Microbiology Chapter 6
the chemical structure of the inhibitor is usually ___ to the substrate
similar
catabolism
cellular process that harvests the energy released during the breakdown of a compound such as glucose and using it to synthesize ATP
anabolism
cellular processes that synthesize and assemble the subunits of macromolecules, using the energy of ATP; biosynthesis
the process that links the electron transport chain to ATP synthesis is called the _____ theory
chemiosmotic theory
Cytochromes
contain heme, a molecule with an iron atom at the center, there are several types
in prokaryotic cells, all the central metabolic pathways occur in the
cytoplasm
What membrane is the ETC in prokaryotes?
cytoplasmic membrane
what is an example of lipase breaking down a molecule?
glycerol is converted to dihydroxyacetone phosphate and then enters glycolysis
The primary pathway used by many organisms to convert glucose to pyruvate is _____
glycolysis
lactic acid is a common fermentation product of which of the following types of cells?
gram-positive organisms called lactic acid bacteria, animal muscle cells when O2 is in short supply
Chemolithotrophs
group of bacteria that can use inorganic compounds as a source of energy
ATP synthase enzyme
harvests the proton motive force to synthesize ATP, uses energy to add phosphate to ADP and 1 ATP is formed per entry of 3 protons
What are some inorganic compounds used for respiration?
hydrogen sulfide and ammonia (H2S and NH3)
precursor metabolites
intermediates of catabolism that can be used in anabolism
__ is required to establish a gradient
energy
A group of membrane-embedded electron carriers that pass electrons sequentially from one to another, ejecting protons in the process, is called the
etc
Can eukaryotes perform respiration with inorganic compounds?
no, only prokaryotes can
coenzymes are ___ cofactors
organic
What are proteins hydrolyzed by?
proteases...the amino groups are deaminated and converted into precursor metabolites
what are flavoproteins?
proteins that are synthesized from the vitamin riboflavin proteins to which a flavin is attached
What are two processes bacteria use to harvest energy from chemicals?
respiration and fermentation
Menaquinone is a quinone used in the electron transport chain of some prokaryotes. It plays an important role for humans and other mammals because it
serves as a source of vitamin k, providing much of the host's requirement via absorption in the intestinal tract
What level is the 2 ATP from fermentation made at
substrate level phosphorylation
example of a competitive inhibitor
sulfa drugs blocking folic acid synthesis
Which organism goes with which fermentation pathway? 2,3-butanediol fermentation ethanol fermentation propionic acid fermentation butyric acid fermentation mixed acids fermentation lactic acid fermentation
1. enterobacteria 2. saccharomyces 3. propionibacterium 4. clostridium 5. streptococcus, lactobacillus 6. e. coli
Fermentation pathway of lactic acid: 1. what microorganisms use this? 2. what are the end products? 3. Consumer products?
1. streptococcus/lactobacillus 2. lactic acid 3. yogurt, cheese, pickles
___ ATP made per electron pair from FADH2
2
what are the end products of the transition step of aerobic respiration of glucose?
2 acetyl CoA 2 CO2 (complete oxidation has not occurred yet) 2 NADH
The pentose phosphate pathway generates which of the following from each molecule of glucose?
2 precursor molecules, a variable amount of NADPH
In response to changing energy needs, cells can regulate allosteric enzymes of catabolic pathways. high levels of which of the following would most likely inhibit such enzymes, thereby slowing down catabolic processes?
atp
is the enzyme used up when a substrate binds to the active site?
no
what is the final electron acceptor in the ETC process of aerobic respiration of glucose?
oxygen!
__ ATP made per electron pair from NADH
3
For a single molecule of glucose, what is the theoretical maximum of ATP gain from oxidative phosphorylation in prokaryotes growing aerobically?
34 ATP
Fermentation pathway of Propionic acid: 1. what microorganisms use this? 2. what are the end products? 3. Consumer products?
1. propionibacterium 2. propionic acid, acetic acid, CO2 3. Swiss Cheese
2 purposes the the ETC in aerobic respiration of glucose
1. regenerate electron carriers 2. synthesize ATP
Fermentation pathway of ethanol: 1. what microorganisms use this? 2. what are the end products? 3. Consumer products?
1. saccharomyces 2. ethanol, CO2 3. wine and beer
two 3-carbon molecules enter the pay-off phase of glycolysis for each initial glucose molecule, meaning the steps of this phase occur twice for each glucose. During this pay-off phase of glycolysis, what is the total number of NADH and ATP molecules produced from a single glucose molecule?
2 nadh, 4 atp
what are the end products of glycolysis with aerobic respiration of glucose?
2 pyruvates, 2 atp, and 2 NADH, 6 precursor metabolites
Products of TCA cycle in aerobic respiration of glucose
4 CO2, 2 ATP, 6 NADH, 2 FADH2 and 2 precursor metabolites
reduction reactions
A chemical reaction in which a substance gains electrons
What is the energy currency for metabolic pathways?
ATP
The membrane-bound enzyme that uses energy from a proton-motive force to add a phosphate group to ADP is called
ATP synthase
The synthesis of ATP is driven by what in the ETC of aerobic respiration of glucose
ATP synthase enzyme
When a cell processes glucose or other organic molecules through its central metabolic pathways, it does so to generate what three critical items?
ATP, reducing power, precursor metabolites
E. coli will preferentially use ____ respiration, but when O2 is not available, it can switch to _____ respiration if a suitable electron acceptor such as nitrate is present
Aerobic, anaerobic
Rank these energy-generating processes from greatest energy yield to least energy yield: -Aerobic respiration -Anaerobic respiration -Fermentation
Aerobic, anaerobic, fermentation
What are the enzymes that break down polysaccharides and disaccharides
Amylases: digest starch Cellulases: digest cellulose
What occurs during the transition step of central metabolism?
CO2 is removed from pyruvate, electrons are transferred to NAD+ reducing it to NADH and H+ The 2-carbon acetyl group is joined to coenzyme A to form acetyl-CoA
Inhibitor binds to the active site of the enzyme, blocking access of the substrate
Competitive inhibition
In prokaryotes, the electron transport chain is located in the ____ membrane, whereas in eukaryotic cells it is in the ____ membrane of ______.
Cytoplasmic, inner, mitochondria
Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will ____ and no longer function
Denature
Why is it difficult, especially in prokaryotes, to calculate an exact ATP yield from oxidative phosphorylation?
Depending on the cell, different carriers are used in the electron transport chain that eject a variable number of protons per pair of electrons Prokaryotes use proton motive force to drive processes other than ATP synthesis
exergonic reaction
Describes a chemical reaction that releases energy because the starting compounds have more free energy than products
What organism uses fermentation for above reasons?
E. coli
What components are necessary for an electron transport chain?
Electron carriers such as quinones, cytochromes, and flavoproteins A membrane Protein complexes that serve as proton pumps
What is the source of energy for nitrifying bacteria?
NH3, HNO2
Dehydrogenation reaction
Oxidation reaction in which both an electron and an accompanying proton are removed
What are some organic compounds microbes can use in respiration other than glucose?
Polysaccharides and disaccharides lipids proteins
Oxidative phosphorylation is the mechanism by which cellular _____ uses the reducing power generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP.
Respiration
Oxidative phosphorylation, the mechanism by which respiration uses the NADH and FADH2 generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP, involves what two steps?
The ETC generates a proton motive force ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP
In fermentation, when glucose is oxidized to form pyruvate, and toxic end products are formed, why do the bacteria keep going on?
To consume reducing power and regenerate NAD+ electron carrier
endergonic reaction
chemical reaction that requires a net input of energy because the products have more free energy than the starting compounds
prokaryotes that extract electrons from inorganic energy sources and pass them to an electron transport chain to generate a proton motive force that is used to make ATP are called
chemolithotrophs
An organic cofactor that functions as a loosely bound carrier of molecules or electrons to assist an enzyme is called a
coenzyme
Some enzymes act with the assistance of a non-protein component. This component is called a ____.
cofactor
When a compound binds to the active site of the enzyme, blocking access of the substrate to that site, the process is called...
competitive inhibition
the competitive inhibitor is ___ dependent
concentration
proteins ___ at higher temperatures
denature
a 10 degree C increase ____ the speed of enzymatic reaction up until max
doubles
what do reducing powers usually do?
easily transfer electrons to molecules; raise energy level of recipient molecule
examples of coenzymes
electron carriers: FAD, NAD+, NADP+
What generates the proton motive force?
electron transport chain
What membrane is the ETC in eukaryotes?
mitochondrial membrane
A cell will usually contain about how many different enzymes?
more than a thousand
enzymes have a ____ range of optimal conditions
narrow
When Nitrate is used as final electron acceptor in anaerobic respiration of glucose, what is produced?
nitrite, ammonia, N2
If an inorganic compound is given to a bacteria for respiration, will it undergo glycolysis?
no!
Is there a TCA/krebs or ETC in fermentation?
no!
Will electron carriers accept more electrons if in the reduced form?
no, always need to be in the oxidized form
is glucose fully broken down after glycolysis?
no, its only partially broken down
When respiration is taking place with inorganic compounds, are all typical pathways used?
no, only ETC is used because you cannot make pyruvic acid without carbon
The TCA cycle completes the _____ of glucose.
oxidation
What are cytochromes?
proteins that contain heme, a molecule that holds an iron atom in its center -There are several different cytochrome types
Flavoproteins
proteins to which flavin is attached (flavin type: FAD which is synthesized from riboflavin)
What do these large protein complexes serve as?
proton pumps
What is an example of a precursor metabolite?
pyretic acid (can be converted into amino acids alanine, leucine, or valine)
Three groups of carriers in ETC
quinones, cytochromes, flavoproteins
electrons are removed from energy source through series of ___ reactions
redox
what is the source of energy for iron bacteria
reduced iron (Fe2+)
Reduced electron carriers represent ____
reducing power
What are the yields of pentose phosphate pathway?
reducing power NADPH, variable amount yields VARY upon the alternative taken 2 precursor metabolites
The ATP generated by fermentation comes from...
substrate-level phosphorylation during glycolysis
oxidative phosphorylation
synthesis of ATP using the energy of a proton motive force created by harvesting chemical energy
substrate-level phosphorylation
synthesis of AtP using the energy releases in an exergonic chemical reaction during the breakdown of the energy source
Role of enzymes
they are biological catalysts that accelerate the conversion of substrate into product by lowering activation energy
why do chemolithotrophs incorporate CO2 into an organic form to fulfill their carbon needs?
they fulfill their energy needs from inorganic compounds such as H2S and NH3 that lack carbon, so they need to obtain their carbon elsewhere
is the action of allosteric inhibitors reversible?
yes
Would reactions occur with enzymes?
yes, but very slowly
Is substrate level phos. or oxidative phos. used with inorganic compounds are given for respiration
oxidative phosphorlyation
What is the ecological and environmental significance of nutrient cycling?
there are some many types of bacteria in the soil that a product of respiration for one bacteria cold be the source of energy for one chemolithotroph
What are some advantages and disadvantages of lactic acid production by fermenting microorganisms?
tooth decay creating flair and texture of cheese and yogurt production of pickles and cured sausages
Ethanol can be produced during fermentation by removing CO2 from pyruvate. Humans have taken advantage of microorganisms capable of this process in a number of ways. which of the following are examples of this?
wine and beer making making biofuels bread making making spirits
Which of the following describe enzyme specificity?
With few exceptions, a unique enzyme is required to catalyze each reaction in a cell The substrate must align spatially wit the active site Hydrogen and ionic bonding occur to induce the correct fit between substrate and active site
Do enzymes provide energy to help reactions proceed more rapidly?
NO
Are there special pathways for these compounds?
No
Inhibitory permanently changes the shape of the enzyme, making the enzyme non-fucntional
Non-competitive inhibition by enzyme poisons
Inhibitor reversibly changes the shape of the enzyme so that the substrate can no longer bind to the active site
Non-competitive inhibition by regulatory molecules
In a biosynthetic pathway, the end product generally acts as the allosteric inhibitor, allowing the cell to shut down the pathway when the product begins accumulating. this mechanism of control is called
feedback inhibition
TCA cycle completes... (aerobic respiration of glucose)
the oxidation of glucose
What allows feedback inhibition?
the regulatory molecule being an end product
What happens at the active site of an enzyme?
the substrate weakly binds
Chemiosmotic theory
the theory that a proton gradient is formed by the ETC chain and then used to power ATP synthesis
What is the active site of an enzyme?
the critical site to which a substrate binds by weak forces
Where does the transition step of aerobic respiration of glucose take place in bacterial cells?
the cytoplasm
When a single molecule of glucose is processed by glycolysis in an E. coli cell, which of the following make up the net gain of this process?
2 molecules of NADH, six precursor metabolites, 2 molecules of ATP
hydrogenation reaction
A reduction reaction in which an electron and an accompanying proton is added to a molecule
Which of the following are reasons an organism might use fermentation?
A suitable inorganic terminal electron acceptor is not available They lack an electron transport chain
enzymes are highly ____
specific, one at each step
What organism only has fermentation as an option and why?
streptococcus pneumoniae and because they lack and ETC
how is the ATP produced in glycolysis of aerobic respiration of glucose?
substrate-level phosphorylation
three processes to generate ATP
substrate-level phosphorylation oxidative phosphorylation photophosphorylation
prokaryotes are diverse in using energy sources...name 3 energy sources they an use
sunlight, organic compounds (glucose, polysaccharides, proteins, lipids), inorganic compounds (H2S, NH3)
what are some environmental factors that influence enzyme activity?
temperature, pH, salt concentration
Is the fermentation process aerobic or anaerobic?
anaerobic
cofactors ___ some enzymes
assist
what is the energy yield of fermentation?
2 atp
what is the source of energy for hydrogen bacteria?
H2
what are some electron carrier examples?
NAD+/NADH NADP+/NADPH FAD/FADH2
Pentose phosphate pathway
-Also breaks glucose down -Important in the biosynthesis of precursor metabolites (ribose 5-phosphate, and erythrose 4-phosphate)
enzyme name ends in ___
-ase
Process of electron transport chain
1. An electron carrier donates electrons to a hydrogen carrier 2. The hydrogen carrier must pick up protons from inside the cell 3. The hydrogen carrier passes electrons to a carrier that only accepts electrons 4. Because the electron carrier only accepts electrons, the protons are released to the outside of the cell 5. A proton motive force is set up as protons are moved from inside of the cell to the outside
fermentation pathway of mixed acids: 1. what microorganisms use this? 2. what are the end products?
1. E. coli 2. acetic acid, lactic acid, succinic acid, ethanol, CO2, H2
Differences between aerobic respiration of glucose and anaerobic respiration of glucose
1. anaerobic harvests less energy than aerobic 2. The composition of ETC is different in anaerobic: carriers may be different 3. the final electron acceptors have lower electron affinities
Fermentation pathway of butyric acid: 1. what microorganisms use this? 2. what are the end products? 3. Consumer products?
1. clostridium 2. butyric acid, butanol, acetone, isopropanol, CO2, and H2 3. biofuels
Fermentation pathway of 2,3-butanediol 1. what microorganisms use this? 2. what are the end products?
1. enterobacter 2. CO2, H2
What are the three steps for aerobic respiration of glucose?
1. glycolysis/pentose phosphate pathway 2A) transition step 2B) TCA or Krebs cycle 3. ETC
In an electron transport chain, electron carriers are found in what two general locations?
Grouped into large protein complexes that function as proton pumps Freely moving in the membrane where they can shuttle electrons between protein complexes
When sulfate is used as a final electron acceptor in anaerobic respiration of glucose, what is produced?
H2S
what is the source of energy for sulfur bacteria?
H2S
How does a non-competitive inhibitor work on an enzyme
It binds to a site other than the active site, altering the shape of the enzyme so the substrate can no longer bind
In respiring bacteria, how does ATP synthase generate ATP?
It uses the energy released from allowing protons to flow back into the cell to add a phosphate group to ADP
What are quinones?
Lipid-soluble organic molecules that move freely in the membrane; includes one that serves as a source of vitamin K for humans and other mammals
About how much energy is harvested in the anaerobic respiration of glucose?
More than 2, less than 38 average number=32/34
If a bacterial cell had no ATP and was given glucose, what would happen with glycolysis?
The cell would be unable to perform glycolysis, since it would lack the initial investment of high-energy phosphate groups
ETC and oxidative phosphorylation
The energy produced from the flow of electrons drives oxidative phosphorylation in which ATP is synthesized
what happens to the enzyme when an allosteric inhibitor binds to the allosteric site?
The enzyme shape is distorted and the substrate can no longer bind to the active site
In competitive inhibition, why is the inhibitor successfully able to bind to the active site, thereby blocking access of the substrate?
The inhibitor has a chemical structure similar to the normal substrate
Which of the following accurately describe the effect of sulfa drugs on the bacterial pathway for the synthesis of folic acid?
They inhibit an enzyme in the pathway They have structure similar to an intermediate in the pathway the effect is concentration dependent; more sulfa drug relative to substrate increases the likelihood of binding
Microorganisms can grow on a variety of organic compounds other than glucose, including polysaccharides, proteins, and lipids. How do they accomplish this?
They break these macromolecules down into appropriate precursor metabolites that are then introduced into central metabolism or used in biosynthesis.
The critical site of an enzyme to which a substrate binds by weak forces is called the
active site
How do cells produced ATP?
adding Pi to ADP using energy
What type of respiration is used when organic compounds are used for respiration?
aerobic OR anaerobic
what is an example of non-competitive inhibitors
allosteric inhibitors
what would be the best definition of respiration?
an energy yielding process using ETC or oxidative phosphorylation from a source of energy
so why not anaerobic?
because you need a final electron acceptor that may not be prsent
What degrades fatty acids?
beta-oxidation to then enter TCA cycle
non-competitive inhibitors
bind to sites other than the active site of an enzyme
competitive inhibitor
binds to the active site of an enzyme
is respiration using inorganic compounds aerobic or anaerobic?
both
Does glycolysis take place aerobically or anaerobically?
both!
enzymes are biological ____
catalysts
Why would bacteria choose the pentose phosphate pathway over glycolysis?
for biosynthetic purposes
Enzyme name reflects ____
function
in fermentation, the ATP-generating reactions are only those of ____
glycolysis
What do microbes excrete when organic compounds are given for respiration?
hydrolytic enzymes to degrade the compounds further to appropriate precursor metabolites and transport subunits into the cell
What is the final electron acceptor in the ETC of anaerobic respiration of glucose?
inorganic molecules such as nitrate, sulfate, carbonate (NO3-, SO4, CO3)
When a substrate binds to the active site of an enzyme, what happens to the enzyme?
it slightly changes shape
Components of the ETC: most carriers are grouped into...
large protein complexes
What enzyme is used to degrade lipids?
lipases
Quinones
lipid-soluble molecules that move freely and can transfer electrons between complexes
what is the energy yield when using inorganic compounds for respiration?
low compared to organic
what are the optimal environmental conditions for enzymes in terms of salt and pH
low salt and neutral pH
examples of cofactors
magnesium, zinc, copper, other trace elements
then why ferment?
maybe there is a lack of oxygen
The ETC is ___-embedded electron carriers
membrane
why is mercury an enzyme poison? Describe the steps
mercury oxidizes the S--H groups of amino acid cysteine, coverts it to cystine, cystine cannot form important disulfide bond, enzyme changes shape and becomes nonfunctional
oxidation reactions
A chemical reaction in which a substances loses electrons
regulatory molecule is usually the ____ product
end
Consider the maximum theoretical ATP yield from oxidative phosphorylation of a single molecule of glucose in prokaryotes. Match the relative contributions of the central metabolic pathways and final yield with their approximate contribution in terms of ATP. TCA Cycle, Total max yield, glycolysis
TCA cycle: 22 tap Glycolysis: 6 ATP total max yield: 34 ATP
ETC uses ____generated by glycolysis, Transition step, and TCA cycle to synthesize ATP in aerobic respiration of glucose
reducing powers NADH and FADH2
Role of electron carriers
electrons that are removed from the energy source are transferred to electron carriers which in turn transfer electrons the the final electron acceptor
Pass ___ sequentially, eject ____ in the process
electrons, protons
Electrons moving through the ETC supply ____ in order to establish a proton gradient across the membrane
energy
The proton motive force results from a gradient: more protons on one side of the membrane relative to the other side. This means that, if protons are allowed to flow back down the gradient, ____ is released that can be harvested to drive ATP synthase.
energy
what are some non-competitive inhibitors that are not reversible
enzyme poisons- mercury
Which of the following are true statements about what happens to glucose inside a cell? -All the glucose molecules are oxidized to CO2, generating ATP and reducing power in the process -Some glucose might be oxidized to CO2, generating the maximum amount of ATP -Glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism -Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis
All but number 1
4 general groups of chemolithotrophs
1. hydrogen bacteria 2. sulfur bacteria 3. iron bacteria 4. nitrifying bacteria
