Proteins and Their Functions Class

Questions and Answers

Which characteristic is true about peptide bonds?

They are covalent bonds that can easily break.

They exhibit partial double bond characteristics. (correct)

They allow free rotation around the C–N bond.

They are only found in fibrous proteins.

What is a common characteristic of globular proteins?

They are elongated and fibrous in structure.

They are spherical in shape. (correct)

They mainly serve protective functions.

They are primarily composed of collagen.

What type of protein is primarily responsible for catalyzing biochemical reactions?

Hormones

Antibodies

Enzymes (correct)

Structural proteins

What happens to the name of the first amino acid in a peptide when naming it?

It is replaced with –yl. Signup and view all the answers

Fibrous proteins are primarily characterized by which of the following?

Their sheet-like conformation. Signup and view all the answers

Which amino acid classification includes Methionine and Cysteine based on their side chains?

Sulfur-containing amino acids Signup and view all the answers

What is the isoelectric point in relation to amino acids?

The pH at which amino acids possess equal positive and negative charges Signup and view all the answers

Which of the following correctly describes the term 'zwitterion' as it relates to amino acids?

An ion that has both positive and negative charges simultaneously Signup and view all the answers

How do basic amino acids differ from acidic amino acids?

Basic amino acids contain an amino group that can accept protons Signup and view all the answers

Which statement best reflects the optical activity of amino acids?

Amino acids can be either dextrorotatory or levorotatory depending on their structure Signup and view all the answers

Study Notes

Types of Proteins

Collagen: Provides structural support in connective tissues.
Actin and Myosin: Key proteins in muscle contraction.
Keratin: Structural protein found in hair, nails, and skin.
Antibodies: Function as protection proteins; serve as natural defense mechanisms.
Enzymes: Catalytic proteins that accelerate biochemical reactions.
Hormones: Chemical messengers that regulate organ and tissue functions through body fluids.

Classification of Proteins by Shape

Fibrous Proteins: Composed of elongated polypeptide chains, offering structural support (e.g., collagen, keratin).
Globular Proteins: Spherical proteins, commonly involved in metabolic functions (e.g., enzymes, antibodies).

Peptide Bonds

Formed through covalent bonding between amino acids.
Link two amino acids as dipeptides, three as tripeptides, and four as tetrapeptides; longer chains referred to as polypeptides.
Structure organization ranges from oligopeptides (few amino acids) to polypeptides (many amino acids).

Naming Peptides

Initiate naming from N-terminal end.
Modify the first amino acid's ending to '-yl' while maintaining the name of the C-terminal end amino acid.

Characteristics of Peptide Bonds

Exhibits a partial double bond character, resulting in restricted rotation around the C-N bond.

Characteristics of Amino Acids

Optical Activity: Dextrorotatory (right) or Levorotatory (left) movement of polarized light.
Amphoteric Nature: Can act as both acids (COOH) and bases (NH2).
Zwitterion Formation: Contains both positive and negative charges; COOH can donate a proton, while NH3 accepts it.
Isoelectric Point: pH at which the zwitterion form is maximized.

Classification of Amino Acids by R-Group

Neutral Amino Acids: Equal amino and carboxyl groups (e.g., Glycine, Alanine).
Branched Chain Amino Acids (BCAAs): Have side chains with a central carbon (e.g., Valine, Leucine).
Acidic Amino Acids: Possess negatively charged R-groups (e.g., Glutamic acid).
Basic Amino Acids: Feature positively charged R-groups (e.g., Lysine, Arginine).
Aromatic Amino Acids (Non-polar): Hydrophobic, engage in hydrophobic interactions (e.g., Phenylalanine, Tyrosine).
Sulfur-containing Amino Acids: Nonpolar, feature a sulfur atom (e.g., Methionine, Cysteine).
Hydroxy-containing Amino Acids: Exhibit aliphatic hydroxyl groups (e.g., Serine, Threonine).
Imino Acids: Related to amino acids with a distinct structural difference (e.g., Proline).

R-Group Classification by Polarity

Aliphatic (Non-polar): Hydrophobic properties (e.g., Glycine, Alanine).
Polar, Uncharged: More hydrophilic due to functional groups (e.g., Serine, Cysteine).

Classification of Amino Acids by Nutritional Importance

Essential Amino Acids: Nine amino acids that must be obtained from diet due to inability to be synthesized by the body.
Non-Essential Amino Acids: Synthesized by the body, not strictly dietary (e.g., Alanine).
Conditional Amino Acids: Generally non-essential but required during illness or stress.

General Characteristics of Proteins

Proteins are macromolecules made of amino acids connected by peptide linkages.
Derived from the Greek word "proteios," meaning "of first importance."
Vital for the structure, function, and regulation of body's tissues and organs.

Description

Explore the various types of proteins and their essential roles in the body. This quiz covers structural proteins, defense proteins, catalytic proteins, and chemical messengers. Delve into the classification based on conformation and shape to deepen your understanding of protein functions.