Proteins Flashcards
Describe the primary structure of a protein.
The exact sequence of amino acid residues within the polypeptide chain.
Describe the secondary structure of a protein.
The spatial arrangement of amino acid residues which are close together in a linear sequence.
Results in alpha helix or Beta pleated sheet
Describe the tertiary structure of a protein.
The spatial arrangement of amino acid residues which are far apart in a linear sequence.
Held together by Hydrogen bonds, Disulphide Bridges, Van Der Waal forces, Ionic Interactions and Hydrophobic Interactions.
Describe the quaternary structure of a protein.
The spatial arrangement of individual polypeptide chains within a multi subunit protein.
What isomer of amino acids do proteins consist of?
L isomer
What type of bond links two amino acid residues in a polypeptide chain?
Peptide bond
What is the R group of Glycine?
H
What is the R group of Alanine?
CH3
What is the R group of Valine?
C(CH3)2H
What is the R group of Tyrosine?
CH2PHENOL
What is the R group of Lysine?
(CH2)4NH2
What degrees of the structure of a protein does denaturation effect?
Secondary and Tertiary.
What are the four main effects of denaturation of a protein?
- Reduced solubility
- Increased digestibility
- Altered water binding ability
- Loss of biological function
What is the mechanism of action of peptidases?
Cleavage of peptide bonds
What is the mechanism of action of exopeptidases?
Cleavage of one amino acid at a time
What is the mechanism of action of endopeptidases?
Cleavage of internal bonds
What is the mechanism of action of carboxypeptidases?
Cleavage at the -COOH terminal
What is the mechanism of action of aminopeptidases?
Cleavage at the -NH2 terminal
What are glycoproteins?
Structures composed of proteins and carbohydrates
Where does glycosylation occur?
At the ER and Golgi Apparatus
What are the functions of glycosylation?
- Proteins stabilisation
- Protein Orientation
- Affects solubility
- Creates compounds which can be used for signalling and cell to cell recognition.
What are lipoproteins?
Structures containing proteins and lipids covalently or non-covalently bonded together,
What is the function of lipoproteins?
The transport of water insoluble fats and cholesterol in the blood.
What are metalloproteins
Protein molecules with a bound metal ion
What is the role of haemoglobin?
Transport oxygen in the blood
What type of protein is haemoglobin?
Quaternary metalloprotein
What is meant by ‘cooperative binding’ of oxygen to haemoglobin?
Once one oxygen has bound to one haem group in the haemoglobin molecule, a conformational change occurs, making it easier for a second oxygen molecule to bind to a second haem group. This process repeats for the third and fourth haem group/ oxygen binding process.
What is a peptide bond?
Covalent bond formed between the amino group on one amino acid and the carboxyl group on another. Involves the elimination of a H20 molecule.
At what part of the cell should a peptide bond form?
At the ribosome
What structure of a protein will not be affected by denaturation?
Primary structure
What is the difference between fibrous and globular proteins?
Fibrous proteins are non- water soluble and have their function in support and structure.
Globular proteins are water soluble and have their function in metabolic reactions (enzymes)
