Enzymes Flashcards
Hydrolyse
the process of hydrolysis
Hydrolysis is a chemical reaction during which polymers (large
molecules) break down into monomers (small molecules). This is a
catabolic process
Temperature and enzymes
As temperature increases the rate of collisions increases but then drop off.
Once temperature is high enough bonds holding the active site together break down which changes its shape temperature is reached - the substrate no longer fits – it is denatured.
Biological catalyst
Enzymes are proteins that act as catalysts.
• Catalysts alter the rate of reaction without undergoing a permanent change so can be used repeatedly and therefore only small amounts are needed
• They do not make reactions happen, they speed up the reaction by lowering the activation energy so reducing the amount of energy needed for the reaction. This is the Ea value.
The induced fit model
This model proposes that the active site forms as the enzyme and substrate interact.
The proximity of the substrate leads to changes in the enzyme that then forms the active site.
In other words, the enzyme is flexible and can mould itself around the substrate in a way that the glove moulds to the shape of the hand.
The enzyme then strains the shape of the substrate molecule which
distorts its bonds which lower the activation energy need to break
Collision theory
For a reaction to take place the molecules must come into physical contact and have an active site that fits
the substrate.
A rise of fall in temperature increase or decreases the kinetic energy of the molecules so they collide more often or less often so changing the rate of the reaction
Enzyme inhibition
Enzyme reactions can be inhibited to reduce the reaction rate. There are two types which can be reversible and irreversible.
Competitive inhibitors bind to the active site preventing substrate binding - lowers the reaction rate
Noncompetitive inhibitors bind to an alternative site on the enzyme. This causes the active site to change shape which prevents substrate binding – lowers the reaction rate
Roles of enzymes (covered in digestion too)
• There are two families (Proteases and Carbohydrases) of enzymes that you need to be aware of and one specific enzyme (lipase).
• Enzymes hydrolyse the bonds between polymers to break them down into their dimers and monomers.
Make the links -
• Proteases for Protein
• Carbohydrases for Carbohydrates
• Lipase for Lipids.
Proteases (peptidases - peptide bonds)
• Enzymes that hydrolyse proteins.
• Endopeptidases - hydrolyse the central region of a protein polymer to create smaller sections of polymers
• Exopeptidases - hydrolyse the ends of the new shorter polymers to release dipeptides and monomers (peptides/amino acids)
• Dipeptidases - hydrolyse the bond between a dipeptide creating monomers (found in the lining of the ilium to allow absorption)
Proteases (peptidases - peptide bonds)
• Enzymes that hydrolyse proteins.
• Endopeptidases - Tyrpsin and Pepsin (pancreas and duodenum)
• Exopeptidases - Carboxypeptidase A (Pancreas)
• Dipeptidases - found in the cell membranes of the microvilli of the small intestine.
Carbohydrases
• Just like proteins - we break the polymer into a disaccharide and then into a monosaccharaide ready for absorption.
• Amylase hydrolyses the 1-4 glyosidic bonds of the polymer starch to produce maltose - a disaccharide. This occurs in two places salivary amylase in the mouth and then pancreatic amylase in the ilium.
• Cells lining the ilium produce maltase in their cell membranes - these are called membrane-bound disaccharidase.
• This enzyme hydrolyse the maltose into glucose ready for absorption.
Carbohydrases and target molecules
Carbohydrases and target molecules
• Maltase hydrolyses maltose into glucose and glucose
• Sucrase hydrolyses sucrose into glucose and fructose
• Lactase hydrolyses lactose into glucose and galactose
Lipase
Lipase is an enzyme that hydrolyse triglycerides by breaking the ester bonds into:
• 2 fatty acid chains
• glycerol and one fatty acid chain (a monoglyceride)
• Lipases are present in pancreatic secretions and participate in fat digestion and metabolism by working on emulsified lipids - the increase in surface area leads to a faster reaction (GCSE)
Summary
