Biochemistry: Introduction to Proteins and Amino Acids

These flashcards cover fundamental concepts in biochemistry regarding proteins and amino acids, aiding in understanding protein synthesis, structure, and analysis.

What initiates protein biosynthesis in cells?

DNA is transcribed to form mRNA in the nucleus.

What is the role of mRNA in protein synthesis?

mRNA is exported to the cytoplasm and translated into a linear sequence of amino acids.

What defines the 20 common amino acids?

R-groups (side chains) attached to the α-carbon distinguish the amino acids.

What is a zwitterion?

At neutral pH, an amino acid has a protonated amine group and a deprotonated carboxylic acid group.

What distinguishes L-amino acids from D-amino acids?

L-amino acids have the amino group on the left in Fischer projection representation.

How do side chains of amino acids vary?

They can be classified as nonpolar (hydrophobic), polar (hydrophilic), or electrically charged (acidic or basic).

What happens during the condensation reaction between two amino acids?

A peptide bond is formed, and water is released.

What is the significance of the imido nitrogen in histidine?

It is important in protein biochemistry, influencing charge and reactivity.

What modifications can occur to amino acids post-translationally?

Modifications can involve signaling pathways, structural stabilization, and functions in gene expression.

What is the function of proteases?

They cleave specific peptide bonds during processes like protein degradation.

What is the charge state of histidine at physiological pH?

Histidine can exist in different charge states depending on the pH.

What is the primary role of the His-tag in protein purification?

The His-tag allows specific binding to metal affinity columns for protein purification.

What determines the elution profile in size exclusion chromatography?

The size of the proteins, with larger proteins eluting first.

What is a consensus sequence?

It illustrates the most conserved amino acid residues among homologous sequences.

What technique is used to sequence proteins and peptides?

Mass spectrometry combined with specific proteolysis methods.