Macromolecules Flashcards
What is the central carbon atom in an amino acid called?
α-carbon
What are the four groups bonded to the α-carbon in amino acids?
- Carboxyl group (COOH) * Amino group (NH2) * Hydrogen atom (H) * Variable side chain (R-group)
What role does the variable side chain (R-group) play in amino acids?
It distinguishes one amino acid from another and dictates the amino acid’s specific chemical properties.
What is a dipeptide?
A molecule formed from the condensation reaction between two amino acids.
What is a peptide bond?
An amide bond formed between the carboxyl group of one amino acid and the amino group of another.
What is released during the formation of a peptide bond?
A water molecule (H₂O)
What are the four levels of protein structure?
- Primary structure * Secondary structure * Tertiary structure * Quaternary structure
Define primary protein structure.
The linear sequence of amino acids in a polypeptide chain.
What stabilizes the primary protein structure?
Peptide bonds
What is secondary protein structure?
Local, three-dimensional arrangements of amino acid residues in a polypeptide chain.
What primarily stabilizes secondary protein structures?
Hydrogen bonds between the backbone amide and carbonyl groups.
What are the two most common types of secondary structures?
- α-helices * β-sheets
Describe the α-helix structure.
A right-handed coiled conformation where hydrogen bonds occur between specific amino acids.
What characterizes β-sheets?
Extended polypeptide chains arranged side-by-side, forming a pleated sheet-like structure.
What is tertiary protein structure?
The three-dimensional arrangement of a polypeptide chain.
List the bonds that stabilize tertiary protein structure.
- Hydrophobic interactions * Hydrogen bonds * Ionic bonds (salt bridges) * Disulfide bonds (covalent bonds)
What is quaternary protein structure?
The arrangement of multiple polypeptide chains into a single functional protein complex.
What happens to a protein’s quaternary structure during denaturation?
It leads to the loss of biological function.
What is the function of hemoglobin?
Transportation of oxygen gas around the body to respiring cells.
What is unique about the quaternary structure of hemoglobin?
It consists of four polypeptide chains (2 alpha and 2 beta chains).
How many oxygen molecules can one hemoglobin molecule carry?
4 molecules of O2 (eight oxygen atoms)
What are the two main types of proteins?
- Globular * Fibrous
Describe globular proteins.
Usually metabolically active, soluble in water, and have a compact, tightly-packed structure.
List examples of globular proteins.
- Enzymes (lysozyme, amylase, trypsin) * Transport proteins (hemoglobin, myoglobin, serum albumin) * Storage proteins (ferritin) * Hormones (insulin) * Antibodies (immunoglobulins)
What are fibrous proteins primarily known for?
Structural roles and being metabolically inactive.
List examples of fibrous proteins.
- Collagen * Elastin * Keratin * Fibroin * Myosin
What is the structural feature of collagen molecules?
They form triple helices.
