Exam 2: The Chemical Basis of Life

You isolate superoxide dismutase from two cell culture lines.One of the lines (SOD1)has a level of SOD activity similar to that found in liver,the tissue from which the cell line was originally obtained.The other cell line (SOD10)has elevated SOD activity.The enzyme in SOD10 is extremely efficient at converting the superoxide free radical to hydrogen peroxide.In a routine check of other critical enzyme activities,catalase was found to have activity levels that were severely depressed in SOD10,while they appeared normal in SOD1.Observations of SOD10 reveal that this cell line cannot be maintained as easily as SOD1.SOD10 cells appear to die at an accelerated rate.What,if anything,can you conclude from these data?

Some proteins have multiple binding partners.In some cases,they have several different binding interfaces and they are thus capable of binding a number of different binding partners at the same time.On the other hand,other such proteins have a single binding interface,which is capable of binding several different partners,but only one at a time.They can play central roles in such processes as cell division and gene expression.What are such proteins called?

Why is silicon not suitable for making covalent bonds stable and strong enough to form the basis of living organisms,even though it is just below carbon on the periodic table?

An infectious agent is discovered that causes a particular disease.It has a relatively low molecular weight.Treatment with phenol or proteolytic enzymes,treatments that destroy proteins,render the infectious agent harmless,while treatment with nucleases and ultraviolet radiation,treatments that damage polynucleotides,has no effect.What is your interpretation of the above data and why?

The most stable atoms and thus those that are typically nonreactive are the atoms that have _______.

Which of the following tripeptides would be most likely to be soluble in an organic (hydrophobic)solvent like benzene: N - phenylalanine - alanine - glutamine - C,N - leucine - alanine - lysine - C,N - proline - phenylalanine - leucine - C,N - arginine - lysine - proline - C,N - glutamate - aspartate - glycine - C? Explain your answer.

Mammals lack the enzyme that hydrolyzes cellulose.Yet many mammals are herbivores and they eat grass and other plant material for nutrition.How can this be,given that they cannot digest the food they are eating?

When it was discovered that CJD could be acquired in addition to being inherited,why was it at first assumed that the infectious agent was a virus?

Many so-called temperature-sensitive mutations have been discovered in a wide variety of organisms.These are proteins that are non-functional at higher temperatures,while,at lower temperatures (often just a few degrees lower),they function normally.For example,the coloration patterns in Siamese Cats arise from a temperature-sensitive mutation.An enzyme required for the synthesis of dark pigment is unable to function in areas close to the body where normal physiological temperatures prevail.However,at the tips of the ears,paws,the tip of the tail and other extremities where the temperature is slightly lower,the enzyme works correctly and dark pigment is produced.What is happening at the molecular level that explains this?

What kind of noncovalent interaction is typified by interactions between two molecules that are so close together that they can experience weak attractive forces bonding them together?

What evidence suggests that lower blood levels of insulin may be important in promoting longevity?

Which of the following tripeptides would be most likely to be soluble in an organic (hydrophobic)solvent like benzene?

What are some common antioxidants found in the body?

The $\beta$ -pleated sheet is characterized by orientation of ______ the molecular axis.

What level of structure in DNA would be disrupted by a reagent that breaks apart hydrogen bonds?

What appears to be the effect of reduced calorie intake on rhesus monkeys?

Where are hydrophobic interactions most likely to occur?

What are some possible explanations for the branched structure of glycogen?

What does the compound,2-phenylaminopyrimidine,inhibit? It was determined that 2-phenylaminopyrimidine would not have made a very effective drug.Why? What is the basis of Gleevec's effectiveness as a drug in the treatment of chronic myelogenous leukemia (CML)? Why do some patients taking Gleevec experience a recurrence of their cancer even though they initially went into remission?

It is thought that most human diseases leave telltale patterns among the thousands of proteins present in the blood or other bodily fluids.It was hoped that analysis of the proteins present in the blood would help in the diagnosis of human disease;however,thus far,searches for these proteins in blood or bodily fluids have been largely unsuccessful and their use in diagnostics largely unreliable.What are these telltale patterns of proteins called?