4 — enzymes Flashcards
Definition of enzymes [5]
Short one: Enzymes are proteins that function as biological catalysts. They catalyse or speed up the rate of chemicals reactions by lowering activation energy required for the chemical reaction and remain chemically unchanged at the end of the reaction. [2]
Enzymes are protein in nature. [1]
It is a biological catalyst which , speeds up the rate of chemical reaction by lowering the activation energy required to start the chemical reaction. [1]
It remains chemically unchanged at the end of chemical reaction, and thus can be reused and required in minute amounts. [1]
Each enzyme is highly specific in action due to its specific three-dimensional shape and it acts on a specific substrate, as only the substrate with a specific three dimensional shape that is complementary to the enzyme’s active site can fit and bind to the active site, forming enzyme-substrate complex. [1]
Sensitive to changes in temperature and pH and works best at optimum temperature and pH. [1] OR can be denatured by extreme changes in temperature or pH [1]
Enzymes catalyse reversible reactions. [1]
Definition of catalyst
A catalyst is a substance that can speed up a chemical reaction without itself being chemically changed at the end of the reaction.
Explain the mode of action of enzymes QS type:
Lock and key hypothesis
- According to the lock and key hypothesis, the enzyme is the lock, the substrate is the key.
- A specific substrate with a 3D shape is complementary to the 3D shape of the enzyme’s active site, which are formed from depressions on the enzyme molecule, fit and bind onto the active site.
- And forms the enzyme-substrate complex. A chemical reaction occurs and
- Substrate molecule is converted into product molecule and leaves the enzyme’s active site. Enzyme molecule remains chemically unchanged at the end of the chem reaction & becomes free for another specific substrate molecule to fit and bind onto.
If: misfolded enzyme (eg phenylketonuria, an enzyme-related disease) -> lock n key hypothesis?
- State enzyme lock, substrate key +Site has been changed/altered
- Due to wutever reason given (defective gene), enzyme is misfolded
- Shape of substrate cannot fit and bind to active site -> no enzyme-substrate complex formed (Can/cannot fit n bind?)
- No chem reaction occurs, no break down of substrate molecule -> product molecules
- X (phenylalanine) lvl builds up in (blood), affect intellect & cause other health issues
- Aspartame, common sugar sub, contains phenylalanine
Describe and explain how enzyme functions are affected by temperature [4]
- At low temperature, ke of molecules is low thus enzyme + substrate molecules move slow. Frequency of effective collision between substrate molecules and enzyme is low/zero -> enzymes are inactive -> enzyme substrate complex formation is slow and rate of reaction is slow. [1]
- As temperature increases + data,
Data+ As temperature increases, the rate of enzyme activity increases. Because the enzyme and substrate molecules have a higher kinetic energy. This increases the frequency of effective collision between the enzyme and substrate. Hence, increases the rate of enzyme-substrate complex formation. [1] - At the optimum temperature + data -> Rate of enzyme activity is highest at: data. Enzymes are most active. Rate of formation of enzyme substrate complex is at its maximum and rate of reaction is the highest. [1]
- Beyond the optimum temperature + data, rate of enzyme activity decreases until zero as enzymes are denatured. [1] Weak hydrogen bonds in 3 dimensional enzyme structure is broken -> Active site(AS) of enzyme molecule begins to lose its original 3D shape -> not complimentary to shape of substrate molecules -> substrate cannot fit n bind to AS ->no enzyme substrate complex formed.
Tempt affecting enzyme graph
- Nvr starts at 0
- Gradual increase till max
- Plunge to 0
- Label optimum tempt
- Label x and y axis
pH affecting enzymes + graph
Below and beyond optimum pH:
Weak hydrogen bonds in 3 dimensional structure is broken. 3 dimensional shape of enzyme is lost and shape of active site is altered. Substrate can no longer bind to active site of enzyme and no enzyme-substrate complexes are formed. Enzyme is denatured and rate of reaction decreases to zero.
Optimum pH:
Enzyme is most active, rate of formation oof enzyme substrate complex is at its maximum and rate of reaction is the highest.
Graph:
- Both ends touch x axis at 0
- Symmetrical
- Label optimum point + x and y axis
Pepsin vs trypsin
Both: Proteins -> short polypeptides
P found in stomach but T found in SI
P produced by stomach but T produced by pancreas
P works well in pH 2 stomach but T works well in pH 7-9 SI
Digestive enzymes in SI
Digestion of disaccharides:
Sucrase: Sucrose -sucrase> glucose + fructose
Maltase: Maltose -maltase> glucose + glucose
Peptidases: Digests polypeptides -peptidases> amino acids
Lactase: Lactose -lactase> glucose + galactose
SMPL all produced by epithelial cells & found in SI:pH 7-9
Digestion of proteins:
Trypsin: Proteins -trypsin> short polypeptides
Produced by pancreas
Digestion of fats:
Lipase (pancreatic)/(intestinal):
Triglycerides (fats) -lipase> glycerol + fatty acids
Produced by pancreas, epithelial cells
Suggest a possible nutritional advantage to the young cow of the action of enzymes rennin which causes liquid milk to clot, forming solid lumps.
Rennin allows milk to remain for a longer period of time in the stomach [1] as it allows liquid milk to clot, for more complete digestion of proteins into polypeptides by pepsin protease. [1] Subsequently the polypeptides can be further digested into amino acids which can be absorbed into the bloodstream of the young cow.
Detergents are biological washing powders that contain 1 or more enzymes. Suggest the advantages of using biological washing powders compared to those without enzymes.
Lower temperature needed hence lesser electricity used
and lower energy cost [1]
Biological washing powder may contain specific enzymes
which can remove specific stains more easily such as
lipase which can catalyse/digest fat stains into fatty acids
and glycerol and remove the stains more easily. [1] (include
eg of enzyme; biological stain; digested products and more
easily removed)
As the enzymes remain chemically unchanged at the end of
the reaction, a small amount of biological powder is needed
for each wash. [1]
Biological washing powders speed up stain removal as
compared to those without enzymes. [1]
Explain, with reference to DNA structure and genes, how it is possible for different microorganisms to contain different enzymes.
[3]
Genes are segments/ sequence of DNA/ nucleotides that code for the synthesis of a specific polypeptide. [1]
The sequence of nucleotides in a gene determines the sequence of amino acids coded, [1]
Variation in the sequence of nucleotides in a gene synthesises different polypeptides and enzymes are made up of polypeptides. [1]
Denaturation definition
The loss of the three dimensional shape of the enzyme and the weak hydrogen bonds in the enzyme are broken and the active site of the enzyme is altered, caused by high heat or extreme pH.
