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Microbiology (BIOL 286) > Unit 1--Lecture 2 (Microbial Cell Structure) > Flashcards

Unit 1--Lecture 2 (Microbial Cell Structure) Flashcards

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Biology 101 flashcards
1
Q

Refraction

A

Passage through lens material bends light

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2
Q

Resolution

A

The ability to distinguish two adjacent objects or points form one another

AKA Resolving Power

RP = (wavelength of light in nm) / (2 X Numerical Aperture)

Numerical Aperture describes the relative efficiency of a lens in bending light rays

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3
Q

Bacterial Cell Shapes

A

Coccus/Cocci: balls

Bacillus/Bacilli: rods

Spirochetes/Spirillum: spiral rods

Diplo: 2

Tetrad: 4

Sarcina: 8

Strepto: chain

Staphylo: grape-like cluster

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4
Q

Advantages to being small

A

more surface area relative to cell volume (higher S/V ratio)

grow faster than larger cells

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5
Q

Cell Membrane

A

The structure that defines the existence of a cell

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6
Q

Membrane Constituents

A

Membranes are approximately equal parts phospholipids and proteins

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7
Q

Phospholipid

A

Glycerol with ester links to 2 fatty acids and a phosphoric head group

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8
Q

Membrane Protein Functions

A

structural support

secretion of virulence factors

transmission of communication signals

ion transport and energy storage

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9
Q

Transport across Cell Membrane

A

The cell membrane acts as a semi-permeable barrier

Selective transport is essential for survival

Small uncharged molecules (O2 & CO2) easily permeate the membrane by diffusion

Water diffuses across the membrane by osmosis

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10
Q

Diffusion of Weak Acids

A

Weak acids and bases can diffuse across the membrane and change the pH of the cell

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11
Q

Transport

A

Polar and charged molecules require transport through specific protein transporters

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12
Q

Passive Transport

A

Molecules move along their concentration gradient

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13
Q

Active Transport

A

Molecules move against their concentration gradient

Requires energy

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14
Q

Membrane Fluidity

A

In eukaryotic membranes, the reinforcing agents are sterols (cholesterol & ergosterol)

In bacteria, the same function is filled by hopanoids, or hopanes

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15
Q

Nucleoid

A

Contains the genetic material

No nuclear membrane

Singel circular chromosome

Haploid

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16
Q

Prokaryote Ribosome

A

Two subunits (30S & 50S)

Total size is 70S

17
Q

Thylakoids (Phototroph Structures)

A

Extensively folded intracellular membranes

18
Q

Carboxysomes (Phototroph Structures)

A

Polyhedral bodies packed with the enzyme rubisco for CO2 fixation

19
Q

Gas Vesicles (Phototroph Structures)

A

To increase buoyancy

20
Q

Other Inclusion Bodies

A

Storage granules

Glycogen, PHB, PHA

Sulfur

Volutin

Magnetosomes

21
Q

Bacterial Cytoskeleton (Shape-determining proteins)

A

FtsZ– forms a “Z ring” for septum placement

MreB– forms a coil inside rod-shaped cells

CreS– “cresentin”- forms a polymer along the inner side of crescent-shaped bacteria

22
Q

The Cell Wall

A

Confers shape and rigidity to the cell and helps it withstand turgor pressure

23
Q

Bacterial Cell Walls

A

Most bacterial cell walls are made up of peptidoglycan (or murein)

The molecule consists of:
NAG and NAM bound to a peptide of 4-6 amino acids

The peptides can form cross-bridges connecting the parallel glycan strands

24
Q

Bacterial Envelopes

A

Provide structural support and protection

Envelope composition defines:

Gram-positive bacteria– thick cell wall (Firmicutes)

Gram-negative bacteria– thin cell wall (Proteobacteria)

25
Q

Gram-Positive

A

Polymers of sugars

Lipoteichoic acid linked to lipids– act to anchor the wall to membrane

26
Q

Mycobacterial Cell Envelopes

A

Complex cell envelopes

Include unusual membrane lipids (mycolic acids) and unusual sugars (arabinogalactans)

27
Q

Gram-Negative

A

The thin peptidoglycan layer consists of one or two sheets

Covered by an outer membrane, which confers defensive abilities and toxigenic properties on many pathogens

28
Q

Lipopolysaccharide

A

Lipid A (six fatty acids)– conserved structure

Core (adaptor structure)– variable composition

O-Antigen (repeats)– important barrier function

29
Q

Mycoplasma

A

True bacteria

Very small

No peptidoglycan wall

Important pathogens

30
Q

Flagellar Arrangements

A

Monotrichous

Amphitrichous

Lophotrichous

Peritrichous

31
Q

Flagella of Spirochetes

A

Axial filaments

Bundles of many flagella

32
Q

Chemotaxis

A

The movement of a bacterium in response to chemical gradients

Attractants cause CCW rotation– flagella bundle together

Repellants cause CW rotation– flagella bundle falls apart

33
Q

Cell Attachment

A

Fimbriae: attach cells to surfaces

Stalks: attach cells to surfaces

Secretion Systems: attach cells to prey (Sex Pilus– similar to type IV secretion system)

34
Q

Capsule (Glycocalyx)

A

Outermost layer of the cell

Made of carbohydrate

Used to avoid phagocytosis

Microbiology (BIOL 286) (36 decks)

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