lecture 27 - prokaryotic cells

Question 1

What proportion of the earth’s biomass are made up of bacteria?

Answer 1

~50%

Question 2

What are the 3 distinct types of shape possible for bacteria?

Answer 2

Cocci, rod, spiral

Question 3

What is the structure of the bacterial chromosome?

Answer 3

bacteria have a single, circular chromosome of DNA

Question 4

Do bacteria have a nuclear membrane?

Answer 4

No

Question 5

How is the bacterial genome contained when there is no nuclear membrane?

Answer 5

It is restricted to the nucleoid

Question 6

What are plasmids?

Answer 6

Small, circular, self-replicating DNA molecule found in the cytosol of a bacterial cell

Question 7

What type of nucleic acid is in a plasmid?

Answer 7

Circular, double stranded DNA

Question 8

What are bacterial cell walls made up of?

Answer 8

Peptidoglycan

Question 9

What is peptidoglycan?

Answer 9

A rigid macro molecular layer that makes up the bacterial cell wall.

Question 10

What is the function of the bacterial peptidoglycan cell wall?

Answer 10

Provides strength, prevents osmotic lysis/rupture, confers cell shape.

Question 11

What is the structure of peptidoglycan?

Answer 11

Polysaccharide chains - alternating NAG and NAM - cross linked by peptides that have amino acid side chains (cross linking via transpeptidase)

Question 12

What enzyme is involved in the peptide cross bridges between polysaccharide chains in peptidoglycan?

Answer 12

Transpeptidase

Question 13

What is gram staining?

Answer 13

A laboratory staining process that will turn certain bacterial purple, and others pink

Question 14

What type of bacteria will turn purple during gram staining?

Answer 14

Gram positive bacteria

Question 15

Why type of bacteria will turn pink during gram staining?

Answer 15

Gram negative bacteria

Question 16

What agent is initially used in gram staining to give the purple colour?

Answer 16

Crystal violet

Question 17

What is the structure of gram positive bacteria, and how does this determine their behaviour during gram staining?

Answer 17

Has a thick cell wall (peptidoglycan layer) above their cell membrane, which traps crystal violet giving them a purple colour.

Question 18

What is the structure of gram negative bacteria, and how does this determine their behaviour during gram staining?

Answer 18

Thin layer of peptidoglycan between outer and inner membranes, meaning crystal violet cannot be effectively trapped.

Question 19

What are bacterial flagella?

Answer 19

Appendages on motile bacteria that allow them to move through a liquid medium.

Question 20

What are bacterial flagella made of?

Answer 20

Proteins - they are proteinacus

Question 21

How many flagella are typically on each motile bacterial cell?

Answer 21

5-10

Question 22

What acts as the ‘motor’ for movement of bacteria via flagella?

Answer 22

‘Motors’ embedded in the cell membranes/peptidoglycan, which use an electrochemical gradient to generate thrust.

Question 23

What is chemotaxis, in terms of bacterial motility?

Answer 23

A tactic response by bacteria, in which they move along a concentration gradient towards a chemical attractant or away from a chemical repellant.

Question 24

What are the 2 types of bacterial adherence factors?

Answer 24

Fimbriae and pili

Question 25

What are fimbriae/adherins

Answer 25

Structures with adhesive properties that are founds on the surface of bacteria and allow them to adhere to surfaces.

Question 26

How do fimbriae differ to flagella on bacteria?

Answer 26

Fimbriae are shorter, smaller in diameter and more numerous than flagella. Are adapted for sticking to surfaces (adherence) rather than motility

Question 27

What are bacterial pili/sex pili?

Answer 27

An adherence factor that allows bacteria to attach to other bacteria and transfer genetic information in a process called conjugation.

Question 28

What is the name for the transfer of genetic information between bacteria using sex pili?

Answer 28

Conjugation

Question 29

What type of gene transfer is conjugation via sex pili?

Answer 29

Horizontal gene transfer

Question 30

How are bacteria able to share genetics and thereby adapt to challenging conditions?

Answer 30

Via horizontal gene transfer, especially through conjugation using sex pili

Question 31

What is glycocalyx?

Answer 31

A gelatinous polysaccharide covering that surrounds bacteria when produced.

Question 32

What is glycocalyx made of?

Answer 32

Polysaccharide and/or peptides, which form a gelatinous substance

Question 33

What are the two types of structure formed by glycocalyx?

Answer 33

Slime layer, capsule

Question 34

What is a bacterial slime layer?

Answer 34

Disorganised glycocalyx layer that adheres loosely to bacterial cell walls.

Question 35

What is a glycocalyx capsule?

Answer 35

A capsule of organised glycocalyx that is attached firmly and evenly to the bacterial cell wall and contains virulence factors.

Question 36

What do glycocalyx capsules contain to protect the bacterial cell?

Answer 36

virulence factors

Question 37

What are virulence factors?

Answer 37

Cellular structures, molecules and regulatory systems that enable microbial pathogens to colonise hosts effectively.

Question 38

What does the glycocalyx capsule protect bacterial cells from?

Answer 38

Phagocytosis/engulfment by immune cells, desiccation (drying out)

Question 39

What are bacterial endospores?

Answer 39

A structure formed within a bacterium that are formed during unfavourable conditions and protect bacteria from stress. They can lie dormant until triggered by environmental stressors.

Question 40

What type of bacteria have bacterial endospores?

Answer 40

Some types of gram-positive bacteria