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Enzymes

Enzymes

Enzymes are protein molecules catalysing biochemical reactions. Their activity can be regulated.

Biology

Keywords

enzyme, enzyme protein, active site, substrate, product, inhibition, activation, allosteric inhibition site, allosteric activation site, coenzyme, NADH, NADPH, FADH₂, Acetyl coenzyme A, ATP, catalyst, biochemistry, biology

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Scenes

Reaction

  • enzyme protein - Enzymes are catalysts: they catalyse biochemical reactions, speeding them up several million times by reducing their activation energy. They act by bringing substrates near each other or modifying their spatial structure. Catalysts are not used up in the reaction.
  • active site - The part of the enzyme that catalyses the reaction.
  • substrate
  • product

Inhibition

  • inhibitor - It can bind to the active site, preventing the substrate from binding.

Activation

  • allosteric activation site - When an activator binds here, the spatial structure of the active site changes.
  • activator

Enzymes

  • enzyme protein - Enzymes are catalysts: they catalyse biochemical reactions, speeding them up several million times by reducing their activation energy. They act by bringing substrates near each other or modifying their spatial structure. Catalysts are not used up in the reaction.
  • active site - The part of the enzyme that catalyses the reaction.
  • substrate - During the enzyme reaction one or more of them are converted into one or more products.

Animation

Narration

Enzymes are catalysts: they catalyse biochemical reactions, speeding them up several million times by reducing their activation energy. Catalysts are not used up in the reaction.

When two substrates are joined, substrate molecules bind to the active site of the enzyme catalysing the reaction, and the enzyme helps to form a bond between them. Without an enzyme this reaction rarely occurs, as substrates have to collide in a certain spatial formation, with a large amount of energy.

When a substrate molecule is broken down, it binds to the active site of the enzyme protein. The enzyme breaks down the substrate. The strong covalent bond is rarely broken spontaneously, enzymes are needed to speed up the reaction.

The key to the regulation of the enzyme mechanism is enzyme inhibition.

One type of inhibition involves an inhibitor binding to the active site, that is, it competes with the substrate. This is called competitive inhibition.

Another type of inhibition is allosteric inhibition. The inhibitor binds to the allosteric inhibitor site, which causes a conformational change in the active site, preventing it from binding the substrate.

Allosteric activation is the opposite of allosteric inhibition. In its default state, without an activator, the enzyme is inactive. When an activator binds to the allosteric activation site, this changes the spatial structure of the active site, enabling it to bind the substrates and catalyse the reaction.

Coenzymes are molecules that transform during the enzyme reaction: they either release or accept certain substances. When the reaction is complete, the coenzyme becomes detached. Important coenzymes include NADH, NADPH, acetyl-CoA, FADH2, ATP and vitamins.

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Structure of proteins

The structure and arrangement of polypeptide chains affects the spatial structure of proteins.

Anatomy of the small intestine

The longest part of the digestive system, where most of the digestion and absorption takes place.

Secondary structure of proteins

Polypeptide chains are composed of amino acids and can appear in alpha-helix or beta-sheet form.

ADP, ATP

ATP is the main source of energy for cells.

Coenzyme A

An acyl-carrier coenzyme taking part in both anabolic and catabolic processes.

Glands connected to the duodenum

The pancreas and the liver empty digestive juices into the duodenum.

Haemoglobin

Oxygen carrier protein in our red blood cells.

NAD⁺, NADP⁺, NADPH

NAD⁺ is a coenzyme that plays an important role mainly in catabolic processes, while NADP is important in anabolic processes as hydrogen carriers.

Photosynthesis

Plants are capable of converting inorganic substances (carbon dioxide and water) into organic sugar.

Transport processes

This animation explains active and passive transport processes occurring through cell membranes

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