Identify the structures of a chemical synapse
Locate vesicles containing neurotransmitter molecules, the gap and receptor proteins.
Extended only (Supplement); Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
Before you begin
- Recall cell membranes, diffusion, sensitivity and the difference between cells, tissues and organs.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which cell region stores the vesicles before release here?
What you will learn
- Read the two sides of the junction
- Name the contents and receiving structures
Identify the structures of a chemical synapse
| Feature | Meaning |
|---|---|
| G | Vesicle containing neurotransmitter molecules |
| H | Neurotransmitter molecules |
| I | Synaptic gap between membranes |
| J | Receptor proteins on the next neurone |
Read the two sides of the junction
The supplied chemical-synapse diagram shows a terminal of the first, presynaptic neurone above a membrane of the next, postsynaptic neurone. The cells remain separate. An electrical impulse arrives along the first neurone, while transmission across the junction involves chemical neurotransmitter molecules. The space between the two membranes is labelled I, the synaptic gap.
Label G points to a synaptic vesicle inside the presynaptic terminal. Vesicles are small membrane-bounded compartments containing neurotransmitter molecules, represented by the small dots labelled H. A vesicle is therefore not one neurotransmitter molecule: it is the container holding many molecules before release. The diagram distinguishes the enclosing membrane from its contents.
Name the contents and receiving structures
Label J points to receptor proteins in the membrane of the postsynaptic neurone. They provide binding sites for the neurotransmitter molecules released by the first cell. Receptor proteins are not the same as the sensory receptors at the start of a reflex arc. Here the term identifies molecular receiving structures at the synaptic junction, rather than an entire skin receptor organ or sensory pathway.
This schematic is not to scale and its colours are teaching choices. It establishes the required arrangement of vesicles containing neurotransmitter molecules, a synaptic gap and receptor proteins on the next neurone. It does not show an electrical impulse jumping through empty space, nor does it mean the two cells have fused. Keep the signal travelling along a cell distinct from the chemical transmission between cells.
Pause and explain
Which identification set matches the diagram?
Worked example
Identify G, H, I and J in the supplied synapse schematic.
Show the worked solution
- G encloses H in the presynaptic terminal.
- I separates the membranes; J is on the next cell.
Answer G synaptic vesicle; H neurotransmitter molecules; I synaptic gap; J receptor proteins.
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.
Identify the four original labels G to J.
Give me a hint
Use the leader endpoints and two separate membranes.
Compare my reasoning
- G is the container and H the enclosed small molecules.
- I is the separating space and J the receiving membrane proteins.
G synaptic vesicle; H neurotransmitter molecules; I synaptic gap; J receptor proteins.
Look for these in your work
- Identify all four
- Use container versus contents
List all three required structural features of the chemical synapse.
Give me a hint
One feature includes both a container and its contents.
Compare my reasoning
- Name vesicles containing neurotransmitter molecules.
- Add the synaptic gap and receptor proteins.
Vesicles containing neurotransmitter molecules, a synaptic gap and receptor proteins on the next neurone.
Look for these in your work
- Include all three features
- State what vesicles contain
A learner draws receptor proteins only inside the releasing vesicles. Correct their position for the supplied receiving model.
Give me a hint
Binding takes place on the next neurone.
Compare my reasoning
- Vesicles in the first terminal contain neurotransmitter.
- Receiving receptor proteins are on the postsynaptic membrane.
The receiving receptor proteins belong on the membrane of the next neurone; vesicles in the presynaptic terminal contain neurotransmitter molecules.
Look for these in your work
- Place receiving receptors correctly
- Keep vesicles and contents distinct
Common mistakes
- Calling a vesicle one neurotransmitter molecule.
- Placing receiving receptors inside the vesicle.
What can you explain now?
Which identification set matches the diagram?
Compare with the explanation
G vesicle; H neurotransmitter; I gap; J receptor proteins
It distinguishes container, contents, space and receiving structure.
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Make it stick
Identify the three required structural features, including what the vesicles contain.
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.