Look at this undecapeptide: Arg Asp Cys Glu Leu Lys Met Phe NH4+. What would each step do to the udecapeptide? Draw the final structure.

a. treatement with iodoacetate that had no affect on the undecapeptide.

b. treatment with 2 x 2-mercaptoethanol yielding a tripe-tide and octapeptide.

c. treatment with carboxypeptidase A liberated leucine.

d. treatment with cyanogen bromide yielding a methionine, a tripeptide and a heptapeptide.

The question states that these amino acids are only some components of the undecapeptide structure and that some amino acids within this structure may be repeated. The point is to determine the correct structure following several treatments. After these treatments, what conclusions can you make about the structure of the undecapeptide? What might the structure be?

Amino Acids and Proteins Lab, post lab questions

1.Which samples gave positive results in the biuret test? Were there any differences in the color and intensity of the positive test results? How general is the biuret test for detecting proteins of different types?

2. Which amino acids are identified by means of the xanthoproteic test? Which protein samples gave positive xanthoproteic test results? Comment on the composition of the protein samples based on the results of this test.

3. Which amino acids are identified by means of the Sakaguchi test? Which protein samples gave positive Sakaguchi test results? Comment on the composition of the protein samples based on the results of this test.

4. Which amino acids are identified by means of the nitroprusside test? Which protein samples gave positive nitroprusside test results? Comment on the composition of the protein samples based on the results of this test.

5. Compare and contrast the effect of strong acid (HCl) on albumin, casein, and gelatin. Which protein was most sensitive to the action of strong acid? Least sensitive?

6. Which metal salts (CuSO4 and AgNO3) caused albumin denaturation? How does this observation relate to the toxicity of silver salts versus copper salts?

7. You have just been to the doctor’s office to receive an inoculation. Before administering the injection, the doctor wipes the area with an alcohol swab. Do the results for albumin denaturation support the use of isopropyl alcohol as a disinfectant? Explain.

8. The biuret test is used to identify proteins. Compare the results obtained in the biuret test with albumin and the filtrate after the salting-out procedure in Part B. How effective is the “salting-out” procedure with ammonium sulfate?

9. Is denaturation of albumin by ammonium sulfate reversible or irreversible? Explain on the basis of your observations for the biuret test with albumin and the redissolved precipitate, respectively.

Fill in the blanks with the following terms:

Lactate NAD+ fermentation
NADH aerobic anaerobic acetyl CoA


When oxygen is available during glycolysis, the three-carbon pyruvate may be oxidized to form:

(1) ___________________ + CO2, The coenzyme (2) _________________ is reduced to (3) ___________.

Under (4) _______________ conditions, pyruvate is reduced to (5) _________________. In yeast, pyruvate forms ethanol in a process known as (6) __________________.

Associate each of the following descriptions with pathways in glycogen metabolism:
a. glycogenesis b. glycogenolysis
1. _____ breakdown of glycogen to glucose 2._____ activated by glucagon
3. _____ starting material is glucose-6-phosphate 4._____ synthesis of glycogen from glucose
5. _____ activated by insulin 6._____ UDP activates glucose


 
Gluconeogenesis: Glucose Synthesis
Associate each of the following descriptions:
a) gluconeogenesis b) pyruvate c) pyruvate kinase
d) pyruvate carboxylase e) Cori cycle

1. _____ an enzyme in glycolysis that cannot be used in gluconeogenesis

2. _____ a typical non-carbohydrate source of carbon atoms for glucose synthesis.

3. _____ a process whereby lactate produced in muscle is used for glucose synthesis in the liver and used again by the muscle.

4. _____ the metabolic pathway that converts non-carbohydrate sources to glucose.

5. _____ an enzyme used in gluconeogenesis that is not used in glycolysis.

6. _____ a metabolic pathway that is activated when glycogen reserves are depleted.

Match each of the following with the correct metabolic pathway:
A. glycolysis B. glycogenolysis C. gluconeogenesis
D. glycogenesis E. fermentation

1. _____ conversion of pyruvate to alcohol
2. _____ breakdown of glucose to pyruvate
3. _____ formation of glycogen
4. _____ synthesis of glucose
5. _____ breakdown of glycogen to glucose

 

Reverse Transcriptase (RTase) is an enzyme found in HIV. What is the function of this enzyme in HIV’s life-cycle? What are some uses of RTase for human applications?

18. What attracts or directs the synthesis enzyme to the template in DNA Replication? a. Start Codon b. Promoter c. 5'-cap d. Primer e. Poly-A Tail

32. Which of the following statements is true regarding introns? a. human genes do not have introns b. introns encode for gene products c. introns are part of the mRNA that are translated d. introns have no function

28.Protein function? a. is determined b interaction of amino groups with other molecules b. is the same even with single amino acid modifications resulting from mutations c. will not change in different environments d. will not be affected by pH e. is dependent on its three-dimensional structure

36.There are FOUR major events in cell division. Which of the following is NOT one of them? a. Cytokinesis, the division of the cytoplasm and separation of the two new cells b. DNA segregation, which is the distribution of the DNA into the two new daugther cells c. Cell cycle arrest to allow the cells to recuperate d. Reproductive signals initiate cell division e. DNA Replication

What types of modifications can occur after a polypeptide chain has been completed by a ribosome? (Choose as many that apply) A) Glycosylation B) Removal of methionine C) Hydrolysis D) Addition of amino acids E) Phosphorylation

What types of modifications can occur after a polypeptide chain has been completed by a ribosome? (Choose as many that apply)

A) Glycosylation

B) Removal of methionine

C) Hydrolysis

D) Addition of amino acids

E) Phosphorylation

You are to test the effectiveness and specificity of ninhydrin by spraying spots of water, the protein bovine serum albumin (BSA), and amino acids with ninhydrin. What do you predict the results will be, and why? What assumptions must you make?

1. a. What are the important amino acids around heme in myoglobin/hemoglobin.

b. Why is Fe a +2 charge in the protein environment but able to oxidize to fe 3+ in a non-protein environment? Why is this pertinent to Oxygen binding?