Topic 2A: Cell structure and division

Question 1

What is a eukaryotic cell?

Answer 1

A cell that has a nucleus and membrane-bound organelles.

Question 2

Name three types of eukaryotic cells.

Answer 2

Animal cells, plant cells, and fungal cells.

Question 3

What is the function of the nucleus?

Answer 3

It contains DNA and controls the cell’s activities.

Question 4

What is the function of mitochondria?

Answer 4

They produce ATP via aerobic respiration.

Question 5

What is the function of ribosomes?

Answer 5

They synthesize proteins.

Question 6

What is the role of the Golgi apparatus?

Answer 6

It processes, modifies, and packages proteins and lipids.

Question 7

How are plant cells different from animal cells?

Answer 7

Plant cells have a cell wall, chloroplasts, and a large central vacuole, which animal cells do not.

Question 8

What is the function of lysosomes?

Answer 8

They contain digestive enzymes that break down waste and unwanted materials in the cell.

Question 9

How do prokaryotic cells differ from eukaryotic cells?

Answer 9

They lack a nucleus and membrane-bound organelles.

Question 10

What is the function of plasmids in prokaryotic cells?

Answer 10

They contain small loops of DNA that may carry advantageous genes (e.g., antibiotic resistance).

Question 11

What is the function of the prokaryotic cell wall?

Answer 11

It provides structural support and is made of murein (a glycoprotein).

Question 12

How do prokaryotes store their DNA?

Answer 12

As a single circular DNA molecule that floats freely in the cytoplasm.

Question 13

What are viruses made of?

Answer 13

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

Question 14

How do viruses reproduce?

Answer 14

They infect host cells and use the host’s machinery to replicate.

Question 15

What is cell fractionation?

Answer 15

A process used to separate different organelles from a cell.

Question 16

What are the three stages of cell fractionation?

Answer 16

Homogenisation, filtration, and ultracentrifugation.

Question 17

Why must the solution in cell fractionation be cold, isotonic, and buffered?

Answer 17

~Cold: Reduces enzyme activity that might break down organelles.
~Isotonic: Prevents osmotic damage to organelles.
~Buffered: Maintains pH to prevent protein denaturation.

Question 18

In ultracentrifugation, which organelle is separated first?

Answer 18

The nucleus (as it is the heaviest/densest).

Question 19

What is an optical (light) microscope used for?

Answer 19

Viewing living cells in color, but with a lower resolution than electron microscopes.

Question 20

How do transmission electron microscopes (TEMs) work?

Answer 20

They pass electrons through a specimen, producing high-resolution 2D images.

Question 21

How do scanning electron microscopes (SEMs) work?

Answer 21

They scan a beam of electrons across a specimen, producing a 3D image.

Question 22

What is the purpose of mitosis?

Answer 22

To produce two genetically identical daughter cells for growth and repair.

Question 23

What are the four main stages of mitosis?

Answer 23

• Prophase: Chromosomes condense; spindle fibers form; nuclear envelope breaks down.
  
  • Metaphase: Chromosomes align at the equator.
  • Anaphase: Sister chromatids are pulled apart to opposite poles.
  • Telophase: Nuclear envelopes reform; cytokinesis follows, splitting the cytoplasm.

Question 24

What is interphase?

Answer 24

The stage before mitosis where the cell grows and DNA is replicated.

Question 25

What happens during the G1 phase of interphase?

Answer 25

The cell grows, new organelles and proteins are made.

Question 26

What happens during the S phase of interphase?

Answer 26

DNA replication occurs, so each chromosome consists of two sister chromatids.

Question 27

What happens during the G2 phase of interphase?

Answer 27

The cell continues to grow, and proteins needed for mitosis are synthesized.

Question 28

What is the role of spindle fibers in mitosis?

Answer 28

They attach to centromeres and pull sister chromatids apart during anaphase.

Question 29

What happens during cytokinesis?

Answer 29

The cytoplasm divides, producing two separate daughter cells.

Question 30

How does mitosis ensure genetic consistency?

Answer 30

It produces daughter cells that are genetically identical to the parent cell.

Question 31

What happens if the cell cycle is uncontrolled?

Answer 31

It can lead to cancer, as cells divide uncontrollably and form tumors.

Question 32

How can the mitotic index be calculated?

Answer 32

Mitotic index = (Number of cells in mitosis / Total number of cells) × 100

Question 33

What stain is commonly used to observe mitosis in root tip cells?

Answer 33

Acetic orcein or toluidine blue, which stains DNA.

Question 34

Why are root tips used to observe mitosis?

Answer 34

They contain a high number of actively dividing cells in the meristem.

Question 35

How is a root tip squash prepared for microscopy?

Answer 35

The root tip is softened in acid, stained, and gently squashed under a coverslip to spread the cells out.

Question 36

Why is a thin layer of tissue used when preparing a slide for mitosis observation?

Answer 36

To allow light to pass through for clearer visibility of the chromosomes.

Question 37

How can you identify different stages of mitosis under a microscope?

Answer 37

~Prophase: Chromosomes condense and become visible. ~Metaphase: Chromosomes align in the center. ~Anaphase: Chromatids are pulled to opposite poles. ~Telophase: Two nuclei form.

Question 38

Why is hydrochloric acid used in root tip mitosis experiments?

Answer 38

It softens the cell walls, making it easier to squash the tissue and spread the cells.

Question 39

What is a Prokaryotic cell?

Answer 39

A cell that lacks a nucleus and membrane-bound organelles.

Question 40

What is an Organelle?

Answer 40

A specialized structure within a cell that performs a specific function.

Question 41

What is a plasmid?

Answer 41

A small circular DNA molecule found in prokaryotic cells.

Question 42

What is a capsid?

Answer 42

The protein coat surrounding a virus.

Question 43

What is Cell fractionation?

Answer 43

A process to separate organelles from a cell.

Question 44

What is Ultracentrifugation?

Answer 44

The spinning of a cell homogenates at high speeds to separate organelles by density.

Question 45

What is Mitosis?

Answer 45

A type of cell division that produces two genetically identical daughter cells.

Question 46

What is interphase?

Answer 46

The phase of the cell cycle where the cell grows and DNA is replicated.

Question 47

What is a Centromere?

Answer 47

The region where two sister chromatids are joined.

Question 48

What are Spindle fibers?

Answer 48

Protein structures that pull chromatids apart during mitosis.

Question 49

What is Cytokinesis?

Answer 49

The division of the cytoplasm following mitosis.

Question 50

What is mitotic index?

Answer 50

The proportion of cells in a tissue sample undergoing mitosis.

Question 51

What is a meristem?

Answer 51

A region in plants where rapid cell division occurs.

Question 52

What is cancer?

Answer 52

Uncontrolled cell division leading to tumor formation.