Enzymes and Their Function Study Guide


Catalysts speed up chemical reactions, and enzymes are biological catalysts that speed up the biochemical reactions in all living things. These proteins are vital for the body’s day-to-day functioning, without which we would not be able to survive.

What are Enzymes?

Enzymes are biological polymers that perform the function of catalyzing chemical reactions in living things. Most enzymes produced by the body are proteins that assist in the various metabolic processes and other reactions in the cells.

There are more than 4000 different chemical reactions in organisms that are known to be catalyzed by enzymes. Without their presence, the chemical reactions will not proceed at a necessary rate for the sustenance of life.

Role of Enzymes in Biochemical Reactions

Most chemical reactions needed to sustain life would not occur under the normal conditions inside cells. The body temperature of almost all living organisms is not high enough to initiate the reaction. Reactants in the body can also be in such low quantities that they are most likely to not meet for a chemical reaction. This is where functional enzymes come into the picture to get things going.

Function of Enzymes in the Body

As catalysts, enzymes do not act as reactants but only to accelerate or initiate chemical reactions. While they can also be used repeatedly, enzymes are produced for highly specific reactions and only when the need arises. Since they are so efficient at speeding up the reaction, they could accelerate what might otherwise take days to a matter of seconds.

How does an Enzyme work?

Enzymes function by modifying the variables in a reaction such as activation energy: increasing the concentration of reactants and offering a substrate for reactions to occur. Activation energy is the energy required to start a chemical reaction. The diagram below shows the extra energy needed by reactants to start a reaction with and without enzymes.

activation energySource

The activation energy of a reaction can be lowered by:

  • Bringing the reactants closer together increases the probability of their interaction without needing excess energy to move around until they collide randomly.
  • This is done by the enzyme acting as a substrate to bind reactants together until they react. The resulting enzyme products then leave the reaction site, and the enzyme stays the same.

By having the reactants bound to the enzyme, the need for the reactants to be positioned correctly to start the reaction is also lower. This would overcome the intermolecular forces that would otherwise push the reactants apart. Enzymes also work by offering a pathway that needs the lowest activation energy.

Variables that affect Enzyme Activity

Depending on what is the function of enzymes in biological systems, the enzyme activity can vary based on the following factors:


The increased temperature speeds up the reaction rate until some point. Beyond the limit, higher temperatures would denature the enzyme and stop its functionality.


pH level or acidity has an effect on the enzyme as a highly acidic environment tends to slow down or even stop reactions.


A higher enzyme concentration means the reactants will have more substrate for chemical reaction, therefore the reaction rate will be higher.


Inhibitors are substances that slow down or stop the functioning of the enzyme. They do that by blocking the binding sites or changing the enzyme’s shape, rendering it ineffective.

Types of Enzymes in the Body

Here are the enzymes in the human body responsible for a range of reactions: – Hydrolases: These enzymes work in the presence of water to break chemical bonds. There are more than 200 types of hydrolases.

– Oxidoreductases: These enzymes are needed to catalyze oxidation and reduction reactions.

– Transferases: These enzymes mediate the transfer of functional groups in the reactants.

– Isomerases: These enzymes cause structural changes in the molecules needed for reactions.

– Ligases: These enzymes help in the repair of DNA breaks.

– Lyases: These are also called synthase enzymes.

Applications of Enzymes

Enzymes find use in many different industries such as: Food processing industries and manufacturing processesPharmaceutical industries in the production of drugsRecycling of paper and other organic wasteChemical industries in the production of household products, textile, beverages, and cleaning products


  • Enzymes are biological catalysts that can speed up reactions
  • The functions of an enzyme involve lowering the activation energy of chemical reactions so they can occur faster and at lower temperatures.
  • Enzymes are highly specific for each reaction and are secreted with active sites that are reactant-specific.


1. What are the 5 main digestive enzymes?

Here are the five digestive enzyme examples:

  1. Amylase
  2. Pepsin
  3. Trypsin
  4. Pancreatic lipase
  5. Ribonuclease and deoxyribonuclease

2. What are the six types of enzymes?

The 6 types of functional enzymes are:

  1. Lyases
  2. Ligases
  3. Isomerases
  4. Hydrolases
  5. Transferases
  6. Oxidoreductases

3. What are the four functions of enzymes?

Enzymes are involved in functions such as:

  • Blood Coagulation
  • Digestion
  • Respiration
  • Cellular metabolism

4. What are the five properties of enzymes?

  • Catalytic property
  • Specificity
  • Reversibility
  • Sensitivity to heat and temperature
  • Specific to pH concentration

5. What are the three features of an enzyme?

  • It decreases the activation energy of the reaction
  • It acts as a substrate for reactants.
  • It holds the reactants in binding sites to start chemical reactions.

6. Are enzymes water soluble?

Yes, some enzymes can also act as water-soluble catalysts.

We hope you enjoyed studying this lesson and learned something cool about Enzymes and Their Function! Join our Discord community to get any questions you may have answered and to engage with other students just like you! Don’t forget to download our App to experience our fun, VR classrooms – we promise, it makes studying much more fun!😎

Continue your learning journey:

  1. Learn more about proteins, RNA, and DNA
  2. Ribosomes and Mitochondria
  3. Translation


  1. Enzymes. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Introductory_Biology_(CK-12)/01%3A_Introduction_to_Biology/1.17%3A_Enzymes. Accessed 9 Dec, 2021.
  2. Enzymes. https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/1.17/primary/lesson/enzymes-bio/. Accessed 9 Dec, 2021.
  3. Enzyme Function. https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/1.18/primary/lesson/enzyme-function-bio/. Accessed 9 Dec, 2021.
  4. Properties of Enzymes. https://www.easybiologyclass.com/properties-of-enzymes-biochemistry-lecture-notes/. Accessed 9 Dec, 2021.

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