Amino Acid Classifications and Structures
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Questions and Answers

What is the primary role of amino acids in the body?

  • They are the main source of vitamins.
  • They function solely as enzymes.
  • They act as energy sources.
  • They are the building blocks of proteins. (correct)

Which part of an amino acid structure is characteristic and varies among different amino acids?

  • Carbon backbone
  • NH2 group
  • COOH group
  • Side Chain (R) (correct)

What reaction process is involved in obtaining amino acids from proteins?

  • Oxidation
  • Transamination
  • Hydrolysis (correct)
  • Condensation

How many standard amino acids are there in proteins?

<p>20 (B)</p> Signup and view all the answers

Which of the following classifications is NOT used for amino acids?

<p>Physical (B)</p> Signup and view all the answers

What groups are present in the general structure of each alpha-amino acid?

<p>COOH and NH2 groups (C)</p> Signup and view all the answers

Which enzyme is involved in the hydrolysis of proteins in the stomach to release amino acids?

<p>Pepsin (A)</p> Signup and view all the answers

The side chain (R) group of an amino acid can vary, influencing its properties. What does this variability primarily affect?

<p>The reactivity and polarity (C)</p> Signup and view all the answers

Which group of amino acids is classified as neutral based on their chemical structure?

<p>Glycine, Alanine (B)</p> Signup and view all the answers

What distinguishes acidic amino acids from neutral amino acids in terms of their chemical groups?

<p>Acidic amino acids carry a negative charge (B)</p> Signup and view all the answers

Which of the following amino acids is considered basic?

<p>Lysine (D)</p> Signup and view all the answers

Which amino acid classification involves amino acids that predominantly carry a positive charge?

<p>Basic amino acids (D)</p> Signup and view all the answers

How many carboxylic acid groups are present in acidic amino acids?

<p>2 (A)</p> Signup and view all the answers

Which of the following statements about neutral amino acids is correct?

<p>They have equal numbers of NH2 and COOH groups (A)</p> Signup and view all the answers

Which amino acids fall under the category of hydrophobic amino acids?

<p>Valine, Isoleucine (D)</p> Signup and view all the answers

What is the primary feature of basic amino acids regarding their amino and carboxylic groups?

<p>More NH2 groups than COOH groups (A)</p> Signup and view all the answers

Which statement accurately describes the chemical classification of amino acids?

<p>Only acidic amino acids have multiple carboxylic groups (B)</p> Signup and view all the answers

Which of the following aliphatic amino acids does not contain a side chain?

<p>Glycine (A)</p> Signup and view all the answers

Which amino acid is correctly classified as a sulfur-containing amino acid?

<p>Cysteine (D)</p> Signup and view all the answers

Among the listed amino acids, which one contains both a $COOH$ and an $NH_2$ group in its structure?

<p>Threonine (A), Histidine (C), Arginine (D)</p> Signup and view all the answers

What characterizes branched-chain amino acids (BCAAs)?

<p>They have a branched hydrocarbon side chain. (C)</p> Signup and view all the answers

Which of the following amino acids contains a hydroxy group ($-OH$) in its structure?

<p>Serine (C)</p> Signup and view all the answers

Which amino acid is classified as basic due to the presence of an additional amino group?

<p>Arginine (B)</p> Signup and view all the answers

Which amino acid has the structure with the formula of $C_3H_7NO_2$?

<p>Alanine (C)</p> Signup and view all the answers

What is the primary functional group present in all amino acids?

<p>Amino group (B), Carboxyl group (D)</p> Signup and view all the answers

Which amino acid is classified as an acidic amino acid due to the presence of an extra carboxyl group?

<p>Glutamic Acid (C)</p> Signup and view all the answers

Which of the following amino acids can be described as both aliphatic and aromatic?

<p>Tyrosine (B)</p> Signup and view all the answers

Which of the following amino acids is classified as semi-essential?

<p>Histidine (A)</p> Signup and view all the answers

Which group of amino acids includes only essential amino acids?

<p>Leucine, Isoleucine, Valine (A)</p> Signup and view all the answers

Which amino acid is not classified as essential?

<p>Tyrosine (B)</p> Signup and view all the answers

Which amino acid is part of the 'VIP' category?

<p>Phenylalanine (B)</p> Signup and view all the answers

Which amino acid is classified as an imino acid?

<p>Proline (C)</p> Signup and view all the answers

Which amino acids do not contain a benzene group?

<p>Cysteine and Lysine (D)</p> Signup and view all the answers

Which amino acids are found in the 'Mall' group?

<p>Methionine, Arginine, Leucine, Lysine (C)</p> Signup and view all the answers

Which of these amino acids is considered non-essential?

<p>Glycine (B)</p> Signup and view all the answers

What is true about essential amino acids?

<p>They must be obtained through diet. (A)</p> Signup and view all the answers

What is the primary reason arginine and histidine are classified as semi-essential?

<p>They are essential during periods of growth. (D)</p> Signup and view all the answers

Which of the following amino acids contains an SH group?

<p>Cysteine (D)</p> Signup and view all the answers

Which amino acid is classified as non-essential?

<p>Arginine (A)</p> Signup and view all the answers

Which of the following pairs contains aromatic amino acids?

<p>Tyrosine and Tryptophan (C)</p> Signup and view all the answers

Which amino acid is usually found in higher concentrations in meat?

<p>Lysine (C)</p> Signup and view all the answers

What characteristic is shared by tryptophan and phenylalanine?

<p>Both are aromatic amino acids. (A), Both are essential amino acids. (B)</p> Signup and view all the answers

Which group does histidine belong to based on nutritional classification?

<p>Semi-essential amino acids (A)</p> Signup and view all the answers

Which statement about cysteine and cystine is true?

<p>Cystine is a dimer of cysteine. (C)</p> Signup and view all the answers

Flashcards

Amino Acid Classification

Amino acids are categorized based on the relative number of amino and carboxylic acid groups.

Neutral Amino Acids

Amino acids with an equal number of amino and carboxylic acid groups, carrying no net charge.

Acidic Amino Acids

Amino acids with more carboxylic acid groups than amino groups, carrying a net negative charge.

Basic Amino Acids

Amino acids with more amino groups than carboxylic acid groups, carrying a net positive charge.

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Glycine

A neutral amino acid.

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Alanine

A neutral amino acid.

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Aspartic Acid

An acidic amino acid, carrying a net negative charge.

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Glutamic Acid

An acidic amino acid.

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Arginine

A basic amino acid, carrying a net positive charge.

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Lysine

A basic amino acid.

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Amino acid definition

Amino acids are the building blocks of proteins.

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Amino acid structure

Each amino acid has a carboxyl group (COOH), an amino group (NH2), and a side chain (R).

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Amino acid classification types

Amino acids are classified based on chemical, nutritional, and metabolic nature.

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How to obtain amino acids

Amino acids are obtained from proteins by hydrolysis (using acid, alkali, or enzymes).

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Number of known amino acids

There are 20 known amino acids; 21 with selenocysteine.

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What is the carboxyl group

A functional group with a Carbon (C), double-bonded Oxygen (O) and a single-bonded OH. (COOH)

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What is the amino group

Functional group with a Nitrogen (N) and two Hydrogen bonds (NH2).

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Side Chain (R) role

Variable chemical group that distinguishes different amino acids, giving them specific characteristics.

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Aliphatic AAs

Amino acids with no side chain.

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Branched-chain AAs

Amino acids with a branched side chain.

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Hydroxyl AAs

Amino acids containing a hydroxyl group (-OH).

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Sulfur-containing AAs

Amino acids with a sulfur atom in their structure.

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Isoleucine

Example of a branched-chain amino acid.

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Amino Acid Components

The basic parts of amino acids are amino group, carboxyl group,and side chain.

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Essential amino acids

Amino acids that the body cannot produce and must be obtained from food.

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Non-essential amino acids

Amino acids that the body can produce.

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Methionine

An amino acid with a sulfur atom.

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Phenylalanine

An aromatic amino acid with a benzene ring.

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Tryptophan

An aromatic amino acid.

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Proline

An imino acid.

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Semi-Essential Amino Acids

Amino acids that are essential for children but not adults. Adults can synthesize them, but children need to get them from diet.

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Histidine

A semi-essential amino acid, important for growth and immune function.

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Leucine, Isoleucine

Two essential branched-chain amino acids, important for muscle protein synthesis.

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Study Notes

Amino Acid Classifications

  • Amino acids are the structural units of proteins.
  • They are obtained from protein via acid, alkali, or enzymatic hydrolysis.
  • There are 20 known amino acids (21 after adding selenocysteine).

General Structure of Amino Acids

  • Each α-amino acid has a carboxyl group (COOH), an amino group (NH2), and a side chain (R group).
  • The R group differentiates amino acids, influencing their chemical and biological properties.

Classification of Amino Acids

  • 1. Chemical Classification: Based on the number of amino and carboxyl groups in the side chain.

    • Neutral Amino Acids: Have one amino and one carboxyl group. Examples: Glycine, Alanine, Serine, Threonine, Cysteine, Cystine, Valine, Leucine, Isoleucine, Phenylalanine, Tyrosine, Tryptophan.
    • Acidic Amino Acids: Have more than one carboxyl group and one amino group; they carry a negative charge. Examples: Aspartic acid, Glutamic acid.
    • Basic Amino Acids: Have more than one amino group and one carboxyl group; they carry a positive charge. Examples: Arginine, Histidine, Lysine.

  • 2. Nutritional Classification: Based on whether the body can synthesize the amino acid.

    • Essential Amino Acids: The body cannot synthesize these, so they must be obtained from diet. Examples: Valine, Leucine, Isoleucine, Tryptophan, Threonine, Methionine, Phenylalanine, Histidine, Lysine.
    • Non-Essential Amino Acids: The body can synthesize these. Examples: Glycine, Alanine, Serine, Tyrosine, Cysteine, Aspartic acid, Glutamic acid, Proline. Some amino acids are considered semi-essential (e.g., arginine and histidine) as the body can produce them, but in insufficient amounts for specific developmental stages.

  • 3. Metabolic Classification: Based on the metabolic fate of the amino acid.

    • Ketogenic Amino Acids: Broken down into ketone bodies. Examples: Leucine, Lysine.
    • Glucogenic Amino Acids: Broken down into glucose. Examples: Alanine, Serine, Glycine, Cysteine, Aspartic acid, Glutamic acid, Proline.
    • Mixed Glucogenic and Ketogenic Amino Acids: Can be broken down into both glucose and ketone bodies. Examples: Phenylalanine, Isoleucine, Tryptophan, Threonine, Tyrosine.

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Amino Acid Classifications PDF

Description

This quiz explores the classifications and structures of amino acids, the building blocks of proteins. Learn about their general structure, how they differ chemically, and their classification into neutral, acidic, and basic types. Understanding these concepts is essential for studying biochemistry.

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