Enzyme Notes

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Enzymes
All enzymes are globular proteins and round in shape
They have the suffix "-ase"
Intracellular enzymes are found inside the cell
Extracellular enzymes act outside the cell (e.g. digestive enzymes) Enzymes are catalysts → speed up chemical reactions
Reduce activation energy required to start a reaction between molecules Substrates (reactants) are converted into products
Reaction may not take place in absence of enzymes (each enzyme has a specific catalytic action) Enzymes catalyse a reaction at max. rate at an optimum state Induced fit theory
Enzyme's shape changes when substrate binds to active site
Amino acids are moulded into a precise form to perform catalytic reaction effectively Enzyme wraps around substrate to distort it
Forms an enzyme-substrate complex → fast reaction
E + S → ES → P + E
Enzyme is not used up in the reaction (unlike substrates)
Changes in pH
Affect attraction between substrate and enzyme and therefore efficiency of conversion process Ionic bonds can break and change shape / enzyme is denatured Charges on amino acids can change, ES complex cannot form

Optimum pH
pH 7 for intracellular enzymes
Acidic range (pH 1-6) in the stomach for digestive enzymes (pepsin) Alkaline range (pH 8-14) in oral cavities (amylase)

Increased Temperature
Increases speed of molecular movement → chances of molecular collisions → more ES complexes Enzymes have optimum temp. for their action (varies between different enzymes) Above ≈42°C, enzyme is denatured due to heavy vibration that break Shape is changed / active site can't be used anymore

Decreased Temperature
Enzymes become less and less active, due to reductions in speed of molecular movement Below freezing point
Inactivated, not denatured
Regain their function when returning to normal temperature
Inhibitors
Slow down rate of reaction of enzyme when necessary (e.g. when temp is too high) Molecule present in highest conc. is most likely to form an ES-complex Competitive Inhibitors
Compete with substrate for active site
Shape similar to substrates / prevents access when bonded
Can slow down a metabolic pathway
Non-competitive Inhibitors
Chemical does not have to resemble the substrate
Binds to enzyme other than at active site
This changes the enzyme's active site and prevents access to it 1. Cell structure and organisation
All living things are made of cells.
All (typical) cells have: (i.e. some for example the red blood cell do not have all these things, no nucleus) Cell Membrane: a membrane that controls the entry and exit of dissolved substances and separates the cell’s contents from its surroundings. Cytoplasm: contains water and dissolved substances such as sugars and salts Nucleus: contains the genetic material (DNA). This carries the coded instructions for controlling the activities and characteristics of the cell. Mitochondria: organelle where aerobic respiration happens.

A typical animal cell (e.g. the liver cell) has all the above things.

Only plant cells have:
Chloroplast: Small organelle which contains chlorophyll (dye used for light absorption) and enzymes necessary for the production of glucose by photosynthesis. (Large permanent) Vacuole: contains water necessary to provide turgor pressure and may store ions and molecules. Cellulose cell wall: provides structural support, permeable for dissolved substances and water and prevents damage when the cell is in a hypotonic solution i.e. cell can’t explode. A typical plant cell (e.g. the palisade cell) has all the above things.

Organelle: a specialized part of a cell that has its own function, e.g. the nucleus or the mitochondrion Cell: the smallest part of a living structure that can operate as an independent unit e.g. the red blood cell Tissue: a group of cells with similar structures, working together to perform a shared function e.g. muscle tissue Organ: a structure made up of a group of tissues, working together to perform specific...