Flashcards in Lesson 5-8 Deck (42)
All peptides, polypeptides and proteins in the mammalian are polymers of...?
The alpha-amino acids in peptides and proteins consists of:
a carboxylic (-COOH) and an amino (-NH4) functional group attached to the same carbon atom. this carbon is the alpha-carbon.
The one amino acid not exhibiting chirality is:
Glycine. Since its "R-group" is a hydrogen atom.
All of the amino acids in proteins exhibit the same absolute...?
steric configuration (based on the arbitrry): proteinogenic L-amino acids are related to the L (levarotatory)-glyceraldehyde.
Where can you find D-amino acids?
Polypeptide antibiotics, microbes, plants and insects. (not in proteins)
What is the Isoelectric point?
= pH value at which the amino acid has no net charge
- have tightly folded peptide chains that are rougly spherical in shape.
- Albumins: such as ovalbumin in eg white, lactalbumin in milk, serum albumin in the blood.
- enzymes, hormones
- water soluble
Gluboular enzyme protein:
- contains polypeptidechains arranged in extended, parallel layers, or shet-like structures
- collagen in CT
- elastins in ligaments and arteries
- keratins in hair, wool, nails and hoofs.
- water soluble
"other type" intermediate proteins:
- long rod-like structure
- myosin in muscle, fibrinogen
- water soluble
Classification of proteins by shape or solubility:
- Globular proteins
- Fibrous proteins
- "other type" intermediate proteins
Classification of proteins by composition
- Simple proteins
- Conjugated proteins
- yield only amino acids (or derivates of amino acids) on hydrolysis
- consist of a simple protein combined with a nonprotein compound
- Glycoproteins, Nucleoproteins, Phosphoproteins, Chromoproteins, Hemoproteins, Lipoproteins, Flavoproteins, Metalloproteins
What is the nonprotein part of a conjugated protein?
The prosthetic group
Classification of proteins by function:
- contractile proteins
- transport proteins
- protein hormones
- protection proteins
- storage proteins
- regulation proteins
- receptor proteins
- toxic proteins
Secondary structure of proteins:
the arrangement of a polypeptide into regularly repeating units (alpha helix, beta structure = beta plated sheet, collagen), random coil or beta-turn configuration by the formation of intramolecular hydrogen bonds along the length of the chain
Sequence of amino acids
Tertiary structure of proteins:
- Regularly repeating units, irregular parts, orientation of side chains and stabilizing bonds.
- The proteins thrre-dimensional (spatial) structure by complete folding of the sheets and helicec of a secondary structure held in position by apolar (inside) and polar (outside) bonds between the chains.
What is the Native conformation?
Each protein has at least one tree-dimensional conformation in which it is stable and active under biological conditions of temperature and pH
What is the Chain-conformation?
The tree-dimensional arrangement (secondary and tertiary structure together) of atoms in a structure.
What is protein folding?
The process by which a protein structure assumes its functional shape, active, native conformation.
What is protein unfolding?
Denaturation resulting in loss of function.
- happens when proteins are heated, or exposed to acids or bases, or high salt concentrations.
denaturation can be revirsible and irreversible.
What is renaturation?
- Denaturation is sometimes reversible; an unfolded protein can be restored to correct folding and regain biological activity. This is called renaturation.
Denaturation by heat:
Heat coagulates almost all protein. The increased motion within the molecules breakes the hydrophobic interactions and hydrogen bonds.
Denaturation by Acid and Bases:
Denature proteins by changing the pH of the solution of the protein, and thus changing carboxyl groups to carboxylate ions, amino acid groups to ammonium ions, or vice versa.
Ionic bonds in the proteins are broken.
Denaturation by Reducing-oxidizing agents:
Convert disulfide bonds to free sulfhydryl groups. Oxidizing agents can convert sulhydryl groups back to disulfide bonds, but the structure of the protein may be significantly different from the native protein.
Denaturation by Hydrogen-bonding solvents:
Denature proteins by disrupting the hydrogen bonds within the molecule.
Denaturation by Heavy metal ions:
Such as Ag+, Hg2+ and Pb2+, denature proteins by reacting with sulfhydryl bonds to form stable metal-sulfur bonds or the carboxylate ions in the side chains of acidic amino acids.