2.1.9 Prokaryotic & Eukaryotic Cells

Question 1

Prokaryotic Cells vs Eukaryotic Cells

Answer 1

Animal and plant cells are types of eukaryotic cells, whereas bacteria are a type of prokaryotic cells
Size
- P = 0.5-5 micrometers in diameter
- E = up to 100 micrometers in diameter
Genome
- P = DNA is circular with no proteins, in the cytoplasm
- E = DNA is associated with histones (proteins) formed into chromosomes
Cell Division
- P = occurs by binary fission, with no spindle involved
- E = occurs by mitosis or meiosis and involves a spindle to separate chromosomes
Ribosomes
- P = 70S ribosomes
- E = 80S ribosomes
Organelles
- P = very few, no membrane-bound organelles, including plasmids, capsules and a flagellum
- E = numerous types of organelles, membrane-bound - single membranes: lysosomes, Golgi apparatus, vacuoles - double-membranes: nucleus, mitochondria, chloroplast - no membrane: - ribosomes, centrioles, microtubules
Cell Wall
- P = made of peptidoglyan (polysaccharide and animo acids) and murein
- E = present in plants (made of cellulose or lignin) and fungi (made of chitin, similar to cellulose but contains nitrogen)

Question 2

Organelles In Prokaryotes

Answer 2

Always present:
- cell wall
- cell surface membrane
- cytoplasm
- circular DNA
- ribosomes
Sometimes Present:
- flagellum
- capsule
- infolding of cells surface membrane
- plasmid
- pili

Question 3

Plasmids

Answer 3

Small loops of DNA that are separate from the main circular DNA molecule
Plasmids contain genes that can be passed between prokaryotes (e.g. genes for antibiotic resistance)
Not present in all prokaryotes

Question 4

Capsule

Answer 4

Some prokaryotes (e.g. bacteria) are surrounded by a final outer layer known as a capsule
This is sometimes called the slime capsule
It helps to protect bacteria from drying out and from attack from cells of the immune system
Not present in all prokaryotes

Question 5

Flagellum (Plural = Flagella)

Answer 5

A long, hair-like structure that rotates, enabling the prokaryotes to move (a bit like a propeller)
Some prokaryotes have more than one
Not present in all prokaryotes

Question 6

Infolding of Cell Surface Membrane

Answer 6

May allow for photosynthesis or carry out nitrogen fixation
Not present in all prokaryotes

Question 7

Pili

Answer 7

For attachment to other cells or surfaces
Involved in sexual reproduction
Not preset in all prokaryotes