2.1.4 enzymes Flashcards
what molecule are enzymes
2.1.4(a)
Enzymes are protein molecules.
what is an enzyme
2.1.4(a)
Enzymes are biological catalysts that reduce the activation energy needed for reactions in living organisms
how is lowering the activation energy useful
2.1.4(a)
This means that metabolic reactions can proceed at the rate needed to sustain life, even at quite low temperatures – e.g. human body temperature, 37oC.
how are higher temperatures detrimental to the enzyme
2.1.4(a)
Higher temperatures would denature the enzymes and so enzymes are crucial to allow life to exist at lower temperature
what do catalysts do
2.1.4(a)
Catalysts reduce activation energy to speed up reactions, and remain unchanged at the end of a reaction
what can a small number of enzymes do
2.1.4(a)
A small number of enzyme molecules can catalyse the conversion of a huge number of substrate molecules into product
-this means the enzyme doesn’t run out until it gets damaged
what is the function in every living cell catalyzed by
2.1.4(a)
Virtually every function in a living cell is catalysed by enzymes, for example respiration and photosynthesis
how are enzyme controlled reactions responsible for the structure of an organism
2.1.4(a)
Enzyme-controlled reactions are also responsible for the structure of an organism, because enzymes are involved in development, for example by synthesis of fibrous proteins like collagen and keratin.
what does intracellular mean
2.1.4(b)
Intracellular means “inside a cell”
where do intracellular enzymes catalyse reactions
2.1.4(b)
Intracellular enzymes catalyse reactions that take place inside cells, in the cytoplasm, or inside one of the organelles e.g. mitochondria or chloroplasts
how many metabolic reactions can take place at the same time inside cells
2.1.4(b)
There may be up to 1000 metabolic reactions taking place at the same time inside a cell.
what is an example of an intracellular enzyme and where is it found
2.1.4(b)
Catalase is an intracellular enzyme. It is found in nearly all living organisms that are exposed to oxygen
what is the function of catalase
2.1.4(b)
Its function is to break down the molecule hydrogen peroxide, H2O2, which is a toxic by-product of metabolic reactions including respiration.
2H2O2 → O2 + 2H2O
where is catalase found
2.1.4(b)
In eukaryotic cells, catalase is found inside small vesicles called peroxisomes
what type of structure does catalase have
2.1.4(b)
Catalase has a quaternary structure. It consists of four polypeptide chains
what is each polypeptide chain bound to
2.1.4(b)
each of which is bound to a prosthetic group. The prosthetic groups in catalase are iron-containing haem groups that allow catalase to catalyse the reaction of H2O2.
what does extracellular mean
2.1.4(b)
Extracellular means “outside a cell
how are extracellular enzymes made
2.1.4(b)
Extracellular enzymes are made by cells and then secreted to the outside of the cell by exocytosis
what is the function of extracellular enzymes
2.1.4(b)
Their function is to catalyse reactions that take place outside of cells.
what is amylase
2.1.4(b)
amylase is a digestive enzyme that hydrolyses amylose into maltose
what is amylase made by
2.1.4(b)
It is made by cells in the salivary glands and secreted into the saliva in the mouth. It is also made by cells in the pancreas, and secreted into the small intestine.
where is trypsin made and where is it secreted
2.1.4(b)
Trypsin is made by cells in the pancreas and secreted into the small intestine
what is the role of trypsin
2.1.4(b)
Trypsin hydrolyses peptide bonds to break down proteins into smaller polypeptides.
what specific area of the active site to substrate molecules fit into
2.1.4(c)
Substrate molecules fit into a specific area of the enzyme molecule called the active site
why can substrates fit the active site
2.14(c)
Substrates can fit the active site because the tertiary structure of the active site is complementary to its substrate,
what happens once the substrate is bound to the active site
2.1.4(c)
Once the substrate is bound to the active site, the enzyme catalyses the reaction of the substrate.
what would happen if the tertiary structure of the active site changed
2.1.4(c)
If the tertiary structure of the active site changed, then the substrate would no longer fit, and so the enzyme would not be able to catalyse the reaction, and the reaction would stop.
what does the lock and key hypothesis describe
that the tertiary structure of the active site is complementary to its substrate
the active site and substrate fit perfectly together
what is the lock and key hypothesis
substrate molecules fit into the enzymes active site and temporary hydrogen bonds hold the two together forming an enzyme-substrate complex
the enzyme catalyses the reaction of the substrate forming products
the products temporarily stay bonded to the active site which is called an enzyme product complex
the products aren’t complementary to unbind and are released
the enzyme is not changed during the reaction
how does the lock and key hypothesis lower the activation energy
it holds the substrates in the correct orientation lowering the activation energy needed for the reaction to take place
what is the induced fit hypothesis
when the substrate binds to the active site it induces a conformational change in the tertiary structure of the active site
the substrate binds to the active site which forms an enzyme substrate complex
the enzyme catalyses the conversion of the substrate, forming products. The products temporarily stay bonded to the active site-this forms an enzyme product complex
the products aren’t complementary to the active site so they unbind and are released
the enzyme is not changed during the reaction
how does induced fit hypothesis reduce the activation energy
when the shape of the active site changes is puts strain on the substrate molecules and weakens the bonds in the substrate so they don’t require as much energy to break
therefore the activation energy has been reduced
what is activation energy
the energy required to break the chemical bonds in the reactants and start a reaction
how would you reach activation energy in a lab setting
this would be achieved by increasing the temperature, such as by using a Bunsen burner. We can’t do this in living organisms, as high temperatures denature proteins and enzymes that living organisms are made of.
draw the graph for pH
in booklet
