Cell structure

Question 1

Describe the structure and function of the nucleus

Answer 1

Surrounded by a nuclear envelope
Nuclear pores allow substances to enter/exit
Contains DNA coiled into chromosomes
Controls the cell

Question 2

Describe the structure and function of mitochondria

Answer 2

Cristae (site of ETC)
Matrix (contains DNA, lipids and proteins)
Site of aerobic respiration
Produces ATP

Question 3

Describe the structure and function of the chloroplasts

Answer 3

Thylakoids (flattened stacked discs)
Stroma (fluid-filled matrix)
Site of photosynthesis
Converts solar energy to chemical energy

Question 4

Describe the structure and function of the Golgi apparatus

Answer 4

Stack of membrane-bound, flattened sacs
Synthesises glycoproteins
Transports and stores proteins

Question 5

Describe the structure and function of a lysosome

Answer 5

Sac surrounded by a glycoprotein coat
Exocytosis of digestive enzymes
Digests contents of phagosome

Question 6

Describe the structure and function of a ribosome

Answer 6

Site of protein synthesis
In cytoplasm or attached to ER

Question 7

Describe the structure and function of the endoplasmic reticulum (ER)

Answer 7

Rough ER = many ribosomes attached for protein synthesis
Smooth ER = lipid synthesis

Question 8

Describe the structure of the cell wall in different organisms and functions it has

Answer 8

Bacteria = murein
Plants = cellulose microfibrils
Mechanical support
Physical barrier against pathogens
Enables easy diffusion

Question 9

Describe the structure and function of the cell vacuole in plants

Answer 9

Absorbs and hydrolyses harmful substances
Acts as a temporary food source

Question 10

State the role of plasmids, the flagella and the capsule in prokaryotes

Answer 10

Plasmids = small ring of DNA carrying non-essential genes
Flagella = tail that propels the organism
Capsule = provides mechanical support + acts as a food reserve

Question 11

Compare and contrast eukaryotic and prokaryotic cells

Answer 11

Both have a cell membrane, ribosomes and cytoplasm
Eukaryotes: Prokaryotes:
multicellular unicellular
nucleus no nucleus
larger ribosomes smaller ribosomes
cellulose cell wall murein cell wall

Question 12

What are viruses?

Answer 12

Viruses are acellular and non-living

Question 13

Describe the structure of a virus

Answer 13

Attachment proteins on the surface
Capsid
Linear genetic material

Question 14

What are the advantages and disadvantages of using an optical (light) microscope?

Answer 14

+ image in colour
+ relatively cheap equipment
- lower resolution than electron microscopes
- 2D image

Question 15

What are the advantages and disadvantages of using a scanning electron microscope (SEM) ?

Answer 15

+ 3D image
+ higher resolution than optical
- requires a vacuum
- black and white image
- expensive

Question 16

What are the advantages and disadvantages of using a transmission electron microscope (TEM) ?

Answer 16

+ higher resolution than optical
+ higher magnification than optical
- 2D image with no colour
- expensive
- longer process

Question 17

What happens during cell fractionation?

Answer 17

1. Homogenize the tissue to release organelles
2. Filter homogenate to remove debris
3. Spin homogenate in centrifuge
4. Most dense organelles form a pellet than can be filtered off
5. It’s then spun again at a higher speed to remove any other organelles

Question 18

What are the stages in the cell cycle?

Answer 18

Interphase
Mitosis (nuclear division)
Cytokinesis (cytoplasmic division)

Question 19

What are the 3 stages that happen during interphase?

Answer 19

G1 = cell synthesises proteins for replication
S = DNA replicates
G2 = organelles divide

Question 20

What happens during the first phase of mitosis?

Answer 20

PROPHASE:
Chromosomes condense, becoming visible
Spindle fibres form

Question 21

What happens during the second phase of mitosis?

Answer 21

METAPHASE:
Sister chromatids line up along equator
Attached to spindles by their centromere

Question 22

What happens during the third stage of mitosis?

Answer 22

ANAPHASE:
Sister chromatids separate into 2 chromosomes
Centromeres divide

Question 23

What happens during the fourth stage of mitosis?

Answer 23

TELOPHASE:
Chromosomes decondense, becoming invisible
Spindle disintegrates

Question 24

How do cancer treatments control the rate of cell division?

Answer 24

Prevent DNA replication
Disrupt spindle formation

Question 25

How do prokaryotic cells replicate?

Answer 25

BINARY FISSION:
1. DNA loop replicates
2. Cell elongates, separating DNA loops
3. Cell membrane contracts
4. Cell splits into 2 identical cells with a DNA loop and varying number of plasmids

Question 26

How do viruses replicate?

Answer 26

1. Attachment proteins attach to receptors on host cell
2. Viruses fuse with cell membrane
3. Host cell synthesises new viral proteins
4. Components of the new viral particle assemble

Question 27

Why is it difficult to treat viruses?

Answer 27

They replicate inside living cells, making them difficult to kill without harming the host cell