Everything from the 2 lessons of this topic on a few pages: the key idea of each lesson, the diagram to remember, the points to learn and the traps examiners set. Read it, cover it, test yourself.
Enzymes are globular proteins that catalyse reactions either inside cells (intracellular, such as catalase) or after being secreted (extracellular, such as amylase in saliva). The substrate binds to the active site, a small region whose shape and charges are complementary to it, forming an enzyme-substrate complex. That makes the enzyme specific. In the lock-and-key hypothesis the site is rigid; in the induced-fit hypothesis it changes shape slightly as the substrate binds, straining its bonds. Either way the enzyme lowers the activation energy, so more collisions succeed at the same temperature, and it leaves the reaction unchanged. Reaction progress is followed by measuring product formed (oxygen from catalase) or substrate lost (starch with amylase), and the initial rate is used to compare conditions.
Say complementary, not the same shape. The substrate and active site fit together like a key and lock, so their shapes are complementary. Also, the enzyme is not used up: it is released unchanged and can bind another substrate molecule.
The curve levels off because the substrate has run out, not because the enzyme has been used up or denatured. If you add more substrate the reaction carries on at once.
Raising the temperature increases kinetic energy and successful collisions until the optimum; above it, hydrogen and ionic bonds break, the active site loses its shape and the enzyme is denatured. Each enzyme has an optimum pH, kept constant in experiments with buffer solutions; other pH values alter the charges on R groups in the active site. Rate rises with enzyme concentration while substrate is in excess, and with substrate concentration until every active site is occupied and the rate reaches Vmax. The Michaelis-Menten constant Km is the substrate concentration giving ½Vmax: a low Km means high affinity. A competitive inhibitor competes for the active site (Vmax unchanged, Km raised); a non-competitive inhibitor binds elsewhere and changes the active site (Vmax lowered). Enzymes immobilised in alginate can be reused, do not contaminate the product and are more stable.
Do not write that enzymes are killed: they are not alive. Say the enzyme is denatured and explain it: bonds in the tertiary structure break, the active site loses its complementary shape, and fewer enzyme-substrate complexes form.
A competitive inhibitor does not lower Vmax: at a very high substrate concentration the substrate out-competes it. Only a non-competitive inhibitor lowers Vmax. And Km is a substrate concentration, read on the x-axis, not a rate.