Biochemistry introduction

1. BIOCHEMICAL
REACTIONS
Standard H.B.2 The student will demonstrate the understanding that the essential functions
of life take place within cells or systems of cells.
H.B.2A The essential functions of a cell involve chemical reactions that take place
between many different types of molecules (including carbohydrates, lipids, proteins and
nucleic acids) and are catalyzed by enzymes.
H.B.2A.2 Plan and conduct investigations to determine how various environmental

2. IN A NUTSHELL
• Biochemical reactions allow organisms to grow, develop, reproduce, and
adapt. A chemical reaction breaks down some substances and forms other
substances.
• Chemical reactions (including biochemical reactions) can occur when
reactants collide with sufficient energy to react.
• The amount of energy that is sufficient for a particular chemical reaction to
occur is called the activation energy.
• Sometimes a chemical reaction must absorb energy for the reaction to start;
often, but not always, this energy is in the form of heat.
• Energy, as heat or light, can also be given off as a result of biochemical
reactions, such as with cellular respiration or bioluminescence.

3. AFFECTING REACTIONS
• There are several factors that affect the rates of biochemical reactions:
• Temperature
• pH
• Enzymes

4. AFFECTING REACTIONS:
TEMPERATURE
• Changes in temperature (gaining or losing heat energy) can affect a
chemical reaction.
• Proteins can denature (be altered or breakdown) if temperature is to high or
even to low

5. AFFECTING REACTIONS: PH
• pH (a measure of the acidity of a solution) in most organisms needs to be
kept within a very narrow range so that pH homeostasis can be maintained.
• A small change in pH can disrupt cell processes.
• Proteins can denature (be altered or breakdown) if pH is to high or to low

6. AFFECTING REACTIONS: ENZYMES
• The essential functions of a cell involve chemical reactions that take place
between many different types of molecules (including carbohydrates, lipids,
proteins and nucleic acids) and are catalyzed by enzymes.
• Enzymes are proteins that serve as catalysts in living organisms.
• Enzymes are very specific. Each particular enzyme can catalyze only one
chemical reaction by working on one particular reactant (substrate).
• Enzymes are involved in many of the chemical reactions necessary for
organisms to live, reproduce, and grow.
• Examples include but are not limited to digestion, respiration, reproduction,
movement and cell regulation.

7. AFFECTING REACTIONS: ENZYMES

8. AFFECTING REACTIONS: ENZYMES
• A catalyst is a substance that changes the
rate of a chemical reaction or allows a
chemical reaction to occur (activate) at a
lower than normal temperature.
• Cofactors and coenzymes
• Each catalyst works best at a specific
temperature and pH.
• Catalysts work by lowering the activation
energy of a chemical reaction.
• A catalyst is not consumed nor altered
during a chemical reaction, so, it can be
used over and over again.

10. ENERGY CAN CHANGE:

11. A. Energy in Chemical Reactions
1. Reactants – molecules you start
with
2. Products – molecules you end with

12. 3. Free energy – available energy
4. Activation energy – energy
needed to
start a reaction
a. catalysts (enzymes) reduce the amount of
activation energy needed to start a reaction
5. Exergonic reactions release
energy
while endergonic reactions
absorb
energy

13. REACTION TYPES
• Endergonic or Endothermic – takes
in energy or heat – reaction vessel
will feel cool to the touch.
• Exergonic or Exothermic – gives off
energy or heat – Reaction vessel will
feel warm to the touch, or light will
be seen.

14. CHECKING FOR UNDERSTANDING
1. How are an enzyme and a catalyst similar?
2. What role does an enzyme have in a biochemical reaction?
3. Any enzyme (can/cannot) work in any chemical reaction?
4. What kind of macromolecule is an enzyme?
5. What is the name given to a reaction that releases chemical
energy?

15. ENZYME ACTION
•An Enzyme-Catalyzed Reaction

16. HOW IS ENZYME ACTIVITY LIKE A
LOCK AND KEY?
• 1. An active site on the enzyme is like the lock and the
substrate is like the key.
• 2. The substrate comes into the enzyme and fits perfectly
on the active site.
• 3. The enzyme then contributes energy to get the
reaction started.
4. Once the reaction is finished, the reactants leave the
active site.
5. The enzyme is free and ready to take on another
substrate.