Biological Molecules Flashcards
Describe the primary structure of all proteins
The sequence of amino acids in a polypeptide chain , determines the proteins ultimate shape and hence its function
Describe a biochemical test to confirm the presence of protein in a solution
Biuret test, changes from blue to purple
Describe 2 ways in which all dipeptides are similar and one way in which they may differ
Both have an amine group within the polypeptide
Both have a carboxyl group
However the R {variable} group will differ
Describe how monomers join to form the primary sequence if a protein
Through a series of condensation reactions , amino acid monomers can be joined together via polymerisation the resulting chain of amino acids is therefore the primary structure
Amino acids are joined together by peptide bonds
Describe one similarity and one difference between the induces fit model and the lock and key model
Similarity - the substrate is still complementary to the active site of the enzyme
Diff - the active site of the induces fit model has to change its shape until its complementary to the substrate whereas the locks and key doesn’t
How do enzymes help reactions to proceed quickly at lower temperatures
They reduce the activation energy and ides less energy to work
Define the quaternary structure of a protein
More than one polypeptide chain
Explain how 2 enzymes with different amino acid sequences can catalyse the same reaction
The enzymes have the same tertiary structure
Active sites have identical amino acid sequences
Catalyses the reaction into the same ESP
What should scientists place in the control tubes of the investigation
The same volume of pH buffer and the same concentration of denatured enzyme
Describe how the structure of a protein depends on the amino acids it contains
The primary structure is the sequence of amino acids
Secondary structure is the different interactions between the different hydrogen bonds to form B pleated sheets and Alpha helices;
The tertiary structure is the different interactions of ionic and disulphide bonds
Quaternary structure is more than 1 polypeptide chain
In antibodies we create a unique shape
Describe the induces fit model of enzyme action and how an enzyme acts as a catalyst
IFM is where the substrate binds to the active site
The active site changes shape until it is complementary to the substrate creating an ESC
The enzyme reduces the activation energy during the reaction by finding alternative pathways
Suggest and explain a procedure the scientists could have used to stop each reaction
Boil to denature the enzyme
Describe the tertiary structure of all proteins in detail what bonds
The alpha helices of the secondary structure can be twisted and folded further to give the complex and often specific tertiary structure
Disulphide bonds which are fairly strong and not easy to break
Ionic bonds which are formed between any carboxyl and amine groups that are not involvesd in forming peptide bonds
They are weaker than disulphide bonds and are easily broken by changes in pH
Hydrogen bonds - numerous but easily broken
What other groups may be associated with in a quaternary structure of a Protein , such as what
Non protein , prosthetic, groups
The iron containing haem group in haemoglobin
What’s the test for proteins
Biuret
Place solution sample in a test tube and add equal amount of sodium hydroxide solution at room temperature
Add a few drops of dilute copper sulfate solution and mix gently
Purple colouration indicates the presence of peptide bonds and hence a protein
What colour will solution be if no protein is present
Solution remains blue
What do fibrous proteins form
Long chains which run parallel to one another
These chains are linked by cross bridges so form very stable molecules
What is collagens molecular structure
The primary structure is an unbranched polypeptide chain
Secondary structure of the chain is tightly wound
Tertiary structure - the chain is twisted into a second helix
Found in tendons
What type of proteins are enzymes and what do they cat as
Globular proteins and act as catalysts
What do catalysts do
The alter the rate of a chemical reaction without undergoing permanent changes themselves
They ca be used repeatedly and are effective in small amounts
They speed up reaction that already occur
What is the minimum amount of energy needed to start a reaction called
Activation energy
What do enzymes do during a reaction
Lower activation energy level so allow reactions to tale place at a lower temperature than normal
Enabling some metabolic processes to occur rapidly at the human body temperature of 37
Describe the induced fit model
Tertiary structure of the active site changes as the substrate molecule appears
As the substrate starts to form bonds with the amino acids in the active site the tertiary structure of the enzyme adjusts to mould itself tightly sprung the substrate
The bonds the substrate forms with the active site help to catalyse the reaction
