Functions and Composition of Proteins

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Questions and Answers

What describes the primary structure of a protein?

Polypeptide chains held side by side by hydrogen bonds.

The sequence of amino acids in a polypeptide chain. (correct)

Corkscrew shape with hydrogen bonds between amino acids.

Three peptide chains woven like a rope.

Which of the following describes a beta pleated sheet?

Polypeptide chains held side by side by hydrogen bonds. (correct)

A structural arrangement involving three intertwined peptide chains.

A corkscrew shape formed by amino acid interactions.

The disruption of bonds in protein structures.

What is an example of denaturation in proteins?

Cooking an egg. (correct)

Formation of a triple helix.

Arranging amino acids in a sequence.

Maintaining a corkscrew shape of alpha helices.

What accurately describes a triple helix structure in proteins?

Three peptide chains woven together like a rope. Signup and view all the answers

Which of the following is considered an essential amino acid that must be obtained from the diet?

Leucine Signup and view all the answers

What does 'D' stand for in the context of D-Alanine?

Dextro Signup and view all the answers

What characterizes a zwitterion?

It carries no net electric charge. Signup and view all the answers

At what pH is an amino acid in its isoelectric point (pI)?

At a neutral pH level. Signup and view all the answers

What happens to an amino acid in a basic solution above its pI?

It donates a proton. Signup and view all the answers

What type of ion does an amino acid become in a solution more acidic than its pI?

Positive ion Signup and view all the answers

How does alanine behave at a pH below its pI?

As a positively charged ion. Signup and view all the answers

Which statement accurately describes L-Alanine?

The H2N group is on the left side. Signup and view all the answers

What occurs at pI for an amino acid?

It has a net zero charge. Signup and view all the answers

In which scenario does the NH3 group donate a proton?

In a basic medium above the pI. Signup and view all the answers

Which of the following is true about amino acids as bases?

They become negatively charged in acidic environments. Signup and view all the answers

What is one of the primary functions of proteins?

To regulate body metabolism Signup and view all the answers

Which of the following amino acids is classified as polar?

Serine Signup and view all the answers

What is another term for protein?

Polypeptide Signup and view all the answers

Which group differentiates one amino acid from another?

R group Signup and view all the answers

What type of amino acid has a carboxylic acid in its R group?

Acidic amino acids Signup and view all the answers

What is the role of hemoglobin in relation to proteins?

It transports oxygen in the blood Signup and view all the answers

Which amino acid is an example of a non-polar amino acid?

Alanine Signup and view all the answers

What is a common property of basic amino acids?

They typically carry a positive charge at physiological pH Signup and view all the answers

Which of the following is a function of proteins in muscle tissue?

Facilitating muscle contraction Signup and view all the answers

What trait identifies polar amino acids?

Hydrophilic side chains Signup and view all the answers

Which amino acid serves as a key building block of proteins and is known for its flexibility?

Glycine Signup and view all the answers

What is the significance of the ionized form of amino acids?

They carry an overall charge, affecting solubility Signup and view all the answers

Which amino acid is considered basic due to its additional amine group?

Histidine Signup and view all the answers

Which statement is true about the function of proteins as enzymes?

They speed up biochemical reactions in the cell. Signup and view all the answers

Study Notes

Function of Proteins

Provide structural components such as collagen, nails, and skin
Contribute to muscle contraction
Facilitate transport, for example, hemoglobin
Store nutrients
Regulate body metabolism
Catalyze biochemical reactions within cells
Protect the body

Protein Composition

Composed of amino acids
Polypoptide is another word for protein
Amino acids are built from a side chain, carboxyl group, and amino group
Only the side chain of the amino acid can change

Types of Amino Acids

Classified by their R-group (side chain):
- Polar: Hydrophilic, includes Serine, Threonine, Glutamine
- Non-polar: Hydrophobic, includes Glycine, Alanine, Phenylalanine
- Acidic: Hydrophilic, includes Aspartame, Glutamate
- Basic: Hydrophilic, includes Lysine, Arginine, Histidine

Zwitterions

Amino acids with equal positive and negative charges.
Occur at the isoelectric point (pI)

Isoelectric Point

The pH at which an amino acid carries zero net electric charge.
Influences the solubility and behavior of amino acids.

Amino Acids as Acids and Bases

Acidic solutions (pH<pI): The COO- group accepts a proton (H+)
Basic solutions (pH>pI): The NH3+ group donates a proton (H+)

Protein Structure

Primary structure: The sequence of amino acids in a polypeptide chain.
Secondary Structure:
- Alpha helix: Corkscrew shape formed by hydrogen bonds between amino acids.
- Beta pleated sheet: Polypeptide chains held side-by-side by hydrogen bonds.
Tertiary structure: The three-dimensional shape of a single polypeptide chain.
Quaternary structure: Two or more protein units (subunits) joined together.

Essential Amino Acids

The body cannot synthesize these amino acids.
Must be obtained through the diet.
Examples include Arginine, Leucine, Isoleucine, Lysine, Valine.

Denaturation

Disruption of bonds in secondary, tertiary, and quaternary protein structures.
Can be caused by heat, alcohol, or other factors.
Example: Cooking an egg or wiping the skin with alcohol.

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Description

Explore the essential functions and composition of proteins in this quiz. Learn about amino acids, types of amino acids, and the significance of zwitterions and isoelectric points. Test your understanding of how proteins contribute to various biological processes.