amino acids and proteins Flashcards
what % of dry weight of most cells do proteins make up
30-50%
what atoms do amino acids usually contain
C, H, O, N, and occasionally S
what is the general structure of an amino acid
H2N-CRH-COOH
WHAT IS PHYSIOLOGICAL pH
pH 7.4
what is pKa
the pH at which there are an equal number of charged and uncharged versions of an ionisable chemical group
what is the pKa of a carboxylic acid
pH 2.3
what is the pKa of an amino group
pH 9.0
what happens when the pH is increased from the pKa
the chemical group is going to become deprotonated so it will lose a H
what happens when the pH is decreased from the pKa
the chemical group will be protonated
what side chain property is non-polar
hydrocarbon chains or rings
what are the side side chain properties of polar but uncharged
contain hydroxyl or amide groups
what are the side chain properties polar acidic
contain carboxylic acid groups - negatively charged at physiological pH
what are the side chain properties of polar basic
contains basic groups which are positively charged at physiological pH
what is the bond which joins two amino acids together
peptide bond
what is the primary structure
amino acid sequence of the polypeptide
what is the secondary structure
alpha helix + beta sheet due to hydrogen bonds associated with the peptide bond
what is the secondary structure
alpha helix + beta sheet due to hydrogen bonds associated with the peptide bond
what is the tertiary structure
3D structure of folded secondary structure held by interactions between R-groups
what is the quaternary structure
association of one or more polypeptide chains held by interactions between R-groups
what is a fibrous protein
- protein that isn’t folded into a tertiary structure (collagen)
- usually have a quarteranry structure
- low water solubility
- structural function
what is a globular protein
- polypeptide chain is folded into a tertiary structure
- may or may not have a quaternary structure
- complex tertiary structure
- has a specific shape
- allows recognition of + binding to other molecules
- catalysts / transport
how are proteins held in suspension with water
through hydrogen bonds
what affects the solubility of a protein
disrupting H bonds interactions q
what affects protein solubility
- iso-electric point
- ionic strength of environment
- heavy metals
- organic acids
- dielectric constant
