Cell Structure & Size Of Specimens

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Notes

Animal Cell Structure

Contains a **nucleus** with a distinct membrane.
No **cellulose cell wall**.
No **chloroplasts** (cannot photosynthesise).
Carbohydrates stored as **glycogen**.

Plant Cell Structure

Contains a **nucleus** with a distinct membrane.
Cell wall made of **cellulose**.
Contains **chloroplasts** for photosynthesis.
Carbohydrates stored as **starch** or **sucrose**.
Has a **permanent vacuole** containing cell sap.

Common Cell Structures & Functions

**Nucleus**: contains DNA, controls cell activities.
**Cytoplasm**: gel-like, site of chemical reactions.
**Cell membrane**: controls entry/exit of substances.
**Ribosomes**: site of **protein synthesis**.
**Mitochondria**: site of **aerobic respiration**.

Bacterial Cell Structure

Single-celled, microscopic prokaryotes.
Cell wall made of **peptidoglycan** (not cellulose).
No nucleus; **circular chromosome** of DNA floats in cytoplasm.
May contain **plasmids** (small rings of extra DNA).
No mitochondria or chloroplasts.
Some have **flagella** for movement.

Specialised Cells

Cells **differentiate** to perform specific functions.
Examples in animals: **ciliated cell**, **nerve cell**, **red blood cell**, **sperm cell**.
Examples in plants: **root hair cell**, **xylem vessel**, **palisade mesophyll cell**.

Levels of Organisation

**Cells** → **Tissues** (group of similar cells) → **Organs** → **Organ systems**.
Tissues are made of **one type of cell**.

Magnification Formula

**Magnification = Image size ÷ Actual size**.
Use the equation triangle: cover the value you need.
Magnification has **no units** (e.g., ×3000).
Always convert units to the same before calculating.

Converting Between Units (Extended)

**1 mm = 1000 μm**; **1 cm = 10,000 μm**.
Convert all measurements to the same unit before using the magnification formula.
Example: leaf thickness 2000 μm = 2 mm; drawing 50 mm → magnification = 50/2 = ×25.

A typical animal cell showing key organelles.

A typical plant cell with cell wall, chloroplasts and vacuole.

A typical bacterial cell with flagellum and plasmids.

Practice questions

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1.Which of the following structures is found in plant cells but not in animal cells?
Easy
- ACell membrane
- BMitochondrion
- CChloroplast
- DNucleus
2.Which of the following is the function of the cell membrane?
Easy
- ASite of protein synthesis
- BControls substances entering and leaving the cell
- CContains genetic material
- DSite of aerobic respiration
3.What is the function of ribosomes?
Easy
- AProtein synthesis
- BPhotosynthesis
- CStorage of cell sap
- DControl of cell activities
4.Which of the following is found in bacteria but not in animal or plant cells?
Easy
- ACell wall
- BPlasmid
- CRibosome
- DCytoplasm
5.The image of a cell is 20 mm long. The actual cell is 0.02 mm long. What is the magnification?
Medium
- A×1000
- B×100
- C×0.001
- D×10
6.A student measures the image of a mitochondrion as 6 mm. The magnification is ×30 000. What is the actual size of the mitochondrion?
Medium
- A0.0002 mm
- B0.2 mm
- C0.02 mm
- D0.002 mm
7.Which of the following is the correct order of levels of organisation in a multicellular organism, from simplest to most complex?
Medium
- ACell → tissue → organ → organ system → organism
- BTissue → cell → organ → organ system → organism
- CCell → organ → tissue → organ system → organism
- DOrgan → tissue → cell → organ system → organism
8.Which of the following is a specialised cell in animals?
Medium
- ARoot hair cell
- BPalisade mesophyll cell
- CSperm cell
- DXylem cell

More questions

9.A bacterium has a flagellum. What is the function of the flagellum?
Hard
- ATo attach to surfaces
- BTo aid movement
- CTo protect the cell
- DTo absorb nutrients
10.Which of the following statements about bacteria is correct?
Hard
- ABacteria have a nucleus containing DNA.
- BBacteria have mitochondria for respiration.
- CBacteria have a cell wall made of cellulose.
- DBacteria have a circular chromosome of DNA in the cytoplasm.
11.The actual thickness of a leaf is 2 mm. The thickness of the leaf in a diagram is 50 mm. What is the magnification of the diagram?
Hard
- A×25
- B×0.04
- C×100
- D×50
12.A student observes a cell under a light microscope and sees a large, central vacuole and chloroplasts. Which type of cell is most likely being observed?
Hard
- AAnimal cell
- BPlant cell
- CBacterial cell
- DFungal cell
13.A student measures the image of a chloroplast as 15 mm. The magnification is ×5000. What is the actual size of the chloroplast in micrometres?
Medium
- A3 μm
- B30 μm
- C0.3 μm
- D300 μm
14.In an experiment, beetroot cores were placed in water baths at different temperatures. The mean percentage transmission of light decreased as temperature increased. Which statement best explains this result?
Hard
- AHigher temperatures damage cell membranes, releasing pigment into the water.
- BHigher temperatures cause the beetroot to produce more pigment.
- CHigher temperatures increase the rate of photosynthesis in beetroot.
- DHigher temperatures cause the beetroot cells to shrink.
15.The diagram shows a plant cell. Which labelled structure is the site of aerobic respiration?
Medium
- AMitochondrion
- BChloroplast
- CNucleus
- DVacuole
16.A student used a cork borer to cut beetroot cores and placed them in water baths at different temperatures. After 30 minutes, the percentage transmission of light was measured using a colorimeter. What is the independent variable in this investigation?
Medium
- ATemperature
- BPercentage transmission of light
- CLength of beetroot core
- DTime in water bath
17.A student observes a cell under a light microscope and sees a large central vacuole and chloroplasts. Which type of cell is being observed?
Hard
- APlant cell
- BAnimal cell
- CBacterial cell
- DFungal cell
18.In an experiment, beetroot cores were placed in water baths at different temperatures. The mean percentage transmission of light decreased as temperature increased. What does this indicate about the cell membranes?
Hard
- AHigher temperatures damage the cell membrane, releasing pigment
- BHigher temperatures cause the membrane to become more selective
- CHigher temperatures increase the rate of photosynthesis
- DHigher temperatures cause the cell wall to thicken
19.A student measured the image of a mitochondrion as 6 mm. The magnification is ×30 000. What is the actual size of the mitochondrion?
Medium
- A0.0002 mm
- B0.2 mm
- C0.02 mm
- D0.002 mm
20.A student observed a cell under a light microscope and saw a nucleus, cytoplasm, cell membrane, and many mitochondria. Which type of cell is most likely being observed?
Hard
- AAnimal cell
- BPlant cell
- CBacterial cell
- DFungal cell
21.A student investigates the effect of temperature on cell membrane permeability using beetroot. Which of the following is the dependent variable?
Hard
- APercentage transmission of light
- BTemperature of water bath
- CLength of beetroot core
- DTime in water bath
22.A student measures the image of a chloroplast as 15 mm. The magnification is ×5000. What is the actual size of the chloroplast in micrometres (μm)?
Hard
- A3 μm
- B0.003 μm
- C30 μm
- D300 μm
23.Which of the following is found in plant cells but not in animal cells?
Easy
- ACell wall made of cellulose
- BCell membrane
- CMitochondria
- DRibosomes
24.What is the function of the cell membrane?
Easy
- AControls which substances enter or leave the cell
- BSite of protein synthesis
- CContains the genetic material
- DSite of aerobic respiration
25.A student used a cork borer to cut beetroot cores and placed them in water baths at different temperatures. After 30 minutes, the percentage transmission of light was measured. What is the dependent variable?
Medium
- APercentage transmission of light
- BTemperature of water bath
- CLength of beetroot core
- DTime in water bath
26.Which of the following structures is found in animal cells?
Easy
- ACell membrane
- BCell wall
- CChloroplast
- DPermanent vacuole
27.What is the main energy-releasing organelle in a cell?
Easy
- AMitochondrion
- BNucleus
- CRibosome
- DChloroplast
28.A student observes a cell under a light microscope and sees a nucleus, cytoplasm, cell membrane, and many mitochondria. Which type of cell is most likely being observed?
Medium
- AAnimal cell
- BPlant cell
- CBacterial cell
- DFungal cell
29.In an experiment, beetroot cores were placed in water baths at different temperatures. The mean percentage transmission of light decreased as temperature increased. What does this indicate?
Hard
- AHigher temperatures damage the cell membrane, releasing pigment.
- BHigher temperatures increase the rate of photosynthesis.
- CHigher temperatures cause cells to absorb more water.
- DHigher temperatures make the cell wall more rigid.
30.Which of the following is a function of the nucleus?
Easy
- AContains DNA and controls cell activities
- BSite of protein synthesis
- CSite of aerobic respiration
- DControls entry and exit of substances
31.Which of the following is found in both plant and animal cells?
Easy
- ACell membrane
- BCell wall
- CChloroplast
- DPermanent vacuole
32.What is the function of the permanent vacuole in a plant cell?
Medium
- AStorage of cell sap and support
- BSite of photosynthesis
- CControl of cell activities
- DProtein synthesis
33.Which of the following is true about bacterial cells?
Medium
- AThey have a circular chromosome of DNA.
- BThey have a nucleus.
- CThey contain mitochondria.
- DThey have chloroplasts.
34.A student observes a cell under an electron microscope and sees rough endoplasmic reticulum. What is the function of the ribosomes attached to it?
Hard
- AProtein synthesis
- BLipid synthesis
- CEnergy release
- DPhotosynthesis
35.A plant cell is 50 μm long. What is its length in mm?
Hard
- A0.05 mm
- B0.5 mm
- C5 mm
- D0.005 mm
36.In an experiment, beetroot cores were placed in water baths at different temperatures. The percentage transmission of light through the water was measured after 30 minutes. The results are shown in the table. Temperature / °C | Mean transmission / % 0 | 99.5 20 | 96.3 40 | 79.6 60 | 30.5 80 | 0.8 100 | 0.0 What conclusion can be drawn from these results?
Medium
- AHigher temperatures increase the permeability of the cell membrane.
- BHigher temperatures decrease the permeability of the cell membrane.
- CTemperature has no effect on cell membrane permeability.
- DThe beetroot pigment is destroyed at high temperatures.
37.A student uses a light microscope to view a plant cell. They see a large central vacuole and chloroplasts. Which of the following statements about this cell is correct?
Hard
- AIt is a palisade mesophyll cell.
- BIt is a root hair cell.
- CIt is an animal cell.
- DIt is a bacterial cell.
38.The image of a bacterium is 40 mm long. The magnification is ×8000. What is the actual length of the bacterium in micrometres (μm)?
Medium
- A5 μm
- B50 μm
- C0.5 μm
- D500 μm
39.Which of the following structures is found in both plant and bacterial cells but not in animal cells?
Easy
- ACell wall
- BNucleus
- CMitochondrion
- DChloroplast
40.A student measures the length of a line AB on a photomicrograph of a bronchus as 55 mm. The actual diameter of the bronchus is 1.5 mm. What is the magnification of the photomicrograph?
Hard
- A×36.7
- B×0.027
- C×36
- D×37

Slides

Animal Cell Structure

Animal cells have a nucleus with a distinct membrane.
They do not have cellulose cell walls.
They do not contain chloroplasts (so cannot photosynthesise).
Carbohydrates are stored as glycogen.

Which of the following is found in animal cells but NOT in plant cells?

Nucleus
Cell wall
Chloroplast
Glycogen storage

Plant Cell Structure

Plant cells have a nucleus with a distinct membrane.
They have cell walls made of cellulose.
They contain chloroplasts for photosynthesis.
Carbohydrates are stored as starch or sucrose.
They have a permanent vacuole containing cell sap.

Which of these are true about plant cells?

They have a cell wall made of cellulose.
They store carbohydrates as glycogen.
They contain chloroplasts for photosynthesis.
They have a permanent vacuole.

Bacterial Cell Structure

Bacteria are microscopic single-celled organisms.
They have a cell wall (peptidoglycan), cell membrane, cytoplasm and ribosomes.
They lack a nucleus but have a circular chromosome of DNA floating in the cytoplasm.
Plasmids (small rings of DNA) may be present.
Some bacteria have a flagellum for movement.

Which structure is found in bacteria but NOT in animal or plant cells?

Cell membrane
Ribosomes
Plasmids
Cytoplasm

Functions of Cell Structures

Nucleus: contains DNA, controls cell activities.
Cytoplasm: gel-like, site of chemical reactions.
Cell membrane: controls what enters/leaves the cell.
Ribosomes: site of protein synthesis.
Mitochondria: site of aerobic respiration.
Cell wall (plants): made of cellulose, provides support.
Chloroplasts: contain chlorophyll for photosynthesis.
Permanent vacuole: stores cell sap, supports shape.

The ____ is the site of aerobic respiration, while ____ are the site of protein synthesis.

Specialised Cells

Specialised cells have adaptations to perform specific functions.
Differentiation is the process by which cells develop these adaptations.
Examples: sperm cell (flagellum for movement), red blood cell (biconcave shape for oxygen transport), root hair cell (large surface area for water absorption).

Which specialised cell has a flagellum to help it move?

Red blood cell
Root hair cell
Sperm cell
Palisade mesophyll cell

Levels of Organisation

Cells are the basic unit of life.
Tissues are groups of similar cells working together.
Organs are made of different tissues.
Organ systems are groups of organs working together.
Example: muscle cell → muscle tissue → heart → circulatory system.

Which of these are correct levels of organisation?

A tissue is made of only one type of cell.
An organ is made of only one type of tissue.
The heart is an organ.
The circulatory system is an organ system.

Magnification Formula

Magnification = Image size ÷ Actual size
Use the triangle: cover the quantity you want to find.
Magnification has no units (e.g., ×10, ×5000).
Always check units – convert to the same unit before calculating.

If an image is 30 mm and magnification is ×3000, the actual size is ____ mm.

Converting Between Units

1 mm = 1000 μm (micrometres)
1 cm = 10,000 μm
Always convert to the same unit before using the magnification formula.
Example: 2000 μm = 2 mm (divide by 1000).

How many micrometres are in 1 mm?

10
100
1000
10000

A leaf's actual thickness is 2000 μm. Convert to mm: ____ mm.

Worked Example: Magnification Calculation

A drawing of a leaf is 50 mm thick. The actual leaf is 2 mm thick.
Magnification = image size ÷ actual size = 50 ÷ 2 = ×25.
Remember: magnification has no units.

A cell is drawn 40 mm long. The actual cell is 0.02 mm long. What is the magnification?

×0.0005
×2000
×200
×20

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