lecture 27 - prokaryotic cells Flashcards

1
Q

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

A

~50%

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2
Q

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

A

Cocci, rod, spiral

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3
Q

What is the structure of the bacterial chromosome?

A

bacteria have a single, circular chromosome of DNA

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4
Q

Do bacteria have a nuclear membrane?

A

No

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5
Q

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

A

It is restricted to the nucleoid

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6
Q

What are plasmids?

A

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

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7
Q

What type of nucleic acid is in a plasmid?

A

Circular, double stranded DNA

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8
Q

What are bacterial cell walls made up of?

A

Peptidoglycan

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9
Q

What is peptidoglycan?

A

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

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10
Q

What is the function of the bacterial peptidoglycan cell wall?

A

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

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11
Q

What is the structure of peptidoglycan?

A

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

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12
Q

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

A

Transpeptidase

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13
Q

What is gram staining?

A

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

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14
Q

What type of bacteria will turn purple during gram staining?

A

Gram positive bacteria

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15
Q

Why type of bacteria will turn pink during gram staining?

A

Gram negative bacteria

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16
Q

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

A

Crystal violet

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17
Q

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

A

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

18
Q

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

A

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

19
Q

What are bacterial flagella?

A

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

20
Q

What are bacterial flagella made of?

A

Proteins - they are proteinacus

21
Q

How many flagella are typically on each motile bacterial cell?

A

5-10

22
Q

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

A

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

23
Q

What is chemotaxis, in terms of bacterial motility?

A

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

24
Q

What are the 2 types of bacterial adherence factors?

A

Fimbriae and pili

25
Q

What are fimbriae/adherins

A

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

26
Q

How do fimbriae differ to flagella on bacteria?

A

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

27
Q

What are bacterial pili/sex pili?

A

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

28
Q

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

A

Conjugation

29
Q

What type of gene transfer is conjugation via sex pili?

A

Horizontal gene transfer

30
Q

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

A

Via horizontal gene transfer, especially through conjugation using sex pili

31
Q

What is glycocalyx?

A

A gelatinous polysaccharide covering that surrounds bacteria when produced.

32
Q

What is glycocalyx made of?

A

Polysaccharide and/or peptides, which form a gelatinous substance

33
Q

What are the two types of structure formed by glycocalyx?

A

Slime layer, capsule

34
Q

What is a bacterial slime layer?

A

Disorganised glycocalyx layer that adheres loosely to bacterial cell walls.

35
Q

What is a glycocalyx capsule?

A

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

36
Q

What do glycocalyx capsules contain to protect the bacterial cell?

A

virulence factors

37
Q

What are virulence factors?

A

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

38
Q

What does the glycocalyx capsule protect bacterial cells from?

A

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

39
Q

What are bacterial endospores?

A

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.

40
Q

What type of bacteria have bacterial endospores?

A

Some types of gram-positive bacteria