Amino Acids and Protein Structure Quiz

Amino Acids and Protein Structure

• Proteins are biomacromolecules composed of amino acids.
• Proteins have diverse functions, including catalysis, transport, signaling, and structural support.
• Learning objectives include listing protein functions, describing amino acid structure, calculating isoelectric points, and recognizing protein structures.

Learning Objectives

• List the functions of proteins.
• Describe the structure of amino acids.
• Calculate isoelectric points.
• Describe the bonds forming proteins.
• Recognize primary, secondary, tertiary, and quaternary structures in proteins.
• Explain protein denaturation.

Proteins

• Proteins are responsible for various important duties.
• They are biomacromolecules made of amino acids.

DNA, RNA, and Protein

• DNA → RNA → Protein
• DNA replication, transcription, and translation are crucial processes.

Protein Functions - Catalysis

• Enzymes increase reaction rates by lowering activation energy.
• Maltose to Glucose in 1 sec, normally it's 300 years.

Protein Functions - Transport

• Proteins transport substances in the circulatory system and between cellular compartments.
• Examples include hemoglobin and lipoproteins.

Protein Functions - Signaling

• Proteins act as hormones, directing and regulating metabolism.
• Receptors receive signals and play vital roles in cellular responses.

Protein Functions - Structural Elements

• Proteins form cytoskeletal elements, muscles, hair, and nails, providing essential structural support.
• Some proteins are solely structural.

Protein Structure

• RNA creates 3D structures.

Amino Acids

• Amino acids have different shapes.
• There are more than 300 amino acids in nature but only 20 are constituents of proteins.
• Some amino acids have special roles, like selenocysteine in eukaryotes.
• Amino acids have a central carbon atom, a carboxyl group, an amino group, and a variable side chain (radical). This side-chain gives it various properties.
• They can be positive, negative, or neutral. The side chains' properties determine how the amino acid interacts with water and other molecules.

Amino Acids - 21st Amino Acid

• In eukaryotes, selenocysteine (21st) is also used.

L- and D- Isomers

• Amino acids in proteins are L-isomers.
• They exist as mirror-image isomers.

Amino Acids - Acidic Side Chains

• Aspartic and glutamic acids.

Amino Acids - Basic Side Chains

• Lysine, arginine, and histidine.

Amino Acids - Polar Uncharged Side Chains

• Serine, threonine, asparagine, glutamine, cysteine, glycine, proline.

Amino Acids - Hydrophobic Side Chains

• Alanine, isoleucine, leucine, methionine, phenylalanine, tryptophan, tyrosine, valine.

Amino Acids and pH

• Amino acids are amphoteric molecules.
• They have both acidic and basic properties.
• The net charge of an amino acid depends on pH.
• Isoelectric point (pI) is the pH where the net charge is zero.

Primary Structure

• Consists of the amino acid sequence arranged in a linear chain.
• Peptide bonds connect amino acids.

Secondary Structure

• Local hydrogen bonds between amino acids result in structures like alpha-helices and beta-sheets.

Tertiary Structure

• Interactions between amino acids form a compact 3D structure with interactions from hydrophobic/hydrophilic amino acids.
• Numerous interactions maintain the shape: disulfide bridges, hydrogen bonds, ionic bonds, and hydrophobic interactions.

Quaternary Structure

• Multiple polypeptide chains form a larger structure, such as in hemoglobin. Also determined by interactions of R groups.

Denaturation

• Denaturation is the loss of protein's 3D structure. This leads to a loss of biological activity.
• Caused by factors such as temperature, pH, organic solvents, heavy metals, and detergents.

Renaturation

• Protein's regaining its natural form after denaturation is called renaturation.
• It depends on specific conditions.

Test your knowledge on amino acids and protein structure. This quiz covers protein functions, amino acid structure, isoelectric points, and the different levels of protein structure. Dive into the essential roles proteins play in biological systems and understand their formation processes.