Bioch Flashcards
An amino acid is an organic compound containing both an amino group (-NH2) and a carboxyl group (-COOH) attached to the same carbon atom, called the α-carbon.
Amino Acids
There are 20 standard α-amino acids found in proteins.
Standard Amino Acids
4 categories of amino acids
Nonpolar, Polar Neutral, Polar Acidic, Polar Basic
Hydrophobic side chains. Nonpolar amino acids include alanine, valine, leucine, proline, methionine, tryptophan, glycine, isoleucine, and phenylalanine.
Nonpolar
Polar side chains that do not carry a charge
Polar Neutral
Contain two amino groups and carry a positive charge at physiological pH. These are arginine (Arg), lysine (Lys), and histidine (His)
Polar Basic
Amino acids that must be obtained from the diet because the body cannot synthesize them in adequate amounts.
Essential Amino Acids
Contain two carboxyl groups and carry a negative charge at physiological pH. These are aspartic acid or aspartate (Asp) and glutamic acid or glutamate (Glu).
Polar Acidic
What are the essential amino acids
Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
Contain all essential amino acids (e.g., animal proteins, soy).
Complete Amino Acids
Lack one or more essential amino acids (e.g., most plant proteins).
incomplete proteins
The essential amino acid missing or in low quantities in an incomplete protein.
Limiting Amino Acids
Examples of limiting amino acids
Lysine (wheat), methionine (beans), tryptophan (corn).
Combining incomplete proteins (e.g., rice and beans) to provide all essential amino acids.
Complementary Proteins
at high pc basic
amino acids lose a proton and carry a negative charge.
At low ph (acidic)
amino acids gain a proton and carry a positive charge
is a molecule with both positive and negative charges but no net charge
Zwitterion
the amino acid has no net charge and does not migrate in an electric field.
isoelectric point
-COOH group is placed at the top, -R group at the bottom.
-NH2 group is horizontal; left for the L-isomer, right for the D-isomer.
Fischer Projection
Unique because its side chain forms a ring with the amino group, making it rigid
Proline
Contains a sulfur atom and forms disulfide bonds, which stabilize protein structure.
Cysteine
Aromatic Amino Acids
Phenylalanine, tryptophan, and tyrosine have aromatic side chains.
refers to the specific sequence of amino acids in a protein.
primary protein structure
Amino acids in the primary structure are linked by peptide bonds.
Bonding
Determined the primary structure of insulin.
Frederick Sanger (1953):
Refers to the spatial arrangement of the protein’s backbone.
Secondary Protein Structure
Consists of 51 amino acids in a specific sequence.
Insulin Structure
Two types of secondary protein structure
Alpha Helix, Beta pleated sheet
Coiled spring stabilized by hydrogen bonds.
Shape: Helical, resembling a coiled spring.
Stabilization: Hydrogen bonds between the carbonyl oxygen and the hydrogen of the amino group in the backbone. are common in fibrous and globular proteins.
Alpha Helix
Chains align side by side, stabilized by hydrogen bonds (can be parallel or antiparallel).
Extended sheet-like structure.
Chain Alignment: Can be parallel (chains run in the same direction) or antiparallel (chains run in opposite directions).
Stabilization: Hydrogen bonds between adjacent chains. Beta sheets are crucial for structural stability in proteins like silk fibroin.
Beta Pleated Sheet
Function: Proteins acting as biochemical catalysts are enzymes.
Importance: Enzymes accelerate biochemical reactions in cells, which are essential for various metabolic processes.
Example: Enzymes involved in digestion and cellular metabolism, such as amylase or lipase.
catalytic protein
