Proteins + Enzyme Flashcards
- what is an Amino Acid
MONOMERS of a POLYPEPTIDE (protein)
- What Is a DIPEPTIDE?
The CONDENSTATION REACTION of 2 Amino Acids
- What is a FUNCTIONAL PROTEIN
1 or more POLYPEPTIDE
- What are the 4 types of Protein Structure
Primary, Secondary, Tertiary, and Quaternary structure.
- What is THE PRIMARY structure of Proteins
sequence of amino structure
- What is THE SECONDARY structure of Proteins
Amino acid sequence, or a primary structure folds into structures called alpha helices or beta-pleated sheets
- What holds alpha helices or beta-pleated sheets?
H Bonds hold them together for stability
- What is THE TERTIARY structure of Proteins and what do they do for enzymes?
Alpha helices or beta-pleated sheet FOLD further to form a specific, 3D structure. These are the bases for enzyme specificity, which allow certain chemical reactions to be catalyzed in the body
- What provides stability to the Protein?
Ionic bonds and disulphide bridges hold structure
- What is THE QUATERNARY structure of Proteins
MORE than 1 POLYPEPTIDE CHAIN bind to a prosthetic/non-protein group (metal ion) e.g. hemoglobin
- Biuret test for proteins
- Add a few drops of Na0H (base) to solution - alkaline
- Add a few drops of aqueous Copper Sulfate to test solution
- Observe color change of test solution
blue = -
purple precipitate = +
- What are Enzymes ?
They are globular Proteins -> biological catalytic. Catalyse reactions lower activation energy to speed up the chemical ROR. Active site is specific to the shape to its substrate = complimentary.
What is the Induced Fit Model ?
- SUBSTRATE INDIUCE A COMFORMATIONAL CHANGE IN THE ACTIVE SITE/ITS TERTIARY STRUCTURE. This allows the SUBSTRATE to BIND to an ACTIVE SITE to form an ENZYME-SUBSTRATE CONPLEX
- Theory states enzyme + substrate complex are almost complimentary but when the substrate enters Active site, interactions between substrate and AMINO ACIDS cause SHAPE of the AS TO CHANGE and become COMPLIMENTARY TO THE SUBSTRATE.
What is Enzyme Specificity
tertiary structure of the AS, its extremely specific. Only complementary substrates to bind to AS to form an enzyme - substrate complexes
How is an enzyme reaction effected by Temperature?
IT GOES UP (A) - as the temp increases = more KE, therefore more successful collisions between E-S complexes. THE PEAK AS IT REACHES OPTIMUM TEMP (B), here E-S complexes formed. THEN GOES DOWN (C) Enzymes denature, The H & ionic bonds break this changes the tertiary structure of the AS, so it is no longer complimentary.
How is an enzyme reaction effected by PH?
(its drawn like TEMP but up and straight down and equal) Either side of optimum PH (Enzymes are sensitive to the change in PH). The Enzymes DENATURE because, the H & ionic bonds break this changes the tertiary structure of the AS, so the substrate and AS are no longer complimentary. (Fewer E-S COMPLEXES FORMED).
How is an enzyme reaction effected by Concentration of Substrate ?
IT GOES CONSTANTLY UP (A). Here the increase in sub conc. = the higher the ROR and successful collisions. The substrate conc. is limiting. THEN IT PLAUES (B) Substrate conc. is no longer l8imiting as the ROR doesn’t increase. Enzyme conc. maybe limiting as all AS maybe in use.
What does Chromatography do?
It superstrates molecules e.g. Amino acids according to their solubility in a solvent
The more soluble the chemical is ….
The higher up the paper it travels
Method of chromatography
- Add drop of solution to origin line, allow to dry & repeat to concentrate the sample
- Calc the RF value of Amino acid = distance travelled by the component / the distance travelled by the solvent
2 - way chromatography
New Solvent front, Diff solvent, New origin line
What does lower affinity mean?
The sample has travelled up the paper more
What does higher solubility mean?
travels up paper faster and will end up closer to the top of the solvent front = higher RF value
What does Competitive inhibition mean for E-S complexes?
Fewer will be formed = block access from the substrate
What is Competitive Inhibition ?
Are structurally analogous to the normal substrate that the enzymes bind to, decreasing its activity as they compete with substrate for the enzyme. The amount of product formed remains the same, however the rate at which product formation occurs decreases. The higher the concentration of competitive inhibitor the lower the reaction rate. Increasing the substrate reverses the effect of competitive inhibitors by outcompeting them.
Non-competitive Inhibitors?
Do not bind to the active site; it binds at another site on the enzyme - the allosteric site. Binding of the non-competitive inhibitors changes the shape of the active site therefore preventing the binding of the substrate. Increasing the concentration of substrate has no effect on non-competitive inhibition.
What is an inhibitor?
An inhibitor is a substance which slows down or stops a reaction by affecting the binding of substrate to the enzymes. Inhibitors can either be reversible and irreversible.
Suggest how Binding of Cytochrome oxidase affects the enzyme
Inhibition (compet and non). Changes the tertiary structure of Enzyme and Blocks AS of enzyme = no E-S complexes formed
Suggest how antidote can reduce poisoning by cyanide
Antidote binds to cyanide so cyanide cannot bind to enzyme
Suggest one advantage of trapping the enzyme within gel beads
- the enzyme can be reused
when flow rate of milk increases, concentration of glucose decreases. explain why. [1]
- too fast for lactose molecules to bind to active site of the lactase enzyme
- enzyme substrate complexes can’t form
Galactose has a similar structure to part of the lactose molecule. Explain how galactose inhibits lactase. [2]
- Galactose is a competitive inhibtitor;
binds to active site instead of lactase - reducing enzyme substrate complexes formed between lactose and lactase enzyme
- fewer available lactase molecules
