Notes for Exam 2

IV. Use of ATP synthax
-electron from glucose, other molecules that we've broken down passed from 1 to next electron transport chain proteins.
H+ = proton

ATP synthase: Protons fall through, sorta like a waterwheel, collect energy from protons falling across ATP synthase "gate"
So, A -> AMP -> ADP -> ATP as one inorganic phosphate is added to Adenosine - based molecule per falling H+
ATP needed to power pretty much all cell processes.

V. Similarity to secretion system
-Pathogenic bacteria may need to ship virulence factors out of cell.
Type III Secretion System
- works some as flagellum, but ships virulence factors outside cell instead of flagellins.

I. Exponential growth vs Logarithmic growth
- Can calculate bacteria by how many generations its gone through.
2n = # of bacteria we'll have starting from 1 bacteria after n generations.

- Logarithmic growth- bacteria have this, not exponential.

II. How an individual bacterium divide
a) Replications of chromosomes
- circular - so no clear "beginning" site for replication
-oric: sequence of DNA on bacterial chromosome where replication starts
-DNA must be unwound to be cupid
-bacterial DNA then copied in a semiconservative fashion
:one strand is new, other a copy

Mutation: change in DNA sequence of organism (compared to original sequence)
2 copies of bacteria chromosome
topoisomerase IV de-links copied chromosome

Change in DNA may -> change in characteristics b/c DNA -> RNA -> protein
Mutation most likely to occur when cells are dividing, copying DNA
b) Elongation of cell
-this done by making new cell envelopes stuff in middle
("stuff" depends on what kind of bacteria it is) gm (+), gm (-), acid-fast

c) Formation of FtsZ ring at septum -> pinching bacteria apart
*Found in all bacteria
FtsZ=similar to a protein in eukaryotes, but still w/ major differences
*has been found in every bacteria tested for FtsZ

d) Building a new cell envelope components of septum.
i) Acquired immunity hypothesis:
*If E. coli become resistant to phages, its b/c of exposure to phages - Bacteria "fight back" in response to phages.

ii) Randomness Hypothesis:
*If E. coli become resistant to T4 phages, it by chance: some E. coli just happened to "be born" with phages - resistance, and then we expose the E. coli to T4 phages on day 3 killed all the bacteria that weren't already resistant.

NOTE: Bacteria are not exposed to phages until final step, when broth are plated.

III) Phages of Bacterial Growth
Lag, Exponential, Stationary, Death
a) Lag Phase
lag on bacteria cell division, b/c bacteria need to manufacture enzymes, etc. needed to build new cells.
b) Exponential Phase
rapid growth in population b/c all bacteria cell division is working, the cells are dividing as quick as possible.
c) Stationary Phase
number of bacteria divided is equal to # dying of bacteria. Little cell division, bacteria trying to conserve resources, may enter dormant state.
d) Death Phase
# Dying bacteria
*bacteria have run out of resources
*also many bacteria will commit suicide @ high population densities.

Bacteria Generation Times:
*bacteria have different generation times
*during exponential phase:
E. coli gen. time = 15 min
S. aureus gen. time = 30 min
Acid fast (M. tubericulosis) gen. time = 24 hours

II. Phages Resistance Experiment
a) Phages = viruses that attack bacteria
* like all viruses phages need a host cell to replicate their (phages) genetic material, and thus to allow phages to reproduce

-can be taken internally
-target cellular parts that are specific to bacteria.

-safe to us on skin
-don't take internally, it would hurt and attack your DNA
-kill cells in a non-specific way
-antiseptics kill cells by attacking common targets to all cells Ex: phospholipids membrane, protein, DNA
Ex: Soap, Purell, hydrogen peroxide, iodine

-used just on inanimate objects
Ex: Bleach, lysol
-only more toxic than antiseptics b/c more concentrated

I. Factors that influence bacterial growth rates
a) Osmotic Pressure and avialability of water
*Osmosis = diffusion of H2O
*Osmotic pressure: pressure put on cells by movement of water.
*too little (water) sucked out of cell
*too much (water) water flows into the cell, could - cell exploding
water activity: how much available water in given environment
pure water : w.a. =1.0
human blood : 0.995
maple syrup/honey : 0.90
candy : 0.70
* Bacteria can't survive if environmental conditions are too different from that bacteria's ideal growth conditions.
i) Halophiles: can grow in a very low w.a.
*they're able to do this by high concentration of solutes on inside of cell
ii) "salt in a wound"
*hurts b/c your cells killed by lack of H2O
*prevents infection for same reason
b) Hydrostatic pressure/atmospheric pressure
*internal pressure in a cell must be equal to external pressure or the cell will:
Smished : External > Internal
Blow up : Internal > External
*cell wall with peptidoglycan key way bacteria dell with osmotic and hydrostatic pressure
c) Oxygen ITS TOXIC!!!!
*very electronegative (very attractive to electrons)
*free radicals - electrons not attached to an atom
*free radicals - DNA, protein damage - mutations to DNA sometimes death of all
*today's atmosphere = 20% oxygen
*2 billion years ago = 1-2% oxygen
i) Anaerobes
Strict : killed by O2
* bacteria that grow in guts are anaerobes
Facultative : Don't need O2 can grow with or without O2
*many soil bacteria anaerobic
Example : C. difficile : soil bacteria that can also grow in guts
ii) Aerobes : need 02 to grow
*b/c use O2 to help produce ATP, b/c O2 is the terminal electron acceptance in electron transport chain
Example : Staphylococci

iii) Other atmospheric requirements
a) Microaerophiles: need 5% O2 to grow, die with more
b) Capnophiles: need 5-10% CO2 to grow, aren't killed by O2

Oxygen, the electron-transport chain & ATP
*every time a proton falls across ATP synthase, a phosphate is added. A - AMP - ADP - ATP
Protons help make ATP… through a ATPsynthase
*Oxygen very attractive to electrons; in aerobic respiration (does involve O2)
oxygen = terminal electron acceptor (last place electrons go)
*chemicals called "decouples" prevent a proton gradient from forming
*In anaerobic respiration, some other inorganic molecule is used as terminal electron acceptor (usually H2S)

*Fermentation also a way of generating ATP w/ O2.
*Fermentation less efficiently at making ATP.

d) temperature
i) psychrophiles: bacteria that grow but at -5C to 10C
*aren't growing in ice
*water with solutes (like NaCl) water under pressure has lowering freezing point.
- cell membrane made out of unsaturated fats (unsaturated-liquid at room temp)
lower concentration of G & C in DNA
higher of A & T
ii) Mesophiles: bacteria that grow best at 25C - 40C (room temp to body temp)
Seems to be the case that all life must have some access to liquid water.
iii) Thermophiles grow best at 60C to 70C
- have more heat stable proteins. Also have different all membrane compostition
- cell membranes made out of saturated fats (solid at room temp.)
Hyperthermophiles grow best at greater than 100C
-salt pressure raises the boiling point for H2O

Unsaturated: more unstable, flexible
Saturated: less flexible, more stable

high {sat. fats} in cell membrane
high concentration G & C in DNA
lower concentration of A & T
A=T connect by 2 hydrogen bonds
G=C connected by 3 H-bonds (3 bonds between G & C)

So easier to denature DNA with lots A=T, harder to denature lots G & C

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