Amino Acids and Proteins Quiz

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which amino acid classification is typically protonated at physiological pH of 7.4?

Polar, basic side chains (correct)

Polar, acidic side chains

Amphiphilic side chains

Non-polar side chains

What characteristic allows certain amino acids to absorb UV light at 270–280 nm?

Charged side groups

Methylene groups in side chains

Presence of sulfur atoms

Delocalized π electrons in aromatic rings (correct)

Which amino acid can form disulfide bonds?

Cysteine (correct)

Methionine

Serine

Proline

At physiological pH of 7.4, which side chains are typically fully ionized and negatively charged?

Polar, acidic side chains Signup and view all the answers

Which of the following best describes non-polar amino acids?

They contain hydrophobic R groups. Signup and view all the answers

What distinguishes amphiphilic amino acids from others?

They possess both polar and non-polar characteristics. Signup and view all the answers

Which amino acid is noted for having one less methylene group compared to lysine?

Ornithine Signup and view all the answers

In what type of proteins are uncommon amino acids commonly found?

Fibrous proteins Signup and view all the answers

What is the average molecular weight of an amino acid residue when accounting for the water released during peptide bond formation?

110 Signup and view all the answers

Which of the following statements is true about the stereochemistry of amino acids?

L amino acids are the only types that are incorporated into proteins. Signup and view all the answers

What unique structural feature is present in all amino acids except proline?

Tetrahedral alpha-carbon Signup and view all the answers

Which property of amino acids allows them to play diverse biological roles?

Their capacity to polymerize Signup and view all the answers

When calculating the approximate number of amino acids in a protein, which molecular weight should you use for a single amino acid?

110 Signup and view all the answers

What is a characteristic of the 'R' group in amino acids?

It can be an aromatic or aliphatic side chain. Signup and view all the answers

Which of the following accurately describes the average molecular weight of all amino acids?

About 138, with a higher prevalence of low MW amino acids. Signup and view all the answers

Why do amino acids have well-suited properties for biological functions?

Their diverse chemical functionalities. Signup and view all the answers

Which compound is derived from the amino acid tryptophan?

5-Hydroxytryptophan Signup and view all the answers

What is the main role of g-Aminobutyric Acid (GABA) in the central nervous system?

Inhibiting neurotransmission Signup and view all the answers

What form do amino acids typically take at neutral pH?

Zwitterionic form Signup and view all the answers

Which of the following is a precursor to catecholamines?

Dihydroxy Phenylalanine Signup and view all the answers

What charge do amino acids have at alkaline pH?

Anionic Signup and view all the answers

Which neurotransmitter is derived from 5-Hydroxytryptophan?

Serotonin Signup and view all the answers

Which hormone is a precursor for Triiodothyronine (T3)?

Thyroxine T4 Signup and view all the answers

Which of the following is primarily involved in neurotransmission within the central nervous system?

Catecholamines Signup and view all the answers

What contributes to the isoelectric point (pI) of a typical peptide?

The terminal amino and carboxyl groups, along with ionizable R groups Signup and view all the answers

Which of the following correctly describes a prosthetic group?

It is a covalently attached cofactor. Signup and view all the answers

In electrophoresis, what happens when an amino acid is placed in a solution with a pH below its pI?

It has a net positive charge and moves toward the cathode. Signup and view all the answers

Which technique is primarily used for protein separation based on differences in physical and chemical properties?

Chromatography Signup and view all the answers

At what pH will an amino acid have a net negative charge?

pH 13 Signup and view all the answers

What type of proteins has carbohydrates as their prosthetic group?

Glycoproteins Signup and view all the answers

What happens to amino acids at a pH lower than their isoelectric point (pI)?

They have a net positive charge. Signup and view all the answers

Which method effectively separates proteins based on charge?

Ion-exchange chromatography Signup and view all the answers

What is the significance of using a gel matrix in electrophoresis?

To provide a medium for size-based separation. Signup and view all the answers

What is the primary contribution of metal ions in metalloproteins?

They are integral to enzymatic activity. Signup and view all the answers

Which amino acid sequence correctly represents an amino terminus?

H2N-Ser-Gly Signup and view all the answers

What does the structure of a protein refer to in a broader sense?

The 3-D shape formed by polypeptide chains. Signup and view all the answers

What is a key property used for the separation and purification of proteins?

Charge, size, and hydrophobicity Signup and view all the answers

Which aspect is NOT covered in the goals and objectives related to amino acids and proteins?

Synthesis of nucleic acids. Signup and view all the answers

Which of the following is NOT a component of conjugated proteins?

Enzymes Signup and view all the answers

Study Notes

Amino Acids

Proteins are linear polymers of alpha (α) amino acids.
α-amino acids are chiral except glycine.
All amino acids (except proline) have an acidic carboxyl group, a basic amino group, and an α-hydrogen.
The fourth substituent on the α-carbon is called the R-group, which varies between amino acids and determines their properties.
Proteins only contain L-amino acids.

Important Amino Acids

Non-polar: Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Isoleucine (Ile), Proline (Pro), Phenylalanine (Phe), Methionine (Met), Tryptophan (Trp).
Polar: Serine (Ser), Threonine (Thr), Cysteine (Cys), Tyrosine (Tyr), Asparagine (Asn), Glutamine (Gln).
Acidic: Aspartic Acid (Asp), Glutamic Acid (Glu).
Basic: Lysine (Lys), Arginine (Arg), Histidine (His).

Peptide Bond Formation

Peptide bonds form between the carboxyl group of one amino acid and the amino group of another.
Water is a byproduct of peptide bond formation.

Peptide Nomenclature

Peptides are named from the N-terminus (amino group) to the C-terminus (carboxyl group).

Ionization of Amino Acids and Peptides

The ionization state of an amino acid or peptide depends on the pH of the surrounding environment.
At low pH, the carboxyl group is protonated (COOH) and the amino group is protonated (NH3+).
At high pH, the carboxyl group is deprotonated (COO-) and the amino group is deprotonated (NH2).
The isoelectric point (pI) is the pH at which the net charge of the amino acid or peptide is zero.

Conjugated Proteins

Some proteins contain other chemical compounds besides amino acids, called cofactors.
Cofactors can be metal ions, organic molecules, or prosthetic groups.
Coenzymes are organic cofactors.
Prosthetic groups are covalently attached cofactors.

Protein Separation and Purification

Crude extracts containing proteins are often separated based on physical and chemical properties such as charge, size, affinity for a ligand, solubility, hydrophobicity, and thermal stability.
Chromatography is a common method for separating and purifying proteins.
Electrophoresis is used to separate proteins based on charge and size.

Electrophoresis

Proteins are loaded onto a gel matrix and subjected to an electric field.
Proteins migrate based on their charge and size.
Smaller proteins migrate faster.
Proteins with a net positive charge migrate towards the negative electrode (cathode), and vice versa.

Protein Structure

Primary structure: The sequence of amino acids in a protein.
Secondary structure: The local folding of the polypeptide chain, often forming α-helices or β-sheets.
Tertiary structure: The overall three-dimensional shape of a single polypeptide chain.
Quaternary structure: The arrangement of multiple polypeptide chains in a protein complex.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on amino acids and their role in protein synthesis. This quiz covers essential amino acids, characteristics, and peptide bond formation concepts. Perfect for students learning about biochemistry and molecular biology.