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.
AT SOME POINT IN TIME: EXPONENTIAL GROWTH STOPS!!

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
WE ARE TALKING ABOUT CULTURED NOT NATURED…..
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

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

Antiseptics
-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

Disinfectants
-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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