2.4 Enzymes

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what is an enzyme
these are biological catalysts which speed up the rate of metabolic reactions. They affect both the structure and function within cells, tissues and organs
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why are enzymes described as specific
the tertiary structure of the active site is crucial, as its shapes i complementary to the shape of the substrate, if this changes then the enzyme is no longer complementary to the substrate and cannot carry out its function so it can only catalyse reacti
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what is the turnover number
the number of reactions that an enzyme molecule can catalyse per second
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what is the structure of an enzyme
Enzymes are proteins so have the primary structure, secondary structure, tertiary structure which is responsible for the shape of the active site and the quaternary structure
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what is the enzyme active site
this is the indented area on the surface of an enzyme molecule, with a shape that is complementary to the shape of the substrate molecule
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what protein structure is the enzyme active site
the tertiary structure
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what the two main places in which enzymes work
Intracellular and Extracellular
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what are extracellular enzymes
these are enzymes that catalyse reactions outside of the cell
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what do extracellular enzymes do
some enzyme are secreted from the cells where they are made and act on their substrates extracellularly
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what are some examples of extracellular enzymes
Amylase - produced in the salivary glands and acts in the mouth to digest starch in maltose
Trypsin - is made in the pancreas and acts in the lumen of the small intestine to digest protein into smaller peptides
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what are intracellular enzymes
they are enzymes which catalyse reaction inside of the cell
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what do intracellular enzymes do
in any cell, there could be up to 1000 metabolic occurring at the same time each catalysed by a different enzyme
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what are some examples of intracellular enzymes
some reactions that happen intracellularly can be catabolic where metabolites are broken down to smaller molecules or anabolic where larger molecule are made from smaller ones and respiration and photosynthesis are examples of this
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what is a cofactor
these are small non-protein molecules that has to be present to ensure that an enzyme catalysed reaction takes place at the appropriate rate
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why do some enzymes need cofactors
so that they can take place at an appropriate rate
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what is prosthetic group
It is a cofactor that is permanently bound by covalent bonds, to an enzyme molecule
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what are some examples of some prosthetic groups
Zinc binds to carbonic anhydrase to catalyse the interconversion of CO2 and water to carbonic acid and amylase only digest starch to maltose in the presence of chloride ions
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what are coenzymes
these are small organic non-protein molecule that bind temporarily to the active site of enzyme molecules
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what is the lock and key hypothesis
substrate molecules fits into the enzyme's active site. Temporary hydrogen bonds hold the enzyme and the substrate together and an enzyme substrate complex is formed
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what is the induced-fit model
when the substrate molecules fit into the enzymes active site, the site changes shape slight to mould itself around the substrate
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how do the lock and key and the induced fit model differ
the active site still holds a shape complementary to the shape of the substrate molecule. But, on binding, the subtle changes of the shape of the side chains R-groups of the amino acids that make up the active site five more precise conformation that exac
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how does temperature affect the activity of an enzyme
this increases the rate of enzyme activity as the extra energy make molecules gain more kinetic energy and move faster and increases the rate of collision and increase the rate of successful collisions
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what does the 'optimum temperature' mean
the optimum is when the rate of enzyme catalysed reactions is at its maximum
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what is pH
it indicates whether a substance is acidic, alkaline or neutral
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how does pH affect the activity of the enzyme
decreasing the pH decreases the rate of reaction as excess hydrogen ions will interfere with these hydrogen bonds and ionic forces so the active site changes and the substrate is no longer complementary and the rate is lowered. Also increase the conc. of
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what is the effect of substrate concentration on the rate of enzyme-catalysed reactions
look at pg 113
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how can this be shown in graph form - effect of substrate concentration
pg 113
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what is the effect of enzyme concentration on the rate of enzyme-catalysed reactions
pg 115
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how can this be shown in graph form - the effect on enzyme concentration
pg 115
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what are inhibitors
are substances that reduce the activity of enzyme. They do this by combing with the enzyme molecule sin a way that influences how the substrate binds to the enzyme or affects the enzyme's turnover number some block the active site or change the shape of i
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what is a competitive inhibitor an how their inhibition be shown in graph form
blocks the active site. Pg 117
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what is non-competitive inhibitor and how can this be shown in graph form
Binds to an allosteric site. Pg 177 -118
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what is end product inhibition
pg 118
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why are enzymes described as specific

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the tertiary structure of the active site is crucial, as its shapes i complementary to the shape of the substrate, if this changes then the enzyme is no longer complementary to the substrate and cannot carry out its function so it can only catalyse reacti

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what is the turnover number

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what is the structure of an enzyme

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what is the enzyme active site

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