Prion Protein Aggregation Overview

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Questions and Answers

Which amino acid classification would best describe serine?

Polar (correct)

Non-polar

Basic

Hydrophobic

What characteristic differentiates hydrophobic amino acids from polar amino acids?

Polar amino acids are typically found in the interior of proteins.

Hydrophobic amino acids contain non-polar side chains. (correct)

Hydrophobic amino acids can form hydrogen bonds.

Polar amino acids do not interact with water.

Which of the following amino acids is considered an acidic amino acid?

Arginine

Lysine

Phenylalanine

Glutamate (correct)

At neutral pH, amino acids exist as zwitterions. Which best describes their structure?

The amino group is positively charged and the carboxyl group is negatively charged. Signup and view all the answers

Which statement correctly describes the ionization state of amino acids at physiological pH?

They exist predominantly in their ionic forms. Signup and view all the answers

Which property of amino acids contributes to the hydrophobic effect during protein folding?

Hydrophobic R groups aggregate to minimize exposure to water. Signup and view all the answers

Why are L isomers of amino acids predominantly found in proteins?

L isomers are more stable than D isomers. Signup and view all the answers

What type of structure is primarily driven by the hydrophobic effect in proteins?

Tertiary structure Signup and view all the answers

What is a primary characteristic of hydrophobic amino acids?

They tend to aggregate in aqueous environments. Signup and view all the answers

Which of the following correctly classifies amino acids based on their side chain properties?

Leucine is an aliphatic amino acid. Signup and view all the answers

Which post-translational modification is crucial for regulating enzyme activity?

Phosphorylation Signup and view all the answers

What results from a lack of appropriate post-translational modifications of amino acid side chains?

Pathological conditions. Signup and view all the answers

Which amino acid is particularly affected by a vitamin C deficiency related to collagen synthesis?

Proline Signup and view all the answers

At physiological pH, which functional group predominates in amino acids?

The zwitterionic form is predominant. Signup and view all the answers

What is the role of PrP in relation to prion diseases?

To catalyze the misfolding of other proteins. Signup and view all the answers

Which property characterizes polar amino acids?

They are hydrophilic and can form hydrogen bonds. Signup and view all the answers

Which statement accurately describes the properties of hydrophobic amino acids?

They pack together to form compact structures. Signup and view all the answers

Which group does histidine belong to based on its charge at physiological pH?

Positively charged amino acids Signup and view all the answers

How do polar amino acids differ from hydrophobic amino acids in terms of side chain properties?

Polar amino acids have side chains that make them hydrophilic. Signup and view all the answers

Which amino acid contains a sulfhydryl group that allows for the formation of disulfide bonds?

Cysteine Signup and view all the answers

What is the significance of pKa in relation to amino acids?

It indicates the charge of the amino acid at a given pH. Signup and view all the answers

At physiological pH (approximately 7.4), which of the following amino acids is likely to be negatively charged?

Aspartic acid Signup and view all the answers

Which of the following statements about peptide bonds is incorrect?

Peptide bonds can rotate freely. Signup and view all the answers

Which amino acid is the bulkiest hydrophobic amino acid with potential for hydrogen bonding?

Tryptophan Signup and view all the answers

What type of secondary structure is stabilized by hydrogen bonds between adjacent beta strands?

Beta pleated sheet Signup and view all the answers

Which amino acids are likely to have ionizable side chains?

Seven amino acids Signup and view all the answers

What is the primary factor that determines the stability of an alpha helix structure?

Hydrogen bonds between the main chain CO and NH groups Signup and view all the answers

Which amino acid group is characterized by a positive charge at physiological pH?

Positively charged amino acids Signup and view all the answers

What results from the oxidation of a pair of cysteine residues?

Creation of disulfide bonds Signup and view all the answers

Study Notes

Proteins and Their Structure

Proteins are linear polymers made of 20 distinct amino acids.
Each amino acid consists of an α-carbon, an amino group, a carboxylic acid group, a hydrogen atom, and a unique R group.
Chiral amino acids exist in two forms: L isomer (used in proteins) and D isomer.

Protein Misfolding and Aggregation

Fibrils can aggregate, with normal prion protein (PrP) converting to an abnormal conformation.
Abnormally folded aggregates act as nuclei to recruit more proteins, enhancing misfolding.
PrPSC catalyzes the conversion of PrP into PrPSC, leading to neuronal cell death, showcasing a pathological consequence of protein misfolding.

Post-Translational Modifications

Post-translational modifications alter protein structure after synthesis, affecting function.
Phosphorylation plays a crucial role in regulating enzyme activity.
Deficiency in vitamin C prevents collagen hydroxylation, resulting in unstable collagen fibers.

Properties of Amino Acids

Amino acids vary in size, shape, charge, and reactivity; categorized as hydrophobic, polar, positively charged, and negatively charged.
The zwitterionic form of amino acids exists at neutral pH, showcasing both charged amino and carboxyl groups that neutralize the overall charge.
Seven amino acids possess ionizable side chains, impacting protein behavior in physiological pH.

Protein Structure Hierarchy

Primary structure is defined by the sequence of amino acids linked by peptide bonds.
Secondary structures include α-helices and β-sheets, stabilized primarily by hydrogen bonding.
Tertiary structure refers to the overall three-dimensional shape, influenced by interactions of R groups.

Secondary Structure Elements

The α-helix consists of a coiled structure with R groups extending outward, stabilized by intrachain hydrogen bonds.
β-sheets form from adjacent β strands linked by hydrogen bonds, which can arrange in parallel or antiparallel formations.
Reverse turns and loops allow polypeptide chains to change direction, aiding in overall protein structure.

Functional Implications

The specific three-dimensional conformation of a protein dictates its biological function.
Flexibility in protein structure allows for conformational changes during ligand binding, crucial for enzyme function.
Hydrophobic interactions play a key role in stabilizing protein structures by promoting nonpolar side chain aggregation.

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Description

This quiz explores the aggregation of fibrils and the conversion of normal prion protein (PrP) into an abnormal conformation. It highlights how these abnormally folded aggregates can recruit more proteins, contributing to pathogenic processes. Delve into the significance of beta-sheet conformation in prion diseases.