Enzymes are biological catalysts made of proteins (or in some cases RNA). Their specific 3D protein structure creates an active site that binds substrates.

Amylase is a carbohydrate-digesting enzyme whose specific substrate is starch, which it hydrolyses into maltose and shorter glucose chains.

In feedback inhibition, the end product of a metabolic pathway binds to and inhibits an earlier enzyme in the pathway, preventing overproduction.

Enzymes are essential for all metabolic reactions; therefore they are present in every living cell throughout the plant, not limited to any one organ.

The protein portion of an enzyme, without its cofactor, is called the apoenzyme. Together with its cofactor it forms the complete holoenzyme.

Digestive (hydrolytic) enzymes in the cell are stored in lysosomes, which are membrane-bound organelles that break down waste materials and cellular debris.

Enzymes are proteins, built from hundreds of amino acids linked by peptide bonds into a polypeptide chain that folds into a specific 3D shape.

High temperatures denature enzymes by disrupting hydrogen bonds and other interactions that maintain their 3D shape, permanently destroying activity.

Enzymes are classified by the International Union of Biochemistry into 6 major classes based on the type of reaction they catalyse (oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases).

Hydrolases catalyse the hydrolytic cleavage of bonds using water, breaking complex molecules like proteins, lipids and carbohydrates into simpler units.

Enzymes speed up reactions by lowering the activation energy required, allowing reactions to proceed faster without being consumed in the process.

Enzymes are biological catalysts and are NOT consumed during reactions. They are regenerated after each reaction cycle and can be used repeatedly.

Enzymes are globular proteins folded into precise 3D shapes. This specific three-dimensional configuration forms the active site that is complementary to the substrate.

A prosthetic group is a non-protein component that is covalently (permanently) bound to an enzyme. If it is loosely attached, it is called a coenzyme.

The complete, catalytically active enzyme consisting of the protein part (apoenzyme) plus its non-protein cofactor or coenzyme is called a holoenzyme.

The enzymes of cellular respiration (Krebs cycle, electron transport chain) are located in the mitochondria, the powerhouse of the cell.

Without enzymes, metabolic reactions would proceed far too slowly to support life. Enzymes accelerate reactions by millions of times by lowering activation energy.

Pepsin works optimally at pH 2, matching the highly acidic environment of the stomach where it is secreted to digest proteins.

Competitive inhibitors are structurally similar to the substrate and can occupy the active site, competing with the substrate and sometimes acting as alternate substrates.

Reverse transcriptase is the enzyme used by retroviruses (like HIV) to synthesise DNA from an RNA template — the reverse of the normal transcription process.

Enzymes are very sensitive to both pH and temperature changes because these affect the ionic bonds and hydrogen bonds that maintain their 3D active site shape.

The specific molecule on which an enzyme acts is called the substrate. It binds to the active site of the enzyme to form an enzyme-substrate complex.

Human enzymes work optimally at 37°C (normal body temperature). Above this temperature, the enzyme begins to denature and activity drops sharply.

Daniel Koshland proposed the Induced Fit Model in 1958, suggesting that the active site changes its shape to accommodate the substrate upon binding.

Enzymes require an aqueous (water-based) medium to function, as water is needed for the hydration of the active site and for most biochemical reactions.

Most enzymes are proteins. However, some RNA molecules called ribozymes also have catalytic activity, but classically enzymes are defined as protein catalysts.

In an enzyme-catalysed reaction, the reactant molecule that binds to the enzyme's active site is called the substrate.

A coenzyme is an organic non-protein molecule that is loosely (non-covalently) attached to an enzyme and assists in its catalytic activity. Many vitamins serve as coenzymes.

Emil Fischer proposed the Lock and Key Model in 1894, suggesting that the enzyme (lock) has a fixed active site that perfectly fits only one specific substrate (key).

In the Induced Fit Model, the enzyme's active site is flexible and changes its conformation to better fit the substrate when it approaches, like a hand in a glove.

Increasing enzyme concentration only increases reaction rate when the substrate is in excess (not rate-limiting). If substrate is limited, extra enzyme molecules remain idle.

Competitive inhibitors have a structure similar to the substrate and compete with it for the same active site, blocking it and reducing enzyme activity.

At very high temperatures, the intense atomic vibrations break the weak bonds (hydrogen, ionic) holding the enzyme's shape, causing denaturation and loss of function.