Flashcards in MIDTERM 2 Fermentation and Respiration Deck (64)
What does Growth Require?
How do microorganisms obtain energy?
By Breaking down food
What are examples of organic molecules and how/what does the microbe convert it?
1. Glucose, Amino Acids, Fatty acids
2. Microbes use catabolic pathways to convert biochemical energy into more usable form of ATP
What are the two key ways of releasing energy?
What is the most efficient way to produce energy from a simple organic molecule?
Oxidative pathways of respiration
True or False: Oxidative respiration is anabolic. if false, explain why.
Its False because its actually Catabolic
What does Oxidative Respiration depend on?
It relies on the complete oxidation of organic compounds, most frequently in the presence of Oxygen, to releaase Hydrogen and the associated electrons.
What happens to the hydrogen and its associated electrons once it gets released by the organic compounds after being oxidized?
These hydrogens and electrons are transferred to the Dinucleotides NAD+ and FAD
What is the significance of NAD+ and FAD
They are coenzymes that ferry the electrons to the ETC
What happens to the terminal electron acceptor and the results of this step?
the terminal electron acceptor gets reduced resulting in the production of ATP through the production of a proton gradient and by oxidative phosphorylation
What makes glycolysis able to function in both aerobic and anaerobic organisms?
1. A cytosolic pathway and
What does it mean to be anaerobic?
does not require oxygen
What are the net products of glycolysis?
1. Converts 1 Glucose --> 2 Pyruvates
2. Makes 2 ATP
3. Makes 2 NADH (through substrate level phosphorylation)
What happens if theres a terminal electron acceptor (oxygen) available around pyruvate?
The pyruvate gets converted to Acetyl-CoA and CO2 by oxidative decarboxylation and the Acetyl-CoA enters the citric acid cycle.
What is the linking step between glycolysis and the TCA cycle?
The conversion of pyruvate to acetyl-CoA
What other product is produced when Pyruvate is converted to Acetyl-CoA
What pathways can the pyruvate produced by glycolysis enter?
1. Respiratory pathway
2. Fermentative pathway
Requirements for pyruvate to enter the TCA cycle?
There must be oxygen ( or another terminal electron acceptor) so that the pyruvate can get converted into acetyl-CoA and then it may enter the TCA cycle combining with oxaloacetate
What happens in the TCA cycle?
its an 8 step process that
1. Oxidizes Acetyl-CoA to CO2
2. Reducing NAD+ to NADH and FADH to FADH2
3. Producing 1 ATP per acetyl-CoA (2 atp per glucose)
What happens to the reduced form of NADH and FADH2 as products of the TCA cycle?
The electrons are handed off to the ETC
How are electrons transferred from one complex to another?
Through a process of reduction and oxidation.
True or False, some Transmembrane complexes are proton pumps
What does the proton pumps do?
they translocate H+ ions into the periplasmic space, Thus creating a proton gradient across the cell membrane
What is oxidative phosphorylation?
ATP synthase Using the proton gradient to produce ATP
What are the component enzymes of the ETC?
What do the component enzymes do?
1. some act as proton pumps
2. Mobile electron carriers (shuttling electrons between complexes)
3. Membrane Bound Electron carriers
4. Terminal electron oxidases or reductases
What can Cytochrome do?
They shuttle electrons between complexes
Where can cytochrome C be found in bacteria?
found on the periplasmic side of the cell membrane
How is the reduced end product formed in ETC?
Electrons are transferred from the last complex to the terminal electron acceptor and combined with H+ ions to produce a reduced end product
What is the end product of the ETC if the terminal electron acceptor is oxygen?
What is the most common terminal electron acceptor?
What are other terminal acceptors microbes can use besides oxygen?
What is Aerobic respiration?
When respiration occurs in the presence of and using oxygen
What is anaerobic respiration?
using a terminal electron acceptor other than oxygen
True or False, Anaerobic respiration does not require all other parts of the respiratory metabolism including glycolysis, TCA cycle, and ETC.
False, they require it.
What is the difference between anaerobic and aerobic respiration?
Anaerobic respiration is less efficient than aerobic respiration and is often less able to support a high growth rate.
How much ATP does a single glucose molecule produce with all the steps of glycolysis, tca cycle, and etc combined?
Out of the four transmembrane complexes in ETC, which complex can be identified using a color indicator?
Complex III ( Heme-containing Catlytic protein cytochrome C)
What does a positive result for cytochrome C tell us?
it establishes the presence of the ETC, and by inference, the presence of the respiratory pathway
What is significance of superoxide?
the ETC is somewhat leaky in transferring electrons thus increasing the production of this free radical. Superoxide can damage cell membranes, proteins, and DNA.
True or False, SuperOxide is only present in microbes that uses oxygen and have an etc
What is a common protective mechanism that deals with superoxides?
What are two possibilities for diagnostic testing based on the components and function of the ETC?
1. Cytochrome C Test
2. Catalse Test
True or False: Pyruvate produced at the end of glycolysis cannot be processed through the TCA cycles and the ETC
True or False: Glycolysis itself is dependent on the presence of oxygen.
False: Glycolysis is independent of oxygen,
How much ATP can glycolysis produce without oxygen?
2 net ATP molecules per glucose, it produces far less ATP per glucose molecule
What are the limitations of glycolysis?
the availability of NAD+.
Since Glycolysis is limited to NAD+, and if theres an absence of an ETC, what must happen
Reduction of pyruvate to lactate or alcohol through fermentation as an alternative method to generate NAD+
4 Main Characteristics of Fermentation
1. Oxygen is not required
2. Its Strictly fermentative
3. Fermentation is an inefficient method
4. Fermentation results in production of waste products
explain characteristic 1 of fermentation: Oxygen is not required
Since pyruvate does not undergo the transition reaction or enter the TCA cycle, NADH generation is entirely from glycolysis and NAD+ regeneration does not use the ETC but a simpler enzymatic reduction of pyruvate
explain characteristic 2 of fermentation: Its strictly fermentative
Strictly fermentative microbes have no need for an ETC and therefore lack it.
1. Facultative anaerobes that have both respiratory and fermentation pathways do not use the ETC when growing in anaerobic environments.
2. test for cytochrome C is likely to produce negative result in strict fermenter
3. may or may not produce positive result in an organism capable of both fermentation and respiration.
explain characteristic 3 of fermentation: Fermentation is an inefficient method
1. at end of fermentation process, most of biochemical energy is trapped in the reduced by product of pyruvate reduction, yielding only 2 atp molecules per glucose consumed. These products are then excreted out causing an energy loss in cells instead of being metabolized.
2. substrate phosphorylation limits number of atp molecules generated for each electron removed from glucose
3. organic compounds are used up rapidly and wastefully so that organisms may grow slowly or to a lower density than respiration
explain characteristic 4 of fermentation: Fermentation results in production of waste products
waste products are very characteristic of different organisms. therefore it can be used to identify a fermenting organism and distinguish among different strains.
2. Fermenting microbes differ in particular sugars they are able to ferment. therefore you can use this to distinguish among microbes
What three categories do fermentation products fall under?
1. Acid - lactic, acetic
2. Neutral products - ethanol, butanediol
3. gases - CO2 and Hydrogen
What are homolactic acid bacteria?
Produces primarily lactic acid
What are heterolactic acid bacteria?
they excrete ethanol, glycerol, and acetic acid as well as lactic acid
What are the 5 main categories microorganisms fall into based on growth in various oxygen conditions
2. strict anaerobes
3. facultative anaerobes
5. aerotolerant anaerobes
What are aerobes
Grow only when oxygen is present
What are strict anaerobes
cannot grow at all in presence of oxygen
What are facultative anaerobes
grow with or without oxygen
What are microaerophiles?
require oxygen but are sensitive to high concentrations
What are aerotolerant anaerobes
anaerobes with some level of protection against oxygen and can grow in the presence of small amounts of oxygen without using it
What conditions satisfies an obligate aerobe?
1. must have respiratory pathway
2. highly likely to show both cytochrome C and catalase activity