PEER LESSON Chapter 6.3, 6.4, 6.5

6.3 HOW IS ENERGY TRANSPORTED WITHIN CELLS?

ENERGY CARRIER MOLECULES

• Glucose cannot be used to fuel the endergonic process

• Therefore the energy released by the breakdown of glucose is transferred to energy carrier molecules

• Energy carrier molecules – high energy molecules that are synthesized at the site of an exergonic reaction where they capture some of the released energy• They behave like rechargeable batteries • They are “charged” by exergonic reactions and

“release” energy to power an endergonic reaction• But these molecules can only capture and transfer

energy within the cell

ATP(adenosine triphosphate)

• When exergonic reactions occur in cells like when sugars and fats are broke down, ATP(adenosine triphosphate) is produced• This is the most common energy carrier molecule in the

body • It is a nucleotide that is composed of the nitrogen

containing base adenine, sugar ribose, and three phosphate groups

• It is also referred to as the “energy currency” of cells because it provides energy to a range of endergonic reactions

6.3 HOW IS ENERGY TRANSPORTED WITHIN CELLS?

(CONT.)

ELECTRON CARRIERS • In addition, in some exergonic reactions

such as the glucose breakdown and the light capturing stage of photosynthesis energy is transferred to the electrons • These electrons combines with

hydrogen ions are captures by electron carriers

• Electron carriers give their high energy electrons to other molecules

COUPLED REACTIONS • Lastly there are coupled reactions

• In these type of reaction an exergonic reaction provides the energy needed to drive an endergonic reaction using ATP or electron carriers as intermediaries

• Carrier molecules are important because almost all organisms use the energy released by exergonic reactions to drive endergonic reactions

• For example, the breakdown of sugar into carbon dioxide or water to synthesis proteins from amino acids

6.4 HOW DO ENZYMES PROMOTE BIOCHEMICAL REACTIONS?

Catalysts Enzymes Enzyme structure How enzymes

regulate

6.4 CATALYSTS Catalysts play a huge role in reducing energy to

start a reactionCatalysts – molecules that speed up the rate of a

chemical reaction without using or permanently altering themselves

They have three major properties By lowering activation energy required for the

reaction to begin the reaction is sped up They ONLY speed up exergonic reactions The reaction that they promote do not consume or

change them

Catalysts are used for example in cars as catalytic reaction

Ex: 2 CO O2 2 CO2 heat energy

A elevator is an example of a catalyst. It speeds people up but the shape or function doesn’t change.

6.4 ENZYMES Enzyme – a highly specified biological catalyst that are mainly proteins

Most enzymes catalyze single reactions involving specific molecules while at the same time leaving very similar molecules unchanged

Enzymes catalyze both endergonic and exergonic reactions They regulate ALL reaction in living cells Enzyme names are NOT specific Due to their structure they are able to catalyze Enzymes catalyze in three steps

Depending on the shape and the charge of the active site substrates enter the enzyme but only in specific orientations

When binding occurs the substrates and active site change shape to cause a reaction

After the reaction occurs between the substrate the products don’t fit in the active site and they diffuse

After this the enzyme goes back to its original size and shape and is ready for more substrates

6.4 THE STRUCTURE AND REGULATION

The structure of the enzyme plays a huge role in the reaction ALL enzymes have a pocket which is the “active site” These pockets allow reactant molecules, also called substrates, to enter They are PROTEINS They have two characteristics that set them aside from non-biological catalystsThey are very specific for the reactions they catalyze There activity is regulated When a breakdown or synthesis of a molecule within a cell occurs , it happens

in many small steps, each catalyzed by a different enzymeEvery enzyme lowers the activation energy for it’s a particular reaction which

allows the reaction to occur readily at body temperature

6.5 HOW ARE ENZYMES REGULATED?

Enzyme regulation Influences in enzyme activity

6.5 ENZYME REGULATION

metabolic pathways are regulated by controlling enzyme synthesis and activity Certain enzymes are controlled by allosteric regulationEnzymes that undergo allosteric regulation have a special regulatory binding

site on the enzyme that is distinct from the enzyme’s active site but similar to a noncompetitive inhibitor site

Allosteric regulation can increase or decrease enzyme activity but noncompetitive inhibition only reduces activity

Feedback inhibition - a negative feedback type of allosteric inhibition which causes metabolic pathways to stop producing its product when quantities reach an optimum level

near the beginning of a metabolic pathway an enzyme is allosterically inhibited by the end product of the pathway

6.5 INFLUENCES OF ENZYME ACTIVITY

three things influence enzyme activity Drugs Poison Environmental conditions How do drugs/poisons influence enzyme activity?

They inhabit enzymes and compete with natural substrates for the active site They can also be noncompetitive or competitive inhibitors Competitive inhibitors of enzymes such as some nerve gases and insecticide will permanently block the active site

Arsenic, mercury, and lead bind permanently to the nonnative sites of various enzymes which inactivated them

What do environmental conditions do to enzymes? These conditions denature enzymes which overall distorts there three dimensional structure which they NEED to

function Enzymes are sensitive to pH as well as salts the temperature, and the presence of coenzymes The denaturing occurs when temperature are too high or too low Salts can in enzymes and destroy their structure Low temperatures slow down molecular movement High temperatures cause enzyme shapes to be altered which overall destroys the function

INTERACTIVE ACTIVITY Morgan Aronoff

Pd. 7

HOW DOES HYDROGEN PEROXIDE ACT AS A SUBSTRATE?

Using the picture, set them up in order

USING THE SHAPES, DEMONSTRATE HOW A CATALYST BONDS TO REACTANTS