Amino Acids and Proteins Flashcards
What determines 3D structure and biological properties of proteins?
The sequence of the AA that are linked together
D or L type proteins are found naturally in humans?
its L-type (but we can metabolize D, just cant incorporate)
D type is the sugars we can handle
Acidic AAs
Aspartic Acid
Glutamic Acid
Basic AAs
Lysine
Non-polar AAs
Glycine, Leucine, Alanine, Phenylalanine
neutral AAs
Serine, Cysteine, Threonine, Tyrosine
Asn
Asp
Gln
Glu
Asparagine
Aspartate
Glutamine
Glutamate
Tell me about the formation of cystine
2 cysteines can spontaneously oxidize to form cystine (the sulfurs bond to each other)
*cystinuria - the transport protein that reabsorbs Arg/Lys/CYSTINE is busted. so cystine cant be reabsorbed and shows up in the urine! (Arg/Lys are soluble)
can have kidney stones (made of cystine)
Primary structure
Secondary structure
sequence of AA
alpha helix or beta pleated sheets (hydrogen bonding)
keratin
hard vs. soft keratins
major component of external protective layers in mammal
- hard have a high sulfur content (nails, horns, beak)
- soft (wool, fur, skin)
Hair cell?
alpha helices 3 alpha helixes = 1 protfibril 11 protofibrils = 1 microfibril 100s of microfibrils = 1 macrofibril many macrofibrils = one hair cell
collagen
major protein component of connective
forms insoluble fibers of great strength
collagen structure
without vitamin C (a cofactor) there can be no hydroxylation of proline/lysine and the necessary bonds between chains cannot form (post-translational modification) that produces collagen
no vitamin C = lack of collagen = scurvy
Tertiary structure
3D structure
proteins fold during and after synthesis (polar groups on surface, non-polar AAs in the interior - drives the folding pattern)
molecular chaperons?
example = heat shock proteins - salvage the denatured protein or break it down if its too far gone
chaperons* - job is actually to delay folding - prevents misfolding, its faster/more efficient
Prion diseases
degeneration of brain tissue caused by conversion of normal protein to misfolded protein
introduction of this misfolded protein by infection, ingestion, or mutation is bad news
- genetic: CDJ (humans), BSE (cows), Scrapie (sheep)
- infection transmitted via pig human growth hormone injection (not relevant today because we use bacteria to synthesize hormones)
Quaternary structure
example = hemoglobin (interaction of 4 myoglobin subunits, each with one site for Oxygen binding)
cooperative binding of oxygen (Hb)
once one Hb subunit binds oxygen the other 3 change confirmation to relaxed state and are more likely to bind oxygen
Bohr effect
Hydrogen ions (and CO2) promote the release of oxygen
source of H+: lactic acid from active muscle tissue
- BPG stabilizes deoxyhemoglobin
- binding of BPG promotes release of oxygen (to tissues that need oxygen most)
Fetal Hb cant bind BPG and therefore has an enhanced affinity for oxygen
Sickle cell
genetic disease - point mutation - cause
- RIGID SICKLE SHAPE - deoxy Hb polymerizes
- ANEMIA (sickle cells more readily broken down) - also because of this billirubin, a breakdown product of RBCs cant be excreted fast enough and accumulates causing gallbladder stones
- ISCHEMIA (their shape causes blockages in blood vessels
What does it mean to denature a protein?
break apart 3D structure (primary structure remains)
extremes of ph or temperature, organic solvents, radiation
What is a conjugated protein?
a protein with a non-protein component attached
lipoproteins (HDL)
glycoproteins (collagen, FSH, TSH)
nucleoproteins (histomes)
Remember this key fact
Information for folding is contained in the sequence of the amino acid
