chapter 2-4 energy and living things. metabolism: an organism’s capacity to acquire energy and use...

CHAPTER 2-4Energy and Living Things

METABOLISM: AN ORGANISM’S CAPACITY TO ACQUIRE ENERGY AND USE IT TO BUILD,

BREAK APART, STORE AND RELEASE SUBSTANCES

CHEMICAL REACTIONS

• Reactants products

• reactions are reversible

• example: H2 + O2 2H2O

2H2O H2 + O2

CHEMICAL REACTIONS WON’T START ON THEIR OWN.

• reactions require “starting energy” to get them going

• “activation energy ”: It’s the push for a chemical reaction!

• If there is not enough activation energy…….nothing will happen (no reaction)

TYPES OF REACTIONS

• When reactions release energy = EXERGONIC, breaking bonds, reducing activation energy needed, speeding up reaction (Think of Exit)

• When reactions absorb (require) energy = ENDERGONIC (Opposite of Exergonic)

Releases energy Absorbs energy

• A reaction will never start if there is not enough activation energy available.

• In cells, catalysts allow reactions to start with LESS activation energy.

• Catalysts SPEED up the reaction rate.

• Ex: Digestion would never occur if catalysts did not start the digestive reactions.

BIOLOGICAL CATALYSTS ARE

CALLED ENZYMES

Demonstration - (DON’T WRITE THIS)

Enzymes in living tissue ---------

Biological catalysts

H2O2 (hydrogen peroxide) is toxic to cells.

It is a by-product of cellular metabolism.

The potato must destroy H202 quickly and turn it into the harmless H20

Liver cells contain the enzyme “catalase” which makes this faster

H202 (l) H20 (l) + O2

Enzymes lower the Activation Energy ( EA) for biological reactions to take place. Bonds are being broken

Reactant Product

Reactant

Product

EA

EA

Without catalyst With catalyst

E

Almost all enzymes are PROTEINS and have a very exact shape.

They are NOT changed at all during a reaction, they do not react.They are only HELPERS.

ENZYMES ARE PROTEINS

Enzyme

The molecules that enzymes will act upon are called

Ex: Substrate = starch Enzyme = amylase

Glucose = Product

SUBSTRATES.

Found in saliva!

Because of the shape of the enzyme, only certain molecules will bind to the enzyme.

Enzymes are VERY SPECIFIC.

·Lactase will only break down lactose….·Amylase will only break down starch….. ·Protease will only break down protein…. Etc…

Active Site = the place where the substrate BINDS to the enzyme.

Lock and Key Theory =Says that only one enzyme will fit a certain substrate. Like a key fits only one lock….

enzyme

substrate

At what number is a chemical bond broken by the enzyme? ___________Label _____ is showing the active site.Label ___ is showing the substrate.Label _____ is showing the productsLabel _____ is showing the enzyme

XW__ZY

2

FORM FITS FUNCTION = If the enzyme loses it shape, it will not function correctly

enzyme

substrate

enzyme

FORM FITS FUNCTION

FACTORS THAT SCREW UP AN ENZYME’S FUNCTION IN OUR BODIESFactors that Mess

UP an enzyme’s

function in our bodies:

· Temperature– enzymes function in a very

narrow range of temperature

In humans: they work best ~ 98.6 o F (37oC)

· pH (acid or base?) · – specific, narrow range (stomach

enzymes ~ pH 2.5 - 3.5 – very acid)

( large intestine ~ pH 7 - neutral)

All of these factors change the shape of the enzyme by disrupting the bonds that hold the enzyme’s shape together – making the enzyme useless to cells.