Proteins Flashcards
What are proteins made up of?
Amino acids
What is in all amino acids?
An amine group (2 hydrogen, 1 nitrogen)
One hydrogen bonded to a carbon in middle
An acid group
And an r group
What is the R group in an amino acid?
Determines what the amino acid is and what it’s name is
Is different for all
What elements do all amino acids contain?
Carbon, nitrogen, hydrogen and oxygen
What extra element do some amino acids contain?
Sulfur
What happens during the condensation of 2 amino acids?
The OH group in one (from acid group)
The H group in another (from amine group)
Release as water in condensation
And form a PEPTIDE BOND
Dipeptide
2 amino acids joined together by a peptide bond from a condensation reaction
Where in the body are dipeptides formed from condensation?
In ribosomes of cells to synthesise proteins
Polypeptide chain
Repetition of the condensation of amino acids to form a long chain joined together by peptide bonds
How can we reverse the formation of polypeptide chains?
Adding water molecules to hydrolyse it back down into amino acids
Where does the hydrolysis of polypeptide chains occur?
In digestive system by protease to break the peptide chain into amino acids for digestion
Are polypeptide chains proteins?
No, to become a protein the chain has to fold into a complex 3d shape/ join with other chains and therefore carry out its function
Protein structure formation
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
Primary structure
The specific order or amino acids in a polypeptide chain
The order of them depending on the r group is critical in determining the secondary structure
What determines the sequence of amino acids?
By the DNA sequence of the gene which encodes for that specific polypeptide chain
Secondary structure
When the polypeptide chain twists and folds to perform specific functions and is held together by HYDROGEN BONDS
Has 2 distinct shapes which are regions that make up this structure
2 secondary structure region shapes
Alpha helix
Beta pleated sheets
How does the hydrogen bonding form between the secondary structure causing it to fold?
The O- atom in acid group is negatively charged
The H+ atom in amine group below from amine group is positively charged
So the chains layer on top of each other and hold the shapes
How is the secondary structure dependent on the primary structure in terms of amino acids?
Because certain amino acids tend to be found in alpha helixes and others in beta pleated sheets
So these regions depend on the acids in this chain
How is the secondary structure dependent on the primary structure in terms of polarity?
Because some amino acids are polar depending on the R group such as containing OH groups so they are hydrophilic and position themselves in the outside to interact with water
Whereas the inverse is true for hydrophobic amino acids which are hydrophobic so the folding is dependent on that
Tertiary structure
When, after the secondary structure regions have formed the protein continues folding which is held together by R groups in amino acids
Different bonds between the R groups in tertiary structure
Disulphide bridge
Ionic bonds
Hydrogen bonds
(Hydrophobic interactions)
What does the quarterly structure apply to?
Only if the protein has 2 or more subunits
Quaternary structure
When 2 or more polypeptide chains work together as a large molecule which is held together by bonds between the polypeptide chains
Bonds between polypeptide chains in the quaternary structure
Same as between r groups in the tertiary structure:
Disulphide bridges
Ionic bonds
Hydrogen bonds
Polypeptide chains in the quaternary structure
Known as subunits
How does the quaternary structure depend on the tertiary structure?
The way individual subunits are arranged is the quaternary structure
And the way they arranged after folding is the tertiary structure so the way are bonded to each other is dependent on that