Proteins Flashcards
why do we need proteins in our diet?
for growth and repair
foods that are rich in protein
meat, fish, lentils, tofu, chickpeas
what are proteins?
large, important molecules (polymers) found in our bodies
each protein within the body has a specific function that is related to its shape.
they are condensation polymers made up of many amino acid molecules linked together
2 types of protein shape
- fibrous (fibres, long chains)
2. globular (globule, spherical shape)
Fibrous proteins
long and thin and are the major structural materials of animal tissue
globular proteins
spiral chains folded into compact units.
involved in the maintenance and regulation of life processes and include enzymes and many hormones.
Collagen
found in tendon, muscle, bone
functions - structural support
nature - fibrous
Keratin
found in hair, skin and nails
function - structural support
nature - fibrous
Insulin
found in pancreas
function - hormone to help control blood glucose levels
nature- globular
what are proteins made up of?
amino acid molecules joined together
what are amino acids?
the building blocks from which proteins are formed
they contain an amino (amine) group (-NH2) and a carboxyl group (-COOH) attached to the same carbon (alpha carbon)
Structure of proteins: what is R?
a variable organic group or a hydrogen
Structure of proteins: Phenylalanine
amine and carboxyl groups attached to carbon
R= CH2 and benzene ring
what are essential amino acids?
the amino acids that cannot be made in our body.
they must be present in our diet.
condensation polymerisation
condensation: molecules join together and water is eliminated.
polymerisation: single units (monomers) joining together to form a large chain of many units (polymer)
condensation reaction
the amino group on one amino acid and the carboxyl group on a neighbouring amino acid join together, with the elimination of water
what is the link that forms between two amino acids called?
an amide link (-CONH)
also known as peptide link
what is a tripeptide
polymers made up of only 3 amino acids
what is a polypeptide
polymer made up of a large number of amino acids
structural formula of condensation polymerisation
-OH removed from carboxyl group and -H removed from amine group.
when are proteins broken up?
during digestion process called hydrolysis to produce amino acids
breakdown of proteins
a water molecule causes the splitting
N-C bond is broken
steps for hydrolysis of proteins
- identify the amide links
- break apart C-N bonds
- redraw individual structures
- add -OH to make carboxyl groups and -H to complete amine group
general condensation definition
when molecules join together with the elimination of a small, stable molecule (eg water)
general hydrolysis definition
when large molecules are broken down into smaller molecules by reaction with water
what is chromatography?
a technique that allows us to separate substances in a complex mixture
describe paper chromatography
HP- hydrolysed protein (mixture of different proteins)
A-D pure samples of various amino acids
solvent added- mobile phase
the extent to which molecules travel up paper depends on size/polarity
no of spots=no of amino acids present
if spots on HP same height as amino acid A-D they are the same
what can be done if the hydrolysed protein contains an amino acid that does not match
another chromatogram can be run with different known samples of pure amino acids.
what are enzymes
proteins which act as biological catalysts
Enzymes are specific for particular chemical reactions. Give an example
Pepsin only catalyses the hydrolysis of proteins and not any other chemical reaction
what is the active site
certain sequences of amino acids form a region known as the active site
the shape of the active site allows specific reactants, known as substrates, to attach (like lock and key)
what happens to incorrect substrates
they are unable to fit the shape of the active site and are not changed
what is enzyme function related to
molecular shapes of proteins
process of catalysis by enzymes
- substrate approaches active site
- substrate attaches to active site
- substrate becomes products
- products released and active site free to react again
how do protein chains react with themselves
intermolecular bonding (often hydrogen bonding)
intermolecular bonding in proteins
- gives the protein a particular shape and creates an ‘active site’ which is unique to that enzyme
- only specific, complementary substrates will fit into this active site
denaturing enzymes
-when the temperature is increased too much or the acidity increases too high the intermolecular bonds will break.
-this means the protein chain will unravel, destroying the active site
-the substrate can no longer bind and so the enzyme no longer functions as a catalyst
(graph of enzyme activity vs temp/pH with narrow optimum range)
a real-life example of denaturing proteins
the protein albumin in eggs becomes denatured and changes colour and texture
