Explain all six required plasma transport roles
Track blood cells, ions, nutrients, urea, hormones and carbon dioxide in the liquid component.
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall plasma, respiration and excretion.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which component carries suspended blood cells?
What you will learn
- Separate suspended cells from dissolved materials
- Follow the role of each cargo
Separate suspended cells from dissolved materials
Plasma is the liquid component of blood. It carries blood cells around the circulation and transports dissolved ions and nutrients, such as glucose and amino acids. Cells are suspended and carried; they are not dissolved into plasma like a soluble ion. Platelets are also carried in this liquid, although the syllabus list explicitly includes blood cells.
The required transport list also includes urea, hormones and carbon dioxide. Urea is a nitrogenous waste carried towards the kidneys for excretion; hormones are chemical messengers carried from secreting organs towards their target tissues. A hormone is not an organ or a blood cell.
Follow the role of each cargo
Carbon dioxide produced by respiring tissues is transported in blood towards the lungs. Much is carried through the plasma in dissolved forms, especially as hydrogen carbonate ions. For this requirement, state plasma transport of carbon dioxide without claiming that every carbon-dioxide molecule remains unchanged or that none is carried in association with red cells.
Use the six-item list to check completeness: blood cells, ions, nutrients, urea, hormones and carbon dioxide. Oxygen transport is mainly associated with red-cell haemoglobin, so listing oxygen alone as plasma’s function misses the specified cargo. A route drawing indicates destinations but provides no concentrations or rates unless measured data are supplied.
Sources for this lesson
Pause and explain
Which list includes all six specified plasma cargo categories?
Worked example
Give plasma cargo examples for kidney excretion, chemical signalling and removal of respiration waste.
Show the worked solution
- Kidney excretion involves transported urea.
- Signalling involves hormones; respiration waste includes carbon dioxide.
Answer Urea → kidneys; hormones → target tissues; carbon dioxide → lungs.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
List all six required plasma transport categories.
Give me a hint
Include cells, small dissolved materials, waste and messengers.
Compare my reasoning
- Start with blood cells, ions and nutrients.
- Add urea, hormones and carbon dioxide.
Blood cells, ions, nutrients, urea, hormones and carbon dioxide.
Look for these in your work
- Include the first three
- Include all three remaining categories
Match glucose, urea and a hormone to nutrient delivery, kidney excretion and signalling.
Give me a hint
Identify what each substance does.
Compare my reasoning
- Glucose is a nutrient delivered to tissues.
- Urea is carried for kidney excretion; a hormone is a messenger to targets.
Glucose → nutrient delivery; urea → kidneys for excretion; hormone → chemical signalling at target tissues.
Look for these in your work
- Assign all three
- Keep waste and messenger distinct
Improve “plasma transports dissolved red cells and only unchanged carbon-dioxide gas”.
Give me a hint
Distinguish suspension from solution and carbon-dioxide transport forms.
Compare my reasoning
- Blood cells are carried in suspension rather than dissolved.
- Carbon dioxide is transported in dissolved forms, much as hydrogen carbonate ions.
Plasma carries suspended blood cells and transports carbon dioxide in dissolved forms; the cells do not dissolve and carbon dioxide need not remain unchanged gas.
Look for these in your work
- Correct cell suspension
- Correct the carbon-dioxide claim
Common mistakes
- Saying blood cells dissolve in plasma.
- Replacing the full list with oxygen alone.
What can you explain now?
Which list includes all six specified plasma cargo categories?
Compare with the explanation
Blood cells, ions, nutrients, urea, hormones and carbon dioxide
It matches every required category.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Recall the six categories and give a useful destination for three.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.