Proteins Flashcards
What is the structure of a polypeptide?
Many amino acids joined by peptide bonds between amine group of one and carboxyl group of another
What is the structure of amino acids?
Central C atom with amine, carboxyl, R, and H attached
H2NCHRCOOH
What is the purpose of the R group?
Makes each amino acid different
Determines how the amino acid interacts & bonds with other amino acids in the polypeptide
How many different amino acids are there?
20 common in all organisms, 10 of which can’t be made by humans so needs to be obtained by diet
What is the function of structural proteins?
Fibrous
Long, strong chains held parallel by cross links
Collagen & keratin
What is the function of transport proteins?
Globular
Fold up due to hydrophobic & hydrophilic amino acids
Transports molecules & ions across membranes
What are the 3 steps to test for a protein?
Add distilled water & Biuret solution (NaOH & copper II sulfate) to sample
Shake & leave upright for 5 mins
If positive blue to violet
What is the primary structure of a protein?
Sequence of amino acids in the polypeptide chain
What determines the primary structure?
The gene encoding the protein so a change to nucleotide sequence could cause a different amino acid to be added, causing a different shape protein with a different structure/function
What is the secondary structure of a protein?
Amino acids in the chain form hydrogen bonds with each other
Coils into alpha helix or folds into beta pleated sheets
What is the stability of the secondary structure?
It is stable, because although individual hydrogen bonds are quite weak, there are many so it’s stronger/more stable
Stability decreases by temp/pH etc
What is the tertiary structure of a protein?
Further folding into a unique 3D shape due to interactions between R groups (ionic bonds, hydrogen bonds, disulfide bridges)
What is the quaternary structure of a protein?
Multiple 3D polypeptides coming together
What is an enzyme?
Biological catalyst that lowers the AE of chemical reactions by binding to substrate & making bond breaking/making process happen easier
What is the active site?
Area that is complementary in shape to a specific substrate, determined by tertiary structure