Proteins

Created by

Daisy

Cards (31)

What is the monomer of a protein?
Amino acid
What elements are always found in amino acids?
Hydrogen, carbon, oxygen, nitrogen
What is the structure of an amino acid?
An amine group and a carboxyl group either side of a central carbon atom bonded to a hydrogen and R group.
What determines the type of amino acid?
The R group
How are dipeptides formed?
A condensation reaction between two amino acids where water is produced and a peptide bond is formed.
Water is formed from the OH from the carboxyl group of one amino acid and the H from the amine group of the other.
The peptide bond is formed between the C of the carboxyl group on one amino acid and the N from the amine group of the other.
What is a polypeptide? 
Many amino acids chemically joined together by peptide bonds.
What is the primary structure of a protein? 
The specific sequence of amino acids in a polypeptide chain.
What is the secondary structure of a protein? 
Localised areas of 3D folding where the polypeptide chain forms alpha helix and beta pleats.
What is the tertiary structure of a protein? 
The folding of a polypeptide into its 3D structure.
What is the bond present in the primary structure? 
Peptide bonds
What is the bond present in the secondary structure? 
Hydrogen bonds
What are the bonds present in the tertiary structure in order of strength (strongest -> weakest) ?
Disulphide bridges, ionic bonds, hydrogen bonds, hydrophobic interactions
What will determine where bonds can form in the tertiary structure?
The presence and location of specific amino acid R groups.
What is the quaternary structure of a protein?
2 or more polypeptide chains held together by hydrogen bonds.
What can a functional protein contain?
One or more polypeptide chains
What are globular proteins? 
Proteins folded into a spherical tertiary or quaternary structure.
Do globular proteins have solubility?
Yes - due to folding, the hydrophobic R groups are in the centre of the molecule and the hydrophilic R groups are on the outside.
What are two examples of globular proteins? 
Enzymes and plasma proteins
What do enzymes do? 
They are in solution and so can catalyse chemical reactions.
What do plasma proteins do? 
They are dissolved in the water of the blood plasma and lower the water potential of the blood.
What type of protein are haemoglobin and antibodies? 
Globular
What are fibrous proteins? 
Structural molecules with elongated, thread-like structures, often containing repeating amino acid sequences.
What are four examples of fibrous proteins? 
Keratin, collagen, actin, myosin
What does keratin do? 
Structural molecule found in hair and fingernails.
What do actin and myosin do? 
Form the structure of your muscles.
What does collagen do? 
Fibrous protein found in bone, cartilage, ligaments, tendons and connective tissue. It makes up 30% of your body mass.
Describe the primary structure of collagen. 
Has a repeating pattern of amino acids containing lots of glycine (the smallest of the amino acids) which enables the polypeptide to coil tightly.
Describe the quaternary structure of collagen.
The individual collagen polypeptide chains are wound tightly around each other (like in a rope) to form a triple helix, giving the molecule strength. The fact glycine is small allows close association between the chains. The external R groups on the molecule are non-polar. Collagen molecules are then bundled together by hydrogen bonds and disulphide bridges to form collagen fibres.
Why is a collagen sheet flexible?
The points where one collagen molecule ends in the fibre and the next begins are spread out throughout the fibre, rather than all being at the same position along it. Multiple fibres are then organised into a collagen sheet that is flexible.
Is collagen soluble or insoluble? Why?
Insoluble
. the external R groups on the molecule are non-polar
What is the test (+ results) for proteins?
. Add biurets reagent and shake
. positive = lilac
. negative = blue