B1.2.1– generalized structure of an amino acid

can essential amino acids be synthesized?

No. it must be obtained from food. Vegan diets require attention to ensure essential amino acids are consumed. Non-essential amino acids can be made from other amino acids.

How is a peptide bond formed

a ribosome condenses two amino acids into a dipeptide

is DNA code variable or narrow?

highly variable!

Does protein length have a limit? What is the shortest and longest polypeptide?

No. it can be any length.

Shortest: 11 AAs long

Longest: Titin, 35,000 AAs long.

there are infinite combos!

denaturation

changing of a proteins 3D shape. it is considered irreversible.

Effect of temperature on protein structure

-heat will denature a protein

-cold does not!

-Most animal proteins are stable at body temperature. Plant proteins are stable at air temps.

effect of pH on protein structure

-pH denatures proteins

-any pH outside of optimal range will cause loss of 3D structure

Primary structure of amino acid

Sequence of amino acids as a result of gene sequence.

R-group will matter later

secondary structure of amino acid

Amino and Carbonyl groups will interact to form Hydrogen bonds.

a-helix will form a spiral structure

Beta-pleated sheets form.

Tertiary Structure

R-group matters here!

3D folding due to R-group interactions (e.g., hydrophobic, ionic, disulfide)

tertiary and primary structure relationship

if primary structure changes, tertiary could change.

R groups

each of the 20 amino acids have unique R-groups

R-groups can be positive or negatively charged, acidic, basic polar, or non-polar

Cysteine

a sulfur containing amino acid. Disulfide bridges are critical to lots of tertiary structure

How do proteins work in watery enviornemnts?

in globular proteins, hydrophobic amino acids are clustered in the middle. keeps it working.

Quaternary structure

Multiple polypeptide chains joined to form one functional protein

conjugated proteins quaternarny

have another molecule in their quaternary structure

Hemoglobin has iron!

Glycoproteins hhave carbohydrates attatched!

non-conjugated proteins quaternary

Purely protein in their quat structure

Insulin!

collagen!

Collagen

long, fibrous protein that formed fibers and can run thru tissue. It makes your skin tight and bones strong

Actin and Myosin

long, fibrous proteins that form cellular cytoskeleton and muscle fibers!

Actin is pulled by myosin to contract a muscle!

Enzymes

globular proteins w a specific 3D shape that binds to other molecules at a specific active site.

They can change shape to catalyze reactions

insulin

globular protein that fits into a receptor that is coupled w/ a glucose channel in cell membranes.

How does insulin work?

WHen insulin binds, the channel opens, allowing glucose to leave blood and enter cells

cyro-electron microscopy

allowed us to visualize proteins for first time