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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
Where is endotoxin found?
Inside gram-negative cells
26
Explain how the outer membrane of gram-negative bacteria can be an impediment to the treatment of disease (2)
- Prevents movement of penicillin to the underlying peptidoglycan - Drug becomes ineffective against many gram-negative pathogens
27
Where is the periplasmic space found?
Between the cytoplasmic membrane and outer membrane of gram-negative bacteria
28
What does the periplasmic space contain?
Digestive enzymes and proteins involved in specific transport
29
What color do gram-negative bacteria stain after performing the gram stain?
Pink
30
What is the cytoplasmic membrane?
Double-layered structure called a ‘phospholipid bilayer’
31
Where is the cytoplasmic membrane found?
Beneath the glycocalyx and cell wall
32
Describe the presence of hydrophobic and hydrophilic characteristics in the phospholipid bilayer
- Hydrophobic lipid tails - Hydrophilic phosphate heads
33
How are phospholipid bilayers ‘selectively permeable’?
Controls the movement of substances into and out of the cell
34
What is the role of proteins in the selectively permeable phospholipid bilayer?
Act as pores, channels, and carriers
35
Why is the cytoplasmic membrane described as a ‘fluid mosaic’?
Mosaic of phospholipids and proteins
36
Describe passive transport
Requires no energy expenditure to move chemicals across the cytoplasmic membrane
37
Describe active transport
Requires energy expenditure (ATP) to transport cells against their concentration gradient
38
What does active transport utilize?
Transmembrane permeate proteins
39
Describe simple diffusion
Solutes cross the cytoplasmic membrane by moving down their concentration gradient
40
Describe facilitated diffusion
Protein channels facilitate the diffusion of chemicals across the cytoplasmic membrane
41
Describe osmosis
The diffusion of water molecules across a selectively permeable membrane
42
Osmosis occurs in response to ...
Differing concentrations of solutes
43
Describe the movement of water during osmosis
Low to high solute concentration
44
Describe hypertonic
The higher concentration of unequal solutions
45
Describe isotonic
Same solute concentration of either side of a selectively permeable membrane
46
Describe hypotonic
The lower concentration of unequal solutions
47
What happens to bacteria if placed in a hypertonic environment?
Cells shrink
48
What happens to bacteria if placed in an isotonic environment?
No net loss / gain of water
49
What happens to bacteria if placed in a hypotonic environment?
Cells swell
50
What is a nucleoid?
Region containing the cell’s DNA
51
Name 2 genera that produce endospores
- Bacillus - Clostridium
52
Describe vegetative cells
A single bacterial cell that transforms into a single endospore
53
Describe endospores
Germinate to grow into a single vegetative cell
54
What is sporulation?
The process of endospore formation
55
What conditions cause sporulation?
Conditions unfavorable for growth (nutrient depletion)
56
Endospores constitute ...
A defensive strategy against hostile / unfavorable conditions
57
What conditions are endospores resistant to in terms of their hardiness? (6)
- Drying - Radiation - Lethal chemicals - Alcohol - Peroxide - Bleach
58
Endospores remain alive in ______ for several hours
Boiling water
59
What is a ribosome?
Site of protein synthesis
60
What are ribosomes composed of? (2)
- Protein - Ribosomal RNA (rRNA)
61
Describe endocytosis
The cytoplasmic membrane swells to form ‘pseudopods’ that surround a substance
62
When is endocytosis termed phagocytosis?
If a solid is brought into the cell
63
When is endocytosis termed pinocytosis?
If a liquid is brought into the cell
64
Describe exocytosis
Enables substances to be exported from the cell
65
Exocytosis is the reverse of ______
Endocytosis
66
Describe lysosomes
Membranous sacs that contain degradative enzymes that damage the cell
67
Where are lysosomes released?
Into the cytosol
68
How are enzymes used in relation to lysosomes? (2)
- Self-destruction of old, damaged, and diseased cells - Digestion of phagocytized microbes
69
Describe the function of white blood cells in relation to lysosomes
Utilize digestive enzymes in lysosomes to destroy phagocytized pathogens
70
Where are lysosomes found?
In animal cells
71
Describe phagosomes (2)
- Food vesicle - Fuse with lysosomes to form phagolysosomes

MICRB 106 - Exam 2 (3 decks)

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