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