AB1: The cell, basic structure

Question 1

What are the differences between prokaryotes and eukaryotes?

Answer 1

1) Prokaryotes have no membrane bound organelles- eukaryotes do
2) Prokaryotes tend to be single celled, eukaryotes can be single and multi-cellular
3) In Prokaryotes all functions are carried out by the same cell, in eukaryotes most cells are specialised to a particular function
4) Eukaryotes have a “true nucleus”, Prokaryotes do not have a nucleus

Question 2

What are the typical features of a Prokaryotic cell?

Answer 2

Plasma membrane, cell wall, flagella, a nucleoid, ribosomes, a capsule, bacterial chromosomes and pili

Question 3

What are the typical feature of a Eukaryotic cell?

Answer 3

Rough and smooth endoplasmic reticulum, nucleus, plasma membrane, ribosomes, Golgi apparatus, lysosomes, mitochondria, peroxisome, microvilli, cytoskeleton, centrioles and flagella

Question 4

What are the typical features of a plant cell?

Answer 4

Rough and smooth endoplasmic reticulum, ribosomes, central vacuole, cytoskeleton, chloroplasts, plasmodesmata, cell wall, plasma membrane, peroxisome, mitochondria, Golgi apparatus, centrosome and nucleus

Question 5

What is a nucleoid?

Answer 5

nuclear region within a prokaryotic cell where genetic material is found- is not membrane bound so is not a nucleus

Question 6

What is the role of the pili?

Answer 6

plays an important role in allowing bacteria to adhere to surfaces such as cells to cause infection in humans

Question 7

What are microvilli?

Answer 7

specialised structures in epithelial cells such as cell lining your gut, give surface of plasma membrane a large surface area over which nutrients, solutes and water can be absorbed across the membrane in kidneys (not found in all animal cells)

Question 8

What are the differences between animal and plant cells?

Answer 8

Plants have a cellulose cell wall, chloroplasts, central vacuole and plasmodesmata, animal cells do not. Animals and some plant cell have flagella, animal cells have lysosomes, plants do not and animals have 2 centrioles within a centrosome- plants have centrosome but no centrioles

Question 9

What are the limitations of schematic diagrams of cells and organelles in books?

Answer 9

1) Colour- most colours are false, problem of absence of colour and contract is overcome by histologist who use staining of fixed cell and tissue samples
2) Scale- Schematic cartoons do not show relative sizes of organelles and shouldn’t be taken literally
3) Fluidity and Dynamics- Cells are not static pieces of technology- their structures and their component molecules are in a constant state of flux

Question 10

What methods are used to study cell structure ?

Answer 10

Microscopy- fixing and staining with coloured or fluorescent dyes or heavy metals for electron microscopy
Homogenisation- involves breaking them up and cell fractionation- spinning them in a centrifuge at many different speed

Question 11

What are the potential problems with the methods of studying cell structure? how are these problems overcome?

Answer 11

These methods are destructive which means that they have the potential to generate artefacts- “something observed in a scientific investigation that is not naturally present but occurs as a result of the method used”
However, these are overcome by using multiple independent methods to be more certain that your results are valid