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Microbiology > Ch 3: Cell Structure and Function > Flashcards

Ch 3: Cell Structure and Function Flashcards

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Biology 101 flashcards
1
Q

Describe prokaryotes

A

generally small (0.2 - 2 microns diameter & 2-8 microns length)

Include bacteria and archaebacteria

no nucleus or other membrane-bound organelles

one circular chromosome (most)

no histone proteins associated with DNA

cell wall generally contains peptidoglycan (complex polysaccharide) (protein and sugar)

divide by binary fission

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2
Q

Describe Eukaryotes

A

large cells (10–100 µm in diameter)

“true nucleus” and other membrane-bound organelles

multiple linear chromosomes

histone proteins always associated with DNA

cell wall does not contains peptidoglycan

divide by mitosis (complex process that requires a nucleus) (nuclear division, not cell division)

Include algae, protozoa, fungi, animals, and plants

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3
Q

Name for sphere shaped bacteria

A

Coccus

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4
Q

Name for rod shaped bacteria

A

Bacillus

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5
Q

Name for very short rod (egg) shaped bacteria

A

Coccobacillus

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6
Q

Name for comma (banana) shaped bacteria

A

Vibrio

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7
Q

Name for spiral shaped & rigid bacteria

A

Spirillium

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8
Q

Name for spiral shaped & flexible bacteria

A

Spirochete

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9
Q

Name for star-shaped bacteria

A

example: Stella

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10
Q

Name for rectangular bacteria

A

example Haloarcula

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11
Q

Bacterial Structure: Glycocalyx

A

AKA: sugar halo, capsule, or slime layer.
A protective capsule secreted by the cell. This often has the appearance and texture of a ‘slime coating’
Impairs phagocytosis
Impairs antibody binding
Adhesion

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12
Q

Bacterial Structure: Pilus

A

AKA Conjugation tube or sex pilus

Transfer tube which allow movement of plasmid DNA from one bacterium to another (horizontal evolution)

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13
Q

Bacterial Structure: Fimbria

A

attachment filament used to adhere to target cell

Some archaea have fimbriae and hami (s. hamus) (grapling hook)

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14
Q

Bacterial Structure: Flagellum

A

Long, whip-like structure seen in some bacteria that propel cells through their environment

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15
Q

Bacterial Structure: Plasmid

A

Extrachromosomal loop of DNA

Resistant genes

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16
Q

Flagellar Arrangements: Who rarely has flagella?

A

Cocci

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17
Q

Flagellar Arrangements: single flagellum located at the pole (end)

A

Monotrichous

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18
Q

Flagellar Arrangements: multiple flagella located at one end

A

Lophitrichous

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19
Q

Flagellar Arrangements: flagella located at both ends

A

Amphitrichous

20
Q

Flagellar Arrangements: flagella scattered over entire surface

A

Peritrichous

21
Q

Flagellar Arrangements: without flagella

A

Atrichous

22
Q

How do bacteria move in response to stimuli? (short answer)

A

Chemotaxis – movement toward favorable chemicals such as nutrients (positive chemotaxis) or away from harmful chemicals (negative chemotaxis)

Phototaxis – movement toward (or away from) light

Attractant – a positive stimulus which attracts bacteria

Repellent – a negative stimulus that bacteria avoid

23
Q

Describe axial filament

A

AKA endoflagellum
Wrap around some spiral-shaped bacteria

Contraction of these filaments produces a corkscrew-like motion of these bacteria

24
Q

Describe bacterial cell walls

What is its purpose and what is it composed of?

A

Provide structure and shape and protect cell from osmotic forces
Assist some cells in attaching to other cells or in resisting antimicrobial drugs
Destroyed with antibiotics
Give bacterial cells characteristic shapes
Composed of peptidoglycan
Two basic types of bacterial cell walls, Gram-positive and Gram-negative

25
Q

Describe peptidoglycan

A

Composed of a network of repeating sugar molecules and proteins (sometimes other molecules)

NAM and NAG are the repeating sugary units

N-acetylglucosamine = NAG

N-acetylmuramic acid = NAM

Tetrapeptides hang off of NAM to create cross-beams

26
Q

Describe gram-positive cell walls

A

Relatively thick layer of peptidoglycan

Contain unique polyalcohols called teichoic acids

Appear purple following Gram staining protocol

Up to 60% mycolic acid (lipid wall) in acid-fast bacteria helps cells survive desiccation (no peptidoglycan at all, purple shows as a false positive due to mycolic acid)

27
Q

Describe gram-negative cell walls

A

Have only a thin layer of peptidoglycan

Outer membrane beyond the peptidoglycan contains phospholipids, transport proteins (porins), and lipopolysaccharide (LPS or endotoxin)

May be impediment to the treatment of disease

Appear pink following Gram staining protocol

28
Q

What is diffusion?

A

The movement of particles from region of high concentration to low concentration.
Tends to continue until evenly distributed throughout the medium.

29
Q

What is osmosis?

A

The diffusion of water across a semi-permeable membrane

Movement of water molecules from an area of high concentration of water to an area of low concentration of water – another way of thinking about it is to say water moves from an area of lower particle concentration to an area of higher particle concentration

Solutions are named based upon relative solute concentration as compared to cells:

30
Q

What is an isotonic solution?

A

equal solute concentrations in cell and solution

31
Q

What is a hypotonic solution?

A

lower concentration of solutes in the solution

32
Q

What is a hypertonic solution?

A

higher concentration of solutes in the solution

33
Q

What is active transport?

A

Protein mediated – proteins act as carrier molecules

Molecules that are needed inside the cell can be transported against the concentration gradient (from an area of LO concentration to an area of HI concentration)

34
Q

Describe cytoplasm of bacteria

A

Cytosol – Liquid (80% water) portion of cytoplasm – being the primary site of bacterial metabolic reactions, this solution also contains proteins, metabolic enzymes, lipids, ribosomes, ions, carbohydrates, RNA, electrolytes, the monomers to build organic molecules, etc.

Inclusions – May include reserve deposits of chemicals like carbohydrates, phosphates, lipids, air bubbles, etc.

Endospores – Unique protective structures only produced by some bacteria that are a defensive strategy against unfavorable conditions

Nonmembranous Organelles

  • Ribosomes
  • -Sites of protein synthesis
  • Cytoskeleton
  • -Plays a role in forming the cell’s basic shape
35
Q

Describe endospores

A

“Hibernative” state formed by some bacteria during times of environmental stress.

Spores are highly resistant to drying & temperature extremes and UV radiation and pH changes . . .
(can survive boiling water for hours!)

Spores can remain dormant for millennia (1000s of years) before being reactivated

36
Q

What is sporulation?

A

the process of forming spores

37
Q

What is germination?

A

spore returning to the vegetative (growing) state

38
Q

Describe the nuclear area aka nucleoid

A

The DNA of a bacterium is not contained in a nucleus (not surrounded by a separate membrane)

The bacterial chromosome is ONE continuous circular loop of
double-stranded DNA

The chromosome is attached to the inner surface of the cell membrane at a spot called the origin (replication begins here)

Occasionally smaller, extrachromosomal loops of DNA called plasmids can be seen separate from the nuclear area

39
Q

Describe ribosomes of bacteria

A

Composed largely of rRNA and some protein, ribosomes are the ‘protein factories’ of the cell, responsible for translating RNA to polypeptides and proteins.

Each bacterial ribosome consists of two subunits
30S
50S
Total 70S
S= Sedimentary rate (rate of which it settles)

40
Q

Describe archaeal cell walls and cytoplasmic membranes of bacteria

A

Most archaea have cell walls

  • Do not have peptidoglycan
  • Contain variety of specialized polysaccharides and proteins

All life, including the archaea, have cytoplasmic membranes for the same basic reasons

  • Maintain electrical and chemical gradients
  • Control import and export of substances from the cell
41
Q

Describe eukaryotic cell walls

A

Fungi, algae, plants, and some protozoa have cell walls

Composed of various polysaccharides
Plant cell walls composed of cellulose
Fungal cell walls composed of cellulose, chitin, and/or glucomannan (yeasts)
Algal cell walls composed of a variety of polysaccharides

42
Q

Describe eukaryotic cytoplasmic membranes

A

As with all life, eukaryotic cells have cytoplasmic membranes, and, like prokaryotic membranes, they are a fluid mosaic of phospholipids and proteins that control movement into and out of cell

Contain steroid lipids (cholesterol) to help maintain fluidity (stability)

Contain regions of lipids and proteins called membrane rafts

43
Q

Describe eukaryotic ribosomes

A

Only minor structural differences compared to prokaryotic ribosomes

There are still two subunits, but each are larger than prokaryotic
a large 60S subunit + a small 40S subunit

They combine to form an 80S ribosome

44
Q

Describe the nucleus

A

Nucleus: contains DNA bound to histones and surrounded by
double-membrane (nuclear envelope) with small pores (nuclear pores)

The DNA can be found in the form of chromatin or chromosomes

Chromatin- in this state 90% of time, uncondensed (opened up and usable)

Chromosomes- in this state 10% of the time, condensed (compact and movable)

Nucleolus:- condensed regions of DNA where several types of RNA is being synthesized

45
Q

Describe mitochondria of eukaryotes

A

Major site of energy (ATP) production for the cell. Mitochondria have both an inner and outer membrane (double membrane)

Enzymes within the matrix (fluid) and cristae (folds in the inner membrane) are involved in the synthesis of ATP via oxidative phosphorylation (cellular respiration)

Mitochondria replicate by binary fission have their own circular DNA & 70S ribosomes

46
Q

Describe chloroplast

A

Membranous inner sacs called thylakoids contain the chlorophyll and enzymes involved in photosynthesis (making sugars from carbon dioxide and sunlight)

Like mitochondria, chloroplasts replicate within the cell by binary fission and have their own circular DNA & 70S ribosomes

47
Q

Explain the endosymbiotic theory (7pt short answer)

A

Eukaryotes formed from union of small aerobic prokaryotes with larger anaerobic prokaryotes (15x more energy)

Smaller prokaryotes became internal parasites
Parasites lost ability to exist independently
Larger cell became dependent on parasites for aerobic ATP production
Aerobic prokaryotes evolved into mitochondria
Similar scenario for origin of chloroplasts

Proposed by Lynn Margulis in 1966 – rejected by 15 scientific journals

Hydrogen hypothesis filled in many blanks to her theory

Microbiology (7 decks)

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