Metabolism Flashcards
What is respiration?
electrons are passed from an electron donor to a terminal electron acceptor via the electron transfer system in the cell membrane forming a proton gradient
What is aerobic respiration?
O2 is the final electron acceptor which then is reduced to H2O
What is anaerobic respiration?
An ion or compound other than O2 is the terminal electron acceptor(nitrite, nitrate, sulfur)
Although the presence of oxygen yields more ATP what is a negative characterization of it?
Forms two highly toxic compounds
Why do anaerobes die in the presence of oxygen?
They lack catalase and superoxide dismutase
Do facultative anaerobes grow faster in aerobe or anaerobe conditions?
Grows faster while respiring aerobically due to a higher yield of ATP per glucose
How do chemoautotrophs generate ATP?
Generate ATP by oxidizing inorganic compounds via respiration and the electron transport system.
Examples of inorganic energy sources
H2S, Fe2+, Mn2+
Gets its energy from sunlight and its carbon from CO 2?
Photoautotrophs
Ex. algae and cyanobacteria
Gets its energy and carbon from inorganic sources? Give examples of inorganic sources of energy and carbon for these microbes.
Chemoautotrophs
-Ex: H2S, Fe2+, Mn2+
Gets its energy from sunlight and its carbon from organic compounds?
Photoheterotrophs
Is most similar to animals in its energy and carbon sources?
Chemoheterotrophs
Is most similar to plants in its energy and carbon sources?
Photoautotrophs
What are ways in which prokaryotes can generate an ion transmembrane gradient?
-Respiration(aerobic or anaerobic)
-photosynthesis(oxygenic or anoxygenic)
-Enzyme ion pumps: membrane protein not associated with electron transport chain can that can pump protons or other ions across the membrane
-scalar reactions: consume or produce ions rather than move them
What is photosynthesis?
Light energy activates electrons in chlorophyll in which flow down through an electron transport system to produce ATP or a reducing power
Cyanobacteria
Have the same oxygenic photosynthesis as algae and plants
- water is the electron donor, oxygen formed
Anoxygenic
-Other bacterias carry out anoxygenic photosynthesis using electron donors other than water such as H2 or H2S
-These bacteria include purple sulfur bacteria, purple non sulfur bacteria, and green sulfur bacteria
Passive Transport
-Difussion
-Facilitated Diffusion: uses channel proteins for specific molecules
-Requires no energy and only occurs if solute is at a higher concentration outside the cell
Active Transport
-requires energy
-Ion coupled: uses energy from the transmembrane ion gradient
-ABC transport: uses ATP hydrolysis to pump a nutrient into the cell after it has bound its corresponding periplasmic binding protein
-Phototransferase system(PTS): uses a high energy phosphate group to chemically modify a solute after it is transported so it can’t exit
How do autotrophs fix CO 2 to make their precursor metabolites?
-uses the Calvin cycle for CO2 fixation
-catalyzes addition of CO2 in RUBISCO
What are 3 common pathways that comprise central metabolism?
Pentose phosphate pathway, glycolysis, and TCA
What is the purpose of the 13 precursor metabolites?
Biosynthesis
of the building
blocks (e.g.
sugars, amino
acids,
nucleotides,
fatty acids)
Prototrophs
Bacteria that have no nutritional requirements for the building blocks
Auxotrophs
are mutants of the prototrophs that now have one or more nutritional requirements for the building blocks
-Can grow if provided with the intermediate after the blocked step
What is feedback inhibition?
- a type of noncompetitive inhibition
-a way to control metabolic pathways in which the final product of the pathway inhibits the enzyme that catalyzes the first step of the pathway
Prokaryotes have an amazing diversity in the ways they can metabolize energy. Which of these ways are also used by plants and animals? Which of these are unique to prokaryotes?
-photoheterotrophy and chemoautotrophy
Transmembrane ion gradient
*proton gradient across the membrane = “proton motive force”
*a proton gradient represents a form of electrochemical energy
*ATP synthase (F 1 F 0 ATPase) mediates the interconversion of the
energy of the gradient with ATP
Define: fermentation. What is the relationship between substrate-level phosphorylation and fermentation? What is NOT needed for fermentation to occur?
-fermentation: pathway in which glucose is partially oxidized into acids and alcohols
-when microbes are fermenting they use substrate level phosphorylation to generate ATP
-Fermentation does not require oxygen to occur
does not involve transmembrane ion gradient
-Many fermentations involve pyruvate
What are the similarities & differences btwn. fermentation & Anaerobic respiration?
→ Similarities: Don’t need O2. Generate ATP.
→ Differences: Fermentation doesn’t use a Transmembrane ion gradient, while Anaerobic resp. does. Anaerobic resp. uses something other than O2 as final electron acceptor in ETC.
What 2 qualities of enzymes make them so critical for life? What is the “active site”? What is an “allosteric site”?
1) Enzymes can catalyze reactions (speed up reactions)
2) Enzymes are very specific, they can control who is in charge of the reaction (lock and key model)
Active site = where the substrate binds to
Allosteric site = site other than active site, when something binds here it changes the enzyme, which doesn’t allow the reaction to go forward since change in shape = change in function for the enzyme
Which 3 macromolecules are most abundant (by weight) in an E. coli cell?
Protein, RNA, phospholipids
Substrate Level Phosphorylation
Transfer of high energy phosphate bond to ADP to make ATP
What are two ways to synthesize ATP?
-substrate level phosphorylation
-transmembrane ion gradient
Competitive Inhibition
A competitive inhibitor competes for binding to the enzyme’s active site
Can CO2 be used as an energy source?
No
Define: oxidation, reduction. Of the following pairs of compounds, state which is more highly reduced: H2O vs. O2; C6H12O6 vs. CO2; NAD+ vs. NADH; Fe3+ vs. Fe2+.
➟ Oxidation: the loss of electrons
➟ Reduction: the gain of electrons
➟ H2O2 vs. O2: H2O2 b/c gain of H
➟ C6H12O6 vs. CO2: C6H12O6 b/c gain of H. Also b/c glucose is a known energy source but CO2 is fully oxidized, so it has no harvestable energy.
➟ NAD+ vs. NADH: NADH b/c gain of H
➟ Fe^3+ vs. Fe^2+: Fe^2+ b/c gain of electrons
What are examples of organic carbon sources?
Lipids, carbohydrates, proteins
What are sulfa drugs example of?
Competitive inhibitors of the bacterial enzyme for making folic acid
Why does fermentation yield less ATP?
Because it needs to regenerate NAD+ so pyruvate is reduced to yield lactate
Who carries out fermentation for fueling and why?
Heterotrophs because fermentation only uses organic molecules as substrates
Define fermentation
Process in which organisms convert carbohydrates into alcohol or acids
