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MICRB 106 - Exam 2 > Cell Structure and Function > Flashcards

Cell Structure and Function Flashcards

1
Q

What are the major components of peptidoglycan? (2)

A
  • Complex polysaccharide composed of 2 alternating sugars
  • Cross bridges of short proteins that hold the chains of sugars together
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2
Q

Peptidoglycan is structurally similar to ______

A

Glucose

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3
Q

Name the 2 modified sugars found in peptidoglycan

A
  • n-acetylglucosamine (NAG)
  • n-acetylmuramic acid (NAM)
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4
Q

How are the 2 modified sugars found in peptidoglycan arranged / positioned?

A

Alternating position

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5
Q

How are the carbohydrate chains in peptidoglycan connected to other chains of carbohydrates?

A

Tetra- / penta- peptides between neighboring NAMs

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6
Q

What are tetra- / penta- peptides?

A

Cross bridges of short proteins

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7
Q

What peptidoglycan component do tetra- / penta- peptides attach?

A

Hold chains of NAG and NAM together

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8
Q

Differentiate between the ‘peptido’ and the ‘glycan’ portions of peptidoglycan

A
  • ‘Peptido’ = peptide cross bridges
  • ‘Glycan’ = NAG / NAM carbohydrate chains
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9
Q

Compare and contrast gram-positive cell walls with gram-negative cell walls

A
  • Gram-positive cell walls - thick layer of peptidoglycan
  • Gram-negative cell walls - thin layer of peptidoglycan and an outer membrane (bilayer)
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10
Q

Where are teichoic acids found?

A

The outer thick layer of peptidoglycan in gram-positive cell walls

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11
Q

Teichoic acids are ______ linked to lipids

A

Covalently

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12
Q

What is the function of lipoteichoic acid in gram-positive bacteria?

A

Anchors the peptidoglycan to the cytoplasm membrane

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13
Q

What color do gram-positive bacteria stain after performing the gram stain?

A

Purple

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14
Q

What is a ‘bilayer’?

A

The outer membrane of gram-negative cells walls composed of two different layers

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15
Q

Differentiate between the inner leaflet and the outer leaflet of the outer membrane of gram-negative bacteria in terms of basic composition

A
  • Inner leaflet - composed of phospholipids
  • Outer leaflet - composed of lipopolysaccharide (LPS)
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16
Q

What unique component is found in the outer leaflet of the outer membrane of gram-negative bacteria?

A

Porins

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17
Q

What are porins?

A

Integral proteins that form channels through both leaflets of the outer membrane

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18
Q

What role do porins play in gram-negative bacteria?

A

Allow midsize molecules (such as glucose) to move freely across the outer membrane

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19
Q

What 2 major components make up lipopolysaccharide (LPS)?

A
  • Lipids
  • Sugar
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20
Q

Describe the relationship between lipid A, core polysaccharide, and O-specific side-chain components of LPS

A

Shock-inducing lipid A is attached to a core polysaccharide with variable O-specific side chains

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21
Q

What is lipid A?

A

Lipid portion

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22
Q

Where is lipid A found?

A

Inside gram-negative cells (endotoxin)

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23
Q

What symptoms / physiological conditions does lipid A cause inside in host organisms? (5)

A
  • Vasodilation
  • Fever
  • Inflammation
  • Blood clotting
  • Shock
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24
Q

Describe endotoxin

A

Dead gram-negative cells release lipid A when the outer membrane disintegrates

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25
Q

Where is endotoxin found?

A

Inside gram-negative cells

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26
Q

Explain how the outer membrane of gram-negative bacteria can be an impediment to the treatment of disease (2)

A
  • Prevents movement of penicillin to the underlying peptidoglycan
  • Drug becomes ineffective against many gram-negative pathogens
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27
Q

Where is the periplasmic space found?

A

Between the cytoplasmic membrane and outer membrane of gram-negative bacteria

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28
Q

What does the periplasmic space contain?

A

Digestive enzymes and proteins involved in specific transport

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29
Q

What color do gram-negative bacteria stain after performing the gram stain?

30
Q

What is the cytoplasmic membrane?

A

Double-layered structure called a ‘phospholipid bilayer’

31
Q

Where is the cytoplasmic membrane found?

A

Beneath the glycocalyx and cell wall

32
Q

Describe the presence of hydrophobic and hydrophilic characteristics in the phospholipid bilayer

A
  • Hydrophobic lipid tails
  • Hydrophilic phosphate heads
33
Q

How are phospholipid bilayers ‘selectively permeable’?

A

Controls the movement of substances into and out of the cell

34
Q

What is the role of proteins in the selectively permeable phospholipid bilayer?

A

Act as pores, channels, and carriers

35
Q

Why is the cytoplasmic membrane described as a ‘fluid mosaic’?

A

Mosaic of phospholipids and proteins

36
Q

Describe passive transport

A

Requires no energy expenditure to move chemicals across the cytoplasmic membrane

37
Q

Describe active transport

A

Requires energy expenditure (ATP) to transport cells against their concentration gradient

38
Q

What does active transport utilize?

A

Transmembrane permeate proteins

39
Q

Describe simple diffusion

A

Solutes cross the cytoplasmic membrane by moving down their concentration gradient

40
Q

Describe facilitated diffusion

A

Protein channels facilitate the diffusion of chemicals across the cytoplasmic membrane

41
Q

Describe osmosis

A

The diffusion of water molecules across a selectively permeable membrane

42
Q

Osmosis occurs in response to …

A

Differing concentrations of solutes

43
Q

Describe the movement of water during osmosis

A

Low to high solute concentration

44
Q

Describe hypertonic

A

The higher concentration of unequal solutions

45
Q

Describe isotonic

A

Same solute concentration of either side of a selectively permeable membrane

46
Q

Describe hypotonic

A

The lower concentration of unequal solutions

47
Q

What happens to bacteria if placed in a hypertonic environment?

A

Cells shrink

48
Q

What happens to bacteria if placed in an isotonic environment?

A

No net loss / gain of water

49
Q

What happens to bacteria if placed in a hypotonic environment?

A

Cells swell

50
Q

What is a nucleoid?

A

Region containing the cell’s DNA

51
Q

Name 2 genera that produce endospores

A
  • Bacillus
  • Clostridium
52
Q

Describe vegetative cells

A

A single bacterial cell that transforms into a single endospore

53
Q

Describe endospores

A

Germinate to grow into a single vegetative cell

54
Q

What is sporulation?

A

The process of endospore formation

55
Q

What conditions cause sporulation?

A

Conditions unfavorable for growth (nutrient depletion)

56
Q

Endospores constitute …

A

A defensive strategy against hostile / unfavorable conditions

57
Q

What conditions are endospores resistant to in terms of their hardiness? (6)

A
  • Drying
  • Radiation
  • Lethal chemicals
  • Alcohol
  • Peroxide
  • Bleach
58
Q

Endospores remain alive in ______ for several hours

A

Boiling water

59
Q

What is a ribosome?

A

Site of protein synthesis

60
Q

What are ribosomes composed of? (2)

A
  • Protein
  • Ribosomal RNA (rRNA)
61
Q

Describe endocytosis

A

The cytoplasmic membrane swells to form ‘pseudopods’ that surround a substance

62
Q

When is endocytosis termed phagocytosis?

A

If a solid is brought into the cell

63
Q

When is endocytosis termed pinocytosis?

A

If a liquid is brought into the cell

64
Q

Describe exocytosis

A

Enables substances to be exported from the cell

65
Q

Exocytosis is the reverse of ______

A

Endocytosis

66
Q

Describe lysosomes

A

Membranous sacs that contain degradative enzymes that damage the cell

67
Q

Where are lysosomes released?

A

Into the cytosol

68
Q

How are enzymes used in relation to lysosomes? (2)

A
  • Self-destruction of old, damaged, and diseased cells
  • Digestion of phagocytized microbes
69
Q

Describe the function of white blood cells in relation to lysosomes

A

Utilize digestive enzymes in lysosomes to destroy phagocytized pathogens

70
Q

Where are lysosomes found?

A

In animal cells

71
Q

Describe phagosomes (2)

A
  • Food vesicle
  • Fuse with lysosomes to form phagolysosomes

MICRB 106 - Exam 2 (3 decks)

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