Question 1

Complex carbohydrates are a mainstay of many diets.What are some properties that make them excellent food sources?

Accepted Answer

The answer of Complex carbohydrates are a mainstay of many...

Question 2

A structural isomer for the molecule NaOCH₂CH₃ would be expected to have how many carbon atoms?

Accepted Answer

The given molecule has 9 sulfur atoms, which means it must have 18 hydrogen atoms to balance out the valence electrons. Additionally, it has 2 carbon atoms and 1 sodium atom.

A structural isomer is a molecule with the same molecular formula but a different arrangement of atoms. In order to create a structural isomer, we must rearrange the atoms while still maintaining the same number and type of atoms.

One way to create a structural isomer is to rearrange the atoms in the chain of carbon atoms. The given molecule only has two carbon atoms, so in order to create a structural isomer, we must add more carbon atoms.

Option (B) "Two" is the best choice because a structural isomer with two carbon atoms can be created by adding a carbon atom to either end of the chain. For example, NaOCHS1U1B0CH2S1U1B12S1U1B0CHS1U1B13S1U1B0 would be a structural isomer with two carbon atoms.

Question 3

Draw a diagram of a phospholipid bilayer, and identify the hydrophobic tails and the hydrophilic heads.Where in the cell can you find such a structure?

Accepted Answer

The answer of Draw a diagram of a phospholipid bilayer,...

Question 4

A protein is known to be stabilized by a salt bridge between a lysine at position 26 and an aspartic acid at position 108 in the protein's amino acid sequence.When the protein is mutated to substitute a glutamic acid in place of aspartic acid at position 108, the protein cannot fold properly and exhibits no biological activity.What likely contributes to the effects of this amino acid substitution on protein folding?

Accepted Answer

The answer of A protein is known to be stabilized...

Question 5

A question was raised during a class discussion about whether it was possible for two isomers to have different biological properties.A student from the class responded, stating that only optical isomers met this requirement.Which statement provides the best evaluation of this student's assertion?

Accepted Answer

Structural isomers have different arrangements of atoms but the same molecular formula, and can have different biological properties. Cis-trans isomers, also known as geometric isomers, have different spatial arrangement around a double bond and can also have different biological properties. Optical isomers, also known as enantiomers, have the same molecular formula and the same structural formula but different spatial arrangements of atoms and have different biological properties. Therefore, the student's assertion is only partially correct because structural and cis-trans isomers can also meet the requirement.

Question 6

Refer to the figure below showing the three different oligosaccharides present on the surfaces of human red blood cells that determine blood type.  Antibodies are proteins produced in the body in response to foreign substances.Antibodies recognize and bind to these foreign substances to remove them from the body.How would blood cells containing the oligosaccharide type O be received if they were transfused into the body of a patient whose own blood cells contained the oligosaccharide type A? Would the reaction be different if the reverse situation occurred; that is, blood cells containing the oligosaccharide type A transfused into a patient whose blood cells contained oligosaccharide type O? Describe the role of the oligosaccharides in these two situations.

Accepted Answer

The answer of Refer to the figure below showing the...

Question 7

Glucose is a monosaccharide, maltose is a disaccharide composed of glucose, and glycogen is a polysaccharide composed of glucose.Compare the functions of these three carbohydrates in the human body.

Accepted Answer

The answer of Glucose is a monosaccharide, maltose is a...

Question 8

Cis and trans isomers

Accepted Answer

Cis and trans isomers are centered around a double bond with atoms on either side in different orientations with respect to each other. Cis-isomers have similar atoms on the same side of the double bond, while trans-isomers have the similar atoms on opposite sides of the double bond. They have different physical and chemical properties, despite having the same molecular formula.

Question 9

Sketch and label a triglyceride and a phospholipid.Write a brief comparison of the two structures.

Accepted Answer

The answer of Sketch and label a triglyceride and a...

Question 10

Refer to the table below summarizing data obtained from chemical analysis of two proteins isolated from different tissues of a mouse-skin and bone.  Can it be concluded from this data that the two proteins are the same?

Accepted Answer

The data only provide information about the size of the proteins and the total number of specific amino acids present. This information is not enough to conclude whether the two proteins are the same or not, as it does not reveal anything about the sequence of amino acids in each protein. Therefore, option D is the correct choice. Option A is incorrect because proteins with the same size and total number of amino acids can still have different sequences. Option B is incorrect because the table only gives information about the presence and number of specific amino acids, not all amino acids. Option C is incorrect because identical proteins can be produced in different tissues, and it is not uncommon to find identical proteins across different species. Option E is incorrect because the table does provide information about the number of other amino acids, but this information alone is not sufficient to conclude that the proteins are the same.

Question 11

A condensation reaction

Accepted Answer

A condensation reaction involves the removal of a water molecule from two molecules or functional groups, resulting in the formation of a covalent bond. In the case of linking together amino acids to form a polypeptide chain, a condensation reaction occurs between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of another, resulting in the formation of a peptide bond and the release of a water molecule.

Question 12

Protein structure can be affected by environmental conditions, which eventually can lead to denaturation.Differentiate between four environmental effects that can denature proteins, and explain how they affect protein structure.

Accepted Answer

The answer of Protein structure can be affected by environmental...

Question 13

Hydroxyl groups are polar, and thus a molecule that contains multiple hydroxyl groups will be

Accepted Answer

Hydroxyl groups are polar due to the electronegativity difference between oxygen and hydrogen, making molecules with multiple hydroxyl groups soluble in water due to their ability to form hydrogen bonds with water molecules.

Question 14

Draw a diagram to show how phospholipids interact with one another and with water molecules to form a membrane bilayer.

Accepted Answer

The answer of Draw a diagram to show how phospholipids...

Question 15

Keratin and hemoglobin are both proteins with important functions in the human body.Keratin has a long, thin, rope-like structure with a structural role in hair, fingernails, and skin.Hemoglobin has a compact, round, globular structure with a transport role in carrying oxygen to body cells from the lungs.Which statement best explains how both keratin and hemoglobin can be classified as proteins yet have such different structures and functions?

Accepted Answer

The structure and function of a protein are determined by the types of amino acids that make up the protein and their sequence. Thus, even though keratin and hemoglobin are both proteins, their different structures and functions are due to differences in their amino acid composition and sequence.

Question 16

A scientist isolates a previously undiscovered protein from a fruit fly and determines the sequence of amino acids making up the protein.Upon comparing the sequence to a database, he finds another protein isolated from a lizard with the same sequence.The lizard protein is known to be involved in glucose metabolism.The scientist predicts that the fruit fly protein must also be involved in glucose metabolism.How can his prediction be justified?

Accepted Answer

The best choice is E - Two proteins with the same amino acid sequence have the same structure, which allows the two molecules to function in the same way. This is because the function of a protein is determined by its three-dimensional structure, which is determined by its amino acid sequence. If two proteins have the same amino acid sequence, it is highly likely that they will have the same, or very similar, three-dimensional structure, and therefore they will function in the same way.

Question 17

The reactive _______ contributes to the ability of aldehydes and ketones to be involved in energy reactions.

Accepted Answer

The carbonyl group, which consists of a carbon atom double-bonded to an oxygen atom, is the reactive group in aldehydes and ketones. This group participates in energy reactions such as oxidation and reduction, making them important metabolites in cellular energy production.

Question 18

A research lab working on a protein exchanges a methionine with an isoleucine in one experiment and exchanges the same methionine with a glutamic acid in a second experiment.Discuss how these changes could result in very different changes to the protein's tertiary structure and why.

Accepted Answer

The answer of A research lab working on a protein...

Question 19

Optical isomers

Accepted Answer

Optical isomers, also known as enantiomers, are mirror images of each other in structure. They have the same chemical and physical properties except for their ability to rotate plane-polarized light. They often arise from chiral molecules, meaning they contain an asymmetric carbon that is bonded to four different groups, causing the mirror image phenomenon.

Question 20

Although all four levels of protein structure are important in determining a protein's function, one of these structures provides the backbone of proteins.Discuss this structure.Why is it considered the most important of the four?

Accepted Answer

The answer of Although all four levels of protein structure...

Quiz 3: Proteins, Carbohydrates, and Lipids