1. In a protein, why does when Ala is replaced with Ile, it loses its activity but when Lys is replaced by Arg and Leu to Ile, it only has little effect on protein structure and function? Explain. 2. Why do proteins cannot be denatured reversibly when they are chemically altered to change the chemical composition of certain side chains? Explain.

1. In a protein, why does when Ala is replaced with Ile, it loses its activity but when Lys is replaced by Arg and Leu to Ile, it only has little effect on protein structure and function? Explain. 2. Why do proteins cannot be denatured reversibly when they are chemically altered to change the chemical composition of certain side chains? Explain.

Biology: The Unity and Diversity of Life (MindTap Course List)

14th Edition

ISBN:9781305073951

Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr

Publisher:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr

Chapter39: Digestion And Nutrition

Section: Chapter Questions

Problem 2CT: A python can survive by eating a large meal once or twice a year. When it does eat, microvilli in...

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6. Which amino acid would most likely be found on the surface of a protein molecule at physiological pH? a. Isoleucine b. Lysine c. Alanine d. Proline 7. Which of the following statements about terpenes is NOT true? a. They are a type of terpenoid. b. They all contain double bonds. c. They are all made up of 5-carbon units. d. They all contain oxygen. 8. How are the plasma membranes of mammalian and bacterial cells similar? a. They typically contain cholesterol. b. They have negatively charged lipids on their surfaces. c. They contain lipids that are involved in signal transduction. d. They are made up of many different types of phospholipids.
3. A biochemist purified a protein from the bloodstream and determined its molecular weight under several conditions. In 8 M urea, which denatures the polypeptide chain, the molecular weight of the protein was 150,000 Da. She found that under reducing conditions the molecular weight of the protein was 75,000 Da, while under oxidizing conditions the molecular weight of the protein was 150,000 Da. Explain these results.
How can strong acids denature proteins? Digestion of proteins in humans begins in the stomach where the environment is very acidic. Explain the significance of the stomach’s acidity to protein digestion. Will the precipitate formed after treating egg white with strong acid dissolve or not in addition of excess acid? Explain why
1. Which of the following forms of lysine would you expect to predominate at low pH, neutral pH and high pH? 2. One of the 20 amino acids is unusual in that its side chain contains a ring that incorporates the amine functional group of the amino acid. What is the name of this amino acid? Write the chemical structure of this amino acid at physiological pH.
Proteins treated with proteolytic enzymes hydrolyzed peptide bonds to yield a mixture of amino acids only. Is the statement TRUE OR FALSE?
1. Proteins carbohydrates and nucleic acids are grouped by common structural features found within a group. what is the basis for grouping substances like lipids? 2. Statins are cholesterol-lowering drugs that block cholesterol synthesis in the human liver. Would you expect the beneficial effects of stanol esters and statins to be duplicative or additive? Explain
1 What is the dominant biochemical activity or molecular interaction that your protein is predicted to carry out? Which sites on the protein contribute to the process directly? Which sites contribute indirectly? protein = amyloid-beta precursor
2. In tabular form explain the specific functions of different of amino acid and how they are acquired in human body.
1. The antibiotics puromycin and erythromycin are known inhibitors of protein synthesis. (a) Which part of the protein synthesis is affected by each antibiotic? (b) What could be the reason why one of them is more effective than the other one when they are given in the same dose?
1. What are congenital disorders of glycosylation (CDGs)?
1. a. Explain why the melting point of palmitic acid (16 carbons, no double bonds) is slightly lower thanthat of stearic acid (18 carbons, no double bonds). Explain why the melting point of oleic acid (18carbons, one double bond) is lower than that of stearic acid b. A mixture of lipids containing phosphatidic acid, cholesterol, testosterone, phosphatidylserine, andphosphatidylethanolamine was applied to a hydrophobic interaction chromatography column. Thecolumn was washed with a high salt buffer, and the lipids were then eluted with decreasing saltconcentrations. In what order would the lipids be eluted from the column? Explain your answer.
Amino acids project from each polypeptide backbone in a β-sheet in an alternating fashion (oneabove the plane and the next below the plane – see Fig 3.8B). Consider the following proteinsequence: Leu-Lys-Val-Asp-Ile-Ser-Leu-Arg-Leu-Lys-Ile-Arg-Phe-Glu.a. Is there a pattern to these amino acids? If so, what is it? b. What does this sequence of amino acids mean for the hydrophobicity/hydrophilicity of theresulting β-sheet? c. Can you make a prediction about how the β-sheet will be arranged in higher levels of protein structure? If so, what prediction would you make?