Skip to main content
Pearson+ LogoPearson+ Logo
Ch.18 Amino Acids and Proteins
McMurry - Fundamentals of GOB 8th Edition
McMurry8th EditionFundamentals of GOBISBN: 9780134015187Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.18 Amino Acids and ProteinsProblem 102a
Chapter 18, Problem 102a

Globular proteins are water-soluble, whereas fibrous proteins are insoluble in water. Indicate whether you expect the following amino acids to be on the surface of a globular protein or on the surface of a fibrous protein.
a. Ala

Verified step by step guidance
1
Understand the difference between globular and fibrous proteins: Globular proteins are water-soluble and typically have hydrophilic (water-attracting) amino acids on their surface, while fibrous proteins are water-insoluble and often have hydrophobic (water-repelling) amino acids on their surface.
Analyze the properties of alanine (Ala): Alanine is a nonpolar amino acid with a methyl group (-CH₃) as its side chain. Nonpolar side chains are hydrophobic, meaning they do not interact well with water.
Determine the likely location of alanine in a globular protein: Since alanine is hydrophobic, it is more likely to be found in the interior of a globular protein, away from the aqueous environment, rather than on the surface.
Determine the likely location of alanine in a fibrous protein: In fibrous proteins, which are typically insoluble in water, hydrophobic amino acids like alanine are often found on the surface, as these proteins are not exposed to a water-soluble environment.
Conclude the placement: Alanine is expected to be on the surface of a fibrous protein due to its hydrophobic nature, but it would likely be buried in the interior of a globular protein to avoid interaction with water.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Globular Proteins

Globular proteins are spherical in shape and are typically water-soluble due to their hydrophilic (water-attracting) side chains. This solubility allows them to function effectively in various biological processes, such as enzyme activity and transport. Their structure is stabilized by various interactions, including hydrogen bonds and hydrophobic interactions, which influence the positioning of amino acids within the protein.
Recommended video:
Guided course
2:01
Digestion of Proteins Concept 1

Fibrous Proteins

Fibrous proteins are elongated and insoluble in water, primarily serving structural roles in organisms. They are composed of long chains of amino acids that form strong, stable structures, such as collagen in connective tissues and keratin in hair and nails. The insolubility of fibrous proteins is due to their hydrophobic (water-repelling) side chains, which aggregate to form fibers that provide strength and support.
Recommended video:
Guided course
2:01
Digestion of Proteins Concept 1

Amino Acid Properties

Amino acids possess distinct properties based on their side chains (R groups), which can be classified as hydrophobic, hydrophilic, acidic, or basic. These properties determine the location of amino acids within proteins; hydrophobic amino acids tend to be buried in the interior of globular proteins, while hydrophilic amino acids are often found on the surface. Understanding these properties is crucial for predicting the behavior of specific amino acids, such as alanine (Ala), in different protein environments.
Recommended video:
Guided course
3:03
Amino Acid Catabolism: Amino Group Example 2
Related Practice
Textbook Question

For each amino acid listed, tell whether its influence on tertiary structure is largely through hydrophobic interactions, hydrogen bonding, formation of salt bridges, covalent bonding, or some combination of these effects.

a. Tyrosine

848
views
Textbook Question

Oxytocin is a small peptide that is used to induce labor by causing contractions in uterine walls. It has the primary structure Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gln. This peptide is held in a cyclic configuration by a disulfide bridge. Draw a diagram of oxytocin, showing the disulfide bridge.

866
views
Textbook Question

Four of the most abundant amino acids in proteins are leucine, alanine, glycine, and valine. What do these amino acids have in common? Would you expect these amino acids to be found on the interior or on the exterior of the protein?

873
views
Textbook Question

A family visits a pediatrician with their sick child. The four-month-old baby is pale, has obvious episodes of pain, and is not thriving. The doctor orders a series of blood tests, including a test for hemoglobin types. The results show that the infant is not only anemic but that the anemia is due to sickle-cell anemia. The family wants to know if their other two children have sickle-cell anemia, sickle-cell trait, or no sickle-cell gene at all.

a. What test will be used?

730
views
Textbook Question

Which would you expect to be more soluble in water, a peptide containing mostly alanine and leucine or a peptide containing mostly lysine and aspartic acid? Explain. (Hint: Consider side-chain interactions with water.)

362
views
Textbook Question

Which of the following amino acids is most likely to be found on the outside of a soluble protein, and which of them is more likely to be found on the inside? Explain each answer. (Hint: Consider the effect of the amino acid side chain in each case and that the protein is folded up into its globular form.)

a. Valine

841
views