Exam One Learning Objectives

Question 1

What is in a prokaryote vs. a eukaryote cell? Name specific characteristics of both

Answer 1

Prokaryotes: no nucleus, usually pretty small, internal structure is different (think plasmids, endospores, capsules, and pili)

Eukaryotes: DNA enclosed in nucleus, usually. bigger, common organelles (also they have cell walls if you’re talking about plants)

Question 2

What things are only found in Gram Negative cells?

Answer 2

-thin cell wall (peptidoglycan layer)
-the outside has an outer membrane (LPS)
-they have porins (proteins that allow molecules to pass through outer membrane)
-they also have periplasms (which are like this gel-like area)

Representative Genera: Neisseria (diplococci), Pseudomonas, E.Coli, Shigella (GI infection), and Salmonella

Question 3

What are characteristics that only apply to Gram Negative Cells?

Answer 3

-It’s harder to get into the cell itself because of the additional outer membrane
-transpeptide bonds between amino acids are fewer in number
-B1-4 (glycocidic bonds) between the NAM-NAG sugars are fewer in number, which makes the cell wall in general weaker than Gram (+)
-DAP (diaminopimelic acid) is a special amino acid in the transpeptide bond

Question 4

What things are only found in Gram Positive Cells?

Answer 4

-thick cell walls (peptidoglycan)
-techoic acids, they extend above the peptidoglycan layer (their function is to strengthen the wall, cell signaling, and provide adhesion)

Question 5

What are characteristics of Gram Positive Cells?

Answer 5

-thick cell wall (peptidoglycan)
-most transpeptide bonds and glycosidic (B1-4) bonds are present, which make it strong

Question 6

What is the LPS and what are its components?

Answer 6

it’s the outer membrane of Gram Neg. cells, andit’s made up of a chain of a lipid (lipid A), o-antigen (sugar), and a core polysaccharide (sugar). The purpose is to make it hard for a lot of molecules to get it and out of the cell

f(x) of LPS: 1) Protection, 2) adhesion (sticky), and 3) cell signaling

It has Porins (protein) that is basically a channel that allows really specific molecules in and out of the cell

Question 7

What does Penicillin do?

Answer 7

It stops transpeptide bonds from being formed, which weakens the cell wall

Question 8

What does Lysozyme do?

Answer 8

It goes in and cuts the B1-4 glycosidic link between the NAM and NAG sugars

Question 9

What is a capsule and how does it interact with the immune system?

Answer 9

A capsule is a distinct gelatinous layer outside the cell wall that protects/allows attachment interaction w/immune system:

1) makes the bacteria too large to be eaten up/destroyed during phagocytosis
2) capsule makes the bacteria look like the host cell so it can’t be detected
3) it can bind to antibodies

Question 10

How do bacteria move and what is the ultrastructure of a flagellum?

Answer 10

They have flagella outside of their cell wall that helps them move around bc they act like propellers

Question 11

Define what a “random biased walk” is

Answer 11

the cell moves randomly when there is no concentration gradient of attractant or repellent

Question 12

What is a tumble vs. a run?

Answer 12

tumble: cell randomly tumbles in place and it’s tumbling counter-clock wise (cell increases the amount of times it tumbles to get AWAY from a toxin it senses)

Run: after tumbling, bacteria randomly picks a direction to propel towards and it runs clock-wise (the runs get longer to get TOWARDS a nutrient)

Question 13

What is chemotaxis?

Answer 13

it’s when the cell tumbles and runs either towards or away something after sensing it through it’s receptors

Question 14

What are pili and what are their functions? There are at least three

Answer 14

pili are short things that stick out of bacteria

1) adhesion
2) motility
3) sex pilis help join bacteria for DNA transfer

they also have this thing where they polymerize/depolymerize to get closer or farther away from something

Question 15

What is a plasmid and what is it used for?

Answer 15

essentially they’re DNA that bacteria sometimes have that don’t encode anything super essential for the cell to live; they’re important because they can be shared w/other bacteria, which is how antibiotic resistance can be spread

Question 16

What are endospores, when do they form, and what is their function and which organisms have them?

Answer 16

it’s a unique type of dormant cell that can remain that way for 100 years or longer. It’s extremely resistant to heat, desiccation, chemicals, ultraviolet light, and boiling water

ex) of bacteria who produce them: Bacillus + Clostridium

Question 17

Know what lag, log, stationary and death phases of a typical growth curve?

Answer 17

Growth Curve: characteristic pattern observed in both broth culture, which is just to say that it’s a closed/manufactured scenario w/phases

five phases: Lag, exponential/log, stationary, and death phased

Question 18

Lag Phase

Answer 18

Phase one of the growth curve, bacteria are getting ready to divide, modifying pH and breaking down nutrients

cell count is around 0-10^4

Question 19

Log/Exponential Phase

Answer 19

Phase 2 of the growth curve, bacteria are actively dividing like crazy

cell count 10^5-9x10^8
mid: 5x10^9

Question 20

Stationary Phase

Answer 20

Phase 3 of the growth curve, nutrients dec and waste products inc, endospores probs being made here

cell count: 9x10^8 to 1x10^9

Question 21

Death Phase

Answer 21

don’t recover! DEATH

1x9^10 and up

Question 22

Binary Fission

Answer 22

the process by which prokaryotic cells divide

Question 23

Generation Time

Answer 23

how long it takes that type of bacteria to divide on average

Question 24

Number of Divisions in a given time

Answer 24

it’s the total amount the experiment is going to take place divided by the generation time

Question 25

Equation for Bacterial Growth

N(t) = N(0) + 2^n

Answer 25

N(t) = the number of cells in population at time t
N(0) = initial number of cells
n= number of generations at that point (total time/generation time)

Question 26

Biofilm

Answer 26

polymer encased communities that attach and live on most surfaces

pathology: they’re important because they resist antibiotics and our immune systems, so they can be found on medical equipment and tools if not sterilized

Question 27

Pure culture

Answer 27

population of cells derived from a single cell; allows study of a single species

it’s important to help study it, although organisms may behave differently. in nature, it’s obtained through using aseptic technique, and only 1% of microorganisms can be cultured

Question 28

Make sure you. know how to practice aseptic technique

Answer 28

it minimizes accidental introduction of other organisms

Question 29

Review which parts of a colony have higher relative oxygen concentrations

Answer 29

growth of bacteria in liquid broth vs. inside our bodies is similar, but it’s different in our bodies because the environment in our bodies varies; the position of a single cell in a colony determine its environment

Edge of a colony: Little competition for O2 and nutrients so they’re probably undergoing the exponential growth phase

Center of a colony: depleted O2 and nutrients and probs in the death phase

Question 30

Obligate Aerobes

Answer 30

requires oxygen to survive, people arre obligate aerobes, live at the top of a test tube!

Question 31

Obligate Anaerobes

Answer 31

cannot use O2 at all, bottom of the test tube

Question 32

Facultative Aerobes

Answer 32

use oxygen, bit don’t require it, live in the middle of the test tube

Question 33

Microaerophiles

Answer 33

require small amounts of O2 only

Question 34

What are reactive oxygen species (ROS) and what examples? How do bacteria protect against them?

Answer 34

ROS are harmful by-products of using O2 in aerobic respiration, the by-products are super oxide (O2) and hydrogen peroxide (H2O2) –> to protect themselves, bacteria create enzymes to break them down

catalase: converts hydrogen peroxide (H2O2) into O2 (oxide) and H20

superoxide dismutase: inactives O2 by turning it into H2O2

Question 35

Define alkaphile and acidophile

Answer 35

Alkaphile: grow optimally at a pH above 8.5 (very basic)

Acidophile: grows optimally at a pH below 5.5 (very acidic)

Question 37

Osmosis

Answer 37

the diffusion of water across the membrane toward the solution w/more solutes

Question 37

Halophiles

Answer 37

require high salt concentrations, usually GRAM (+) grow on your skin cuz it’s salty and relatively dry there

Question 37

Complex Media

Answer 37

contains a variety of things in it, you’re not really sure what’s inside of it

Question 37

Psychophile

Answer 37

lowest temp values bacteria optimally grow at (0-20 degrees C)

Question 37

Hyperthermophile

Answer 37

bacteria that grow at 80-110 degrees C

Question 37

Mesophile

Answer 37

medium temp values bacteria grow at (20-40 degrees C)

Question 37

Thermophile

Answer 37

bacteria that grow at 40-80 degrees C

Question 37

Understand how organisms get carbon from their environment (auto vs. heterotroph)

Answer 37

Autotroph: things that get carbon from the atmosphere (plants and photosynthesis).

Heterotroph: you get carbon from another source

Question 37

Compare different energy acquisition for bacteria (photo vs. chemotroph)

Answer 37

Phototroph: your light source is energy
Chemotroph: energy source is chemically breaking something dow, like eating

Question 37

Recall what phile is vs. tolerant

Answer 37

phile- loves/requirement for the bacteria
tolerant: can withstand

Question 38

Defined Media

Answer 38

you know exactly what’s inside of it, like it literally lists the exact amount of pure chemicals

Question 39

Selective Media

Answer 39

inhibit growth of certain species in a mixed sample, while allowing growth of species of interest

MacConkey is selective for Gram (-)

Question 40

Differential Media

Answer 40

incorporates something which allows you to physically distinguish different colonies based on their metabolism

MacConkey is differential for lactose fermenters