air movement: Rapid increases transpiration.
• What is the role of haemoglobin in oxygen transport?

  • Binds reversibly with up to four oxygen molecules.
  • Loading occurs in the lungs; unloading occurs in tissues.
  • Affinity for oxygen changes with conditions.
• What is the significance of the cardiac cycle in mammals?

  • Involves diastole and systole phases.
  • Cardiac output is calculated as stroke volume x heart rate.
  • Pressure changes occur in the heart chambers during the cycle.
• What cannot be (re)absorbed and builds up in plants?

  Id
• Why is the idea of excess important in plant transport?

  It indicates that certain substances cannot be reabsorbed and may accumulate.
• What is the main force that pulls water through the xylem in plants?

  • Evaporation of water from the leaves (transpiration)
• How does temperature affect transpiration in plants?

  High temperature increases transpiration due to increased kinetic energy of water molecules.
• What effect does high humidity have on transpiration?

  High humidity decreases transpiration by reducing the water potential gradient.