Enzymes Flashcards
Define the term enzymes
Enzymes are biological catalysts that interact with substrate molecules to facilitate chemical reactions. Usually globular proteins.
Define the term substrate
A substance used or acted on, by another process or substance. For example a reactant in an enzyme-catalysed reaction.
Define the term product
The result of a chemical reaction.
Explain why enzymes are necessary to life.
Most processes necessary to life involve chemical reactions which need to happen very fast -so are catalysed by an enzyme.
Define the term anabolic reactions
Anabolism refers to chemical reactions in which simpler substances are combined to form more complex molecules.
Anabolic reactions build new molecules and or store energy. And they normally require energy.
Define the term catabolic reactions
Catabolism refers to chemical reactions that result in the breakdown of more complex organic molecules into simpler substances.
Catabolic reactions usually release energy that is used to drive chemical reactions i.e. anabolic reactions.
Define the term metabolism
Metabolism is a term that is used to describe all chemical reactions involved in maintaining the living state of the cells and the organism. All reactions that occur in the body.
Explain how enzymes can affect both the structure and function of cells and whole organisms.
Enzymes can affect the structures in and organism e.g. enzymes are involves in the production of collagen and other proteins. These can affect the structures of cells and organisms.
Enzymes are specific so carry out a specific function, so can change the function of cells.
Define the term intracellular enzymes
Enzymes inside cells
Catalase
Define the term extracellular enzymes
Enzymes outside cells
Amylase and trypsin
State the substrates and products for the enzymes catalase
Catalyses the breakdown of hydrogen peroxide to oxygen and water.
Hydrogen peroxide is a toxic by-product of several cellular reactions- can kill cells if builds up.
State the substrates and products for the enzymes amylase.
Catalyses the hydrolysis of starch into maltose in the mouth.
Maltose is broken down to glucose by maltase which is in the small intestine.
It is found in saliva and secreted into the mouth by the salivary glands.
State the substrates and products for the enzymes trypsin.
Catalyses the hydrolyses of peptide bonds turning big polypeptides into smaller ones.
Produced in the pancreas and secreted into the small intestine.
Explain the role of extracellular enzymes in general..
They breakdown large nutrient molecules into smaller molecules by the process of digestion.
Define the terms “active site”
The area of an enzyme with a shape complementary to a specific substrate, allowing the enzyme to bind to a substrate with specificity
Define the terms complementary shape.
The shape of the active sites of enzymes are exactly complementary to the shape of the substrate.
Lock and Key hypothesis
Define the term specific
The active site is only complementary to one type of substrate.
Explain why an enzyme only catalyses one type of reaction.
Because for an enzyme to work the substrate has to fit into the active site- its shape has to be complementary. If the shape doesn’t match the active site the reaction won’t be catalysed.
State the sequence of events in an enzyme-controlled reaction.
A substrate binds to the active site forming an enzyme-substrate complex- lowers activation energy.
Describe the “lock and key” hypothesis of enzyme action.
The substrate fits into the enzyme int e same way a key fits into a lock- the active site and substrate have a complementary shape.
Describe the “induced-fit” hypothesis of enzyme action.
This helps to explain why enzymes are so specific and only bound to one particular substrate. The substrate doesn’t only have to be the right shape it has to make the active site change shape in the right way.
The active site changes shape slightly when the substrate binds to it, making it a tighter fit.
Suggest how the R-groups of amino acids are involved in catalysing reactions.
The R-groups contain features which are responsible for the tertiary structure. The tertiary structure determines the active site shape.
Define the term “activation energy”
The energy required to initiate a reaction
Define the term “rate of reaction”.
The speed at which a chemical reaction proceeds.
Draw an energy-level graph to show how a reaction progresses with and without an enzyme present (the transition state model).
With an enzyme the peak is lower and it declines faster.