M1

Question 1

Why dont microbiologists study human eggs and sperm cells?

Answer 1

They dont study eukaryotes. They focus on bacteria and archaea.

Question 2

Whats the difference between cellular and acellular

Answer 2

Acellular microbes rely on cellular microbes to grow bc they are unable to metabolize organic materials by themselves.

Question 3

Describe how LUCA branched off to BAE. How do we know?

Answer 3

B and E first split then A split from E. This means that Eand A are closely related.

We know this from using molecular clocks which tend to have conserved regions, neutral changes, and found in all the organisms we’re trying to compare. A good example is small unite rRNA

Question 4

Describe how SA:Volume ratio affects growth

Answer 4

In order for a bacterial cell to grow efficiently, it wants a larger SA because this allows diffusion of nutrients, waste, etc better.

Question 5

Define resolution and what factors increase it?

Answer 5

resolution is the shortest distance between two objects that can still be distinguished as two separate objects.

High resolution = shorter distance differentiation

limit of resolution is defined as d = 0.5 (wavelength) / NA
-the shorter the wavelength, the lower the limit of resolution so the higher the resolution

Question 6

Describe when to use each microscope:

Light Microscopy:
Phase Constant:
Fluorescence:
Electron Microscope:
Atomic Force Microscopy:

Answer 6

Light microscopy w/ staining: to identify the basic cell wall structure of an unknown bacteria
- ex: gram +/-

Phase contrast: to identify if a bacterium can swim in a liquid fluid

• phase contrast doesnt need staining / fixing of cells so we can keep cells alive
• can see flagella / pili

Fluorescence: to watch proteins of the divisome to see how they change their location in dividing cells
-fluorochromes are engineered into the genes = can still be alive

Electron: to visualize the repeating crytsalline structure of s-layer

• Scanning EM views exterioir
• Transmission EM views internal structures

Atomic Force Microscopy: to see a single membrane complex on the surface of a cell
-can see porins

Question 7

What does penicillin do to cell walls?

Answer 7

Inhibits peptidoglycan synthesis. Since peptidoglycan protects against osmotic stress its easier to burst the cell when penicillin is given.

Question 8

What are the main differences between gram + and gram - bacterias?

Answer 8

Gram (-) bacterias have a thin wall of peptidoglycan which requires the cell to have an outer membrane and inner memebrane for protection. Outer membrane has LPS which trigger immune system reaction

Question 9

What type of bond does peptidoglycan have and what type of protection do we have against bacteria with peptidoglycan?

Answer 9

It has B-1,4 bonds between NAG and NAM. Our tears heave lysozymes the can cleave this bond = degrades peptidoglycan

Question 10

Whats the benefit of having both S-layer and capsule?

Answer 10

the capsule covers the s layer that has glycans that can trigger an immune response. In other words it helps avoid the detection form immune cells.

Question 11

Describe each flagellar arrangement of :
monotrichous:
lopotrichous:
peritrichous:
axial filament:

Answer 11

monotrichous: 1 flagella @ one end
lopotrichous: 2+ flagella coiming out of either / both ends
peritrichous: lots of flagella coming out of perimeter
axial filament: flagella remains inside of cell

Question 12

what powers the rotation of the flagella?

Answer 12

PMF

Question 13

What are the three functions of a pilus?

Answer 13

conjugation, attachment (with fimbria tip that is sticky to certain receptors), and twitching motility

Question 14

Describe how the singular circular chromosome of bacterias superocoils?

Answer 14

Negative supercoil: done by gyrase which is ATP dependent. Most bacterias have a negative supercoil

Positive supercoil: done by reverse gyrase that is also dependent on ATP. Bacterias will only revert to this supercoil if they are growing in v. high temps

Topoisomerase I relaxes the chromosome and does not need ATP

Question 15

Describe the specialized structures bacteria can use for metabolic rxns with toxic side products

Answer 15

Protein shells to enclose reactions

• gas vessicles: protein shell is only permeable to gas and not water
• thylakoids: enhances light gathering abilities (note that membrane is from cell membrane extension)
• carboxysomes: enhances RuBisCo environment to fix CO2
• enterosome: pumps out only non toxic end products
• storage granules: stores useful materials when abundant to release later when lacking
• magnetosomes: iron containing structures that can serve as compass needle

Question 16

Why are archaea more suited to live is extremely high temperatures in comparison to bacteria?

Answer 16

Archaea can have monolayer membranes which are more rigid

Question 17

Define each type of growth media:

• minimal medium
• defined medium
• Undefined medium
• Rich Medium

Answer 17

Minimal medium: only contains the absolute necessary components for minimal growth (defined bc we know each exact quantity)

Defined medium: every component and quantity is known (usually defines the chemical composition)

Undefined: some components are not know exactly (ex: yeast extract)

Rich medium: contains components allowing for hugh grwoth rates

Question 18

Define the ways to count the # of cells in a medium

• Optical density absorbance (turbidity)
• Viable Cell count
• Direct cell count
• Flow cytometry

Answer 18

• Optical density absorbance (turbidity) : can determine doubling time of bacteria
• Viable Cell count : can count how cells are left living (can be useful in assessing cleansing agents to kill bacteria)
• Direct cell count : count cells one by one by viewing inmicroscope (can’t tell between live or not live)
• Flow cytometry: count cels with laser detector (can be used with staining for specific interesting feature)

Question 19

Describe the different phases of bacterial growth

Answer 19

1) Lag phase: cells adapting to new environment and changing their gene patterns to prepare for growth
2) exponential phase: cells grow and divide as quickly as possible
3) stationary phase: dying cells = new cells bc of limited resources
4) death phase: cell population lowers exponentially

Question 20

Describe how / why the death phase can be a long term stationary phase

Answer 20

as cell die other suck up their nutrients and mutations can also help cell outcompete others

Question 21

PRACTICE CELL GROWTH EQUATIONS # 21 #22

Answer 21

21 #22

Question 22

Since FtsZ can be a temperature sensitive mutant past temperautre higer than 42 Celsius they:

Answer 22

produce long filaments bc they are unable to divide

Question 23

What data shows that microbes are able to grow below their optimum temperature than above it?

Answer 23

In a temperature vs. growth graph there is a sharp right side (high temp) which suggests a fast decline of growth with higher temps.

high temps can denature proteins

Question 24

define and describe how to:

sterilization:
Disinfection:
Sanitization:
Antisepsis:

Answer 24

sterilization: destroys all living cells and spores - autoclave

Disinfection: killing / inhibitting growth of disease causing microbes (not 100%) - wiping down with alcohol

Sanitization: microbial levels are reduced below a set standard (washing dishes)

Antisepsis: killing / removal of microbes on living tissue (washing a cut under running water / soap

Question 25

what does the d-value tell you? how can you measure this?

Answer 25

d-value is the time it takes to kill 90% of the microbes in the sample. This can be measured for a minutes of exposure vs LOG number of survivors. a difference of 1 log = 90% death so just calculate the difference in time bwteen the logs. large d-value = it takes a long time to kill the microbes small d-value = it takes a short time to kill the microbes (strong)

Question 26

Describe what pasteurization does

Answer 26

kills the microbes responsible for spoiling. it does not kill all the microbes but is able to slow down spoilage by decreasing the # of microbes

Question 27

# define the energy source and carbon source for: photoautotrophs: photoheterotrophs: chemoautotrophs: chemoheterotrophs:

Answer 27

photoautotrophs: Uses light an energy source and CO2 as a carbon source to make organic carbon compounds like glucose photoheterotrophs: Uses light energy to break down organic compounds for further use in biosythesis chemoautotrophs: uses inorganic compound as energy like sulfate reduction to convert CO2 into ogranic carbon chemherotrophs: Uses organic compounds an energy an carbon source

Question 28

What is and are types or reducing powers in a cell?

Answer 28

they are stored reduced compounds used to power biosynthesis or other cellular needs like motility and quorom sensing. Ex: NADH ATP FADH

Question 29

Describe how electrons move in terms on reduction potentials

Answer 29

electrons will flow form a more negative reduction potential to a more positive one spontaneously. The larger the gap between the energy potentials. The one with a more negative reduction potential will be the electron donor and the more positive reduction potential will be the electron acceptor

Question 30

what is substrate level phosphorylation and when / where does it occur

Answer 30

It is the addition of a phosphate from a high energy molecule dirctly onto ADP/ GDP It occurs in TCA cycle and glycolysis

Question 31

Whats the main difference between fermentation and respiration?

Answer 31

Respiration can be aerobic or anaerobic and will produce alot more ATP because it is able to use the ETC for oxidative phosphorylation Fermentation does not use ETC and only does substrate level phosphorylation so it doesnt make as much ATP. BUT its important in reproducing NAD+ which is needed in glycolysis

Question 32

whats the difference between cyclic and noncyclic photosynthesis?

Answer 32

cyclic : e- acceptor can be the OG chlorophyll that donated e-. noncyclic: e- acceptor goes on to further rxns so it needs a new e-acceptor every time

Question 33

Whats the difference between anoxygenic photosynthesis and oxygenic photosynthesis?

Answer 33

anoxygenic photosynthesis do not generate O2. Some can even shift from photosynthesis to respiration. Can use cyclic on non-cyclic photosynthesis. oxygenic photosynthesis: produces O2 and ALWAYS noncyclic

Question 34

what are chemoautotrophs and how do they use the ETC?

Answer 34

chemoautotrophs use respiration to make energy to fix CO2... They can run the ETC cycle forwards and back. Forward for NADH production which is needed for biosynthesis and forward of ATP is needed. They need to run ETC backwards becuase they are using inorganic carbons an energy sources which means they are not running glycolysis so no formation of NADh.

Question 35

What is the autotrophic feeder pathway?

Answer 35

Fixes CO2 into organic carbons. | -calvin cycle, reductive TCA cycle, etc.

Question 36

What are the big 3 cycles of the central pathways

Answer 36

Glyoclysis, TCA, and PPP note that they are all connected to one another. All together they make the 13 precursor metabolites

Question 37

assimilation of nitrogen and sulfur needs to be reduced into?

Answer 37

Nitrogen has to reduced to ammonium/ammonia | Sulfur has to be reduced to sulfide

Question 38

Why is the building block of DNA synthesis the most energetically expensive step of DNA synthesis and not polymerization?

Answer 38

It's bc nucleotides are made in the activated state, ready for polymerization = they have enrgy needed to polymerize themsleves