Proteins Flashcards
Describe basic structure of an amino acid
carboxyl group
side chain
amino group
What are the different R group properites of amino acids?
Polar or non-polar
hydrophilic/hydrophobic
acidic or basic
What is the significance of the R group characteristics?
They determine how the Amino acid will behave in the polypeptide
Which Amino acid has the smallest R group?
Glycine - has a single hydrogen as the R group
What are the essential hydrophobic amino acids?
Valine
Leucine
Isoleucine
Phenylalanine
and Tryptophan
Which amino acid interacts with carbohydrates and allows for glycosylation of proteins?
Asparagine (has a partial positive charge)
Which amino acid allows for phosphorylation of the protein along with threonine?
Serine
they both have a hydroxyl group with a partial negative charge
Which charged amino acid (hydrophilic) is also an essential amino acid?
Threonine and lysine
Which amino acid is only considered essential in children?
Arginine
What charge do aspartic acid and glutamic acid carry?
They carry a negative charge at normal body pH
Which amino acid contains an aromatic ring with a hydroxyl group - giving it a partial or full negative charge?
Tyrosine
Which amino acid forms sulfur hydrogen bonds in a protein structure?
Cysteine
Which amino acid is found in the bends of a protein chain?
proline - it’s the kinky amino acid
what type of bond is a peptide bond?
It’s an amide bond- where the carboxyl group of one amino acid interacts with the amino group of the second amino aicd
what sort of reaction produces a peptide bond?
a condensation reaction - results in a loss of H2O
What controls the folding of a polypeptide?
amino acid sequence controls the folding - due to R group interactions/attractions
Describe the alpha helix formation
spiral structure - where the side chains extend outwards into a helical array - stabilized by hydrogen bonds formed between every fourth amino acid -
how many amino acid residues per 360 degree turn of the helix?
3.6
Describe the beta pleated sheet formation
stretched otu sheet structure
hydrogenb bonds between the NH and CO in side polypeptide chains
adjacent chains can run in the same direction (parallel) or in opposite directions (antiparallel)
What type of structure makes up collagen? How about Silk?
collagen is made up of alpha helices
silk is made up of beta sheets
What drives the formation of a tertiary protein structure?
it is driven by the strong tendency of hydrophobic residues to congregate away from the water
it is stabilized by disuphide bonds, hydrophobic interactions, hydrogen bonding and ionic interactions
What are fibrous proteins rich in?
They are usually long, rigid structures, with three polypeptide alpha chains wound around one another in a rope like helix - they are generaly rich in proline and glycine as a result
Why is vitamin C deficiency detrimental to the collagen structure?
Without Vitamin C, the lycine and proline are not hydroxylated properly and you get leaky collagen layers due to the weak interactions between chains - this explains the common symptom of scurvey = bleeding gums
What holds together the quaternary structure of proteins?
non-covalent ineractions and interchain disulphide bonds
What is the native conformation of a protein?
it is the fully functional folded protein structure - that determines the biological function of the protein
What is post-translational modification of the protein ?
It is chemical modification of a protein after translation - where a functional group is attached to an amino acid and it results in change in protein function
What are the common post translational modifications of proteins?
phosphorylation- of a serine, threonine, or tyrosine residue
glycosylation - of an asparagine, serine, or threonine
acylation = add fatty acid
ubiquitination = add ubiquitin = death signal
nitrosylation = add nitric oxide
