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AS · Practice questions · Blood cells, water and tissue fluid

Name the cell, then follow the fluid.

Six original Cambridge-style questions on blood cells, water as a transport medium and tissue fluid, from identifying a cell by its nucleus to explaining oedema.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Nucleus first, then pressure.

01
Recall
[3 marks]

State three functions of tissue fluid.

  • It bathes the cells, providing the medium through which substances are exchanged. ✓
  • It supplies cells with oxygen, glucose, amino acids and ions from the blood. ✓
  • It removes waste products such as carbon dioxide and urea from the cells back into the blood (or lymph). ✓
02
Recall
[4 marks]

Describe how you would distinguish a neutrophil, a monocyte and a lymphocyte on a stained blood smear, and state one way all three differ from a red blood cell.

  • Neutrophil: nucleus with several lobes; granular cytoplasm. ✓
  • Monocyte: the largest white cell; a large kidney- or bean-shaped nucleus. ✓
  • Lymphocyte: small; a large round nucleus that fills most of the cell, with a thin rim of cytoplasm. ✓
  • All three have a nucleus and are larger than a red blood cell, which has no nucleus and is a biconcave disc. ✓
03
Explain
[4 marks]

Relate two properties of water to its role in transport in mammals.

  • Water is polar, so it is a good solvent. ✓
  • Glucose, amino acids, ions, urea and hormones dissolve in plasma and are carried in solution to and from cells. ✓
  • Water has a high specific heat capacity: a lot of energy is needed to raise its temperature. ✓
  • So blood can absorb and carry heat from active organs to the rest of the body without a large change in its own temperature. ✓
04
Explain
[5 marks]

Describe and explain how tissue fluid forms at the arterial end of a capillary and returns at the venous end.

  • At the arterial end the hydrostatic pressure of the blood is high (from the contraction of the ventricles). ✓
  • It is greater than the effect of the lower water potential of the blood, so water and small solutes are forced out through gaps in the capillary wall. ✓
  • Cells and large plasma proteins remain in the capillary, so the water potential of the blood stays lower than that of the tissue fluid. ✓
  • Along the capillary the hydrostatic pressure falls as fluid is lost and resistance slows the blood. ✓
  • At the venous end water moves back into the capillary by osmosis; excess tissue fluid drains into lymph vessels. ✓
05
Analysis
[3 marks]

A person with a liver disease makes too little plasma protein. Suggest and explain why tissue fluid builds up in the tissues of this person.

  • Fewer plasma proteins means the water potential of the blood is higher (less negative) than normal. ✓
  • The water potential gradient from tissue fluid into the capillary at the venous end is smaller. ✓
  • Less water returns by osmosis, while fluid still leaves at the arterial end, so fluid accumulates (oedema). ✓
06
Data
[3 marks]

In a capillary, the hydrostatic pressure is 4.3 kPa at the arterial end and 1.7 kPa at the venous end. The opposing effect of the water potential of the blood is 3.3 kPa all along. Calculate the net pressure at each end and state the direction of fluid movement at each.

  • Arterial end: 4.3 - 3.3 = 1.0 kPa outwards. ✓
  • Venous end: 3.3 - 1.7 = 1.6 kPa inwards. ✓
  • So fluid leaves the capillary at the arterial end and water returns by osmosis at the venous end. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.