1. Compare coenzymes with substrates. Explain how they both collaborate in enzyme catalysis.

2. High levels of ammonia (NH3) are toxic to mammals. One reason is that ammonia bonds with alphaketoglutarate in the citric acid cycle, forming the amino acid glutamate. This removes alphaketoglutarate from the Krebs cycle. Explain what consequences this will have for the cell.

3.  Pyruvate + NADH + H+ à lactate + NAD+

Name the oxidizing agent in the above reaction. Explain

4. Trace the steps of a carbon atom from a starch molecule contained in the Donut you just eat until it ends up in a muscle protein.

Please answer ASAP!!

Thank you.

The bacterial one-hybrid assay holds E. coli cells hostage until our protein of interest can active transcription and translation of enzymes from the HIS3 and URA3 genes. These enzymes are needed to produce Histidine and Uridine, which are both needed for cells to grow and divide. Make an estimate, based on enzyme kinetics and any other information you may need, of how many HIS3 and URA3 enzymes will an E. coli cell need to grow and divide at a normal rate. How many are needed when we add 10 mM 3-amino-1,2,4-triazole (3AT) to the growth medium as a competitive inhibitor of HIS3?

1. What effect does an absence of oxygen (O2) have on the electron transport chain? What would happen if, in this anaerobic environment, you artificially decreased the pH of the intermembrane space of the mitochondrion? Explain.

2. Would you expect high levels of ATP to inhibit or activate glycolysis? Explain your answer.

3. A glucose-fed yeast cell is moved from an aerobic environment to an anaerobic one. How would its rate of glucose consumption change if ATP were to be generated in the yeast at the same rate as before? Explain.

4. Imagine you are a pharmacological researcher who wants to design a drug that inhibits a particular enzyme. Upon reading the scientific literature, you find that the enzyme's active site is similar to that of several other unrelated enzymes. Would a competitive or noncompetitive inhibitor be a better drug? Explain.

1. Alcohol intake in excess of normal daily caloric requirements results in an increase in?

1. NADH/NAD⁺
2. Thiamin absorption
3. The ability of the liver to synthesize ATP
4. Weight
5. Gluconeogenesis

2. In aqueous solution, amphiphilic lipids such as lecithin:

1. Dissolve well due to the ability of the phosphate group to ionize.
2. Cannot interact with water because as lipids they are predominantly hydrophobic.
3. Can dissociate into a soluble hydrophobic portion and an insoluble hydrophilic portion.
4. Form sheets(micelles) composed of two layers.
5. Dissolve well due to the permanent positive charge on the choline nitrogen

3. Enzyme co-factors ALWAYS

1. Are inorganic molecules
2. Are covalently bound to enzymes
3. Form a complex with the substrate to make it more accessible to the enzyme
4. Maintain the native conformation of the enzyme
5. Provide a reactive group not found in the enzyme but necessary for its activity.

4. Proteolytic activation

1. Occurs at a modulator site that is distinct from the active site
2. Is initiated by an end product acting as a positive modulator
3. Occurs when a peptide segment is removed from a protein
4. Involves transcription of a regulatory protease
5. Produces a regulatory protein which activates the enzym

5. A nutrient known to be essential in ALL human diets is

1. Cholesterol
2. Choline
3. Palmitic acid
4. Sphingomyelin
5. Linoleic acid

The herbicide glyphosate kills plants by inhibiting an enzyme needed for synthesis of phenylalanine. Deprived of phenylalanine, the plant cannot make the proteins it needs, and it gradually weakens and dies. Although a small amount of glyphosate is deadly to a plant, its human toxicity is quite low.

(a) Suggest why this powerful herbicide has little effect on humans.

(b) Discuss the chemical properties of Glyphosate as an herbicide.

Which of the following reactions are catalyzed by kinases:

Peptides hold great potential for the cancer therapy because of their ease of rational design. During your first undergraduate research project, you conducted a screen to find peptides that inhibit proliferation of cancer cells. From a large library of 9-residue-long peptides, you got a hit!

Unfortunately, someone mislabeled the vial containing the active peptide, so now you can’t be sure of its entire sequence.

The 3rd amino acid could be any one of the 20 amino acids!!

           M I   _ S E L F I E

Luckily, you collected information about the net charge of all the peptides in your library as a function of pH

(a) Based on the information below, what is the full sequence of this peptide? (please provide a rationale for your answer)

At pH 3, net charge = +1
At pH 7, net charge = -1
At pH 12, net charge = -2

Peptide Sequence:

(b) Estimate the isoelectic point (pI) of the peptide and show how you determined this value.

Part 8

Choose all that apply. The ability to perform differential gene expression is essential to cells because; (hint: three correct choices)

What is the function of the terminator?

• A. stops metastasis of cancers

• B. stops transcription of a gene

• C. stops DNA replication

• D. stops protein synthesis

By definition, a mutation is;

• A. change in a cell cycle controlling protein

• B. replacement of a nucleotide with another

• C. a permanent change in normal DNA sequence

• D. always a harmful event in a cell

What is the function of rRNAs in protein synthesis?

• A. bring the message from the gene to make proteins

• B. makeup the structure of the ribosome

• C. choose the correct amino acid to be added to the chain

• D. bring amino acids to be added to a growing protein chain

1. Sulfide, Indole, Motility (SIM): Bacteria that have the enzyme tryptophanase, can convert the amino acid tryptophan to indole. Indole reacts with Kovac’s reagent to form a Black Color. T or F

2. GROWTH ON EMB & MAC: Which Observations are INCORRECT?

1. both EMB and MAC contain dyes that inhibits gram-positive bacteria.
2. both EMB and MAC differentiate gram negative organisms based on their ability to ferment lactose
3. both EMB and MAC indicate that the pH becomes basic (alkaline) because of fermentation
4. all the above are incorrect
5. none of the above

3. GROWTH On MSA (7.5% NaCl). Which Observations are CORRECT?
   1.    MSA is selective for Staphylococci
   2. Staphylococci species are Gram +
   3.     MSA is differential based on acid production
   4. Acid production on MSA changes the phenol red (acid indictor) to yellow
   5.    All the above

4. Blood Agar is differential with respect to Hemolysis. Which of the following is CORRECT?
   1. hemolytic enzymes are produced in produced hemolysis
   2. Beta (ß) hemolysis and results in the complete breakdown of the RBCs
   3. Alpha (a) hemolysis Partial destruction of the RBCs leads to a greenish brown color
   4. Gamma(γ)hemolysis causes no damage to the RBCs
   5. all the above are correct

5. Blood Agar Plates have the enzyme catalase. We use blood agar to determine whether an unknown bacterium is catalase positive. T or F

6. Differential and/or Selective Media include EMB, MSA, MAC, Blood Agar Plates, Simmons Citrate & SIM Tubes. Regarding what was observed on these media, which is CORRECT?
   1.     a change in color on any of those media means we are looking at the result of enzyme activity
   2.   acid production, or no -acid production indicate the presence or absence of specific enzymes
   3.     all the above are correct
   4.   none of the above are correct

7. A pH sensitive dye (in media) responds to acid production with a change in color, and
   1. MacConkey (MAC) media turns reddish
   2. Eosin Methylene Blue (EMB) agar media inoculated with Escherichia coli produces a green metallic sheen
   3. Mannitol-salt agar (MSA) turns yellow
   4. all the above
   5. none of the above

8. Page 284 of Benson’s summaries some “characteristics of common Gram-positive and Gram-negative bacterial Species.”. The Table identifies a list of Gram (-) bacteria that are all catalase +. Which of the following makes sense?
   1.    the catalase test can be used to categorize bacteria., i.e. they can be categorized as catalase (+ or -)
   2. the catalase test alone could be used to identify a specific Gram (-) bacteria on that list
   3.   all the above makes sense
   4. none of the above makes sense

1. If we inoculated MSA (which has 7.5% NaCl) with Gram negative bacteria, what would be the result? We would find that the growth of MOST Gram-negative bacteria is inhibited by the 7.5% NaCl. T or F

2. If we inoculated MAC with Staphylococcus aureus, what would be the result?

1. we would observe growth and acid production (fermentation)
2. we would observe growth, but no acid production (fermentation)
3. we would observe no growth
4. none of the above

3. If we inoculated EMB with Staphylococcus aureus, what would be the result?

1. we would observe growth and acid production (fermentation)
2. we would observe growth, but no acid production (fermentation)
3. we would observe no growth
4. none of the above

4. S. aureus is catalase positive, which means 2H₂O+ catalase -> O₂ (gas) + 2H₂     T or F

5. Selective & Differential media have specific carbohydrate substrates. Which is CORRECT?
   1. the carbohydrate substrate in MAC is mannitol
   2. the carbohydrate substrate in EMB is eosin
   3. the carbohydrate substrate in MSA is mannitol
   4.   all the above
   5. None of the above