Questions and Answers of Biochemistry Concepts And Connections

Succulent plants from arid regions generally have waxy surface coatings. Suggest why such a coating is valuable for the survival of the plant.
In the produce department of supermarkets, vegetables and fruits (cucumbers are an example) have been coated with wax for shipping and storage. Suggest a reason why this is done.
Egg yolks contain a high amount of cholesterol, but they also contain a high amount of lecithin. From a diet and health standpoint, how do these two molecules complement each other?
In the preparation of sauces that involve mixing water and melted butter, egg yolks are added to prevent separation.How do the egg yolks prevent separation?
When water birds have had their feathers fouled with crude oil after an oil spill, they are cleaned by rescuers to remove the spilled oil. Why are they not released immediately after they are cleaned?
Which of the following lipids are not found in animal membranes?(a) Phosphoglycerides(b) Cholesterol(c) Triacylglycerols(d) Glycolipids(e) Sphingolipids
Why might some food companies find it economically advantageous to advertise their product (for example, triacylglycerols) as being composed of polyunsaturated fatty acids with trans-double bonds?
Proteins, nucleic acids, and carbohydrates are grouped by common structural features found within their group. What is the basis for grouping substances as lipids?
Briefly discuss the structure of myelin and its role in the nervous system.
Why does the American Heart Association recommend the use of canola oil or olive oil rather than coconut oil in cooking?
Suggest a reason why animals that live in cold climates tend to have higher proportions of polyunsaturated fatty acid residues in their lipids than do animals that live in warm climate
What is the energetic driving force for the formation of phospholipid bilayers?
Are the relative amounts of cholesterol and phophatidylcholine the same in all the kinds of membranes found in a typical mammalian cell?
Define glycoprotein and glycolipid.
Do all proteins associated with membranes span the membrane from one side to another?
Do all proteins associated with membranes span the membrane from one side to another?
Suggest a reason why the same protein system moves both sodium and potassium ions into and out of the cell.
What role does phosphorylation of tyrosine residues play in the action of receptor proteins?
What does the hydrolysis of GTP have to do with the actions of receptor proteins?
List two classes of compounds derived from arachidonic acid. Suggest some reasons for the amount of biomedical research devoted to these compounds.
What is the structural difference between thymine and uracil?
What is the structural difference between adenine and hypoxanthine?
Suggest a reason why inorganic ions, such as K+, Na+, Ca2+, and Mg2+, do not cross biological membranes by simple diffusion.
Which statements are consistent with the known facts about membrane transport?(a) Active transport moves a substance from a region in which its concentration is lower to one in which its
What happens to the human growth hormone receptor when it binds hGH?
What is JAK2 and why is it important to the effect of hGH?
What is the structural relationship between vitamin D3 and cholesterol?
List an important chemical property of vitamin E.
What are isoprene units? What do they have to do with the material of this chapter?
List the fat-soluble vitamins, and give a physiological role for each.
What is the role in vision of the cis–trans isomerization of retinal?
Why is it possible to argue that vitamin D is not a vitamin?
Give a reason for the toxicity that can be caused by overdoses of lipid-soluble vitamins.
Why can some vitamin-K antagonists act as anticoagulants?
Why are many vitamin supplements sold as antioxidants? How does this relate to material in this chapter?
A health-conscious friend asks whether eating carrots is better for the eyesight or for preventing cancer. What do you tell your friend? Explain.
Define omega-3 fatty acid.
What are the main structural features of leukotrienes
What are the main structural features of prostaglandins?
Outline a possible connection between the material in this chapter and the integrity of blood platelets.
What is the difference between ATP and dATP?
Give the sequence on the opposite strand for ACGTAT, AGATCT, and ATGGTA (all read 5' → 3').
Are the sequences shown in Question 6 those of RNA or DNA? How can you tell?Question 6Give the sequence on the opposite strand for ACGTAT, AGATCT, and ATGGTA (all read 5' → 3').
A friend tells you that only four different kinds of bases are found in RNA. What would you say in reply?
In the early days of molecular biology, some researchers speculated that RNA, but not DNA, might have a branched rather than linear covalent structure. Why might this speculation have come about?
Why is RNA more vulnerable to alkaline hydro lysis than DNA?
Draw a G—C base pair. Draw an A—T base pair.
Which of the following statements is (are) true?(a) Bacterial ribosomes consist of 40S and 60S subunits.(b) Prokaryotic DNA is normally complexed with histones.(c) Prokaryotic DNA normally exists as
Describe the landmark case that set the stage for the biotech patent battles of today.
How do the major and minor grooves in B-DNA compare to those in A-DNA?
Which of the following statements is (are) true?(a) The two strands of DNA run parallel from their 5' to their 3' ends.(b) An adenine–thymine base pair contains three hydrogen
What is propeller twist?
What is an AG/CT step?
Why does propeller-twist occur?
What is the difference between B-DNA and Z-DNA?
If circular B-DNA is positively supercoiled, will these supercoils be left- or right-handed?
Briefly describe the structure of chromatin.
What is the motive behind Genome Project 10 K?
List three mechanisms that relax the twisting stress in helical DNA molecules.
Explain how DNA gyrase works.
One of the original structures proposed for DNA had all the phosphate groups positioned at the center of a long fiber. Give a reason why this proposal was rejected.
What is the complete base composition of a double-stranded eukaryotic DNA that contains 22% guanine?
Why was it necessary to specify that the DNA in Question 33 is double-stranded?Question 33What is the complete base composition of a double-stranded eukaryotic DNA that contains 22% guanine?
What would be the most obvious characteristic of the base distribution of a single-stranded DNA molecule?
Why does DNA with a high A—T content have a lower transition temperature, Tm, than DNA with a high G—C content?
What are the three primary RNA types?
What determines the base sequence of all types of RNA?
What is the name of the process that produces RNA from a DNA template?
What is the basic purpose of tRNA?
The base sequence of which type of RNA is responsible for determining the order of amino acids in a protein?
What is the name of the process by which amino acids are linked together in the correct order based on an RNA sequence?
What are some key differences in how mRNA is processed in prokaryotes versus eukaryotes?
What are small nuclear RNAs?
What are micro RNAs?
Why do we say that micro RNAs are involved in the oldest evolutionary relationship?
Sketch a typical cloverleaf structure for transfer RNA. Point out any similarities between the cloverleaf pattern and the proposed structures of ribosomal RNA.
Which type of RNA is the biggest? Which is the smallest?
Which type of RNA has the least amount of secondary structure?
What is the role of ATP(CTP): tRNA nucleotidyletransferase?
What is RNA interference?
The structures of tRNAs contain several unusual bases in addition to the typical four. Suggest a function for the unusual bases.
Explain why a 50S ribosomal subunit and a 30S ribosomal subunit combine to form a 70S subunit, instead of an 80S subunit.
What is long noncoding RNA?
How is antisense RNA used to treat hypercholesterolemia?
How are miRNA used to treat hepatitis C?
How are siRNA used to treat Ebola?
What is the difference between miRNA and siRNA?
Why do researchers believe they can use CRISPR/Cas to treat disease?
Why do researchers believe lncRNA is a promising field for developing drug therapies?
Define replication, transcription, and translation.
Is the following statement true or false?Why? “The flow of genetic information in the cell is always DNA → RNA → protein.”
Why is it more important for DNA to be replicated accurately than transcribed accurately?
What is a replication fork? Why is it important in replication?
Describe the structural features of an origin of replication.
Why is it necessary to unwind the DNA helix in the replication process?
Suggest a reason why it would be unlikely for replication to take place without unwinding the DNA helix.
Do DNA-polymerase enzymes also function as exonucleases?
Compare and contrast the properties of the enzymes DNA polymerase I and polymerase III from E. coli.
Define processivity, and indicate the importance of this concept in DNA replication.
Comment on the dual role of the monomeric reactants in replication.

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