How are animal, plant, fungal and bacterial cells built, and how do their structures suit their jobs?
The ultrastructure of animal, plant, fungal and bacterial cells, the function of each organelle, and the differences in cell wall composition and the presence of a true nucleus, plasmids, chloroplasts and vacuoles.
An SQA National 5 Biology answer on cell structure, covering the ultrastructure of animal, plant, fungal and bacterial cells, the function of each organelle, the differences in cell wall composition, and the presence of a true nucleus, plasmids, chloroplasts and vacuoles.
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What this dot point is asking
The SQA wants you to identify the structures (organelles) inside animal, plant, fungal and bacterial cells, state what each one does, and explain how these cell types differ, in particular the cell wall material, the presence or absence of a true nucleus, and which cells carry plasmids, chloroplasts and vacuoles.
Structures common to all cells
Every cell, whatever its type, shares three structures:
The cell membrane is selectively permeable, meaning it lets some substances pass through more easily than others. This control is what allows the cell to take in useful materials such as glucose and oxygen while keeping unwanted substances out.
The nucleus and where DNA is held
Animal, plant and fungal cells all have a true nucleus that contains the DNA. A bacterial cell has no true nucleus: its DNA lies free in the cytoplasm. Bacteria also carry small circular rings of extra DNA called plasmids, which are not found in animal, plant or fungal cells. Plasmids matter later in the course because they are the tool used in genetic engineering.
Mitochondria and energy
Mitochondria are the site of aerobic respiration, where energy is released from glucose to make ATP. They are present in animal, plant and fungal cells. Cells that need a lot of energy, such as muscle cells, have many mitochondria.
Structures unique to plant cells
Plant cells have three extra structures that animal cells lack:
- Cell wall. A rigid outer layer made of cellulose that gives the cell support and a fixed shape, and stops the cell bursting when it takes in water.
- Chloroplasts. The site of photosynthesis; they contain the green pigment chlorophyll that traps light energy.
- Sap vacuole. A large fluid-filled space that stores cell sap and helps keep the cell turgid (firm), giving the plant support.
Cell walls: same idea, different material
A cell wall is found in plant, fungal and bacterial cells but not in animal cells. The wall does the same job (support and protection) but is made of a different material in each:
- Plant cell walls are made of cellulose.
- Fungal cell walls are made of chitin (a different material, not cellulose).
- Bacterial cell walls are made of yet another material, again not cellulose.
Examples in context
Example 1. Root hair cells and surface area. A root hair cell is a specialised plant cell with a long thin extension that increases its surface area for absorbing water and minerals from the soil. It still has the standard plant features (cell wall, membrane, cytoplasm, nucleus, vacuole) but lacks chloroplasts, because it is underground and does not photosynthesise. This shows how a basic cell plan is adapted to a job.
Example 2. Yeast as a fungal cell. Yeast, used in brewing and baking, is a single-celled fungus. It has a cell membrane, cytoplasm, ribosomes, a true nucleus and mitochondria, plus a cell wall made of chitin rather than cellulose. It has no chloroplasts, because fungi feed on ready-made food rather than photosynthesising.
Try this
Q1. Name the three structures found in every cell, whatever its type. [1 mark]
- Cue. Cell membrane, cytoplasm and ribosomes.
Q2. State one structure found in a bacterial cell that is not found in a plant cell. [1 mark]
- Cue. A plasmid (a small ring of DNA).
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 style4 marksName two structures found in a plant cell but not in an animal cell, and state the function of each.Show worked answer →
A 4-mark name-and-function answer needs two structures, each with its job, so plan two name marks and two function marks.
A plant cell has a cell wall made of cellulose, which gives the cell support and a fixed shape. An animal cell has no cell wall.
A plant cell also has chloroplasts, which are the site of photosynthesis and contain the green pigment chlorophyll. Animal cells have no chloroplasts.
A sap vacuole would also score: it stores cell sap and helps keep the cell turgid for support.
Markers reward each correctly named structure (1 mark) and its correct function (1 mark). Naming a structure that is also in animal cells, such as the nucleus or mitochondria, scores nothing here.
SQA N5 style3 marksDescribe three differences between a bacterial cell and a plant cell.Show worked answer →
This is a compare question, so each difference must mention both cell types to score.
Difference 1. A plant cell has a true nucleus that holds its DNA, while a bacterial cell has no true nucleus and its DNA lies free in the cytoplasm.
Difference 2. A bacterial cell carries small circular rings of DNA called plasmids; a plant cell does not have plasmids.
Difference 3. The cell wall of a plant is made of cellulose, while a bacterial cell wall is made of a different material, not cellulose. A further mark could come from chloroplasts being present in plant cells but absent in bacteria.
Markers reward each clear comparative point. Stating only what the bacterial cell has, without the contrast, loses the mark.
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Sources & how we know this
- SQA National 5 Biology Course Specification — SQA (2019)