Biomolecules Life… It’s all about chemistry…

How does it all work though? There is one more class of biomolecules that really makes life possible… Many of the functions of carbohydrates, lipids, proteins, and nucleic acids would not be feasible without this class of molecules. This class of molecules facilitates (makes possible) the countless chemical changes in your body every day.

Enzymes make it possible! Enzymes - Proteins that catalyze (increase the rate of) chemical reactions. Enzymes catalyze 4000 different biological reactions. Used by the body to break down food in digestion, and then to build other molecules we need.

Enzymes Enzymes lower the activation energy (E a ‡ ) for a chemical reaction. Because the energy to start the reaction is lower, the reaction occurs more easily and quickly. Most reactions are millions of times faster with enzymes.

Enzymes For example: Orotidylic Acid is used to make uracil (RNA base). The chemical reaction that produces Orotidylic Acid takes 78 million years… unless you use an enzyme. With the enzyme it takes 25 milliseconds.

Enzymes Shape is important to all molecules, but especially enzymes and the molecules they catalyze. The molecule(s) the enzyme works with is the substrate, and the molecule(s) produced by the enzyme is called the product…

Enzymes There are also molecules called inhibitors that keep enzymes from going crazy and doing reactions all day. Many medicines we use are really enzyme blockers called inhibitors that prevent certain things from happening in our bodies. If you stop the enzymes, you stop the cell processes that hurt you.

Enzymes Here’s how it works…

Enzymes Enzyme-Substrate Complex – The molecules of an enzymatic reaction when attached. Active Site – The place where the substrate attaches to the enzyme itself.

Enzymes Each enzyme is made by the body specifically for one and only one substrate. Only this one specific type of molecule can ever use the enzyme that matches it. This setup is just like a key and a lock. One key (enzyme) can open an unlimited number of locks (substrates) much more quickly than they can be picked, but the key is only useful on locks that were built with the same shape as the key.

Enzymes In addition to shape, temperature and pH are the other factors that influence an enzyme’s ability to catalyze a chemical reaction. Enzymes are almost as sensitive to temperature and pH as they are to changes in shape, and changes in temperature and pH frequently cause changes in shape.

Enzymes – Changes in pH pH is a measure of how many hydrogen ions (charged particles) are in a substance. pH effects the types of chemical reactions that occur. It is a measure of the chemical energy within a substance. The pH scale ranges from 0-14, with 7 being neutral. Substance with a pH from 0-7 are called an acids, and substances from 7-14 are bases. All enzymes have a range of pH where they can do their reactions, but outside of that range, they are ineffective.

Enzymes – Changes in pH All substances have a pH, which tells the reactivity of the substance. pH stands for “power of Hydrogen.” The further away from 7 on the scale a substance is, the more power Hydrogen has.

Enzymes – Changes in pH Since pH controls the reactivity of a substance, and enzymes assist in chemical reactions, the pH and the enzyme must “line up” with one another. Each enzyme has a sweet spot on the pH scale where it is much more effective at causing the desired chemical reaction. Note how each enzyme has a spot where it’s reaction rate is much higher. This is the “sweet spot.”

Enzymes – Changes in Temperature Temperature is also an extremely important factor for enzymatic reactions. Temperature is the measure of how much thermal energy is within a substance. The more energy in a substance, the more prone it is to undergo chemical reactions. The amount of thermal energy is important because extra thermal energy bends, twists, and jiggles molecules which makes them behave differently.

Enzymes – Changes in Temperature When molecules are heated, the extra excitement causes shape to change, therefore causing the enzyme and substrate to not match. This also applies to temperatures that are too cold. When there is not enough energy, the molecule changes shape. If the enzyme’s active site and the substrate do not line up, there will be no chemical reaction. In most cases, the temperature and pH must be within a small range in order to have an enzymatic reaction.

Enzymes – Changes in Temperature Again, the affectivity of an enzyme at different temperatures can be shown with a graph. At 33°C the enzyme is producing the most oxygen per minute, so this must be the optimal temperature for the this enzyme. Outside of the optimal range, an enzyme’s effectiveness decreases steeply. Why do you think a fever of just a few degrees makes you feel so bad?

Enzymes Continued Remember that the shape of the active site and the substrate must match in order to perform a chemical reaction. Changes in pH and temperature lead to changes in shape for the enzyme. When the shape of the enzyme is changed, it is called denaturing.

Enzyme Denaturing A normal enzyme works like this... The enzyme matches the shape of the substrate and causes a chemical change to happen, resulting in the products.

Enzyme Denaturing When an enzyme’s temperature changes, it changes shape due to expansion (heat) or contraction (cold). If an enzyme, or any protein, changes shape, the substrates cannot fit onto the active site, so the enzyme cannot break the chemical bonds anymore. When an enzyme is exposed to conditions that make it unable to work, this is called denaturing and can also be done by changes in pH.

Enzyme Denaturing A denatured enzyme works like this... Added heat changes the shape of the enzyme, which can no longer fit the substrate and therefore cannot produce the desired products..

Enzymes Here’s how it works… again

Enzymes you should know One of the most important enzymes you will study this year produces your actual DNA. DNA Polymerase can “code” DNA strands and also “proofread” the strand. This enzyme prevents DNA coding errors (mutations) and makes cell replication possible The ending –ase tells us this molecule is an enzyme.

Enzymes What do enzymes do to our food? Amylase breaks down starch into sugar. Lipase breaks down fats to be absorbed in the intestines. Pepsin breaks apart proteins in food for their amino acids. Catalase turns hydrogen peroxide into water and oxygen.

Biomolecules Life… It’s all about chemistry…