general properties of proteins + many proteins and enzymes Flashcards
what are proteins?
large molecules, made up of many small molecules known as amino acids, amino acids are therefore the monomers from which proteins are made
what are small chain of amino acids called?
peptide chain or polypeptide
amino acids are amphoteric, what does this mean?
they possess both acid and alkali properties, this is caused by an acid group being located at one end of the molecule and an alkali group at the other
at the right pH which is specific to each Amino acid, the molecules will ionise, what does this mean?
that the molecule now has one positively charged (amino) end and one negatively charged (carboxyl) end
what are the molecules called that possess the quality to have both positively charged and negatively charged ends when ionised?
zwitterions
what is glycine?
the simplest amino acid, its side group is just a hydrogen atom
amino acids can bond with each other in much the same ways as monomers bond in organic chemistry to form polymers, what bonds are these?
peptide bonds
how are dipeptides formed?
by the condensation of two amino acids
how are polypeptides formed?
by the condensation of many amino acids
what is a protein structure?
proteins are large polymer like structures, consisting of many amino acid molecules joined together by peptide bonds
what are the structures of proteins?
primary, secondary, tertiary and quaternary structures
what are the two main types of proteins?
simple proteins and conjugated proteins
what are simple proteins?
proteins that only contain amino acids
what are conjugated proteins?
proteins that contain other molecules too, knows as prosthetics.
what are examples of conjugated proteins?
haemoglobin
what is the primary structure?
the structure of amino acids that make up its polypeptide chain or chains
what is the secondary structure?
it is controlled and dictated by the hydrogen bonds that form between the NH group of one amino acid and the C=O group of another
depending on how the bonds form a polypeptide can either take two forms, they are…
-alpha-helix shape
-beta-pleated sheet shape
what is the tertiary structure?
the overall three dimensional shape of an entire protein molecule is the tertiary structure
what is the quaternary structure?
essentially the interaction between these chains and in some cases, prosthetic groups
what changes can cause a protein to denature?
changes in;
-pH
-temperature
-pressure (including osmotic pressure)
what is the biuret test for proteins?
to test a substance to see if it contains proteins we use this test, its a two step process.
-making the substance an alkaline to ensure the test will work
1)add a few drops of sodium hydroxide solution to the sample
2)then add copper (II) sulphate solution
if protein is present what colour will the solution turn?
purple
if protein is not present what colour will the solution remain?
blue
what are enzymes?
they act as catalysts in living organisms, they enable and speed up chemical reactions by lowering the activation energy without themselves being changed or used up
enzymes act on a wide range of which reactions?
intracellular and extracellular reactions
what is the activation energy?
the initial input of energy needed to start a reaction
what is the lock and key theory?
the active site of an enzyme as a rigid shape, much like a lock. the substrate is essentially like a key which fits perfectly into that lock (activation site) this theory explains why enzymes are so specific and why even the smallest change in the shape of an enzyme will render it useless (as the substrate will no longer fit in the activation site)
what is the induced fit theory?
the enzyme does not require the substrate to fir perfectly into the activation site, the activation site will change shape slightly to accommodate the shape of the substrate.
what are inhibitors?
are biological molecules that regulate chemical reactions by slowing down or blocking them from occurring
what are the two main types of inhibitors?
competitive inhibitors and non-competitive inhibitors
what are competitive inhibitors?
are substances that compete with an enzymes normal substrate and will bind to the enzymes active site and prevent the enzyme catalysing any reactions with its normal substrate
examples of competitive inhibitors
antibiotics
what are non-competitive inhibitors?
they do not bind to the active site of an enzyme, but instead they do bind to the enzyme in a different place and in doing so, causes the active site to change shape, rendering it useless
examples of non-competitive inhibitors
many poisons such as heavy metals
what will the reaction do when all the enzymes that are not bound to the inhibitor are saturated with substrate?
plateau
what is it called when the enzyme can only increase the rate of reaction to a certain point?
their optimum efficiency
the rate of reaction hits a plateau when the enzyme is what?
saturated
what are factors which affect enzyme activity?
temperature, pH, substrate concentration, enzyme concentration and inhibitors
what does temperature have to do with enzymes?
firstly, all enzymes have an optimum temperature at which they work most efficiently, this temperature is different for different types of enzymes
increasing the temperature also increases the what that molecules possess.
kinetic energy
since enzymes catalyse reactions by colliding with substrate molecules, increasing temperature also increases the what?
the rate of reaction, forming more product
increasing temperature also increases the what that molecules have?
the vibrational energy
what does the vibrational energy cause?
strain on the bonds that can hold them together
as the temperature increases, more bonds will break as a result of the strain, breaking bonds within the enzyme will cause what?
the active site to change shape
what is pH?
a measure of acidity or alkalinity of a solution
what is it called when the shape of their active site is the most complementary to their substance?
the optimum pH
any change in pH above or below the optimum will quickly cause a what?
a decrease in the rate of reaction
if there is an extreme change in pH can cause enzymes to what?
permanently denature
changing the enzyme or substrate concentration affects the rate of a what?
an enzyme catalysed reaction
increasing substrate concentration increases what?
the rate of reaction
why will increasing the substrate concentration increase the rate of reaction?
because more substrate molecules will collide with more enzyme molecules, so more product will be formed
increasing enzyme concentration will increase what?
there rate of reaction
why will increasing there enzyme concentration increase the rate of reaction?
as more enzymes will collide with more substrate molecules.
what is a cofactor?
enzymes that need other chemicals to work efficiently
cofactors are organic materials are more commonly known as what?
coenzymes
what is an activator?
an inorganic molecule that acts as a cofactor
