Proteins unit 4

Primary, secondary, tertiary, quaternary

What are the levels of protein structure

Tertiary level

What level did all functional proteins have up to?

Primary structure

The linear sequence of amino acids in a polypeptide chain.

Residue or moiety

In the primary structure, each component of the amino acid in a polypeptide chain is called a ____ or _____.

Peptide bonds

Primary structure is determined by _____ bonds.

Genetic information

In the primary structure, it is encoded by the _____ ____.

Sequence

In the primary structure, the ____ determines higher levels of structure.

Primary structure

Determines the final structure and function of a protein

Sickle cell disease

Example of diseases caused by the changes in the primary structure

Sickle cell disease

Disease caused by a single amino acid substitution in hemoglobin.

6th; B-globin chain

The ___ amino acid in the ___ chain is changed in the sickle cell disease

Valine

In the sickle cell disease, what amino acid was the reason for the change?

Site-directed mutagenesis

Scientists study the effects of amino acid changes using biology techniques. Replacing one amino acid with another in a protein.

Secondary structure

It is the local folding of the polypeptide chain due to hydrogen bonding between backbone atoms.

A-helix, b-pleated sheet

What are the main types of the secondary structure

Spiral

The a helix of the secondary structure is a ____ structure.

H-bonding

The a helix of the secondary structure is stabilized by ______ between carbonyl oxygen and amide hydrogen within a strand.

Outwards

The a-helix of the secondary structure has side chains that extend _____.

3.6

In the secondary a helix, there are ____ amino acids per turn

Globular proteins

Alpha helical segments are found in many ___ proteins such as myoglobins and troponin.

Pitch

___ of the helix is the linear distance between corresponding points on successive turns.

Proline

Amino acid rich in polypeptide chains that cannot form a helix because it has a rigid ring structure, preventing rotation around the N-C bond, and creating a kink that destabilized the helix.

Glutamic acid

Polypeptides with many ____ ___ residues also fail to form a a-helix because the negatively charged carboxyl groups repel each other, disrupting helix formation.

Zig-zag

The polypeptide backbone of a b-pleated sheet is extended in a _____ arrangement, forming a sheet-like structure.

Hydrogen

___ bonds form between neighboring peptide chains in a b-pleated sheet.

Parallel, and anti-parallel

Types of b-pleated sheets

Parallel

A type of b-pleated sheet whose chains run in the same direction

Anti-parallel

A type of b-pleated sheet whose chains run in different directions

Wool and fibrous proteins of muscles

Examples of a-helix secondary structure

Silk and spider’s web

Example of b-pleated sheet secondary structure. These proteins cannot be stretched.

Supersecondary structure

Proteins often contain combinations of secondary structures thar form _____

Supersecondary structure

Formed by specific arrangements of a helices and b-sheets

Structural motifs

Supersecondary structures are also called _____

B-a-b unit

Is a common supersecondary structure that has two parallel b-strands connected by an a-helix

A-a unit

Two antiparallel a-helices stabilized by the interactions between side chains

B-meander

Antiparallel b-sheet connected by tight turns

Greek key motif

Antiparallel b-strands where the chain folds back on itself

Motif

Is a repetitive supersecondary structure

B-meander and Greek key

Examples of motifs

B-barrel structure

Some motifs can form largers truc