Chapter 2: 2.6

Question 1

Describe background information on prokaryotic cells

Answer 1

• Appeared 3.5 billion years ago
• Adapted to live in extremes of salinity, pH and temperature
• Found in hydrothermal vents and salt lakes
• Recently found in soil + human digestive system
• Prokaryotic organisms are always unicellular
• DNA not in a nucleus
• No membrane-bound organelles

Question 2

*Describe the DNA in prokaryotes

Answer 2

One DNA molecule - a chromosome - supercoiled to make it more compact
*Genes on chromosome are grouped into operons, meaning many genes are switched on/off at the same time

Question 3

Describe the ribosomes in prokaryotes

Answer 3

70S - smaller than in eukaryotes

Question 4

What is the cell wall in prokaryotes made up of?

Answer 4

Peptidoglycan

Question 5

Describe the flagella in prokaryotes

Answer 5

Thinner than in eukaryotes
Energy to rotate filament forming flagellum supplied by chemiosmosis, not ATP like in eukaryotes
*Attached to cell membrane of bacteria by a basal body and rotated by molecular motor
*Basal body attaches filament to cell membrane of bacteria
*Molecular motor gives the filament a whip-like movement which propels the cell

Question 6

Describe background information on eukaryotic cells

Answer 6

-First appeared 1.5 billion years ago
-DNA present within nucleus + exists as many chromosomes
-Chromosomes supercoiled + each chromosome wraps around lots of proteins called histones, forming complex
Complex = chromatin
Chromatin = coils + condenses to form chromosomes

Question 7

Compare the nucleus of prokaryotes and eukaryotes

Answer 7

P = absent
E = present

Question 8

Compare the DNA of prokaryotes and eukaryotes

Answer 8

P = circular
E = linear

Question 9

Compare the DNA organisation of prokaryotes and eukaryotes

Answer 9

P = proteins fold + condense DNA
E = associates with proteins called histones

Question 10

Compare the extra chromosomal DNA of prokaryotes and eukaryotes

Answer 10

P = circular DNA called plasmids
E = only present in some organelles e.g. chloroplasts and mitochondria

Question 11

Compare the organelles of prokaryotes and eukaryotes

Answer 11

P = not membrane bound
E = membrane + non membrane bound

Question 12

Compare the cell wall of prokaryotes and eukaryotes

Answer 12

P = peptidoglycan
E = chitin in fungi, cellulose in plants, absent in animals

Question 13

Compare the ribosomes of prokaryotes and eukaryotes

Answer 13

P = smaller, 70S
E = bigger, 80S

Question 14

Compare the cytoskeleton of prokaryotes and eukaryotes

Answer 14

P = present
E = present, more complex

Question 15

Compare the reproduction of prokaryotes and eukaryotes

Answer 15

P = binary fission
E = asexual/sexual

Question 16

Compare the cell type of prokaryotes and eukaryotes

Answer 16

P = unicellular
E = uni + multicellular

Question 17

Compare the cell-surface membrane of prokaryotes and eukaryotes

Answer 17

P = present
E = present