Protein Structure and Function Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following techniques is NOT used to determine secondary structure?

Nuclear Magnetic Resonance (NMR) spectroscopy (correct)

Fourier transform infrared spectroscopy (FTIR)

Circular dichroism (CD) spectroscopy

X-ray crystallography

What is a characteristic feature of the α-helix structure?

It allows the formation with proline residues.

The side chains extend into the core.

Each turn contains 3.6 amino acids. (correct)

It has left-handed coiling.

What amino acids make up glutathione?

Glutamate, lysine, leucine

Arginine, cysteine, phenylalanine

Glutamate, cysteine, glycine (correct)

Aspartate, cysteine, glycine

Which functional group is associated with glutathione?

Thiol group Signup and view all the answers

Which of the following best describes antiparallel β-sheets?

They join two or more segments running in opposite directions. Signup and view all the answers

What role do β-bends play in protein structure?

They assist in forming a compact, globular shape. Signup and view all the answers

What is the primary function of glutathione related to hydrogen peroxide?

It removes the toxicity of hydrogen peroxide. Signup and view all the answers

What characterizes the tertiary structure of proteins?

It refers to the arrangement of domains in the polypeptide chain. Signup and view all the answers

What does the primary structure of a protein refer to?

The sequence of amino acids in a protein chain Signup and view all the answers

Which technique is NOT used to determine the primary structure of a protein?

NMR spectroscopy Signup and view all the answers

Which bond is primarily responsible for maintaining a protein's secondary structure?

Hydrogen bonds Signup and view all the answers

Which of the following is NOT a function of glutathione?

Cleaving peptide bonds of proteins Signup and view all the answers

What characterizes a protein's tertiary structure?

The overall three-dimensional shape of a single polypeptide Signup and view all the answers

What color does proline produce when it reacts with ninhydrin?

Yellow Signup and view all the answers

Which reaction is specific to phenolic amino acids?

Millon's reaction Signup and view all the answers

What is the product when tyrosine reacts with mercuric salts in Millon's reaction?

Red color Signup and view all the answers

Which reaction can lead to the formation of a purple ring with tryptophan?

Rosenheim test Signup and view all the answers

What type of peptide consists of 2 amino acids linked by one peptide bond?

Dipeptide Signup and view all the answers

Which peptide contains 29 amino acids and is known for its regulatory function in glucose metabolism?

Glucagon Signup and view all the answers

What is the primary effect of the atrial natriuretic factor (ANF)?

Increases urine sodium excretion Signup and view all the answers

Which of these peptides is known as an antibiotic that consists of cysteine and D-valine residues?

Penicillin Signup and view all the answers

What is the primary role of glucagon in the body during fasting?

It increases plasma glucose levels Signup and view all the answers

Which hormone is secreted by parathyroid glands during hypocalcemia?

Parathyroid hormone (PTH) Signup and view all the answers

How many amino acids make up the hormone calcitonin?

32 Signup and view all the answers

What is the function of fibrillin in the body?

Provides a scaffold for elastin deposition Signup and view all the answers

Which technique separates proteins based on their sizes and densities?

Ultracentrifugation Signup and view all the answers

Which of the following is true about the precipitation method of protein separation?

Albumin is precipitated by half saturated (NH₄)₂SO₄ Signup and view all the answers

What type of protein is fibronectin?

A fibrous protein that assists in cell adhesion Signup and view all the answers

What does the dialysis method separate in a mixture?

Proteins from salts Signup and view all the answers

What is the primary function of collagen in the body?

Structural support Signup and view all the answers

What happens during a negative nitrogen balance?

Nitrogen intake is less than nitrogen loss Signup and view all the answers

Which of the following is not a function of proteins?

Storing energy Signup and view all the answers

What type of molecule are immunoglobulins classified as?

Defence molecules Signup and view all the answers

Which amino acid classification does not have a net charge at neutral pH?

Uncharged polar side chain amino acids Signup and view all the answers

Which of the following amino acids has a unique imino group?

Proline Signup and view all the answers

Which of these proteins is known to be part of blood clotting?

Fibrinogen Signup and view all the answers

How many of the discovered amino acids are coded for by DNA in mammals?

20 Signup and view all the answers

What type of proteins are characterized by their compact forms resulting from the folding of polypeptide chains?

Globular proteins Signup and view all the answers

Which type of bond is NOT responsible for maintaining the tertiary structure of proteins?

Peptide bonds Signup and view all the answers

Which of the following is an example of a fibrous protein?

Collagen Signup and view all the answers

Which forces contribute to the stability of quaternary structure in proteins?

Hydrogen bonds and van der Waals forces Signup and view all the answers

Chaperones are known for which primary function in protein folding?

Preventing faulty folding of proteins Signup and view all the answers

What does salting in refer to in the context of protein solubility?

Boosting protein solubility with small amounts of salt Signup and view all the answers

Which of the following proteins is known to lose function when its subunits are dissociated?

Hemoglobin Signup and view all the answers

Which type of proteins are typically water insoluble due to their non-polar side chains?

Fibrous proteins Signup and view all the answers

Study Notes

Proteins and Amino Acids

Proteins are large polymers of L-amino acids
Proteins are the most abundant and functionally important molecules in living systems.
Main functions of proteins include:
- Structural functions: Collagen in bones, elastin in lungs
- Enzymes: Pepsin, lipase, urease
- Hormones: Growth hormone, insulin, glucagon, oxytocin
- Transporters: Lipoproteins, hemoglobin
- Blood clotting factors: Fibrinogen, prothrombin
- Receptors: Insulin receptor
- Defence molecules: Immunoglobulins (IgM, IgA, IgG, IgE, IgD)
- Storage: Myoglobin (oxygen), ferritin (iron)
- Contractile proteins: Actin, tubulin
Nitrogen balance:
- Nitrogen intake equals nitrogen loss (balanced)
- Nitrogen intake greater than loss (positive) e.g. growing children, pregnancy
- Nitrogen intake less than loss (negative) e.g. fasting, starvation, disease
Over 300 amino acids exist in nature, but only 20 are common in mammalian proteins.
These 20 amino acids are coded for by DNA

Structure of Amino Acids

Each amino acid has a central carbon atom (α-carbon) bonded to:
- A carboxyl group (COOH)
- An amino group (NH2)
- A hydrogen atom
- A variable side chain (R group)
Proline has a secondary amino group (imino group)

Classification of Amino Acids

Amino acids are classified based on chemical structure, nutritional importance, and metabolic fate.
1. Amino acids with non-polar side chains (hydrophobic): Glycine, alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, methionine, proline
1. Amino acids with uncharged polar side chains: These have zero net charge at a neutral pH. Serine, threonine, tyrosine, asparagine, glutamine, cysteine
1. Amino acids with charged polar side chains, which are either acidic or basic: These amino acids are either negatively (acidic) or positively (basic) charged. Aspartic acid, glutamic acid, lysine, arginine, histidine

Summary of Chemical Classification of Amino Acids (Table)

Glycine, Alanine, Valine, Leucine, Isoleucine, Phenylalanine, Tryptophan, Methionine, and Proline: Non-polar amino acids
Serine, Threonine, Tyrosine, Cysteine, Asparagine, and Glutamine: Polar neutral amino acids
Aspartic acid, Glutamic acid, Lysine, Arginine, and Histidine: Polar charged amino acids
Phenylalanine, Tryptophan, Tyrosine: Aromatic amino acids
Serine, Threonine, Tyrosine, Cysteine, Asparagine, and Glutamine: Alcohlic OH amino acids
Other amino acids: based on their characteristics.

1- Essential Amino Acids (8)

Cannot be synthesized in the body
Need to be obtained from diet, these include: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

2- Semi-Essential Amino Acids (2)

Synthesized in the body, but not in enough amounts for growing children. These include: Arginine, Histidine

3- Non-Essential Amino Acids (10)

Synthesized in the body in sufficient quantities, these include: Alanine, Asparagine, Aspartic acid, cysteine, Glutamic acid, Glutamine, Glycine, Proline, Serine, Tyrosine

Metabolic Classification of Amino Acids

Ketogenic: Leucine (only pure ketogenic amino acid), can be used for energy, forming ketone bodies(only one)
Ketogenic and Glucogenic (glycogenic): phenylalanine, tyrosine, tryptophan, lysine, threonine, can be used for both energy and glucose production
Glucogenic (glycogenic): All others used for energy and glucose production.

Protein Reactions, classification of proteins

Protein denaturation, breaking down of peptide structures, primarily proteins
Important features about denaturation of proteins
Chemical changes like H-bonds, S-S bonds, and ionic interactions are broken.
All protein levels (except primary) are lost.
Biological activity is lost.
Denatured protein is insoluble.
Denaturation can be reversible or irreversible.

Protein Structures

Primary: Sequence of amino acids
Secondary: Formation of alpha-helices and beta-sheets; hydrogen bond formation
Tertiary: Three-dimensional structure of a polypeptide chain; formation of bonds within or between segments
Quaternary: Structure of a multi-subunit protein; multiple tertiary protein assemblies

Fibrous Proteins

Extended form proteins: e.g., Keratin, Collagen, Myosin
Bonds in fibrous structures: hydrogen bonds, hydrophobic interactions, disulfide bonds, ionic interactions,
Characteristics: Structural role, water insoluble, strong, and fibrous.

Globular Proteins

Spherical shape;
Examples: (albumins, globulins, protamines, histones, etc.)

Conjugated Proteins

Composed of protein and non-protein components: eg. Nucleoproteins, lipoprotein, glycoproteins, phosphoproteins, metalloproteins.
These components provide various functional roles.

Methods of Protein Separation

Chromatography
Electrophoresis
Precipitation
Ultracentrifugation
Dialysis

Studying That Suits You

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

Description

Test your knowledge on protein structure, particularly the secondary and tertiary structures, as well as the functions of amino acids like glutathione. This quiz covers key concepts, techniques utilized in protein analysis, and specific reactions related to amino acids. Challenge yourself and see how well you understand these important biochemical topics!