cell structure

Question 1

What are eukaryotic cells?

Answer 1

Large, complex cells with a nucleus and membrane-bound organelles; DNA is wrapped around histone proteins.

Question 2

What are prokaryotic cells?

Answer 2

Small, simple cells with no nucleus or membrane-bound organelles. DNA is in a loop (nucleoid) and not associated with histones.

Question 3

Key differences between prokaryotic and eukaryotic cells?

Answer 3

Eukaryotes: nucleus, larger, complex organelles
Prokaryotes: no nucleus, smaller, may have plasmids, flagella, capsule.

Question 4

What is the function of the nucleus?

Answer 4

Contains DNA (in chromosomes), controls cell activities, and contains a nucleolus.

Question 5

What is the mitochondrion for?

Answer 5

Site of aerobic respiration; the matrix contains enzymes for respiration.

Question 6

What is the function of chloroplasts?

Answer 6

Site of photosynthesis; some parts occur in the grana, others in the stroma.

Question 7

What is the Golgi apparatus?

Answer 7

Modifies, processes, and packages proteins and lipids; makes lysosomes.

Question 8

What is a Golgi vesicle?

Answer 8

A transport vesicle for lipids and proteins from the Golgi.

Question 9

What is a lysosome?

Answer 9

A vesicle containing digestive enzymes (lysozymes) for breaking down waste or pathogens.

Question 10

What is a ribosome?

Answer 10

Site of protein synthesis; can float free or be attached to the RER; not membrane-bound.

Question 11

Function of rough endoplasmic reticulum (RER)?

Answer 11

Folds and processes proteins made by ribosomes.

Question 12

Function of smooth endoplasmic reticulum (SER)?

Answer 12

Synthesises and processes lipids.

Question 13

What does the vacuole do?

Answer 13

Contains cell sap; helps maintain turgor pressure in plant cells; surrounded by a tonoplast.

Question 14

What are epithelial cells specialised for?

Answer 14

Absorption — have villi, microvilli, and many mitochondria for active transport.

Question 15

What is murein?

Answer 15

A glycoprotein that makes up the cell wall in prokaryotes.

Question 16

What is a slime capsule?

Answer 16

A protective outer layer that helps evade the immune system.

Question 17

What are plasmids?

Answer 17

Small circular DNA molecules, often carrying genes like antibiotic resistance.

Question 18

What is a flagellum?

Answer 18

A tail-like structure used for movement.

Question 19

Are viruses living?

Answer 19

No — they are non-living particles.

Question 20

What is the structure of a virus?

Answer 20

Genetic material (DNA or RNA), capsid (protein coat), and attachment proteins.

Question 21

How do viruses replicate?

Answer 21

Use attachment proteins to bind to host cell → inject genetic material → host replicates virus.

Question 22

What is binary fission?

Answer 22

A method of asexual reproduction in prokaryotes.

DNA and plasmids replicate; cell enlarges; cytoplasm divides; two daughter cells produced (may have different numbers of plasmids).

Question 23

What is magnification?

Answer 23

Image size ÷ Actual size.

Question 24

What is resolution?

Answer 24

The ability to distinguish between two separate points.

Question 25

Features of a light microscope?

Answer 25

Uses light; Max resolution: 0.2 µm; Max magnification: x1500; Cannot view small organelles (e.g. ribosomes).

Question 26

Features of an electron microscope?

Answer 26

Uses electrons; Higher resolution: 0.0002 µm; Max magnification: x1,500,000.

Question 27

What is a transmission electron microscope (TEM)?

Answer 27

Electrons pass through thin sample; provides high resolution internal images; only thin specimens.

Question 28

What is a scanning electron microscope (SEM)?

Answer 28

Electrons scan surface; produces 3D surface images; lower resolution than TEM; can be used on thick specimens.

Question 29

What is the purpose of cell fractionation?

Answer 29

To separate different organelles from a cell.

Question 30

Steps of cell fractionation?

Answer 30

Homogenisation: grind cells, ice-cold, isotonic, buffered solution; Filtration: remove large debris; Ultracentrifugation: spin at different speeds to separate organelles (nuclei → mitochondria → lysosomes → ER → ribosomes).

Question 31

What is mitosis?

Answer 31

Division of a parent cell into 2 genetically identical daughter cells — used for growth and repair.

Question 32

What are the 4 stages of the cell cycle?

Answer 32

G₁: cell growth, new proteins/organelles; S: DNA replication; G₂: further growth, protein synthesis; M: mitosis.

Question 33

What happens during interphase?

Answer 33

DNA replicates, organelles double, ATP levels increase — cell prepares for division.

Question 34

What happens during prophase?

Answer 34

Chromosomes condense; centrioles move; spindle forms; nuclear envelope breaks down.

Question 35

What happens during metaphase?

Answer 35

Chromosomes line up; spindle fibres attach to centromeres.

Question 36

What happens during anaphase?

Answer 36

Centromeres divide; chromatids pulled to poles; appear V-shaped.

Question 37

What happens during telophase + cytokinesis?

Answer 37

Chromatids uncoil; nuclear envelope reforms; cytoplasm divides → 2 cells.

Question 38

What causes cancer?

Answer 38

Uncontrolled cell division forming tumours.

Question 39

How do cancer treatments target the cell cycle?

Answer 39

Prevent DNA replication (G1); Damage DNA (S) so cell self-destructs; Prevent formation of spindle (M).

Question 40

Why do these treatments affect healthy cells?

Answer 40

They target all rapidly dividing cells (e.g. hair, gut lining), but cancer cells divide more frequently so are affected more.

Question 41

What is the mitotic index?

Answer 41

Mitotic index = Number of cells in mitosis ÷ Total number of cells.

Question 42

What are artefacts in microscopy?

Answer 42

Things seen under the microscope not part of the specimen (e.g. dust, air bubbles) — common in EM due to sample prep.