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Regulation of metabolism at the level of transcription is very common in prok. cells, but much less than in euk. systems. What is a good reason for this?
- more efficient in prok. because they have no mRNA processing, so transcipts can be directly translated to proteins
- faster as prok. cells do transcription/translation in the cytosol
- operons facilitate regulation
The complete oxidation of glucose typically involves which three stages?
glycolysis, TCA cycle, and electron transport system
Which of the following is not a product of fermentation?
Regulation of a branched biosynthesis pathway by means of a key enzyme with allosteric sites that bind two different end products is best described as
concerted feedback inhibition
Which of the following is NOT a feature of group translocation of sugars?
It uses energy from chemiosmosis to move solutes across the membrane (chemiosmosis is when ions move across a semi-permeable membrane, such as the membrane inside mitochondria)
Which statement best summarizes the reactions of the Embden Meyerhof pathway?
Glucose + 2 ATP + 2 NAD+ -> 2 pyruvate + 4 ATP 2 NADH
Which bacterial membrane transport mechanism would be MOST effective for importing solutes that are scarce in the environment in acidic conditions?
Anaerobic photosynthesis differs from aerobic photosynthesis in that ...
Anaerobic photosynthesis does not produce oxygen.
All of the following statements about transport of nitrogen compounds are true except:
Nitrogen compounds are transported exclusively by ABC mechanisms
In ________ conditions, proton symport may be augmented by the symport of molecules in conjunction with the movement of ________.
Compared with respiration, fermentation ...
does not require an electron transport chain
The metabolic reactions of all cells are governed by ...
the laws of thermodynamics
The main processes of central metabolism in cells can be considered to be
Amphibolic (used to describe a biochemical pathway that involves both catabolism and anabolism)
In the overall process of oxygenic photosynthesis and carbon fixation:
carbon dioxide is reduced and water is oxidized
Prokaryotic cells maintain intracellular pools of metabolic intermediates and key nutrients. Which of the following is true of these pools?
Cells typically maintain high concentrations of nucleotide triphosphates relative to di- and mono-phosphates
The pentose phosphate pathway in prokaryotes:
produces reducing power in the form of NAD(P)H
Which of the following statements about the Entner-Doudoroff pathway is true?
The ratio of ATP used:ATP produced is the same as the Embden-Meyerhof pathway (the Entner-Doudoroff pathway is a metabolic pathway that uses different enzymes to catabolize glucose to pyruvate)
The enzyme alcohol dehydrogenase
reduces acetaldehyde to ethanol
The glyoxylate cycle allows cells to carry out the net conversion of fatty acids to carbohydrates by modifying the TCA cycle to:
Skip two decarboxylation steps
Which of these statements is true about metabolism of amino acids by prokaryotic cells?
Amino acids can be synthesized from intermediates of central metabolism
Which of the following is the best example of primary active transport?
ENERGETICS OF MEMBRANE TRANSPORT: Chemiosmotic mechanisms can use the facilitated diffusion of protons along their concentrations gradient to power transport of solutes (e.g. proton symport). Why is this considered active transport, not passive transport?
- the solute being transported is moved against its own gradient
- this is linked to the proton gradient/PMF
- the proton motive force must be established/maintained by an input of energy (cellular, or even sunlight)
MECHANISMS OF MEMBRANE TRANSPORT: Describe at least two advantages/benefits that come from the use of group translocation. Use the example of the glucose phosphotransferase system.
- chemically changing the glucose to G6P keeps the intracellular glucose concentration low, making it easier to import
- phosphorylating glucose adds charges, effectively "trapping" it inside the cell (ex. it cannot diffuse out or pass through glucose transporters)
- phosphorylation of Glc G6P is the first step of glycolysis, so this step aids central metabolism by generating hexose phosphate
CARBON METABOLISM: Describe two distinct metabolic outcomes for the catabolism of glucose in the absence of oxygen. Consider two cases: one cell (Cell X) that has a functioning ETS, and another cell (Cell Y) that does not.
A. Name two categories of catabolic energy metabolism, based on the fates of the carbon atoms and electrons that are found in pyruvates produced by glycolysis (one will be used by each cell)
B. What are the fates of the electrons in each of the two pathways you described for part A (where do they end up, in what molecules or in what form)?
- Cell X would likely carry out anaerobic respiration
- In cell X, carbon would be fully oxidized by TCA to carbon dioxide, electrons would go through ETS to a terminal electron acceptor other than oxygen (an example compound could be provided here as well).
- Cell Y would likely carry out fermentation
- In cell Y, carbons would exit glycolysis as pyruvate and electrons would exit glycolysis as NADH, both carbons and electrons would likely end up in the same compound (an example such as lactate, ethanol, butanediol, etc. could be provided here as well).
A. Describe the feedback and regulatory effects on the pathway of the accumulation of both products (ADP and GMP) at the same time.
B. In this example, why would PRPP amidotransferase (enzyme 2) be a better regulation point than PRPP synthetase (enzyme 1)? Consider overall cell metabolism and cellular processes, not just this one pathway.
A. Accumulation of both end products would display feedback inhibition at two key points: both ADP and GMP would inhibit the beginning of the entire pathway; ADP would inhibit its own branch (enzyme 3) and GMP would inhibit its own branch (enzyme 5).
B. Answer should express the idea that regulation of purine nucleotide synthesis would be best regulated at the first unique/committed step for purines (PRPP amidotransferase); PRPP is a key precursor for other cellular processes such a pyrimidine synthesis that might be required even if the purine synthesis is not.
Which of the following statements about cell membranes of psychrophiles (low temperatures, ranging from -20 degrees to +10 degrees is true?
They have less branching in the fatty acid tails of their membrane lipids
Psychrophilic organisms have adaptations to _______ environments, including membranes with _________.
low temperature, more unsaturated FA chains
Unlike eukaryoties, in prokaryotes oxidative phosphorylation and chemiosomosis
occurs at the plasma membrane and not in the mitochondria
An electron transport system requires all of the following except:
A culture which is maintained in a chemostat and stays in log phase indefinitely is displaying
Some halophiles such as those found in the Great Salt Lake can use the pigment bacteriorhodopsin to:
use light energy to pump protons across cell membranes without ETC
What statement is true of extremophiles
Most extremophiles are Bacteria, but most Archaea are extremophiles
Cytoplasmic decarboxylase enzyme reactions remove protons from solution and produce carbon dioxide, and can be used as a survival strategy by which bacteria?
Which of the following methods best exemplifies a direct method of quantifying bacterial growth?
Plate counts of a bacterial culture
Prokaryotes in extreme hydrogen ion conditions must maintain plasma membrane homeostasis regarding inside/outside:
all of these (PMF, chemical concentration, pH, charge)
All of the following steps are involved in aerobic electron transport chain of a chemoheterotrophic bacterial cell. Which step happens last?
Oxidase reduces O2
If you were to move cells in mid-log phase growth from an inorganic minimal medium to a rich organic medium and plot the growth curve, you would expect:
a lag phase, then continued growth at a faster rate
Which of the following may be used as terminal electron acceptors for bacterial respiration?
Which type of radiation is most dangerous to cells because it causes double-stranded DNA to form thymine-thymine dimers?
Far UV (200-290 nm)
If you were to move cells in mid-log phase growth from a rich organic medium to an inorganic minimal medium and plot the growth curve, you would expect:
a lag phase, then continued growth at a slower
The standard bacterial growth curve may include all of the following except
Synchronous growth of bacterial culture can be described as:
Balanced growth in which all cells are at the same point in the cell cycle
"The Great Plate Count Anomaly" describes the fact that culture-based techniques for quantifying microbial growth almost always underestimate the number of living cells in a sample. What most likely accounts for this phenomenon?
some cells may be in the VBNC state
The gut bacterium Heliobacter pylori is not an acidophile, but lives in extremely acidic conditions. It can actively change its pH environment outside the cell by:
urea hydrolysis producing ammonia to absorb protons
In growing pure culture of bacteria (in a closed system), which of the following statements is true?
DNA content of cells is greater at the beginning of log phase vs. the end of log phase
Which of the following statements about teichoic acids (TA) is correct?
TA containing polyribitol phosphate are attached to peptidoglycan through a sugar-containing linker moiety
Which of the following would be the best way to determine whether a newly discovered microbe belongs to the domain Archaea, Bacteria, or Eukarya?
determine gene sequence for small ribosomal subunit rRNA
Prokaryotic cells may form polyhydroxybutyrate granules:
in carbon-rich conditions to store nutrients
A key difference between archaea and bacteria is:
archaea have 80S ribosomes; bacteria have 70S ribosomes
The fundamental structure of a peptidoglycan molecule is formed by:
Long NAM-NAG polymers crosslinked by peptides between NAM in one chain and NAM in another
Examples of nonpolar lipids found in prokaryotic plasma membranes include
Carotenoids and quinones
All of the following are true of bacterial polyhydroxybutryate bodies except:
they contain large amounts of inorganic polyphosphate
A bacillus bacterium with a single flagellum at each end is described as
Which of the following statements is NOT true about prokaryotes and eukaryoes?
Euk. lack cell walls, prok. have cell walls
Cell-wall-less prokaryotes with cell membranes containing large amounts of cholesterol or protein for stability include:
Prokaryotic cells may form cyanophycin granules:
in nitrogen-rich conditions to store nutrients
Which of the following statements about prokaryotic plasma membranes is correct?
In archael phospholipids, isoprenyl alcohol tails are almost always connected to the glycerol backbone by ether bonds
Gram-positive cell walls may contain all of the following acidic polymers except
In addition to providing structure and protection, which of the following is a key function of prokaryotic cell walls?
They give the cell its morphological character
An example of homopolymeric bacterial capsule material would be
polymers made entirely of poly-D-glucose
Which system of motion is commonly used by groups of bacteria to swim en masse and is important in biofilm formation?
Which type of microscope uses electrons to provide a cross-sectional view of the interior of a prepared sample?
Transmission electron microscope
Cell disruption methods commonly used for the study of prokaryotic organisms include all of the following except:
Regulation of cell motility in response to the environment requires all of the following EXCEPT:
Switching from anaerobic to aerobic metabolism
Which of the following statements about prokaryotic plasma membranes is correct?
Archaeal plasma membranes can be one molecule in thickness.
What are all the terminal electron acceptors used in aerobic respiration?
what do we call it if we use molecular oxygen as a terminal electron acceptor?
what is the terminal electron acceptor in aerobic respiration?
Inhibition mechanisms: Regulation of Metabolism
2 different enzymes that catalyze same rxn
Concerted feedback inhibition
1 enzyme, with the same enzymes
Sequential feedback inhibition
common precursor inhibits enzymes
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