enzymes Flashcards
(28 cards)
enzyme features
- globular proteins (have a tertiary structure)
- act as biological catalysts
- alter rate without bring permanently changed or used up
- able to be reused
how are enzymes biological catalysts
they speed up many metabolic reactions in living organisms
what is the turnover number
the number of reactions an enzyme can catalyse per second
how are enzymes (biological catalysts) different to chemical catalysts
- chemical catalysts usually need high temps, increased pressures and an extreme ph
—> however biological catalysts can speed reactions up to 10^12 times at lower temps, normal pressure and a neutral ph - enzymes are more specific
- enzymes dont produce unwanted products
how do enzymes help if 2 substrates need to be joined
being attached to the enzyme holds them close together and reduces any repulsion so they can bond easily
how does an enzyme help break a stubstrate down
when the substrate fits into the active site, a strain is put onto the bonds in it, making it break down easier into smaller molecules
how do enzymes get their structure
- they’re chains of AAs, therefore theyre coded for by the dna of the organism
- the instructions for making enzymes are encoded in genes
what happens to the enzyme if a gene has a mutation on
- it will alter the sequence of AAs
- this may alter the enzymes tertiary structure and prevent it from functioning
- this can then lead to problems with metabolic functions from; digestion, or the formation of blood vessel walls, joints and connective tissues
what is the active site
- a specific indentation or cleft on the surface of an enzyme, it consists of about 6-10 AA
- shape is complementary to the shape of the substrate
- shape can be altered by temp or ph changes
where do enzymes work
they can catalyse both intracellular and extracellular reactions inside and outside of the cell
what are intracellular enzymes
- work WITHIN cells and organelles
- often over 1000 reactions occur simultaneously, each being catalysed by a different enzyme
—> some of these are part of a metabolic pathway
what is a metabolic pathway
a series of connected chemical reactions that feed one another, each step catalysed by a different enzyme
what are metabolites
the intermediate products of metabolic reactions
what are the two types of metabolic pathways
anabolic - E is used to synthesise smaller molecules into larger ones
catabolic - large molecules are broken down into smaller ones, releasing E
what is catalase
- a type of intracellular enzyme which identifies found in nearly all living organisms exposed to O
- fastest acting enzyme - turnover number is 6mil per second
- optimum pH in humans is ph7
- optimum temp in humans is 45 degrees
- found in vesicles - peroxisomes
what does catalase do
- protects cells from damage by breaking down hydrogen peroxide into water and oxygen
- used by WBCs to kill invading microbes when WBCs try to ingest pathogens
catalase structure
- 4 polypeptide chains and a haem group with iron
what are extracellular enzymes
enzymes that have been secreted from cells and act on substrates outside of cells
how is fungi use extracellular enzymes
it releases extracellular hydrolytic enzymes onto food (such as bread) which digest carbs, proteins and lipids, and then the products of digestion are absorbed into the fungal hyphae for growth and respiration
what are cofactors
non -protein molecules that attach to enzymes and help them catalyse reactions, especially redox reactions
what are prosthetic groups
they’re cofactors which are permanently bound, by covalent bonds, to an enzyme
what is the prosthetic group on carbonic anhydrase
a zinc ion
what is the equation for carbonic anhydrase and what does it do
carbon dioxide and water <—> carbonic acid <—> bicarbonate and H ion
- the reaction enables CO2 to be carried in the blood from respiring tissues to the lungs
what is an enzyme substrate complex
it forms when the substrate and enzyme molecules temporarily bind together
