Proteins Flashcards
What are proteins made up of?
Amino acid chains made of C, H, O, N mainly.
What are functions of proteins?
Structure, metabolic roles, transport
How many naturally occurring amino acids are there?
20
How are peptide bonds formed?
2 amino acids join by a condensation reactions to form a dipeptide
How is a polypeptide formed?
A series of condensation reactions joining many amino acids
What is the primary structure?
Specific sequence of amino acids in a polypeptide chain.
What is the secondary structure?
Curling/folding of the polypeptide chain into alpha helices or beta pleated sheets as H bonds form
What is the tertiary structure?
Overall 3D shape of a protein, determined by interactions between R groups and their properties
What types of bonds form between R groups?
Hydrogen, ionic, disulphide bridges.
What is the quaternary structure?
Specific 3D shape of a protein determined by the multiple polypeptide chains/prosthetic groups.
How do hydrophilic and hydrophobic R groups work?
Hydrophobic amino acids are found in the middle of the protein, and hydrophilic R groups are found on the outside.
What is a globular protein?
A protein with a spherical shape. Soluble in water, normally have metabolic roles.
What are examples of globular proteins?
Haemoglobin, insulin and pepsin.
What is the structure of haemoglobin?
4 polypeptide chains with an iron ion on each so it is a conjugated protein. The haem groups bind to O2
What is the structure of insulin?
2 polypeptide chains folded and joined by disulphide bonds. Specifically binds to receptors to lower blood glucose.
What is the structure of pepsin?
1 polypeptide chain in a symmetrical tertiary structure. Have many acidic R groups so it is less affected by the low pH in the stomach
What are fibrous proteins?
Long polypeptide chains with repeating sequences, insoluble in water and can form fibres.
What are examples of fibrous proteins?
Collagen, keratin, elastin
What is the function of collagen?
In artery walls to stop them bursting, make tendons and bone, forms cartilage and connective tissue
What is the function of keratin?
It is very hard and strong so makes up nails, horns, hooves. Has high levels of cysteine.
What is the function of elastin?
In the lungs so they can change shape, in the bladder and in blood vessel walls.
