[OLD] Biological Molecules - Proteins Flashcards
What is the monomers for a protein?
amino acid
What is an amino acid made from?
an amino group (at one end) - NH2 a carboxylic acid group (at the other end) - COOH a central carbon a hydrogen an R group
How many different amino acids are there?
20
What is the only difference between the different amino acids?
the R group
what are essential amino acids?
amino acids that can’t be made in the body and have to be obtained from the body
What is the primary structure of a protein?
the sequence if amino acids in a polypeptide chain (determined by DNA sequence)
what is the secondary structure of a protein?
the H bonds between NH2 and COOH groups pull the polypeptide into either an alpha helix or a beta pleated sheet conformation
what is the tertiary structure of a protein?
interaction between R groups fold the polypeptide into a specific 3D shape
what are the 4 different interactions between R groups?
hydrogen bonds
ionic bonds
disulphide bridge
hydrophilic / hydrophobic interactions
describe hydrogen bonds interactions
slightly positive region on one R group forms a bond to slightly negative region on another R group
describe ionic bonds interactions
positively charged R group attracted to negatively charged R group
describe disulphide bridge interactions
a specific covalent bond that forms between the sulphur containing R groups of 2 cysteine amino acids
describe hydrophobic / hydrophilic interactions
some R groups are non-polar and hydrophobic. The polypeptide chain will bend to position these R groups in the centre of the molecule away from the surrounding water. Other R groups will be polar/charged and hydrophilic. They want to interact with water and so the polypeptide will twist so that they are positioned to the outside of the ,olé use in contact with the surrounding water.
what is the quaternary structure of a protein?
The interactions between two different polypeptide chains (if a protein consists of more than one polypeptide chain). These bonds may be H bonds, ionic bonds, disulphide bonds or hydrophobic / hydrophilic interactions.
4 different types of specialised proteins
enzymes
antibodies
transport proteins
structural proteins
structure of enzyme
usually roughly spherical in shape due to tight folding of polypeptide chains. soluble and have roles in metabolism
structure of antibodies
made up of two short polypeptide chains and two long polypeptide chains bonded together. they have variable regions and the amino acid sequences in these regions vary greatly.
structure of transport proteins
channel proteins are present in cell membranes and contain hydrophobic and hydrophilic amino acids, which cause the protein to fold up and form a channel. these proteins transport molecules and ions across membranes.
structure of structural proteins
physically strong, consisting of long polypeptide chains lying parallel to each other with cross-links between them.
examples are keratin (found in hair and nails) and collagen (found in connective tissue)
what is the biuret test for proteins?
1) the test solution needs to be alkaline, so add a few drops of sodium hydroxide solution
2) add some copper(II) sulfate solution
if it turns purple then protein is present
otherwise it will stay blue
4 different types of specialised proteins
enzymes
antibodies
transport proteins
structural proteins
structure of enzyme
usually roughly spherical in shape due to tight folding of polypeptide chains. soluble and have roles in metabolism
structure of antibodies
made up of two short polypeptide chains and two long polypeptide chains bonded together. they have variable regions and the amino acid sequences in these regions vary greatly.
structure of transport proteins
channel proteins are present in cell membranes and contain hydrophobic and hydrophilic amino acids, which cause the protein to fold up and form a channel. these proteins transport molecules and ions across membranes.
structure of structural proteins
physically strong, consisting of long polypeptide chains lying parallel to each other with cross-links between them.
examples are keratin (found in hair and nails) and collagen (found in connective tissue)
what is the biuret test for proteins?
1) the test solution needs to be alkaline, so add a few drops of sodium hydroxide solution
2) add some copper(II) sulfate solution
if it turns purple then protein is present
otherwise it will stay blue
