Proteins Flashcards
How do you form zwitterion?
Remove H+ from COOH
Add H+ to NH2
What happens when you lower pH of zwitterion?
H+ added to COO-
Positive charge
What happens when you increase pH of zwitterion?
H+ removed from NH2
Negative charge
What time of hormone is insulin?
Peptide hormone
Where is insulin produced from?
Beta cells, pancreas
What does insulin do?
Regulate metabolism of carbohydrates, fats + proteins
By promoting absorption of glucose from blood to liver
Why is insulin injected
Too large to pass through phospholipid bilayer of GI tract
+ protein = digested by enzymes in GI tract
Why is folding important?
NOT CORRECT folding = might not fit receptor
Does correct folding require energy?
YES
What is protein in functional, folded conformations called?
Native proteins
What are folds held together by?
Sulphur, peptide + covalent bonds
London forces
Metal ions stabilise protein
What does Ca2+ do in calmodulin?
Make protein more stable = lowers energy state = low Gibb’s Free Energy state
Why do many proteins not have disulphide bonds?
Within cell = highly reducing as high conc reductants = sulphur used up in cell
Where are disulphide bonds normally found?
Secreted, extracellular proteins
What is an example of a protein with disulphide bonds?
Insulin
2x disulphide bonds
What does hydration affect?
Solubility BUT folding
How does hydration affect folding?
Cause certain amino acids to move away
Why can’t you dry and weigh protein drugs?
Remove H2O molecules = alter pattern of proteins
= impossible to weigh insulin
What can insulin be produced by?
Recombinant DNA technology
Why does a protein have a hydrophobic core?
Hydrophobic side chains cluster in protein’s interior
= fold = core
What is secondary structure?
Amino acids form own configuration
Helix or alpha/beta sheet
What is alpha helix?
Single turn of helix, 3.6 residues
Repeat unit
Why does alpha helix form more readily?
H helical bonds
Structure stabilised by H bonds between H-atom attached to electronegative N atom of peptide linkage + electronegative carbonyl O of 4th amino acid on amino-terminal side of peptide bond
What is beta found in?
Sheets
Describe appearance of beta sheet
Backbone polypeptide chain extended into zigzag
Individual polypeptides = pleated appearance of sheet
What does Alzheimer’s disease do?
Change structure of protein
= form beta sheets
