44 terms

Micro Biology Exam 3

Chapters 13-16
Define Metabolism
the energy it takes for all cells to move, set of chemical reactions to sustain life
Define Catabolism
the breakdown of complex molecules such as cellulose to smaller molecules such as carbon dioxide (makes ATP)
Define Anabolism
reactions that build microbial cells from the energy of catabolism (uses ATP)
Energy versus Entropy
energy is the ability to do work like cell growth, whereas entropy is the disorder of the universe
What are energy carriers?
ATP, NADH, molecules that gain and release energy and reversible reactions/ they are used to transfer energy
What are electron donors and acceptors?
they transfer electrons/donor is a reducing agent/acceptor is an oxidizing reagent
Fermentation versus Respiration
Fermentation is the partial breakdown of organic compounds without oxygen. It is organic to inorganic.
Respiration is the complete breakdown and creates more energy than fermentation. Organic to O2 or Nitrate/Sulfate without the presence of oxygen creating anaerobic respiration. Respiration is catabolic breakdown plus transfer of electrons.
What is Energy of Activation?
Ea determines the rate of reaction. Activation energy exceeds the kinetic energy. It is the input energy needed to generate the high energy transition to products, it can be lowered by a catalyst (enzyme).
Explain the EMP pathway
The EMP pathway (also termed glycolysis) can occur with or without oxygen and takes place in the cytoplasm. It is the catabolism of glucose. It produces 2 ATP and 2 NADH, by two phosphate groups splitting the glucose into to pyruvate molecules.
ATP usage/production in the EMP pathway
glucose is "activated" by phosphorylations (2 ATP) that ultimately convert it into fructose-1,6-biphosphate and 2 ATP are expended. This is cleaved into G3P
NADH production in the EMP pathway
The G3P is converted into pyruvate by redox reactions producing 2 NADH
Why can an organism not survive on glycolysis alone?
The ETS and fermentation need to be present in order to recycle the NAD to regenerate the cycle.
The ED pathway produces how many ATP/NADH/NADPH?
Many gut flora use the ED pathway because...
it involves fewer substrate phosphorylation steps, produces less ATP, uses gluconate (a sugar found in the intestinal mucus)
Why is fermentation important for microbial survival?
It is the completion of catabolism w/o the ETC & electron acceptor. Hydrogens from NADH are transferred back to pyruvate.
What is produced by the TCA cycle? Why can't microbes in general survive on glycolysis and TCA cycle alone?
The TCA cycle produces 3CO2, 4NADH, 1FADH2, 1ATP per pyruvate. Because they need the ETC to recycle the NADH to NAD and provide more energy.
Respiration versus Lithotrophy
Respiration involves organic e- donors and inorganic or organic e- acceptors.
Lithotrophy involves inorganic e- donnors and inorganic or organic terminal e- acceptors.
What is the purpose of the ETS?
transfer of e- through membrane to maintain a gradient that creates an ion potential that drives cell forces such as the recycling of NAD to make ATP
What is the key purpose of the first step of ETS?
to regenerate NAD
The complexes of the ETS are called _________ because they pump protons from inside the cell to outside the cell
proton pumps
PMF force is important for many functions such as? And drives what?
Rotation of flagella, uptake of nutrients, and the efflux of toxic drugs.
It drives the ATP synthase to produce ATP
What is the F1F0 ATP synthase? What does it do and how?
F0 complex translocates protons across the membrane
F1 complex consists of 6 alternating subunits of types. alpha & beta surrounding a gamma subunit that acts as a drive shaft
One proton at a time enters the subunit-a channel and moves into a C subunit of F0
The flux of three protons through F0 is coupled to forming one molecule of ATP by one alpha-beta gamma unit of F1.
How many ATPs are made in prokaryotes through aerobic respiration glycolysis thru ETS?
34 ATP
Know a couple examples of electron acceptors for anaerobic respiration
Nitrate, Nitrite, Fumarate
What is the purpose of the Calvin cycle?
fixes carbon from CO2 into biomass by adding Carbon to a chain. and removes atmospheric CO2.
Noncyclic photosystem vs. Cyclic photosystem
Noncyclic photosystem is e- to NAD and NADP/ produces NADH, NADPH
Cyclic photosystem is e- to ETS and chlorophyll/ produces ATP
What is the purpose of fermentation of foods?
1. to preserve food: by limiting microbial growth
2. to improve digestibility: by breaking down fibers
3. to add nutrients (such as vitamins) and flavor molecules
What to "esters" contribute to fermented foods?
flavor and smell
What is Acidic Fermentation of Dairy products?
Milk fermentation begins w/lactic acid fermentation w/lactobacillus and streptococcus, followed by rennet proteolysis rendering casein insoluble, forming semisolid curd & liquid portion whey
Whey versus Curds
lactic acid bacteria & stomach enzymes cause coagulation of milk proteins called curd and a liquid portion called whey
What is the purpose of rennet?
cheese formation takes an additional step of casein coagulation. it is accomplished by the protease rennet (derived from the fourth stomach of a calf). it includes chymosin & pepsin.
What do the lactic acid bacteria do?
they ferment & are responsible for 1st step in cheese production they acidify the food
What are the differences between the varieties of cheese?
Soft, unripened cheese is w/o rennet, spoils easily, high water content
Semihard, rimpened cheese includes rennet, cheese is aged for several months
Hard cheese, very low water content, aged for several months or years
Brine cheese, permeated w/ concentrated salt that limits bacteria growth and develops flavor
Microbial metabolism generates by-products that confer __________________.
characteristic aroma & flavor
Why do soybeans have to be fermented?
To get rid of substances that decrease their nutritive value
How is soy sauce made? What are the starting products that are fermented?
Soy beans plus wheat (aspergillus mold)
Pickling involves fermentation is brine. What is the purpose of the brine?
the salt pulls out juices from the food & breaks down cell walls, softening the food, and discourages the growth of bacteria. It allows the growth of only specific bacteria
In bread production why use yeast? What does it produce? Why do I care?
Yeast acts as a rising agent b/c it produces CO2 & ethanol/ it makes it easier to digest and chew
Beer: Why did people begin to drink it? What produces the flavor? What happens if there is too much O2?
It was more fermented than water/long chain alcohols & esters/too much oxygen over stimulates the yeast
Wine: why higher level of alcohol from fruit than grain? White versus Red?
There is an exceptionally high monosaccharide content in fruit/white skin is removed red skin is left on
What pathogen is the leading cause of hospitalization/death from a foodborne pathogen?
Botulinum toxin causes _______ paralysis
Home canning versus Commercial sterilization
Home canning sterilization is meant to kill everything. Commercial canning only meant to kill clostridium botulinum, not thermophiles
Why is pasteurization not sterilization?
It is heating of food at a temperature & time combination that will kill spores of coxiella