What are  Catalysts/Biological Catalysts?

Catalysts are the substances that speed up/increase any chemical reaction but does not consume during the chemical reaction.  So a biological catalyst can be recovered chemically unaffected at the completion of the chemical reaction.

What are the enzymes/Biological Catalysts?

Enzymes are biological catalysts.

  • All the time in our body, chemical reactions are taking place. These chemical reactions need to be at a faster rate , so for that Enzymes are special compounds produced within the living cells in a body of an organism that allows chemical reactions to take place at a quicker rate.
  • They act as catalysts.
  • They are made up of proteins.
  • Chemical reaction will speed up without being chemically changed or used in the chemical reaction.
  • Each enzyme has a unique and specific shape.

Why are enzymes essential for our life?

They are vital for life and serve a wide range of essential functions in the body, such as helping in digestion and metabolism.

Enzymes can either:

    • break down complex substances into simpler substances  ( catabolism ); OR
    • build up complex substances from simpler substances  ( anabolism ).


What are different Examples of Enzymes/ biological catalyst in living organisms?:

Digestion is a catabolic activity, so different kinds of enzymes used in this process.For example,salivary amylase, pepsin,rennin,trypsin,lipase, maltase,lactase are few examples.

Photosynthesis, which builds sugars out of smaller molecules, is a “building up,” or anabolic, pathway. Some enzymes are there that help to capture the energy from the sun to build up the bigger sugar molecules.

Cellular respiration which breaks sugar down into smaller molecules and is a “breaking down,” or catabolic, pathway. Different enzymes are used to break the mega sugar molecules into a smaller one.

What Do Enzymes Do?

Enzymes make chemical reactions faster or catalyse the reaction. In biology, this means that they speed up the rate of reactions by lowering the  activation energy of the chemical reaction(the energy required to get the reaction done.)


As the image above shows that the presence of an enzyme has lowered the activation energy, but it is essential to know that all of the reactions would still happen even if the enzymes were not there. But they would happen much more slowly and require a lot of energy.

So, Enzymes are vital to our health to change the rate of chemical reactions on which it happens, but without any external energy source added or by being changed themselves.

How can we Classify the Biological catalysts/enzymes?

We can categorize the enzymes into two types because enzymes can work inside and outside the cell

  •  INTRACELLULAR  ENZYMES are the enzymes that work inside the cell. for Example,ATP synthase,DNA polymerase,RNA polymerase.
  • EXOENZYME OR  EXTRACELLULAR ENZYMES are the enzymes that are made by the cells, but they work outside the cell. They are made in the cell , packed and sent outside the cell to carry out their function.For example most of the enzymes that work with the digestive system.


How do we name these Enzyme/biological catalysts? (Nomenclatures):

The Common method to write the name of the enzyme is just add the suffix ASE at the end of the food it acted upon.

For Example:

Maltose is acted upon by maltase.

Sucrose is acted upon by sucrase.

A lipid is acted upon by lipase.

Cellulose is acted upon by cellulase.

Examples of different Enzymes:

  • Amylase(an enzyme for the digestion of carbohydrates) is found in seeds and in the human body as well. Following conversions happen in plants when the seed begins to germinate:

Amylase is activated, and a breakdown of insoluble starch happens into soluble Maltose.

Then  Maltose, as a source of energy, will be sued by a growing embryo that will make cellulose for the new cell wall.

  • Mostly Biological washing powders contain enzymes that are often gained from microorganisms such as Bacteria/biological cell or Fungi( eukaryotic organisms). The enzymes taken from these microbes break down proteins or fats on the fabric, forming them water-soluble. Then these fats or proteins are removed with water.
  • In fruits, cell walls are made up of Pectinase, which breaks them quickly, and extracting the juice from fruits becomes easier.
  • In a fermenter, the antibiotic penicillin is made by cultivating the fungus Penicillium. In that fermenter, the correct pH and temperature for the fungus enzymes to work well are kept.


What are the primary and general properties of different Enzymes/biological catalysts?

  1. Enzymes are specific for specific reactions.
  1. Enzymes are manufactured naturally in living organisms’ cells.
  2. They are made up of proteins.
  3. For a large amount of chemical change, only a very minute amount of enzymes are required.
  4. Enzymes do not become part of any chemical reaction, and they remain the same.
  5. Enzymes work in two ways directions. For example, Starch can be broken to Maltose and then Maltose can form Starch as well.
  6.  Every Enzyme work at specific pH. Enzymes that work best in alkaline conditions cannot work best in acidic conditions.
  7. They are inactivated by chemical reactions e.g. cyanide (poison); such chemicals are called inhibitors.
  8. They are denatured by heat.

How does an enzyme work?

  • Substrates: A  substrate is a reactant in a chemical reaction which acted upon by an enzyme.
  • Active site: The active site is the site of an enzyme to which substrates bind and where a reaction is catalyzed.
  • Enzyme-Substrate Complex: When an enzyme comes in contact with its substrate, it forms an enzyme-substrate complex.

What is a lock and key hypothesis?

A lock is an enzyme molecule that contains an active site.

The Key is a substrate molecule that has to fit in the active site.

Enzymes contain specific active sites of particular or complementary in shape to the substrate molecule, where a special substrate molecule exactly fits, and an enzyme-substrate complex is made.

Enzyme temporarily holds substrate molecules in the active site until some substrate molecules split or breakdown to form products as in catabolic reactions.


What are anabolic reactions?

In an anabolic reaction, substrates join and develop new bonds to make products. When the reaction is completed, the product molecules are released and the enzyme with its active site remains unchanged.

How does an enzyme activity is affected by temperature and pH?

Effect of Temperature:

At optimum temperature, the activity of an enzyme is at the highest rate of reaction.

At low temperatures, enzymes are inactive.

But as the temperature/heat rises, the rate of reaction also increases because heating leads to an increase in the kinetic energy (energy for the motion) of molecules. This leads to more successful collisions and more formation of enzyme-substrate complexes.

Beyond the optimum temperature, the enzyme activity decreases as the enzyme is denatured.


Enzymes are protein in nature that are denatured at high temperatures, and denaturation is irreversible.

Why does the denaturation of enzymes occur?

The 3D shape of the active site is determined by weak hydrogen bonds that hold the chains of amino acids in place. Due to an increase in temperature, more kinetic energy is imparted to molecules, so vibrations in the atoms of the enzyme become faster, causing the hydrogen bonds that are chemical bonds in their structure are broken, and shape of the active site changed, and the overall shape of the enzyme is destroyed. Now the structure of the protein is damaged and cannot be restored.


The active site loses its shape and is no longer complementary to the substrate. Now enzymes will not act as catalyst. as



How does the activity of an enzyme is affected by pH:

Enzymes are affected by the acidity or alkalinity of solutions. Some work best in the acidic environment e.g., pepsin.Some enzymes work best in the alkaline environment, e.g., intestinal enzymes e.g., amylase Extreme changes in pH can denature the enzymes. Enzymes are made of proteins. The 3D shape of the active site is determined by weak hydrogen bonds that hold the chains of amino acids in place. Interference of the H+ or OH ions with the hydrogen bonds causes them to be damaged. The active site loses its specific shape and is no longer complementary to the substrate. Thus the enzyme becomes denatured.


What do you mean by limiting factors in an enzyme activity?

A limiting factor is a variable that causes an apparent change in output or another measure of a type of system. It can also be defined as it is a variable that inhibits or slows down the chemical reaction.

For example, when the amount of available substrate exceeds than the number of enzymes, then no more substrate can be broken down. Then the enzyme concentration becomes the limiting factor slowing the reaction.

What do you mean by Substrate Enzyme Concentration?

On an available amount of enzyme, the rate of enzymatic reaction increases as the substrate concentration increases until a limiting factor is reached, after which further increase in the substrate concentration produces no significant change in the chemical reaction rate. At this point, so much substrate is enough, so all of the enzyme active sites have substrate bound to them.

In other words, the enzyme molecules are saturated with substrate molecules. The excess substrate molecules cannot react until the substrate is already bound to the enzymes has reacted and been released (or been released without reacting).


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