Protein and enzyme 12.2 Flashcards
structure of amino acid
Each amino acid contains a central(alpha )
carbon atom which a nitrogen containing group (H2N) and a carboxyl group (COOH) are attached
R groups are….and can be…
Variable groups
- R-groups can be:Positively charged +Negatively charged -Hydrophilic (attracted to water)Hydrophobic (repelled by water)
The bond between amino acids is…
formed by a condensation reaction (forming a peptide bond)
What groups are on each end of the chain?
A peptide chain will always have an amine group at one end and a carboxyl group in the other end.
The number of peptide bonds in a chain will be…
one less than the total number of amino acids originally joined together (dipeptide is 2 amino acids so 1 peptide bond)
Primary structure is…
the number and sequence of amino acids in a polypeptide chain.
Secondary structure is…
The way the polypeptide chain folds OR coils into:
ALPHA HELIXES AND/OR BETA PLEATED SHEETS
these are held together by weak hydrogen bonds ONLY
Tertiary structure is…
Further folding the polypeptide chain the specific complex 3D shape
The R-groups determine how the polypeptide chain folds into the specific 3D shape. The 3D shape is help together by bonds between the R groups of amino acids
3 types of bonds in tertiary structure is…
WEAK HYDROGEN BONDS - between C=O and NH of adjacent amino acids)
IONINC BONDS - also weak bonds which form between oppositely charged R groups.
DISULPHIDE BRIDGES - strong bonds that form between cysteine amino acids only
SPECIFIC tertiary structure + SPECIFIC shape = ??????
SPECIFIC function
THE QUATERNARY STRUCTURE IS….
Some proteins consists of 2 or more polypeptide chains joined together
Proteins denature…
at HIGH temperature and changes to the pH
Increased temperature…
Increases kinetic energy of molecules making them vibrate more which breaks the hydrogen bonds in the secondary and tertiary structure.
Changing pH breaks ionic bonds between R groups in tertiary structure
Biuret test
put small volume of sample in a labelled test tube
add equal amount of buret solution
If present it will change to lilac/purple/violet
Enzymes are a globular protein that act as…
biological catalysts
What is a catalyst?
increase rate of reaction but remain unchanged or unaffected by the reaction
They take part in the reaction but don’t get used up
What do enzymes lower?
Activation energy
When enzyme-substrate complexes form, what do they do to the bonds?
distort/stress them
All proteins have binding sites only enzymes have…
Active sites
Enzymes have a specific…
tertiary structure
Active sites are made up of…
less than 10 amino acid R groups
Explain the lock and key model
Active site is specifically complementary to its substrate like a key and lock
Active site -lock
substrate - Key
STAGES OF LOCK AND KEY
- Active site is rigid and doesn’t change shape
- Substrate binds to the enzymes active site
- Substrate fits exactly into the active site (complementary)
- Produces are formed and no longer fit into active sit so its released
- Enzyme can take part in another reaction
STAGES OF INDUCED FIT MODEL
- substrate enters active site and binds to it forming enzyme-substrate complex
- binding of substrate induces the change of shape in the active site
- “slight” change in shape of the specific 3D tertiary structure of the active site applies stress or distorts the bonds within the substrates molecules with lowers the activation energy of the reaction
- When the substrate leaves the active site reruns to original shape
FACTORS AFFECTING ENZYME ACTION
- Temperature and pH
- Inhibitors
- Substrate concentration
how temperature effects enzyme action
Inc temperature = inc kinetic energy which bring more successful collisions so more forming of Enzyme-Substrate complexes.
Optimum temp - maximum energy that can be supplied before hydrogen and ionic bonds start to weaken
OVER OPT TEMP - change in shape of active site so no longer complementary so less ES complexes are formed.