Actions Of Enzymes Flashcards
what is an enzyme
Enzymes speed up chemical reactions by acting as biological catalysts.
They catalyse metabolic reactions
both at a cellular level (e.g. respiration) and for the organism as a whole
(e.g. digestion in mammals).
Is catalase intracellular or Extracellular
Intracellular
What does catalase do
Hydrogen peroxide is the toxic by-product of several cellular reactions.
If left to build up, it can kill cells.
Catalase is an enzyme that works inside cells to catalyse the breakdown of hydrogen peroxide to harmless oxygen
and water
What do amylase and trypsin do
Amylase and trypsin both work outside cells in the human digestive system.
Amylase is found in saliva. It’s secreted into the mouth by cells in the salivary glands.It catalyses the hydrolysis (breakdown) of starch into maltose (a sugar) in the mouth
Trypsin catalyses the hydrolysis of peptide bonds - turning big polypeptides into smaller ones, Trypsin is produced by cell in the pancreas and secreted into the small intestine.
Is amylase and trypsin intracellular or Extracellular
Extracellular
What can Enzymes do to a cell
Enzymes can affect structures in an organism as well as functions
What does intracellular mean
Within cells
What does Extracellular mean
Outside cells
What type of proteins are enzymes
Enzymes are globular proteins
What is the structure of an enzyme
Enzymes have an active site, which has a specific shape. The active site is the part of the enzyme that the substrate molecules bind to.
The specific shape of the active site is determined by the enzyme’s tertiary structure
Why does a substrate have to fit into the active site
For the enzyme to work, the substrate has to fit into the active site, its shape has to be complementary. If the substrate shape doesn’t match the active site, the reaction won’t be catalysed. This means that enzymes work with very few substrates - usually only one.
What is the activation energy
In a chemical reaction, a certain amount of energy needs to be supplied to the chemicals before the reaction will start. This is called the activation energy - it’s often provided as heat.
What happens when enzymes reduce activation energy
Enzymes reduce the amount of activation energy that’s needed, often making reactions happen at a lower temperature than they could without an enzyme. This speeds up the rate of reaction.
How does an enzyme substantiate complex lower the activation energy
When a substance binds to an enzyme’s active site, an enzyme-substrate complex is formed. It’s the formation of the enzyme-substrate complex that lower the activation energy.
Why does an enzyme substantiate complex being formed lower the activation energy
1)If two substrate molecules need to be joined, attaching to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily.
2) If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate.
This strain means the substrate molecule breaks up more easily.
What is the lock and key model
Enzymes are a bit picky. They only work with substrates that fit their active site. Early scientists studying the action of enzymes came up with the ‘lock and key’ model. This is where the substrate fits into the enzyme in the same way that a key fits into a lock.
Why did scientists modify the lock and key model for the induced fit model
Scientists soon realised that the lock and key model didn’t give the full story. The enzyme and substrate do have to fit together in the first place, but new evidence showed that the enzyme-substrate complex changed shape slightly to complete the fit. This locks the substrate even more tightly to the enzyme. Scientists modified the old lock and key model and came up with the ‘induced fit’ model.
What is the induced fit model
The ‘induced fit’ model helps to explain why enzymes are so specific and only bond to one particular substrate.
The substrate doesn’t only have to be the right shape to fit the active site, it has to make the active site change shape in the right way as well.
What is the enzyme substrate complex
Enzyme has a specific shape, so it only works with specific substrates that fit the active site
