Energy, Enzymes, and Chemical Reactions

Defining Energy Potential energy is the capacity to do work. Kinetic energy is the energy of motion.

Chemical energy Potential energy of molecules Thermal (heat) energy Energy that is not given off as kinetic energy ; is considered “wasted energy”

Laws of Thermodynamics First law –Energy is not created or destroyed only transferred between forms. The total amount of energy in the universe remains constant.

Second law -- No energy conversion can ever be 100% efficient. Energy always flows from more useful forms of energy to forms that are less useful.

Endergonic reaction Energy is put into the reaction Uphill reaction For example: Glycolysis

Exergonic reaction Energy is released during the reaction Downhill reaction Example: The Kreb’s cycle and electron transport system

A DENOSINE T RI P HOSPHATE --Is the cell’s energy source Is a nucleotide consisting of three phosphate groups, a five-carbon sugar (ribose), and the nitrogen base (adenine).

Adenine Ribose 3 Phosphate groups Adenosine

I MPORTANCE OF ATP Cells transfer energy from food to ATP ATP delivers energy where ever energy is needed. movement chemical reactions growth

H OW IS ENERGY RELEASED ? When a phosphate group is removed (energy is released when the bonds that hold the phosphate groups together are broken). Results – ATP becomes ADP ( A denosine D i p hosphate) Adenosine Ribose 2 Phosphate groups

ADP is changed into ATP when a phosphate group is added.ADP is changed into ATP when a phosphate group is added.

Chemical Reactions

Indicators of chemical reactions Formation of a gas Release of light or heat Formation of a precipitate Color change Release of odor

All chemical reactions: Have two parts 1. Reactants - the substances you start with 2. Products- the substances you end up with The reactants turn into the products. Reactants  Products

Symbols used in equations indicates a reversible reaction. or indicates the direction in which a reaction occurred.

All chemical reactions are accompanied by a change in energy. Exothermic - reactions that release energy to their surroundings (usually in the form of heat) Endothermic - reactions that need to absorb heat from their surroundings to proceed. Reaction Energy

What is a catalyst? A substance that decreases the activation energy needed to start a chemical reaction and increases the rate of the chemical reaction. Are not changed or used up during a chemical reaction.

Enzyme Structure & Function

 Enzymes – catalysts that speed up the rate of a reaction.  Equilibrium - when a reaction is running at the same rate forward as well as in reverse.

Four shared features 1. Enzymes don’t make anything happen that could not happen on its own, it just makes it happen faster. 1. Enzymes can not be permanently changed or used up.

 The same type of enzyme usually works whether the reaction is occurring in a forward or reverse motion  Each type of enzyme is very picky

Enzyme-Substrate interactions  Substrates attach to enzymes at the enzyme’s active site.  Enzymes have one or more active sites  Active site- A specific shape that will only fit a specific substrate.

Active Site  A specific shape that will only fit a specific substrate. (Like a lock & Key).  When the substrate locks into the active site, the reaction begins with lower activation energy because of weaker bonds within the molecule.

Enzyme Lock–and–Key Model

1 A substrate (reactants) attaches to an enzyme’s active site. 2 Enzyme- Substrate Complex The enzyme reduces the activation energy of the reaction. 3 The enzyme is NOT changed by the reaction. A new product is formed.

Factors influencing enzyme activity  Temperature  pH  Salinity  Feedback Inhibition