Unit 1 - proteins Flashcards
Proteins
- most diverse mol
- 50% of dry mass of cells
- protein is a polymer w many subunits folded into a three-dimensional structure
Function of Protein (7)
Support
- collagen/elastin
Transport
- hemoglobin
Communication
-Hormones (insulin)
Receptors
- cell membrane proteins
Movement
- actin / myosin
Defense
-antibodies
Reaction Catalysis
- enzymes
Amino Acids
all proteins r polymers made from amino acids
structure: central carbon bonded to an amino group (NH2), carboxyl group (COOH) and a hydrogen atom.
-diff lies in the R group
How Many Amino Acids r there
20 different amino acids
- 9 amino acids essential to consume in r diets
-11 amino acids r non essential our cells build
Amino Acids determine what
a proteins shape, size, and function
Acidic amino acids
posses a carboxyl group on their R-group
Basic amino acids
possess an amino group on their R-group
Proteins bonds
holds AA together through peptide bonds
( a form of dehydration synthesis rxn)
- occurs between amino group + carboxyl group
each polypeptide is code for one gene in DNA
Peptides
- covalent bonds hold aa together through peptide bonds
- a polypeptide is a peptide greater than 50 aa in length
Protein shape = 4 structures
- primary
- secondary
- teriatry
- quaternary
1) primary structure
sequence of amino acids in a polypeptide chain
- altering one amino acid can alter the 3D shape or function making it a non -functional protein
ie. sickle cell anemia
Sickle cell anemia
when one single amino acid substitution at the 6 position (6th AA)
go from GLU to VAL
2) secondary structure
as the PPC grows, it coils and folds at various locations along its length. this results in H-bonding between diff parts of same AA.
ie. B-pleated sheets vs a-helix
a-helix
H-bonds form between the partially negative O of the carboxyl group in one peptide bond and the partially positive H of the amino group four peptide bonds away = chain to coil making an a-helix.
b-pleated sheet
a b-pleated sheet forms when hydrogen bonds form between portions of a polypeptide chain that lie parallel to one another (strength of silk)
3) tertiary structure
OVERALL 3D SHAPE of polypeptide (how it folds)
due to bonding interactions of R group
the force of attraction and repulsion between pp and its environment cause folding.
3) tertiary structure r group inportance
w water
aa w a polar R group r attracted to water while non-polar R groups r not. this cause non-polar R groups to fold into the interior of the structure.
3) tertiary structure types of bonds
1) hydrogen bond
2) ionic interactions
3) hydrophobic interactions
4)disulfide bridge
hydrogen bonds
between polar R groups (POLAR)
ionic interactions
between charged (acidic or basic) R groups
ie. salt bridge
hydrophobic interactions
between non-polar R groups
disulfide bridge
bond that is formed when the -SH groups of 2 cysteine amino acids line up and react to form an S-S covalent bond
(strong bond that can stabilize shape)
4) quaternary structure
clustering of two or more 3) polypeptides
- functional proteins
ie. hemoglobin is composed of 4 polypeptides, each w more than 140 aa.
protein prosthetic groups
many proteins require non-protein components called prosthetic groups
-often enzymes require these groups that contain metal ions in order to function
protein folding
- is spontaneous
- aided by chaperone protein
prtoen denaturation
if a protein’s 3D shape is changed due to the environment, ph, temperature etc. and bonds r broken the protein is denatured and can no longer carry out its intended biological function. this process is often irreversible.
ex of denaturation
cooking and egg as hydrogen bonds r hydrophobic interactions between non-polar R groups
level or protein structure in each
a) beta-pleated sheets
b) order of aa in protein
c) a protein w 2 or more peptide chains
d) shape of globular protein
e) disulfide bonds between R group
a) 2
b) 1
c) 4
d) 3
e) 3
