Lecture 3 Flashcards
where are proteins synthesized
-in the liver
what are the functions of proteins
1.catalyzing reactions - enzymes
2.transport metals - Fe Cu
3.hormone receptor- thyroid/steroid receptors
4.structure and support- Collagen
5.part of immune response - AB
6.coaugulation - fibrinogen
7.maintaining oncotic pressure - albumin
what is the protein composed of?
C- CARBON
H-hydrogen
O-Oxygen
N-Nitrogen
S-Sulphur
proteins are made up of amino acids
what are differences in proteins determined by
-number of amino acids
-sequence of amino acids
-the way the protein is folded
-chemical properties
how many AA are there
-there are 9 essential dietary intake
-6 semi essential - premies cannot make them so they may be given them
-6 non essential and made by the body
what is the structure of amino acids
1 amino acids has 1 amino group (NH2) and 1 carboxyl (cooh)
-has one r group (side chain - creates the functionality) and hydrogen atom
-the NH2 and COOH are attached to the alpha carbon atom (the middle carbon)
- have a ball and stick model
-are tetrahedral structures
What is the chiral carbon
-amino acid structure 4 groups are attached
-the alpha carbon is asymmetric in all amino acids except glycine
-the alpha carbon is known as the chiral carbon since 4 groups can attach themselves to it
-meaning it is optically active
-can exist as enantiomers or optical isomers
what is an enantiomer
-D and L forms of amino acids
-they are mirror groups but not superimposable
-D form is dextrorotatory clockwise
-L form levorotatory- rotating counterclockwise
-lights is rotated through the fluid
all naturally occurring
amino acids in nature are in the L form
LOOK AT SLIDE
What are the amphoteric properties of AA
- aa ionize in solution which can yield a zwitterion
-can act as acid or base
-Acids donate H+ COOH is donor (cation)
-base accepts H+ - NH2 is an acceptor (anion)
what is the isoelectric point
-pH when aa has net zero charge
-equal pos and neg charges
-molecule is dipolar - ampholyte (can be pos OR neg)
-each aa has different IEP
adding acid -net pos
adding OH - net basic
what is a buffer
-needs weak acid/base with corresponding salt
-aa and proteins are buffers
what classifies an amino acid
R group
and groups of non polar and polar
what is a non polar AA
-hydrophobic
-9 amino acids
Aliphatic - r group is a straight chain
aromatic- has benzene/aromatic rings
What is a polar amino acid
Neutral - the cooh=amino groups
-contain hydroxy, sulfur or amide R–C=O
-not charged
-polar side chains making them hydrophilic
Acidic-more cooh than amino
-2 amino acids
-highly polar, negatively charged at physi pH
Basic - more amino than cooh
-3 amino acids
-contains an amine NH3
-side chain is positively charged
-heterocyclic - ring structure with O or N
what are peptides and how are they formed
-amino acids are joined together through amide linkages called peptide bonds
-amide is NH-C=O (the bond between the N and C)
formed through covalent bonds via reactions like condensation
how are polypeptides named*** learn how
-the amino group NH2 that joins for the peptide bond keeps their full name
- if a cooh is supplied it ends with yl
what is the primary structure of protein
-linear linked by peptide bonds - genetic code
-number and sequence determine shape and function
-info contained in DNA
-aa substitutions can cause mutations
what is the 2ndry structure of proteins
- aa in chains start folding
-3D shape through bends and coils
-becomes a alpha helix shape that is stabilized by intrachain hydrogen bonds between aa and cooh
-parallel or anti parallel strands
-no R group involvement
intrachain H bonds are weak
what is the tertiary structure of proteins
-2ndary structures that condense to form the tert structure
-3D globular shape from the folding and bending of the helical coil
-structures stabilized by R group interactions***
-salt linkages
-van der waals forces
-dipole - dipole interactions
-disulfide linkages
-the hydrophobic groups get clustered in middle leaving the philic chains outside
-enzymes
-final form for some
What are quaternary structures of proteins
-more than one folded unit, singles all joined together
-joined by non covalent bonds (ionic, hydrogen, dipole-dipole)
-like hemoglobin 4 polypep chains and 4 heme groups carries O
what is denaturation
-change that alters protein shape while leaving peptide bonds intact
-irreversible
-decreases solubility
-increases susceptibility
what are forms of physical denaturation
shaking
* H bonding disrupted by
agitation
heating
60-70°C
UV rad
* high frequency
vibration breaks H bonding
* sterilization
microwave
what are forms of chemical denaturation
-organic solvents like alcohol or acetone which disrupt intra H bonds by forming intermolecular H bonds with protein
pH extremes -
acidic/basic conditions - disrupt H and diS bonds
- strong acids can degrade protein
- proteins precipitate when IEP is reached
salts of heavy metal
- salt linkages are disrupted and proteins end up precipitating out of solution
-reducing agents - break s-s bonds
what is the hydrolysis of proteins
-when covalent bonds are cleaved by addition of water molecules
- the primary structure is destroyed
-results in constituent aa
-denaturation makes proteins more susceptible to hydrolysis
-strong acids or bases and high temps can cause complete hydrolysis resulting in amino acids
enzymes like proteases, trypsin, chymotrypsin neutral pH and body temperature partake in incomplete hydrolysis which gives peptides and aa
