Amino Acids Overview

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Questions and Answers

What characterizes an alpha-amino acid?

Contains both an amino group and a carboxylate group (correct)

Is a simple hydrocarbon chain

Has no side chains attached

Contains a hydroxyl group and a carboxylate group

How are amino acids predominantly categorized?

Based on their molecular weight

Based on the polarity of their R groups (correct)

Based on their solubility in water

Based on the sequence of nucleotides

In protein structure, what role do hydrogen bonds play?

They are critical in the secondary structure (correct)

They mainly contribute to the tertiary structure

They stabilize the primary structure of proteins

They have no significant role in protein structure

What term refers to the specific sequence of amino acids in a protein?

Primary structure Signup and view all the answers

What distinguishes fibrous proteins from globular proteins?

Fibrous proteins typically perform structural roles Signup and view all the answers

Which option describes the quaternary structure of proteins?

Interactions between multiple polypeptide chains Signup and view all the answers

Which of the following conditions can lead to protein denaturation?

All of the above Signup and view all the answers

What is NOT true regarding the formation of peptides?

They require a carbohydrate group Signup and view all the answers

What occurs to the group of the zwitterion in basic solution?

It loses a proton Signup and view all the answers

Cysteine can be oxidized to form which of the following structures?

Disulfide bond Signup and view all the answers

Which protein has the highest number of amino acid residues?

Gamma globulin Signup and view all the answers

What is formed when two amino acids are bonded by an amide linkage?

Dipeptide Signup and view all the answers

Why is the order of linkage important when forming dipeptides?

Two different dipeptides can be formed from unique amino acids Signup and view all the answers

What structural feature is common to both α-helices and β-pleated sheets?

Formation of hydrogen bonds between amide groups Signup and view all the answers

Which protein is primarily associated with muscle tissue?

Myoglobin Signup and view all the answers

What type of secondary protein structure is characterized by hydrogen bonds between carbonyl oxygen and amide hydrogen atoms of adjacent chains?

β-Pleated Sheet Signup and view all the answers

Which definition describes a polypeptide?

An intermediate chain length polymer with less than 50 amino acids Signup and view all the answers

What is the primary bond that stabilizes the α-helix structure?

Hydrogen bonds between carbonyl oxygens and amide hydrogens Signup and view all the answers

What does the term 'amino acid residue' refer to?

An amino acid that is part of a peptide, polypeptide, or protein chain Signup and view all the answers

Which type of R-group interaction is specifically formed between cysteine residues?

Disulfide bridges Signup and view all the answers

How is the tertiary structure of a protein primarily determined?

Interactions between R groups of amino acids Signup and view all the answers

According to convention, how are peptides written?

With the N-terminal residue on the left and the C-terminal residue on the right Signup and view all the answers

How many amino acid residues are present in trypsinogen?

229 Signup and view all the answers

In an aqueous environment, which interactions determine the protein shape based on the properties of side chains?

Hydrophilic and hydrophobic interactions Signup and view all the answers

What type of bond is referred to as an amide linkage in the formation of peptides?

Covalent bond between carbon and nitrogen Signup and view all the answers

What type of secondary structure do two or more helices form in α-Keratin?

A cable-like structure Signup and view all the answers

Which structure is extensively found in silk proteins?

β-Pleated Sheet Signup and view all the answers

Which of the following is NOT a component of secondary protein structure?

Disulfide bridges Signup and view all the answers

What is the function of fibrin in blood?

Aid in blood clotting Signup and view all the answers

Which type of R-group interaction involves ionic bonds?

Salt bridges Signup and view all the answers

What drives the formation of hydrophobic interactions within proteins?

Repulsion of nonpolar residues by water Signup and view all the answers

Which interaction does NOT play a significant role in stabilizing tertiary structure?

Peptide bonds Signup and view all the answers

Which statement accurately describes simple proteins?

They are made up entirely of amino acid residues. Signup and view all the answers

What are prosthetic groups in conjugated proteins?

Non-amino acid parts that are essential for protein function. Signup and view all the answers

Which class of conjugated proteins contains nucleic acids as prosthetic groups?

Nucleoproteins Signup and view all the answers

What is the significance of primary protein structure?

It dictates secondary and tertiary structures of proteins. Signup and view all the answers

Which of the following is an example of a hemoprotein?

Hemoglobin Signup and view all the answers

Which type of conjugated protein primarily contains carbohydrates?

Glycoproteins Signup and view all the answers

What can lead to profound differences in the functioning of proteins?

Variations in the primary structure. Signup and view all the answers

What distinguishes conjugated proteins from simple proteins?

Conjugated proteins contain additional organic or inorganic components. Signup and view all the answers

Study Notes

Amino Acids

The building blocks of proteins
Only 20 amino acids are commonly found in natural proteins
Alpha-amino acid: Contains both a carboxyl and amino functional group
The amino group is directly attached to the carbon next to the carboxyl group
Each amino acid has a name, a three-letter abbreviation, and a one-letter abbreviation.

Amino Acids and R Groups

Amino acids are categorized into groups based on the polarity of the R groups
Neutral and nonpolar side chains are hydrophobic
Polar side chains are hydrophilic

Amino Acids - Ionizable Groups

Amino acids exist in solution as zwitterions
A zwitterion is a molecule that is electrically neutral, but contains both a positive and a negative charge
In acidic solutions, the carboxylate group accepts a proton, and the zwitterion becomes positively charged
In basic solutions, the amino group loses a proton, and the zwitterion becomes negatively charged

Reaction of Amino Acids - Oxidation

Cysteine, the only sulfhydryl (—SH)-containing amino acid, can easily be oxidized to form a disulfide bond (—S—S—)

Reactions of Amino Acids - Peptide Formation

Peptide bond formation enables amino acids to make polymers by forming amide linkages
Dipeptides are compounds formed when two amino acids are bonded by a peptide bond
A peptide bond or peptide linkage is an amide linkage between amino acids that results when the amino group of one acid reacts with the carboxylate group of another
The order of linkage is important because two different dipeptides can be formed when two unique amino acids react
Peptide: Amino acid polymer of short chain length
Polypeptide: Intermediate chain length polymer with less than 50 amino acids
Protein: Polymer with more than 50 amino acids
Amino acid residue: Amino acid that is a part of a peptide, polypeptide, or protein chain

Classification of Proteins Based on Composition

Simple proteins: Made up entirely of amino acid residues
Conjugated proteins: Contain amino acid residues and other organic or inorganic components
Prosthetic groups: Non–amino acid parts of conjugated proteins

Primary Protein Structure

Linear sequence of amino acid residues in a protein chain
Determines secondary and tertiary structures
Important for the functioning of proteins
Small variations in the primary structure can cause profound differences in the functioning of proteins

Secondary Protein Structure

Arrangement of protein chains into patterns as a result of hydrogen bonds between amide groups of amino acid residues in the chain
Includes:
- α-helix
- β-pleated sheet

α-Helix Structure

Occurs when a single protein chain twists to resemble a coiled helical spring
Held in shape by intramolecular hydrogen bonds between carbonyl oxygens and amide hydrogens in adjacent turns of the helical backbone
All amide groups in the helix are hydrogen bonded
Two or more helices interact to form a cable in α-Keratin (found in hair), myosin (found in muscle), epidermin (found in skin), and fibrin (found in blood clots)

β-Pleated Sheet

Occurs when several protein chains lie side by side and are held in position by hydrogen bonds between the carbonyl oxygen atoms of one chain and the amide hydrogen atoms of an adjacent chain
Found extensively only in silk protein

Tertiary Protein Structure

Specific three-dimensional shape of a protein resulting from interactions between R groups of amino acid residues
Types of R-group interactions:
- Disulfide bridges: Form between cysteine residues
- Salt bridges: Result of ionic bonds that form between the ionized side chain of an acidic amino acid and the side chain of a basic amino acid
- Hydrogen bonds: Form between side chains that possess the following functional groups: —OH, —SH, —NH2, and —C=O
- Hydrophobic interactions: Form between nonpolar residues
The interaction of hydrophilic and hydrophobic side chains with water determines shape in an aqueous environment.

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Description

This quiz covers the essential concepts of amino acids, including their structure, categorization based on R groups, and their behavior in different pH solutions. Understand the fundamental role of amino acids as the building blocks of proteins and how their properties influence biological function.