2.1.4 enzymes Flashcards
(28 cards)
what is an enzyme?
biological catalyst
globular protein that interacts with the substrate molecules causing them to react at a much faster rate without other environmental conditions
what do enzymes do?
they are used in chemical reactions to speed up the rate of reaction
they catalyse reactions
what is an anabolic reaction?
builds bonds
what is a catabolic reaction?
breaks down bonds
why are anabolic reactions needed?
required for growth
catalysed by enzymes
why are catabolic reactions needed?
required for energy release from large organic molecules
catalysed by enzymes
what is metabolism?
the sum of all the different reactions and reaction pathways happening in the cell
it can only happen as a result of the control and order imposed by enzymes
environmental conditions that speed up cellular reactions include:
temperature
pressure
pH
what is the Vmax?
maximum initial velocity or rate of the enzyme-catalysed reaction
enzymes can only increase the rates of reaction up to the Vmax
what happens when high temperatures and pressures are applied to a reaction?
result in the speed of molecules increasing
meaning the number of successful collisions increase
resulting in an increased rate of reaction
what is the specificity of the enzyme?
many different enzymes are produced by living organisms as each enzyme catalyses on biochemical reaction of which there are thousands in any given cell
what is activation energy?
energy needed for the reaction to start
hypotheses for how enzymes help molecules collide successfully and reduce activation energy
lock and key hypothesis
induced-fit hypothesis
explain the lock and key hypothesis
active site within the tertiary structure of the enzyme is an area of the enzyme that has a shape complementary to the shape of the specific substrate molecule that fits into the active site
when the substrate is bound to the active site, an enzyme-substrate complex is formed
they then react to form an enzyme-product complex
products are then released, enzyme is unchanged and able to react in other reactions
explain the induced-fit hypothesis
the active site of the enzyme changes shape slightly when the substrate enters
the initial interaction between the enzyme and substrate is weak - these weak interactions rapidly induce changes to the enzymes tertiary structure that strengthen binding, putting strain on the substrate weakening a bond in the substrate
which lowers the activation energy of the reaction
what is an intracellular enzyme?
enzymes that are produced and function inside the cell
what is an extracellular enzyme?
enzymes that are secreted by cells and catalyse reactions outside cells
example of intracellular enzyme and its function
catalase
- hydrogen peroxide is produced as a by-product of many metabolic reactions
- harmful to cells
- catalase converts hydrogen peroxide into water and oxygen, preventing any damage to cells or tissues
example of extracellular enzyme and its function
amylase
- digestion is usually carried out by extracellular enzymes
- because the macromolecules being digested are too large to enter the cell
- amylase hydrolyses starch into simple sugars
digestion of starch
-> starch is partially broken down into maltose (disaccharide) by amylase - produced by salivary glands (mouth) and pancreatic juice (pancreas)
-> maltose is broken down into glucose (monosaccharide) by maltase - produced in the small intestine
-> glucose is small enough to be absorbed by the cells lining the digestive system and absorbed into the bloodstream
digestion of proteins
-> protein catalysed into peptides by trypsin (by pancreas) in pancreatic juices in the small intestine
-> peptides broken down into amino acids by other proteases
-> amino acids are absorbed by the cells lining the digestive system and absorbed into the bloodstream
enzymes have a specific optimum temperature
catalyse reactions at the maximum rate
what do lower temperatures in a reaction do?
slow the reaction down
- molecules move slower due to less kinetic energy
- lower frequency of successful collisions between substrate and active sites
- leads to less frequent enzyme-substrate complex formation
- substrates and active sites collide with less energy - less likely for bonds to form or break
what does higher temperatures in a reaction do?
speed up the reaction
- molecules move more quickly - more kinetic energy
- results in higher frequency of successful collisions between substrate and active sites
- leads to more frequent enzyme-substrate complex formation
- substrate and active sites collide with more energy - more likely for bonds to be formed or broken
