2.2.1 - Prokaryotic cells

Question 1

List some structures of a prokaryotic cell.

Answer 1

Cell membrane
Plasmids
70S ribosomes
Slime capsule
Nucleoid (circular strand of DNA)

Question 2

Differences between prokaryotic cells and eukaryotic cells?

Answer 2

No membrane bound organelles
DNA found in cytoplasm
70S ribosomes - not 80S
Have plasmids

Question 3

What part of a bacterial cell allow it to attach to surfaces?

Answer 3

Pili

Question 4

What is the function of lipid droplets and glycogen granules?

Answer 4

Act as nutrient stores

Question 5

What is the name given to the infoldings of the cell membrane in a bacterial cell?

Answer 5

Mesosome

Question 6

What is peptidoglycan made from?

Answer 6

Polysaccharide chains

Question 7

Feature of a bacterial cell wall?

Answer 7

Hypertonic meaning water can move in by osmosis.

Question 8

What is significant about a gram positive bacteria cell wall?

Answer 8

Thick peptidoglycan layer

Question 9

What is significant about a gram negative bacteria cell wall?

Answer 9

Thin peptidoglycan layer

Question 10

What is the method of testing between gran positive and gram negative bacterial cell walls?

Answer 10

Stain with crystal violet/iodine
Wash with alcohol
Add red safranin stain

Question 11

What are the colours of gram positive and gram negative bacteria after being tested with stains?

Answer 11

Gram positive = purple/blue
Gram negative = Red

Question 12

Why does gram positive bacteria turn purple/blue when tested with stains?

Answer 12

Crystal violet/iodine gets stuck in peptidoglycan layer.
Resists being decolourised with alcohol.
So don’t pick up red safranin stain.

Question 13

Why does gram negative bacteria turn red when tested with stains?

Answer 13

Crystal violet/ iodine doesn’t get stuck in peptidoglycan layer when washed with alcohol.
So turns red when stained with red safranin stain.

Question 14

What part of bacterial cells do antibiotics target?

Answer 14

Cell walls and ribosomes.

Question 15

What do beta lactam antibiotics do?

Answer 15

Inhibit formation of peptidoglycan cell wall.

Question 16

What do glycopeptide antibiotics do?

Answer 16

Polar molecules which work against gram positive as they can’t penetrate cell wall.

Question 17

What do polypeptide antibiotics do?

Answer 17

Work against gram negative bacteria as they interact with phospholipids.

Question 18

How can antibiotic treatment identify type of bacterium?

Answer 18

If antibiotics work, the bacteria is gram positive.
Gram positive have a thick peptidoglycan layer in cell wall.
Therefore larger target site for antibodies.

Question 19

What are obligate anaerobes?

Answer 19

Bacteria that are destroyed by normal oxygen concentrations.

Question 20

What are obligate aerobes?

Answer 20

Bacteria that require oxygen to survive.

Question 21

What are facultative anaerobes?

Answer 21

Bacteria that can live in the presence of oxygen but don’t need it.

Question 22

Some antibiotics affect the enzymes involved in the growth of bacteria.

(i) Explain why Gram positive bacteria and Gram negative bacteria react differently to some antibiotics.

Answer 22

Gram positive bacteria have a thick layer of peptidoglycan in their cell wall.
Some antibiotics inhibit the enzymes involved in the formation of peptidoglycan so are effective against gram positive bacteria.
Some antibiotics are not able to cross the peptidoglycan layer so they are only effective against gram negative bacteria.