2.4.1 enzymes as biological catalysts Flashcards
active site
indented area on the surface of an ezyme molecule, with a shape that’s complementary to the shape of the substrate molecule
catalyst
chemical that speeds up the rate of reaction & remains unchanged/reusable at the end of the reaction
extracellular
outside the cell
intracellular
inside the cell
metabolic/metabolism
the chemical reactions that take place inside living cells/organisms
product
molecule produced from substrate molecules, by an enzyme-catalysed reaction
substrate
molecule that’s altered by an enzyme-catalysed reaction
why are enzymes called biological catalysts
speed up metabolic reactions in living organisms & their actions affect both structure/function within cells, tissues & organs
how effective is a small amount of catalyst
can catalyse the conversion of a large number of substrate molecules into product molecules
turnover number
the number of reactions an enzyme molecule can catalyse per second
why are biological catalysts better than chemical catalysts - conditions
- chemical catalysts require very high temperatures, increased pressures & extremes in pH
- enzymes speed up metabolic reactions by up to 10x12 at lower temperatures, often at neutral pH & normal pressures
why are biological catalysts better than chemical catalysts - specificity
- enzymes are more specific —> do not produce unwanted by-products & rarely make mistakes
- the cells where they’re made &/or act can also regulate their production & activity to fit the needs of the cell/organism at the time
how enzyme structure determines function
- for catalysing some reactions, may need help of cofactors
- instructions for production are encoded in genes —> if the gene has a mutation which alters the amino acid sequence in the protein, this may alter the enzymes tertiary structure & prevent it from functioning
- if an enzyme that catalyses a metabolic reaction is deficient then a metabolic disorder results
- catalyse formation of organisms structural components (eg. collagen in bone, cartilage) —> some genetic disorders cause malformations of connective tissue & can be harmful (eg. ‘stone man syndrome’)
how many amino acids consist in the active site
about 6-10
why is the tertiary structure of the active site crucial
it’s shape is complementary to the shape of the substrate molecule
each type of enzyme is highly specific in it’s function - how does this impact the active site?
the enzyme can only catalyse a reaction involving the particular substrate molecule that fits into it’s active site
how can the shape of the active site be altered
by changes in temp. & pH which affect the bonds that hold the proteins in their tertiary structure
what do enzymes catalyse
wide range of intracellular & extracellular reactions
properties of intracellular enzymes
- each metabolic pathway in a living cell is 1 of a series if consecutive reactions & every steps catalysed by a specific enzyme that produces a specific product
- various reactants & intermediates act as substrates for specific enzymes
- respiration & photosynthesis are examples of complex metabolic pathways, with many enzymes involved
what are the reactions, intermediates & products known as (intracellular)
metabolites
what are described as catabolic (intracellular)
some metabolic pathways where metabolites are broken down to smaller molecules & release energy
what are described as anabolic (intracellular)
other metabolic pathways where energy is used to synthesise larger molecules from smaller ones
what’s catalase
- found in nearly all living organisms that are exposed to oxygen
- very important enzyme
—> protects cells from damage by reactive oxygen by quickly breaking down hydrogen peroxide to water and oxygen
what’s hydrogen peroxide
a potentially harmful by-product of many metabolic reactions
what does catalase consist of
4 polypeptide chains & contains a haem group with iron
is it a fast acting enzyme - whats its turnover number
- fastest-acting enzyme
- highest turnover number known of about 6 million per second
where is catalase found in eukaryotic cells
found inside small vesicles called peroxisomes
how do white blood cells use catalse
when they ingest pathogens they use it to help kill the invading microbe
what’s the optimum pH/temp for catalase in different environments
- human catalse: around pH 7 & 45 degrees
- other species it varies between pH 4 & 11
- for some thermophilic archaea it’s 90 degrees
describe extracellular enzymes - use example of fungi
- some enzymes are secreted from the cells once made & act on their substrates outside
- fungi (eg. bread mould ‘mucor’) release hydrolytic enzymes from their thread-like hyphae —> enzymes digest carbohydrates, proteins & lipids in the bread & the products of digestion - glucose, amino acids, glycerol & fatty acids - are absorbed into the fungal hyphae for use in respiration & growth
how do extracellular enzymes work in our digestive system
- many are secreted from cells lining the alimentary canal, into the gut lumen
- they extracellulay digest large molecules (eg. proteins, lipids, carbohydrates & nucleic acids) found in food
- products of digestion are absorbed (via epithelial cells of the gut wall) into the bloodstream to be used for respiration, growth & tissue repair
where is amylase produced & what does it do
- salivary glands in the mouth & in pancreas
- mouth: digests polysaccharide starch into disaccharide maltose
- pancreas: catalyses same reaction^ in lumen of small intestine
where is trypsin made & what does it do
- what’s its optimum pH
- pancreas
- acts in lumen of small intestine to digest smaller peptides by hydrolysing peptide bonds
- optimum pH = between 7.5 & 8.5
