model answers animals

• What is the pathway a red blood cell takes in the circulatory system from a kidney to the lungs?

  Renal vein,

  Vena cava to right atrium,

  Right ventricle to pulmonary artery.
• Explain how water from tissue fluid is returned to the circulatory system?

  Plasma/proteins remain,

  Reducing the water potential of blood,

  Water moves to blood by osmosis,

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

  Muscles contract,

  narrow lumen
• Explain how a valve maintains a unidirectional flow of blood(Heart chambers)?

  Pressure in the left atrium is higher than in the ventricle causing the valve to open.

  Pressure in the left ventricle is higher than in atrium causing valve to close.
• Binding of the first molecule of oxygen makes it easier for a second oxygen molecule to bind. Why?

  Binding of the first oxygen changes the tertiary structure of haemoglobin,

  uncovering another haem group to bind to.