Cell Structure

Question 1

Eukaryotes.

What is a eukaryotic cell?

Answer 1

A cell that has a nucleus enclosing its genetic material.

Usually contains mitochondria for respiration.

In plant cells, chloroplasts are also present for photosynthesis.

Examples include animal, plant, fungal, and algal cells.

Question 2

Eukaryotes

What is a prokaryotic cell?

Answer 2

A bacterial cell with no nucleus.

Genetic material is a single circular loop of DNA, sometimes with plasmids.

The DNA is found free in the cytoplasm.

Question 3

Eukaryotes and Pro

: Describe four differences between eukaryotic and prokaryotic cells. (4 marks)

Answer 3

Prokaryotes are much smaller in size.

Their genetic material is not enclosed in a nucleus.

They have a single DNA loop, and may contain plasmids.

They lack mitochondria and chloroplasts.

Question 4

Organellles

What is a nucleus?

Answer 4

A membrane-bound organelle that contained cells genetic material
Controls all activities of the cell and contains DNA that codes for proteins.

Question 5

Organelles

What is cytoplasm?

Answer 5

A liquid gel where most chemical reactions take place, such as respiration and protein synthesis.
Contains enzymes like biological catalysts
Organelles are found in it.

Question 6

Organelles

What is the cell membrane?

Answer 6

A partially permeable barrier that controls what enters and leaves the cell.

Question 7

Organelles

What are mitochondria?

Answer 7

Organelles where aerobic respiration occurs, releasing/providing energy for the cell’s activities.

Question 8

Organelles

What are ribosomes?

Answer 8

Sites of protein synthesis, where enzymes and other proteins are produced.

Question 9

Organelles

What is a cell wall?

Answer 9

A rigid layer made of cellulose in plant cells that strengthens and supports the cell.

Question 10

Organelles

What are chloroplasts?

Answer 10

Organelles that absorb light energy to carry out photosynthesis, providing food for the plant
Contain the chlorophyll making leave green, which harvests the light needed for photosynthesis.

Question 11

Organelles

What is a permanent vacuole?

Answer 11

A fluid-filled space in the cytoplasm containing cell sap that helps maintain rigidity for structural support.

Question 12

Differentiations

What is cell differentiation?

Answer 12

The process by which a cell changes to become specialised for a particular function.

Question 13

Specialised cells

What are specialised cells?

Answer 13

Cells that have developed specific adaptations to carry out particular roles within an organism.

Question 14

Root Hair cells

What are the adaptations of root hair cells?

Answer 14

Long extensions (root hairs) increase surface area for absorption.

Many mitochondria provide energy for active transport of minerals.

Function: Absorb water and mineral ions from the soil.

Question 15

Sperm cells

What are the adaptations of a sperm cell?

Answer 15

Long tail and streamlined head for swimming.

Many mitochondria to release energy for movement.

Acrosome contains digestive enzymes to penetrate the egg.

Function: Fertilises the egg cell by delivering male DNA.

Question 16

RBC

What are the adaptations of red blood cells

Answer 16

Contain haemoglobin to transport oxygen.

Have no nucleus – more space for haemoglobin.

Biconcave shape increases surface area for oxygen diffusion.

Function: Carry oxygen around the body.

Question 17

Nerve cells

What is the function of a nerve cell?

Answer 17

To transmit electrical impulses rapidly around the body.

Adaptations:

Long axon carries impulses long distances.

Branched dendrites connect with other nerve cells.

Myelin sheath insulates axon and speeds up transmission.

Question 18

Fat cells

What are fat cells and their adaptations?

Answer 18

Function: Store fat to provide energy and insulation.

Adaptations:

Small amount of cytoplasm to make space for fat.

Few mitochondria – use little energy.

Can expand to store more fat.

Question 19

Photosynthetic cells

What are photosynthetic cells?

Answer 19

Found in leaves and stems.

Contain many chloroplasts to absorb light for photosynthesis.

Function: Produce food (glucose) for the plant.

Question 20

Storage Tissues

What are storage tissues?

Answer 20

Tissues that store extra food as starch, providing energy reserves for the plant.

Question 21

Micrometers

How many micrometres (µm) are in a millimetre (mm)?

Answer 21

1 mm = 1000 µm

Question 22

Organelles

What’s a single circular strand of DNA?

Answer 22

a continuous loop of genetic material with no free ends

Question 23

Bacteria cells

What are plasmids and what do they allow bacterial cells to do?

Answer 23

Plasmids are small, circular DNA molecules found in the cytoplasm.

They allow bacteria to transfer genes (e.g. antibiotic resistance) between cells.

Question 24

Bacteria cells

Name 5 things Bacterial cells have.

Answer 24

Cytoplasm
Cell Membrane
Cell wall
Single circular strand of DNA
Plasmids

Question 25

# Bacteria cells Is a bacterium a prokaryotic or eukaryotic cell?

Answer 25

Prokaryotic

Question 26

# Bacteria cells : Which cells are smaller — plant or bacterial cells?

Answer 26

Bacterial cells are smaller.

Question 27

# Bacteria cells In bacteria, which structure performs the role of mitochondria and chloroplasts?

Answer 27

The cytoplasm, where respiration and other reactions occur.

Question 28

# Diameter What is the typical diameter of cells?

Answer 28

Plant cell ≈ 0.1 mm (100 µm) Animal cell ≈ 0.02 mm (20 µm) Prokaryotic cell ≈ 0.002 mm (2 µm)

Question 29

# Magnification What is the equation for magnification?

Answer 29

Magnification= Actual Size/ Image Size​

Question 30

# Microscopy Compare light and electron microscopes.

Answer 30

Light microscopes: Use visible light and glass lenses. Magnify up to ×2000; resolution ≈ 200 nm. Used for tissues, whole cells, large organelles. Electron microscopes: Use beams of electrons. Magnify up to ×2,000,000; resolution ≈ 0.2 nm. Reveal details of sub-cellular structures (e.g. ribosomes, mitochondria).

Question 31

# Microscopy When coming across large numbers in microscopy calculations what math format should you use?

Answer 31

Standard formula

Question 32

# Microscopy: Light What are the magnification and resolution limits of a light microscope, and what does this mean?

Answer 32

* Maximum magnification: about ×2,000. * Resolving power (resolution): around 200 nm (0.2 µm). * Resolution = the ability to distinguish between two close points. * The lower the resolving power, the clearer the image detail. * Therefore, light microscopes can show overall structure, but not fine details of organelles.

Question 33

# Microsocpy Describe the required practical to observe, draw and label cells using a light microscope.

Answer 33

1. * Peel a thin layer of epidermal tissue from an onion. 2 *Place it flat on a microscope slide - handle glass slides carefully to avoid cuts 3* Add a drop of iodine solution carefully and avoid contact with skin/eyes. (stains the cell to make structures visible). 4* Carefully lower the cover slip using a mounted needle to avoid air bubbles. 5* Place the slide under the light microscope. 6* Start with low power objective lens → focus with coarse adjustment knob. 7* Switch to higher power → use fine adjustment knob for detail. *** Draw one or two clearly visible cells: *m No shading *,m Use a sharp pencil *m Add labels (cell wall, nucleus, cytoplasm, vacuole) *m Add a title and magnification used.**

Question 34

# Microscopy What are the variables of the Microscopy Experiment?

Answer 34

Independent variable: Type of cell being observed (e.g. onion, cheek). Dependent variable: What you observe — cell structures / measured size. Control variables: Same stain used (e.g. iodine). Same magnification setting. Same lighting / illumination. Similar thickness of specimen slice.