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Microbiology 1 > Lecture #2 - Cell Structure & Function > Flashcards

Lecture #2 - Cell Structure & Function Flashcards

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1
Q

What are the relative sizes of objects & what microscope? Review slide 2

A

done

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2
Q

Large protozoa

A

euk microbe

  • has euk cell structure
  • larger than a prok, but smaller than a plant
  • light microscope
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3
Q

RBC’s

A

human cell

  • have to go 1 by 1 (small)
  • @ maturity, they lose all their internal compartments to be smaller
  • no organelles
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4
Q

Describe chloroplast

A

used to be prok. syn. bacteria (unicellular bacterium) which is why its large
- according to endosymbiotic theory

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5
Q

Mitochondria

A

used to be prok. syn. bacteria (unicellular bacterium) which is why it’s large

  • according to endosymbiotic theory
  • an organelle, inside of Euk cell
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6
Q

Describe Chlamydia

A

bacteria

  • OBLIGATELY INTRACELLULAR (sounds like a virus)
  • smaller than bacteria (b/c cell provides a lot for it)
  • go into Euk cell to facilitate infection (goes into RT, & cytoplasm of cell where it’ll grow)
  • antiobiotic that goes into ECF & cytoplasm of cell has GOOD TISSUE PENETRATION (blood –> tissue –> ECF –> cytoplasm to find target)
  • DON’T KNOW HOW TO GROW IT (need a cell, so have to use nucleic acid testing (looking for genetic material)
  • had ribosomes (& lots of cellular material) that made it large but lost a lot to make it smaller
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7
Q

If someone had chlamydia & got a swab. After its been spread on petri dish & incubated, will there be chlamydia growth the next day?

A

NO - b/c that growth med. will not be what they need

- still don’t know how to grow it

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8
Q

Describe rickettsia

A

an INTRACELLULAR ORGANISM

  • ancestor of mitochondria
  • goes into a cell
  • may have got trapped to act like a mitochondria (replicated)
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9
Q

Describe viruses

A

OBLIGATE INTRACELLULAR parasites

- small packet of genetic material & bare min. needed for life cycle

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10
Q

Describe Ribosomes

A

made up of protein & rRNA

- organelle that doesn’t originate from cell - smaller

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11
Q

Order from largest to smallest (relative sizes of objects)

A
  1. Dog
  2. Human heart
  3. Tick
  4. Human egg
  5. Large protozoa
  6. RBC
  7. Chloroplast
  8. Bacteria (prok. uni - but exceptions)
  9. Mitochondrion
  10. Rickettsia
  11. Chlamydia
  12. Virsuses
  13. Ribosomes
  14. Proteins
  15. Diameter of DNA
  16. AA’s
  17. Atoms
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12
Q

What can be seen with the unaided human eye?

A

tick, human heart, dog

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13
Q

What can be seen with the compound light microscope?

A

Chlamydia, rickettsia, mitochondrion, bacteria, chloroplast, RBC, large protozoa, human egg, tick

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14
Q

What can be seen with the scanning electron microscope?

A

Ribosomes, viruses, chlamydia, rickettsia, mitochondrion, bacteria, chloroplast, RBC, Large protozoa, human egg, tick

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15
Q

What can be seen with a transmission electron microscope?

A

AA’s, diameter of DNA, proteins, ribosomes, viruses, chlamydia, rickettsia, mitochondrion, bacteria, chloroplast, RBC, large protozoa, human egg

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16
Q

What does a compound light microscope use?

A

visible light to illuminate cells

  • light bulb
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17
Q

Light bulb

A

= low energy source to illuminate specimen, therefore limitations

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18
Q

What are the many different types of light microscopy?

A
  • Bright-field
  • Phase-contrast
  • Dark-field
  • Fluorescence
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19
Q

What is a Bright-field scope light microscope?

A

• Specimens are visualized because of differences in contrast between specimen (cell of interest) and surroundings (background they’re on)
- DARK cells on BRIGHT background

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20
Q

Why do we call the bright-field scope a compound light microscope?

A

b/c it compounds the magn. that the 1st lens is giving you by further magnifying it through a 2nd lens

  • Two sets of lenses form the image
  • Objective lens (can choose/change) (usually 10x -100x mag.) & ocular lens (can’t change) (usually 10x – 20x mag.)
  • Total magnification = objective magnification ✕ ocular magnification
  • Maximum magnification is ~2,000✕
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21
Q

Condenser

A

creates a beam of light so it’s condensed/focused to be able to move through the microscope slide

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22
Q

Describe the magnification light path

A
  1. Light from light source
  2. Condenser - focuses it into a beam so it’s interacting with the specimen
  3. Once the specimen comes through the objective lens (10X, 40X, or 100X (oil)), it’s inverted in position & magnified to whatever you chose
  4. When the specimen comes through the ocular lens (10X) it is inverted again to OG position & magnified further, so even larger
  5. Then you see it at either 100X, 400X, 1000X
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23
Q

Magnification

A

the ability to make an object larger

- e- microscopes are 2000x magnification or more

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24
Q

Resolution

A

(AKA resolving power)
the ability to distinguish two adjacent objects as separate and distinct
- the amount of light passing b/t will create a clear image & how much space is needed to do that is the resolving power

think: 2 hands touching & able to see 2 hands (not perfectly lined up)

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25
Q

What is the limit of resolution for light microscope?

A

about 0.2 μm

  • MIN distance that 2 objects need to be apart from 1 another, in order for that microscope to show you separate objects
  • if those 2 objects are less than that distance apart (closer together), the microscope cannot get energy source that it’s using b/t them, so you see a blurry image (not separate objects)
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26
Q

Limit of resolution for light microscope is about 0.2 μm, what does this mean? What happens if it is smaller or bigger?

A

If we report a resolving power/limited resolution = to 0.2 μm. That means, this microscope with the energy source it’s using can provide light that can only get through spaces that are AT LEAST 0.2 μm

  • anything BIGGER works too
  • anything smaller, the light CAN’T fit, therefore can’t energize sample or provide a clear image
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27
Q

If we had a better microscope, what would we expect the limit of resolution value to be?

A

SMALLER - b/c then those 2 objects can be even closer together & you can still see a clear image (ex: e- microscopes)

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28
Q

How do we calculate magnification?

A
  • Magnification = ocular x objective
  • ex. Ocular = 10x, objective = 40x
  • Magnification = 10 40 = 400x
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29
Q

Resolution explained

A
  • The ability of a lens to distinguish small objects that are close together
  • Ex) resolving power of 0.2μm
  • Two points can be distinguished if they are at least 0.2 μm apart
  • Light must pass between two points for them to be viewed as separate objects (providing clarity)
  • As wavelength decreases resolution improves
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30
Q

Wavelength & energy are _______

A

INVERSELY PROPORTIONAL

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31
Q

Shorter wavelength =

A

↑ ENERGY

↑ RESOLUTION

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32
Q

Longer wavelength

A

↓ ENERGY

↓ RESOLUTION

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33
Q

Ex’s of ↑ energy - shorter wavelengths

A
  • gamma rays
  • x-rays
  • ultra-violet rays
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34
Q

↑ energy - shorter wavelengths =

A

DANGEROUS b/c energy it carries can be transferred all the way to DNA for ex & can result in damage/mutation that can lead to cancer
- ↑ energy radiation is dangerous b/c energy it carries will then be transferred to other objects its in contact with

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35
Q

Ex’s of ↓ energy - longer wavelengths

A
  • infrared rays
  • microwaves
  • radio waves
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36
Q

↓ energy - longer wavelengths =

A

safer

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37
Q

If you have 2 microscopes, both with the same magnification, but diff. resolving powers. Will they provide the same image?

A

NO - b/c as you magnify, it doesn’t mean the resolution maintains clarity
- ex: zooming on phone doesn’t mean it will still be clear

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38
Q

GREATER magnification…

A

DOESN’T mean/guarantee resolution will also increase; dependent on microscope you chose

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39
Q

Throw ink-covered objects at target (“E”):

  1. Basketballs - longest wavelength
  2. Tennis balls - slightly shorter wavelength
  3. Jelly beans
  4. Beads - shortest wavelength
A
  1. CANNOT fit b/t arms, poor resolution
  2. Fit b/t arms, resolution improves

3 & 4. As DIAMETER of objects thrown DECREASES, GREATER NUMBERS pass b/t the arms & the RESOLUTION INCREASES (no size limitation - ton of clarity)

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40
Q

Improving contrast results in…

A

a better final image

- STICK OUT BETTER, BETTER CLARITY & you can see better dets of cell

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41
Q

Staining improves _____

A

CONTRAST

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42
Q

How does staining improve contrast?

A

• Dyes are organic compounds (carbon containing CH2-COO-) that bind to specific cellular materials (inside the cell)

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43
Q

Ex’s of common stains:

A

methylene blue, safranin, and crystal violet

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44
Q

What are the 2 types of staining?

A
  1. Simple staining

2. Differential stains

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45
Q

Simple staining

A

One dye used to color specimen
- just shows if something is THERE or NOT - 1 size fits all (1 colour only)

think: taking attendance at exam, are you there or not?

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46
Q

Chromophore

A

colored portion of a dye
- colour your cell will appear as a conseq. of that dye adhering to portions of the cell or cellular structures

Ex: red chromophore

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47
Q

What are the 2 types of simple stains/dyes?

A
  1. Basic dye

2. Acidic dye

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48
Q

A living cell, whether it’s a bacterial cell, fungal cell or human cell, will….

A

ALWAYS HAVE A NET (-) CHARGE

  • if you apply a basic stain it will adhere
  • if you apply an acidic stain it will repel
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49
Q

Basic dye

A

positively charged chromophore
• Binds to negatively charged molecules on cell surface

  • (+) at pH=7
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50
Q

Acidic dye

A

negatively charged chromophore
• Repelled by cell surface
• Used to stain background (cells will stick out)
• Negative stain

  • (-) at pH=7
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51
Q

Ex of basic stain:

A

crystal violet - cells are violet

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52
Q

Ex of acidic stain:

A

nigrosin - background is purple ish

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53
Q

How to prepare samples for staining

A
  1. PREPARING A SMEAR
    - Spread culture in THIN film over slide
  2. a. Dry in air
    OR
    b. HEAT FIXING & STAINING
    - Pass slide through flame to heat fix
    (think: cleaning pan next day - hard to get off, dehydrating sample so it is stuck on slide, therefore it doesn’t get rinsed off in next step)
    - Flood slide with stain (engaging with cells or background - depending on if basic/acidic)
  3. Microscopy
    - Place drop of oil on slide; examine with 100X objective lens
    - not gonna get differentiation, just able to see if it’s there
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54
Q

Gram - & gram + will BOTH…

A

be (-)ly charged on their external surface

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55
Q

What is the difference b/t gram + & gram -?

A

architecture of their cell wall is different

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56
Q

The Gram Stain

A

a differential stain; a staining procedure where you can create differences based on the cell structure, that allow you to identify if the bacterium that you have in your sample is gram + or gram -

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57
Q

What are 2 reasons to do the gram stain?

A
  1. Narrows the pool of suspects
    - so you can investigate knowing which it is
  2. Gram + or gram - are targeted by certain antibiotics
    - & some antibiotics target both
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58
Q

If someone has a gram + infection & you give them an antibiotic that targets a gram + bacterium…

A

the good thing is you leave your gram - bacteria that are good alone
- the drug won’t harm all of the good bacteria - means better toxicity just to what you want so general state of health can be more or less maintained

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59
Q

Gram + general features

A
  • plasma membrane

- THICK peptidoglycan

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60
Q

Gram - general features

A
  • plasma membrane
  • THIN peptidoglycan layer
  • outer membrane
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61
Q

What is the Gram Stain procedure?

A
  1. Apply CRYSTAL VIOLET stain purple & basic:
    Gram + = purple
    Gram - = purple
    Human cell = purple
  2. Apply IODINE = a mordant - intensifies bound stain
    Gram + = purple
    Gram - = purple
    Human cell = purple
  3. Apply ALCOHOL = a decolourizer
    Gram + = purple (trapped in cage like structure - alc bulked them up so they can’t get mordant & crystal violet out)
    Gram - = colourless
    Human cell = colourless (b/c no cell wall)
  4. Apply SAFRANIN (pink & basic) - sticks to any living cell
    Gram + = purple (pink will stick but will stay purple b/c it never came off & its darker)
    Gram - = pink
    Human cell = pink
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62
Q

What are the differential stains?

A
  • The Gram Stain
  • Acid fast stain
  • Endospore stain
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63
Q

The Gram Stain

A
  • Differential Stains
  • Gram positive
  • Gram negative
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64
Q

Gram positive

A

cells that retain a primary stain

• Purple

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65
Q

Gram negative

A

cells that lose the primary stain
• Take color of counterstain
• Red or pink

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66
Q

Why do gram + not turn pink after step 4?

A

purple is darker so it will trump

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67
Q

If I gave you a staining procedure, & in that staining procedure it was like a gram stain but everything was mixed up/added diff. things. If in step 1 of this gram staining protocol, inside of crystal violet, she added a yellow basic stain & in step 4 instead of safranin, I added a black basic stain, what will be the outcome for that gram stain result/ For a gram +, - & euk?

A

everything will be BLACK - b/c you added (+)ly charged stains, but you added the darker one AFTER the alcohol decolourization so it’s gonna stick to gram -‘s just like safranin would have, sticks to gram +’s & is gonna trump yellow b/c it’s darker

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68
Q

Acid fast stain

A
  • differential stains
  • Detects mycolic acid in the cell wall of the genus Mycobacterium
  • Mycobacterium – retains primary stain
    • Fuchsia (pink)

Anything else on slide – color of counterstain
• Blue

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69
Q

Endospore stain

A
  • Endospores retain primary
  • Green - malachite green - sticks to endospores if present
  • Cells counterstained
  • Pink - safranin + - stick to all things that contain a - charge
  • Ex. Bacillus anthracis spores.

ONLY produced by SOME bacteria
- always be a gram + bacterium

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70
Q

Mycobacterium genus

A

has plasma membrane, gram +, & MYCOLIC ACID (hydrophobic) as the outside of their peptidoglycan

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71
Q

Mycolic acid

A
  • hydrophobic
  • outside of their peptidoglycan
  • unique to members of mycobacterium genus
  • can engage with things ALSO hydrophobic
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72
Q

Mycobacterium CANNOT…

A

undergo a gram stain

- so has to do AFS

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73
Q

Will mycobacterium be able to engage with a basic or an acidic stain?

A

No - b/c “like dissolve like”

  • can engage with things that are also hydrophobic
  • acidic/basic carry a charge so it’s hydrophobic
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74
Q

When you gram stain a gram + bacterium, what’s the outcome you expect?

A

the stain to remain purple b/c it’s trapped, it won’t come out (not outer membrane)

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75
Q

Mycobacterium

A

retains primary stain

• Fuchsia (pink) - carbol fushin sticks to mycolic acid

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76
Q

Methylene blue (basic & blue)

A

Anything else on slide – color of counterstain
• Blue - methylene blue (basic & blue)
- basic is +, so blue stain will stick to cells (any cell that’s not acid fast); so other gram +’s, -‘s, human cells that might be in the sample (anything with a net - charge on its outermost surface, methylene blue will try to stick too trying to create a differential output

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77
Q

What are endospores?

A

resilient structures

ex: if a bacterium finds themselves in a situation where water/nutrients are limited, they can enter in spore state (metabolically inactive) where he hides out until conditions become more fav. for survival, then he comes out & wakes up & starts metabolism & being normal again
ex: rice
- when they fuel replication from those conditions, the microbial count goes up!
- & if you take it & put it on fridge, it will grow slowly
- can destroy with an autoclave- combines temp & pressure for ex

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78
Q

How would you expect a (-) endospore stain to look?

A

everything would be pink

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79
Q

If everything here was pink (- endospore stain), would you be able to tell me what the result of a gram stain is?

A 
def not - b/c you'll have bugs there that the pink is sticking too but you don't know if its gram + or - (it can be either)
- it's only when you know it produces endospores, that you know it must be gram + & therefore will produce a purple stain
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80
Q

If you chose this endospore forming organism, but instead chose to do a gram stain. What would I see as a result of the gram stain on an organism that produces a (+) endospore stain?

A

purple - b/c it’s an endospore forming & gram + are the only kind of bug that’ll form an endospore & it’s not all

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81
Q

What does the result of this AFS mean (on slide with blue and pink)? How would you interpret the results?

A

mycobacterium is gonna be there - pink will be members of mycobacterium genus

  • BLUE (hydrophilic stuff) is other cell types - everything else that’s there
  • (+) result
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82
Q

How would you expect this AFS stain to look if it was a (-) result?

A

no pink - everything blue (just blue would tell you no mycobacterium, but won’t tell you gram +/-)

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83
Q

Phase-contrast microscopy

A

Phase ring amplifies differences in the refractive index of cell and surroundings

• Improves the contrast of a sample without the use of a stain
- therefore, doesn’t constitute characteristics of viability

• Allows for the visualization of LIVE SAMPLES
- so you study further or to protect if it’s the last one

• Resulting image is dark cells on a light background

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84
Q

Dark field microscopy

A
  • inverted like how we saw in the previous
    • Specimen is illuminated with a hollow cone of light

• Only refracted (bent) light enters the objective
- everything else will go around so it’s not gonna make its way up through the lens & will not be part of the image you get as a result of the eye piece

• Specimen appears as a bright object on a dark background

  • Used to observe bacteria that don’t stain well (meaning it’s gonna be hard to visualize)
  • Ex) Treponema pallidum – the causative agent of syphilis
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85
Q

Fluorescence microscopy

A
  • Used to visualize specimens that fluoresce
  • Emit light of one color when illuminated with another color of light

absorption wavelength: characteristic of the chemical properties of a fluorescent particle

  • have to know what this is so it can be absorbed
  • have to strike this with light of a particular wavelength

emission wavelength: what’s given off to provide the fluorescents that you see

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86
Q

If absorption wavelength is 450 nm, what can you say about the emission wavelength?

A

LARGER wavelength - b/c of the energy that was absorbed, some of it was converted to heat - so not all of it will be there
- b/c there is a loss of heat, when this gets absorbed you’re gonna have less that’ll come out which means that wavelength must be larger b/c larger wavelength is lower energy which counts for amount spent in absorption activity

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87
Q

Cells may fluoresce naturally

A

• Ex. Photosynthetic Cyanobacteria (ORIGIN OF THE EUKARYOTIC CHLOROPHYLL) have chlorophyll
- have photosyn. pigments that have the opportunity to absorb light

  • Absorbs light at 430 nm (blue-violet)
  • Emits at 670 nm (red)
88
Q

Or after staining with Fluorescent dye

A

Ex) DAPI (has affinity for DNA) specifically binds to DNA (allows you to localize it)
- anything in fluorescent blue is an indication of DNA

89
Q

Immunofluorescence

A
  1. Take antibodies (highly specific to 1 antigen)
    - HIGH SPECIFICITY of binding to a target
  2. Couple it to a fluorescent particle on the other end
  3. That fluorescent particle has a certain absorption & emission wavelength
  4. Take a cell, & apply the antibody, knowing fully well it will go in & bind to a SPECIFIC REGION of the cell
  5. TREAT cell with the absorption wavelength, & then leave it alone so it emits & you have a detector to pick up on the emission wavelength

Can use a # of antibodies, targeting a # of diff fluorescent particles, in order to allow the opp. to be able to see things inside the cell

BENEFIT: more bang for your buck - b/c you’re not just staining for 1 thing, but for other things as well!

90
Q

Differential interference contrast (DIC) microscopy

A
  • Uses a polarizer to create two distinct beams of polarized light
  • Gives structures such as endospores, vacuoles, and granules a three- dimensional appearance (but still a light microscope - so not amazing but not perfect)
  • Structures not visible by bright-field microscopy are sometimes visible by DIC
  • can see curvature & dimensions of nucleus
91
Q

What microscopes improve Contrast in Light Microscopy

A
  1. Phase-contrast microscopy
  2. Dark field microscopy
  3. Fluorescence microscopy
92
Q

What microscopes image cells in 3-D?

A
  1. Differential interference contrast (DIC) microscopy

2. Confocal scanning laser microscopy (CSLM)

93
Q

Confocal scanning laser microscopy (CSLM)

A

• Uses a computerized microscope coupled with a laser source to generate a three- dimensional image (will see layers of the cell b/c of where the laser is engaging)

  • when you get that layer, you take it & put it together with another layer of laser image - stack on top of one another)
  • building image of the cell
  • Computer can focus the laser on single layers of the specimen
  • Different layers can then be compiled for a three-dimensional image (can tell a lot of dets)

• Resolution is 0.1 μm for CSLM (μm = light microscope)
- not clearest ever

94
Q

μm =

A

LIGHT microscope

95
Q

e- microscopes =

A

nm ranges of resolution

- smaller than light microscopes

96
Q

Electron microscopes

A

use electrons instead of photons to image cells and structures
• Wavelength of electrons is much shorter than light (therefore higher E) –> higher resolution

BETTER UPPER LIMIT OF MAGNIFICATION
- also even if you HOLD magnification constant the resolution beats a light microscope!

97
Q

Two types of electron microscopes:

A
  • Transmission electron microscopes (TEM)

* Scanning electron microscopes (SEM)

98
Q

Transmission Electron Microscope

A
  • Electron beam focused on specimen by a condenser
  • Magnets used as lenses
  • Electrons that pass through the specimen are focused by two sets of lenses
  • Compound microscope (combining 2 things that are happening)

• Electrons strike a fluorescent viewing screen (providing the image)

  • magnet is condenser & inverted same way as light microscope
  • High magnification and resolution (0.2 nm) (nm = 10^-9m)
  • Specimen must be very thin (20 – 60 nm)

*stained adhered differently based on the characteristics of those structures, which means that now the image that’s created as the e-‘s are deflected back to the viewing screen is gonna be heavily detailed

99
Q

Unstained cells do a poor job of scattering electrons

A
  • won’t be able to see anything - b/c e-‘s have poor penetrin

• Must be stained with (heavy) metals (means sebitonic particle # is high & so e- # is high, creates e- density that allows you to visualize when e- beam strikes the sample)–> lead or uranium

  • therefore heavy metal stain is gonna be e- dense
  • stick to thin section diff. on a ribosome then it would stick to a DNA region/membrane

• Bind to cell structures to make them more electron dense

• Enables visualization of structures at molecular level
- can see inside of cell (not alive not) but lot of work

THINK: egg - has to cut to visualize the inside

  • slice to see diff. dets
  • BUT cell is 60-80% water
  • think: cutting water balloon
  • so must permeate it with a resin - resin is injected as a liquid to polymerize & harden once it goes inside
  • then all internal materials of that cell are fixed & isolated to 1 particular region
  • then use a microtome = diamond knife to do thin sectioning
  • see diff. in texture, see morphology of nucleoid region where chromosome located, see characteristics of mem. cross-section & all fine dets on surface on cell
100
Q

Microtone

A

= diamond knife to do thin sectioning

101
Q

When to use a Transmission Electron Microscopy (TEM)

A

when you wanna see INSIDE of cell

102
Q

Light vs. Electron microscope (450x)

A

e- microscope:

  • way better than light
  • even when magn. is constant
  • great solution

therefore, even when magn. is set constant, the e- microscope provides such a great clarity b/c resolving power is gonna be much smaller than the light microscope

103
Q

Scanning Electron Microscopy (SEM)

A

• Specimen is coated with a thin film of heavy metal - e- dense! (e.g., gold)
• An electron beam SCANS the object
• Scattered electrons are collected by a detector, and an image is produced
• Allows an accurate 3D image of specimen’s SURFACE.
- clarity
- can see surface dets (round, amount of space, arrangement, contour)
- good job at providing external dets

104
Q

Scanning Electron Microscopy (SEM) process

A

e-‘s sprayed on an angle on the surface
- thin coat of heavy metal adhering to the side

e- beam slowly scans

  • provides it’s blunt at bottom, narrow at top, out like this on side
  • fine surface dets
105
Q

When to use a Scanning Electron Microscopy (SEM)

A

when you want to see OUTSIDE of cell (contour)

106
Q

Prokaryotes (before nucleus)

A
  • bachelor suite (everything happens in the open - no separate compartments, everything within boundaries of plasma membrane)

• NO membrane bound nucleus or organelles
- genetic material floating

• Generally smaller than eukaryotes
- pack a lot less

  • Simple internal structure
  • Divide by binary fission (EQUIVALENT OT MITOSIS)

• Most are unicellular
- if they’re multi they will not have tissue differentiation (just will be power in #’s)

107
Q

How is binary fission in prok’s equivalent to mitosis?

A
  • such that in the absence of any error during DNA replication, this process produces genetically identical daughter cells, so you don’t expect any genetic variation - it’s meant solely as a means of increasing cell #
  • diff. when we do mitosis, we get a total cell # that’s higher
  • but when BF is completed they get a whole new organism b/c they are unicellular
108
Q

Bacteria (Eubacteria)

A

true bacteria

• Diverse metabolism

  • allows them to explore so many of the diff. environments that exist on the face of the earth
  • means ton of diversity & a vital role in every ecosystem found (creating imp. characteristics - if removed, it’ll be impactful)

• Live in a broad range of ecosystems

• Pathogens (cause disease) and non-pathogens (cannot cause disease)
- a lot of change can potentially occur - not consistent all throughout life (genetically plastic)

109
Q

Archaea (Archaebacteria)

A

NOT BACTERIA - only thing they share with bacteria is their prok. cell structure

  • Diverse metabolism
  • Live in extreme environments
  • that allow them opp. to thrive, b/c can live under low pH conditions sometimes & increased salt
  • but can also live in mild ones (like our gut)
    • some can live @ 30% NaCl (& still can maintain water nonetheless), our blood is 0.9%

• Non-pathogens

  • has capacity to change
  • through picking something up (a weapon)
  • via a gene set that can be produced into a toxin or capsule that can lend ability to cause disease
110
Q

Cell Morphology

A
  • -> shape!
  • diff. in morphology have nothing to do with intelligential ability, height, weight, interpret lang, etc.
  • as well as nothing to do with genetics of cell, comparisons & contrasts of other species, just a unique characteristic to fully understand the organism
  • physical characteristic totally unrelated to almost all other characteristics
  • shape gives a bit of a push to a direction/hint of the cause based on how it looks to diagnose an infection
111
Q

Cell Morphology types

A
  • Coccus (pl. cocci)
  • Bacillus (pl. bacilli)
  • Spirillum (pl. spirilla)
  • Cells with unusual shapes
  • Budding & appendaged bacteria
  • Filamentous bacteria
112
Q

Coccus (pl. cocci)

A

• Roughly spherical
• Ex) Streptococcus pyogenes
- causes strep throat/flesh eating disease (organisms are not the same strain)
- like “tall” in name

113
Q

Bacillus (pl. bacilli)

A
  • Rod shaped (asymmetrical shape)

* Ex) E. coli

114
Q

Spirillum (pl. spirilla)

A
  • Spiral shaped

* Ex) Spirillum volutans

115
Q

Cells with unusual shapes

A

• Spirochete
- LONGER in length, allows them to bend (FLEXIBLE)

• Ex) Treponema pallidum
- cause disease of syphilis

116
Q

Budding & appendaged bacteria

A

appendaged - allows opp. to make contact with the surface (attachment is imp.)

  • appendage to allow opp. to bind to a particular structure
  • stick to surface to not get flushed away
  • we are flushing clean (vomit, urinate, defectate, etc.), these so we need to have an organism that can grab on if it has capacity to stick when it gets deposited to inside of body, otherwise all these self-cleaning mech’s are gonna eject organism from where it came from

Ex) Caulobacter crescentus

117
Q

Filamentous bacteria

A

Ex) Streptomyces griseus
- produces imp. antibiotics

  • increase SA for things like absoprtion
  • b/c long & thin
  • better opp. to take nutrients in
118
Q

Morphology typically does not…

A

Morphology typically does not predict physiology, ecology, phylogeny, etc. of a prokaryotic cell

119
Q

Cell Morphology may be…

A

selective forces involved in setting the morphology

120
Q

What are the selective forces that may be involved in setting the morphology?

A

• Optimization for nutrient uptake (small cells and those with high surface-to- volume ratio)

  • SA:V will do better
  • b/c they have better/more membrane to interact with their environ., allowing the opp. for the cell to protect itself against environ. changes
  • nutrients come in, get distributed & cell is benefiting from that

• Swimming motility in viscous environments or near surfaces (helical or spiral-shaped cells)
- if a cell has a particular shape its able to cut a lot of that material so its able to disseminate & relocate to other locations

• Gliding motility (filamentous bacteria)

  • filamentous structures have opp. to glid over the surface (move from A –> B in order to max. contact with environ., use physical support as a means of locomotion)
  • use physical support as a means of locomotion rather than free-living movement
121
Q

Describe cocci & the different types

A

cooci - individual cell structures
- can choose to arrange themselves in more complex patterns

  • -if they choose to get together in a more high level organization, they are still individualized cells that live autonomously
  • still indiv. cells that are free living but chose to get together
  • diplococcus (diplococci)
  • diplobaccillus (diplobacilli)
  • streptococcus (streptococci)
  • staphylococcus (staphylocci)
122
Q

Streptococcus (streptococci)

A

doesn’t have anything to do with the name but ppl chose to include morphological dets & arrangements within the name/genus name (strepto)

123
Q

If you took a throat swab from a person who has streptococcal infection (strept throat) & you looked at it under the microscope & saw what would you be thinking in terms of the causative agent of that person’s pharyngitis?

A

strept throat - whereas if you didn’t see that or if you saw a baccilis, autonomically you’d be realizing its something else

124
Q

Mono

A

manifests almost same as strept throat, doctors confuse/misdiagnose

  • virus WOULDN’T grow freely b/c it’s not a free living cell, so you wouldn’t see anything if you took a throat swab to try to identify
  • therefore, wouldn’t see infection agent b/c virus’ can’t be cultured that way (would just see normal flora)
125
Q

Why would the cocci WAIT until they have power in #’s to do something bad?

A

a lot easier to kill one

- then they will start transcribing/translating a toxin or something

126
Q

Prokaryote Sizes

A
  • Average
    • E.coli (asymmetrical) ~ 1.0x3.0μm
    • Staphylococcus aureus ~ 1.0 μm diameter
  • Very small
    • Mycoplasma (as genus more have cell wall) genitalium ~ 0.3 μm
  • exception
  • respon. for sexually transmitted infection (STI)
  • anomaly b/c it does NOT have a cell wall –> outermost component = plasma membrane (sounds like an ANIMAL cell b/c no cell wall)
  • also small b/c they’ve come to rely on the host for many things
  • extremely efficient - pack lighter
  • pathogenic & really tiny so when they enter body they can enter tight tissue
  • Very large
    • Epulopiscium fishelsonii ~ 80 x 600 μm.
127
Q

Mycoplasma (as genus more have cell wall) genitalium ~ 0.3 μm

A
  • very small
  • exception (as genus none have cell wall)
  • respon. for sexually transmitted infection (STI)
  • anomaly b/c it does NOT have a cell wall –> outermost component = plasma membrane (sounds like an ANIMAL cell b/c no cell wall)
  • also small b/c they’ve come to rely on the host for many things
  • extremely efficient - pack lighter
  • pathogenic & really tiny so when they enter body they can enter tight tissue
128
Q

Would you put Mycoplasma genitalium (very small prokaryote) in a gram +/- designation or not?

How would they look if you did a gram stain & they were part of the sample?

A

No

Appear pink - look like a Euk

  • b/c alc would destain their membrane & then go on & stain pink by the end
  • doesn’t mean gram - either, but just the way all organisms without a cell wall will appear
  • so gram staining not effective for identifying this b/c it will look like any gram - cell
129
Q

Cell Size and the Significance of Being Small

A

Surface-to-volume ratios, growth rates, and evolution
• Advantages to being small

• Small cells have more surface area relative to cell volume than large cells (i.e., higher S/V)
• Support greater nutrient exchange per unit cell volume
- distributes nutrients & have less to make everytime you have to make a new cell (b/c small & don’t have to make organelles)
• Tend to grow faster than larger cells
- v. efficient
- turn over cell a lot faster

130
Q

Significance of Being Small

A 
Large cell
V = 1
- membrane you're able to interact with your envir. with to bring nutrients in etc.
SA:V
↓↓↓: 1
ex) 2
Individual (small) cells
V = 1
- small, therefore tons of opp. to bring nutrients in & share those nutrients with entire volume on inside of cell
SA:V
↑↑↑:1
ex) 10
5x greater
131
Q

Lower limits of cell size

A
  • you wanna be small & pack light but you can only get so light before you can’t bring your essentials with you

• Cellular organisms <0.15 μm in diameter are unlikely (b/c can’t fit dets req. for survival (ribosomes ex)
- anything smaller they can’t fit key dets

  • Open oceans tend to contain small cells (0.2–0.4 μm in diameter)
  • Many pathogenic bacteria are also small (missing many genes whose functions are supplied to them by host)
  • rips out pages of recipe book they don’t use anymore b/c they grow it in garden
  • able to whizzle way in tissue (has to be small)
132
Q

What are key points of the Membrane Structure (Cytoplasmic membrane (cell or plasma membrane))?

A

• THIN structure that surrounds the cell
- thinner it is, the easier it will be for nutrients to be able to transit into cell & wastes to exit cell

  • Vital BARRIER that SEPARATES cytoplasm from environment
  • Highly SELECTIVE PERMEABLE BARRIER (can chose what goes in/out (control); enables concentration of specific metabolites and excretion of waste products
  • metabolites - necessary for metabolism & fuel generation (ex: ability to let glucose in)
  • waste products - imp. b/c can be toxic if accumulated
133
Q

What is a key defining characteristic of a cell? & why is this not one for viruses?

A 
CYTOPLASMIC MEMBRANE (cell or plasma membrane) is the key defining characteristic of a LIVING cell 
- prok, euks

BUT except viruses - b/c no plasma membrane, therefore no living features to be able to move things in/out & control things imp. for life

134
Q

What is the composition of membranes?

A
  • General structure is PHOSPHOLIPID BILAYER
  • Contain both HYDROPHOBIC (fatty acid) and HYDROPHILIC (glycerol-phosphate) components
  • Can exist in many different chemical forms as a result of variation in the groups attached to the GLYCEROL BACKBONE
  • Fatty acids point INWARD to form hydrophobic environment; hydrophilic portions remain EXPOSED to external environment or the cytoplasm
135
Q

Amphipathic

A

phospholipid bilayer is this b/c it has a head group that prefers interactions with water (hydrophilic) & tails that prefer interaction away from water (hydrophobic)

136
Q

Describe the glycerol backbone & attachments

A

has a head group that DETERMINES IDENTITY & also TAIL LENGTH & UNSATURATION that can also determine characteristics/behav. of the structure

ex: longer tails –> more sturdy
unsat. creates more fluidity

137
Q

How is the phospholipid bilayer based on the Hydrophobic Effect?

A

phospholipids naturally come together in water in order to promote fav. interaction & circularize (won’t be living in water)
- therefore, won’t be exposed b/c their touching water which is undesired but they become an uniform structure

138
Q

Imagine a beaker with oil and you put PL’s in. What will they do in terms of the motivation forming a higher level structure?

A

Will stick head groups to inside so they have fav. int with each other & tails pointing out getting fav. int. with oil (“hydrophobic like hydrophobic”)
- think: inverse micelle

139
Q

Ester phospholipids consist of:

A
  • 2 Fatty acids
  • Phosphate
  • Side chain (optional)
140
Q

Ester

A 
CH2-C=0
         |
        O 
         |
        C

carbonyl group attached
- impacts heat stability & beh.

141
Q

Amphipathic

A

has both polar and non-polar characteristics

- arranged to meet demands of both ends of molecule

142
Q

Polar

A

molecule carries full or partial charge

• Hydrophillic

143
Q

Non-polar

A

molecule is uncharged (CH2 - no charge - therefore non-polar)
• Hydrophobic

144
Q

What can we say about the bonds b/t N & H in +NH3?

A

e-‘s held closer to N b/c polar covalent bond

- therefore, partial +

145
Q

Cytoplasmic membrane

A
  • 8–10 nm wide
  • Embedded proteins
  • Stabilized by HYDROGEN BONDS and HYDROPHOBIC interactions
  • Mg2+ and Ca2+ help STABILIZE membrane by forming ionic bonds with negative charges on the phospholipids
  • SOMEWHAT fluid
146
Q

What particularly will be determining width of membrane?

A

LENGTH OF FA CHAINS

  • will determine how far apart head groups will be from 1 another
  • if you adjusted the FA tail length (bigger or smaller), the protein wouldn’t have portions that are hydrophobic contacting tails properly & portions that are hydrophilic contacting the tails properly
  • critical to have tail length how it should be otherwise like & like won’t be interacting as it should!
147
Q

What’s the net charge on a membrane?

A

(-)

148
Q

How do membranes stay together so nicely if they have a compounded net (-) charge?

A 
DIVALENT CATIONS (Mg2+ & Ca2+)
- bring (+)ity to bond & alleviate repulsion - stabilizes (-)ity so membrane don't have strong forces (repel) forcing it apart
149
Q

How is the larger structure held together in an organized way in the Cytoplasmic membrane? In the f.a tail region

A

WdW’s

  • weak int. b/t non-polar group
  • still take heat to break
150
Q

What interactions stabilize the 4 points on the protein and b/t the head groups in a Cytoplasmic membrane?

A

H BONDS & IONIC BONDS

- respons. for creating a higher level structure in these regions

151
Q

Explain how the Cytoplasmic membrane is somewhat fluid

A

VdWs require heat to break

  • monounsat tails allows VdW’s int. that req. heat to break
  • since tail is far apart - you are not forming VdW’s there so it creates a FLUIDITY
  • imp. to be somewhat fluid for optimal function
152
Q

Membrane proteins

A

• Outer surface of cytoplasmic membrane faces the environment

• In gram-negative bacteria, interacts with a variety of proteins (periplasmic proteins) that bind substrates or process large molecules for transport
- meaning diff. proteins floating in periplasmic space & outer surface will interact with those proteins

  • Inner surface of cytoplasmic membrane interacts with proteins involved in ENERGY-YIELDING REACTIONS and other important cellular functions
  • Integral membrane proteins
  • Peripheral membrane proteins
153
Q

Integral membrane proteins

A

Firmly embedded in the membrane

can be transmembrane integral or just integral

154
Q

Peripheral membrane proteins

A

One portion anchored in the membrane

  • usually attached to EC face of mem. or IC face attached to hydrophilic regions, usually H+ bonds & ionic int. (electrostatic int. b/t (+) & (-)ly charged areas)
  • to stay fixed
155
Q

Which proteins will you expect to find on the INNER surface of the plasma membrane of a bacterium, that’s involved in the production of energy?

A

on inner mitochondrial membrane is ETC
- the inner surface of cytoplasmic membrane is analogous to inner mitochondrial membrane which will have ETC present within

156
Q

Archea prefer…

A

EXTREME enviromental conditions (therefore, must have cell structure able to tolerate)

157
Q

____ linkages in phospholipids of Archaea

A

ETHER
- O holding together

  • better thermal stability
  • stronger
  • able to survive more environmental extremes
158
Q

Bacteria and Eukarya that have ____ linkages in phospholipids

A

ESTER

- carboxylic acid

159
Q

Archaeal membranes

A
  • Archaeal lipids LACK fatty acids; have isoprenes instead
  • Major lipids are glycerol diethers and tetraethers
  • Can exist as lipid monolayers, bilayers, or mixture
160
Q

Isoprenes

A

in Archaeal membranes

C5 tails
hydrophobic & come together
C5 + C5 = C10
C10 + C5 = C15

161
Q

Glycerol diether

A
  • glycerol structure that has a phosphate as part of its head group
  • 2 hydrophobic tails attached to glycerol by just O (2 ether linkages)

bilayer

in Archaeal membranes

162
Q

Diglycerol tetraethers

A
  • 2 glycerols
  • tails are connecting them
    • forms a mono layer - NO gap b/t 2 tail structures
  • will get more VdWs
  • which means we have more that we’ll have to break to be able to melt
  • @ higher temps. the membrane will be able to hold its shape better with more VdWs
163
Q

Archaeal membranes can also have a mixture for their lipid layer

A

depending on how many of each you have - it’ll determine at a partic. temp if you’re solid, semi-fluid or liq

  • membrane ALWAYS must be semi-fluid
  • mixture will have lil bit of fluidity & also lil bit of stability
164
Q

What Archaea membrane would they want @ 4 degrees celsius?

A

want gaps in b/t - lipid bilayer to prevent solidification

165
Q

What Archaea membrane would they want @ 60 degrees celsius?

A

no gaps in b/t - lipid monolayer - a lot of stability to prevent melting

166
Q

Lipid bilayer vs. Lipid monolayer

A

Lipid bilayer:

  • gap
  • no VdW’s
  • separated –> less thermal stability

Lipid monolayer:
- 1 layer - no gaps

167
Q

In contrast to lipid bilayers, lipid monolayer membranes are…

A

extremely heat resistant

↑↑ VdWs

168
Q

Lipid monolayer membranes are extremely heat resistant. So where are they commonly found?

A

Commonly found in hyperthermophilic Archaea (grow best at temperatures above 80oC)

  • Archea that perfers extrem. or excessively high temps
  • increasing # of monolayers, having more VdW’s, allows them to be semi-fluid @ those temps
169
Q

What is able to pass through the lipid bilayer?

A

small/non-polar molecules from [high] to [low]

170
Q

What is able to pass through the lipid bilayer VIA A PORE?

A

*polar molecules are more controlled/need transporters/channels

pores are highly specific, polar material can move

171
Q

Membrane Function

A

• PERMEABILITY BARRIER

  • Polar and charged molecules must be transported
  • Transport proteins accumulate solutes AGAINST the concentration gradient (active transport)
    (ex: glc transport does this from low to high concen., therefore where it isn’t there that part of the mem. is non-permeable to that solute so unable to so you can concen. it against its gradient)

PROTEIN ANCHOR
• Holds transport proteins in place
- to be in the right location for function

ENERGY CONSERVATION
• Generation of proton motive force

172
Q

Do the proteins 1-4 have to stay in that position, or can they move?

A

MUST stay in that order (anchored) or else they will lose function of ETC

173
Q

How do protons move then?

A

can move protons to outside of cell thorugh complexes 1,3 & 4 - building a [ ] gradient, where they can flow back in to allow for ATP synthase
- producing energy

174
Q

If proteins were able to flow wherever they wanted b/c charge didn’t prevent that from happening, what would be the issue? (high H+ outside, didn’t have to use ATP syn)

A

GRADIENT WOULD DISSIPATE (energy stored within would be lost - not harvested)
- protons have to stay there & then flow in - controlled

175
Q

Cyanide (toxin) makes a membrane leaky to proton. Explain

A

Makes a membrane leaky to proton.

Able to move from high to low concen. (don’t need to use ATP syn).

Lose ability to harvest that energy & ability to produce ATP & drive Na+/K+/ATPase to keep gradient from neurons firing.

Becomes lethal - energy prod. goes to a hault & brain runs out of fas

176
Q

Carrier-mediated transport systems

A
  • Show saturation effect

* Highly specific

177
Q

Simple diffusion

A

molecule is moving directly through the plasma membrane (moving along [ ] gradient)

  • no transporter/transmembrane protein
  • inefficient
178
Q

Why is simple diffusion inefficient?

A

b/c inside of mem. is not really hospitable to that movement (wait a long time for it to come in)
- can use a transporter to help

179
Q

Transporter

A

carrier; physically binding to, & then guiding a molecule into a cell to let it go

180
Q

Explain the effect of a transmembrane protein(carrier)/transporter/transporter saturation

A

polar inside

  • get dramatic increase in solute entry & then levels off when all binding sites are saturated inside of carrier protein, it can’t go any faster in terms of internalization
  • saturation effect
  • & is highly specific-bringing in 1 particular molecule
181
Q

Three major classes of transport systems in prokaryotes

A
  • Simple transport
  • Group translocation
  • ABC system
182
Q

What do all 3 major classes of transport systems in prokaryotes require?

A

All require energy in some form, usually proton motive force or ATP
- ALL ACTIVE!

183
Q

Simple transport:

A

driven by the energy in the proton motive force

*SECONDARY ACTIVE TRANSPORT - energy released from PROTON movement from [high] to [low] funds energy needed to move another SOLUTE from [low] to [high]

184
Q

Group translocation:

A

chemical modification of the transported substance driven by phosphoenolpyruvate

  • solute will STOP moving into cell @ equilibrium
  • wants to EXCEED equil. since they’re in an envir. with abundance of nutrients (wants to bring more in past equil.) b/c it’s not sure if in a hour or so there won’t be any nutrients
  • by MODIFYING it when they bring more in
185
Q

How does solute exceed equil (bring more in past equil.) when equil. is reached?

A

by MODIFYING it when they bring more in

  • modification comes with phosphorylation
  • once modified, it’s not the same molecule again (think: hat on head (changed - not same)
  • so won’t reach an equil. b/t molecule & molecule phosphorylated (diff.)
  • outcome is that conc. of solute inside the cell, consistently stays low, therefore you can bring in even more (maximizes your intake potential)
186
Q

ABC system:

A

periplasmic binding proteins are involved & energy comes from ATP

  • PRIMARY active transport
  • ATP binding domain on inside of cell that allows transporter to take ATP & hydrolyze it; releasing energy
  • energy is then used to pay for solute that moves across the mem. to inside of cell
187
Q

Three transport events are possible:

A

uniport, symport, and antiport

188
Q

Uniporters

A

transport in one direction across the membrane

189
Q

Symporters

A

function as co-transporters

190
Q

Antiporters

A

transport a molecule across the membrane while simultaneously transporting another molecule in the opposite direction
- cotransport - move 2 solutes with same transporter

191
Q

Protons ALWAYS HIGHER ______ celll

A

OUTSIDE

192
Q

Describe E. coli ex with a symporter

A

Lac permease is bringing H+ into cell (releasing energy b/c high to low) & then the lactose is active (going against - req. energy)

  • proton is being used to pay for movement of the lactose
  • nutrients that have been taken up are the lactose
193
Q

Simple transport: Lac permease of Escherichia coli

A
  • Lactose is transported into E.coli by the simple transporter lac permease, a same direction
  • Activity of lac permease is energy-driven (to pay for it)
  • Transports lactose and a H+ into the cell simultaneously
194
Q

Group Translocation - e.g. phosphotransferase system in E. coli

A

(takes up glucose)

  • Sugar is phosphorylated during transport across the membrane
  • Moves glucose, fructose, and mannose
  • Phosphoenolpyruvate (PEP) donates a P to a phosphorelay system
  • P is transferred through a series of carrier proteins and deposited onto the sugar as it is brought into the cell
  • normally energy release here is used to form ATP by substrate level phosphorylation
  • but here, you take phosphate group & use energy from that rxn to transfer it through those enzymes & then drops it on glucose that’s coming through
  • PE-P is the most energy rich molecule that exists (breaking it releases energy that is used for substrate level phosphorylation - to produce an ATP molecule)
  • trying to est. equil., the outcome is it will eventually equalize, putting a stop to glucose uptake by phosphorylating it
  • becomes Glucose 6-P (no longer glucose - therefore no longer part of glc gradient & so glc can continue to come in)
195
Q

ABC (ATP-binding cassette) transport systems

A

• Involved in uptake of ORGANIC compounds (e.g., sugars, amino acids), INORGANIC nutrients (e.g., sulfate, phosphate), and trace metals
- BRINGING IN VITAL THINGS for cell

  • Typically display HIGH substrate SPECIFICITY
  • Gram-NEGATIVES employ periplasmic-binding proteins and ATP-driven transport proteins
  • Gram-POSITIVES employ substrate-binding lipoproteins (anchored to external surface of cell membrane) and ATP-driven transport proteins
196
Q

Gram-_______ employ periplasmic-binding proteins and ATP-driven transport proteins

A

negatives

197
Q

Gram-_______ employ substrate-binding lipoproteins (anchored to external surface of cell membrane) and ATP-driven transport proteins

A

positives

198
Q

What does, “typically display high substrate specificity” mean for ABC transport?

A
  • NEED A LOT, v. imp. nutrient uptake & life
  • specific - separate one for each molecule
  • huge part of genome is dedicated to providing instructions to make these diff. ABC transporters b/c you need a separate 1 for each nutrient & protein info in order to assemble the structure originates from genes within the DNA
199
Q

Porin non-specific transmembrane protein

A

molecules can pass through, as long as they are polar & have the appro. size characteristics, the molecules are able to pass through
- think: fence

200
Q

Periplasmic binding protein

A

specific to nutrient

201
Q

ABC Transport is…

A

highly specific

202
Q

Describe ABC transport systems in a Gram - cell

A
  1. PORIN in OUTER mem. that’s NON-SPECIFIC as long as you meet size criteria & polarity, you can go through
  2. Wandering around as a nutrient in PERIPLASMIC SPACE that’s large & endless
  3. PERIPLASMIC BINDING PROTEIN (SPECIFIC) for good guys-nutrients to that nutrient & deliver to the ABC transporter (HIGHLY SPECIFIC) which will allow the nutrient to be taken to the inside of the cell
203
Q

Describe ABC transport systems in a Gram + cell

A
  1. Reaching around, swishing around in ECF
  2. Finds nutrient for which its specific (substrate binding lipoprotein - specific)
  3. Brings to door & guides it through ABC transporter (highly specific)

(no outer mem. to create boundary & periplasmic space)

204
Q

ABC transporters (ATP-binding cassette)

A

Solute binding protein
• Periplasm
• Binds specific substrate

Integral membrane proteins (transporter)

ATP-hydrolyzing proteins
• Supply energy for the transport event (costs 2 ATP)

205
Q

Cell Walls of Bacteria and Archaea

A

Outside the cell membrane
- Rigid –> Helps determine cell shape (regardless of how mem. might appear underneath - will see the outermost strong layer)

  • NOT a major permeability barrier (as long as the molecule is small enough (unrestricted) it can bypass that layer
  • Porous to most SMALL molecules (think: jungle gym net - anything that can fit through; provided that it’s the right size (small) - will go through that layer
  • Protects the cell from osmotic changes
206
Q

The cell wall of Bacteria and Archaea are, “Not a major permeability barrier,” & “Porous to most small molecules.” How is this imp. for designing antibiotics?

A

imp. for designing antibiotics that go into a cell to target a ribosome & inhibit protein syn., antibiotic must have size characteristics that allow it to go through the cell

207
Q

______ is a unique feature for every single living cell

A

plasma membrane

208
Q

Plasma membrane =

A

our skin - our guaranteed outermost layer

209
Q

Describe an ex of a hypertonic cell in a hypotonic solution

A

water will rush in by osmosis [low] to [high] b/c of the hyper/hypo

  • plasma mem. will swell (bigger) b/c of additional water
  • & cell wall pushes back exerting a counter pressure but the cell won’t burst b/c the cell wall protects from osmotic changes
210
Q

In terms of cell wall:

A
  1. Cell wall won’t be able to provide indefinit protection (can only protect so much)
    - if cell continues to swell b/c of continuous influx of water
    - outcome is it will rupture
  2. Cell wants this added layer of protection b/c anything that happens to this 1 cell could be the end of the organism as a whole –> highly protective
  3. ECF & cytoplasm has 0.9% [NaCl]
    - but bacterium can find itself anywhere so constantly will have alternate external environment
    - so need to be able to adopt or prevent serious changes to cell structure since it is not constant like ours is
211
Q

Explain if a deflated balloon is in a glass and then air goes in

A

balloon = plasma membrane

air - makes bigger until glass exerts counter pressure on that expanded balloon

glass = cell wall

if you keep adding more air in, the glass is not gonna help & the outcome is the balloon will blow

212
Q

What does penicillin actively interfere with?

A

Penicillin actively interferes with formation of peptidoglycan

  • peptidoglycan on an organism that’s growing doesn’t have cross links (not strong)
  • a bacterium trying to grow in presence of penicillin, will have holes blown in side of its plasma membrane b/c cell burst without a strong cell wall there to protect against osmolarity issues
213
Q

Function of the cell wall

A

• Cell wall prevents cell expansion – protects against osmotic lysis

• Protects against toxic substances – LARGE hydrophobic molecules (CAN’T fit through pores therefore unable to get through - outcome: cell is protected against chemical threats in this way)
Ex) detergents, antibiotics

• Pathogenicity (ability to be able to escape immune detection or immune capture - able to get away from immune system & the destruction of its own self)

  • Helps evade host immune system (imp. for survival)
  • Helps bacterium stick to surfaces (better chance for bacterium to persist inside the body - since body is trying to constantly flush clean)

• Partly (b/c some might also have a cytoskeleton) responsible for cell shape (cocci, bacillum, spirilum). (b/c its a rigid structure - even if mem. has dehydrated away - the cell wall maintains external shape)

214
Q

Describe isotonic, hypotonic & hypertonic

A

Isotonic: no net movement of water

Hypotonic: water moves into the cell & may cause the cell to burst if the wall is weak or damaged (osmotic lysis)
- not living anymore (internal contents leak out)

Hypertonic: water moves out of cell, (b/c water always moves to more hypertonic envir.) causing its cytoplasm to shrink (plasmolysis)

  • cytoplasm pulls back from cell wall
  • not dead, just dehydrated
  • can rehydrate & become metabolically active
215
Q

Describe why honey doesn’t need to be refrigerated

A
  • doesn’t need to be refrigerated
  • it’s so hypertonic that bacteria in there are dehydrated (therefore, impossible to spoil)
  • not enough water to metabolize sugar & grow and increase in #
  • can store at RT b/c maintains semi-fluid viscous material
216
Q

Cell wall is…

A

anything outside of plasma membrane

Microbiology 1 (15 decks)

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