Prokaryotes and Eukaryotes

Question 1

What is a prokaryote?

Answer 1

A prokaryote is an organism that does not have a nucleus or any other membrane bound organelles.

Question 2

What is a eukaryote?

Answer 2

A eukaryote is an organism whose cells are organised into complex structures by internal membranes and a cytoplasm including a membrane bound nucleus.

Question 3

Describe the difference between genetic material in prokaryote cells and eukaryote cells

Answer 3

Eukaryotes have true nuclei and their DNA is organised into tightly bound chromosomes.
Prokaryotes have a single loop of chromosomal DNA stored in a region called the nucleoid. Genes are also stored in plasmids (satellite DNA structures).

Question 4

Describe the difference between metabolic processes in prokaryote cells and eukaryote cells

Answer 4

In eukaryotes metabolic processes are carried out by mitochondria (and chloroplasts in plants).
In prokaryotes similar metabolic processes are carried out across the membrane

Question 5

Describe the difference between size in prokaryotic cells and eukaryote cells

Answer 5

Eukaryotes have bigger cells (10-100um in diameter)

Prokaryotes have smaller cells (less than 2um in diameter)

Question 6

Describe the difference between genetic recombination in prokaryote cells and eukaryote cells

Answer 6

In eukaryotes: meiosis and fusion of gametes

In prokaryotes: by partial undirectional transfer of DNA

Question 7

Describe the difference between in ATP production prokaryote cells and eukaryote cells

Answer 7

In eukaryotes it is produced in mitochondria

In prokaryotes it is produced in specialised infolded regions of the cell surface membrane (mesosomes)

Question 8

Outline the features of prokaryotic cells, what extra organelles do eukaryotes have?

Answer 8

Features of prokaryotes 
1. small ribosomes 
2. vesicles 
3. sub microscopic flagella 
4. no nuclear membrane 
5. vacuoles 
Extra organelles that eukaryotes have:
- lysosomes 
- endoplasmic reticulum 
- mitochondria 
- golgi apparatus

Question 9

Do prokaryotes and eukaryotes have a cell wall?

Answer 9

In Eukaryotes this varies...
- animals do not 
- plants do (made of cellulose)
- fungi do (made of chitin)
In prokaryotes the cell wall is formed of a different molecule- peptidoglycan

Question 10

What is the usual cell type of prokaryotes and the usual cell type of eukaryotes?

Answer 10

Prokaryotes are usually unicellular

Eukaryotes are usually multicellular

Question 11

Give a general example, and then a more specific example, of a prokaryote and a eukaryote.

Answer 11

Eukaryotes:
- animals and plants 
- human liver cell 
Prokaryotes 
- bacteria 
- E.Coli bacterium

Question 12

Describe the difference between the volume to surface area in prokaryote cells and eukaryote cells

Answer 12

Eukaryotes - Small ratio

Prokaryotes - Larger ratio, consequently they have a higher metabolic and growth rate but shorter generation time

Question 13

Describe the difference between the flagella found in prokaryote cells and eukaryote cells

Answer 13

In eukaryotes- made of microtubule proteins

In prokaryotes- made of a protein called falgellin

Question 14

What is the endosymbiotic theory?

Answer 14

The endosymbiotic theory suggests that mitochondria and chloroplasts found in eukaryotic cells represent formerly free-living bacteria that were absorbed into a larger cell

Question 15

How did the endosymbiotic theory originate?

Answer 15

Mitochondria and chloroplasts both use their own circular chromosomes to make some proteins needed for their function

Question 16

What features of mitochondria support the endosymbiotic theory?

Answer 16

• chloroplasts have their own DNA
• mitochondrion contain ribosomes that are smaller than those found in the cytoplasm
• mitochondria are a similar size to bacteria

Question 17

If this theory is correct, what did mitochondria lose in their evolution from a prokaryote?

Answer 17

Their cell wall

Question 18

What features of a bacterial cell would you be able to see with an electron microscope?

Answer 18

1. DNA in the form of a circular chromosome
2. cell surface membrane and cell wall
3. plasmids (rings of DNA)
4. small ribosomes
5. flagellum tail used to propel the cell

Question 19

Some prokaryotes cause disease, how do some strains become resistant to antibiotics?

Answer 19

• random mutation makes it resistant
• resistance is coded on plasmid DNA
  This can be passed on:
  1. bacteria can share plasmids with each other
  2. binary fusion, passed onto daughter cells

Question 20

What are four helpful uses of prokaryotes?

Answer 20

1. food industry to produce cheese and yogurt
2. on skin as a natural flora to prevent harmful microorganisms entering our bodies
3. in mammalian intestines to help digest foods
4. for natural recycling and sewage treatment (bacterial cells digest waste material whilst respiring)