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Ch.18 Amino Acids and Proteins
McMurry - Fundamentals of General, Organic, and Biological Chemistry 8th Edition
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187당신이 사용하는 게 아니라요?교과서 변경
모든 교과서McMurry 8th EditionCh.18 Amino Acids and Proteins문제 7
18장, 문제 7

Valine is an amino acid with a nonpolar side chain and serine is one with a polar side chain. Draw the two amino acids.
a. Why is the side chain for valine nonpolar, whereas the side chain for serine is polar?

검증된 단계별 안내
1
Step 1: Understand the structure of an amino acid. Each amino acid consists of a central carbon atom (called the alpha carbon) bonded to four groups: an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a unique side chain (R group) that determines the properties of the amino acid.
Step 2: Draw the structure of valine. The side chain (R group) of valine is an isopropyl group (-CH(CH₃)₂), which consists only of carbon and hydrogen atoms. These atoms share electrons almost equally, making the side chain nonpolar and hydrophobic.
Step 3: Draw the structure of serine. The side chain (R group) of serine is a hydroxymethyl group (-CH₂OH), which contains an -OH group. The oxygen atom in the -OH group is highly electronegative, creating a polar bond due to the unequal sharing of electrons between oxygen and hydrogen.
Step 4: Explain why valine's side chain is nonpolar. The isopropyl group in valine's side chain lacks electronegative atoms like oxygen or nitrogen, so it does not form significant dipoles. This makes the side chain nonpolar and hydrophobic, meaning it does not interact well with water.
Step 5: Explain why serine's side chain is polar. The hydroxyl (-OH) group in serine's side chain creates a dipole due to the electronegativity difference between oxygen and hydrogen. This makes the side chain polar and hydrophilic, meaning it can form hydrogen bonds and interact well with water.

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주요 개념

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Amino Acid Structure

Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid consists of a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group). The nature of the side chain determines the amino acid's properties, such as polarity and hydrophobicity.
추천 영상:
가이드 코스
3:03
Amino Acid Catabolism: Amino Group Example 2

Polarity of Side Chains

The polarity of an amino acid's side chain is determined by the presence of functional groups that can form hydrogen bonds with water. Nonpolar side chains, like that of valine, consist mainly of hydrocarbons, making them hydrophobic and less likely to interact with water. In contrast, polar side chains, such as that of serine, contain hydroxyl (-OH) or other polar groups, allowing them to interact favorably with water.
추천 영상:
가이드 코스
01:34
Molecular Polarity (Simplified) Concept 1

Hydrophobic and Hydrophilic Interactions

Hydrophobic interactions occur when nonpolar molecules or regions of molecules aggregate to avoid contact with water, while hydrophilic interactions involve polar molecules that readily interact with water. These interactions are crucial in determining the structure and function of proteins, influencing how amino acids with different side chains behave in aqueous environments.
추천 영상:
가이드 코스
2:41
Interactions within the Tertiary Structure Concept 2
관련 실천
교과서 질문

Two of the 20 common amino acids have two chiral carbon atoms in their structures. Identify these amino acids and their chiral carbon atoms.

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교과서 질문

Examine the ball-and-stick model of valine below. Identify the carboxyl group, the amino group, and the R group.

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교과서 질문

Is serine chiral? Draw serine and identify the chiral atom. Explain why serine is chiral.

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교과서 질문

Indicate whether each of the following molecules is an α-amino acid or not, and explain why.  

a.

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교과서 질문

Which amino acid is hydrophilic (dissolves in aqueous solutions)? Why?

a. isoleucine

b. phenylalanine

c. aspartic acid

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교과서 질문

Using Table 18.3, name the α-amino acids that (a) contain an aromatic ring, (b) contain sulfur, (c) are alcohols, and (d) have alkyl-group side chains.

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