• They lack an enzyme: LACTASE
• Vocab:• Sugars end in “-ose”• Enzymes end in “-ase”
• But…what is an enzyme?
What do people who are lactose-intolerant lack?
Why do we study chemical reactions in biology?
• Chemistry isn’t just what life is made of, chemistry is also what life does
• Everything that happens in an organism is based on chemical reactions (growth, response to environment, etc.)
Chemical Reaction
• A process that changes reactants into products (the end substance in a the reaction).
• Slow Reactions vs. Fast Reactions
CATABOLIC PATHWAY (CATABOLISM)Release of energy by the breakdown of complex molecules to simpler compoundsEX: digestive enzymes break down food
ANABOLIC PATHWAY (ANABOLISM)consumes energy to build complicated molecules from simpler onesEX: linking amino acids to form proteins
http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/nanoscience/sci_media/images/chemical_reactions_involve_making_new_combinations/53823-2-eng-NZ/chemical_reactions_involve_making_new_combinations_full_size_landscape.jpg
THERMODYNAMICS = the study of energy transformations
• CLOSED system (EX: liquid in a thermos) = isolated from its surroundings
• OPEN system energy + matter can be transferred between the system and its surroundings
• Organisms are open systems
http://ag.ansc.purdue.edu/sheep/ansc442/Semprojs/2003/spiderlamb/eatsheep.gif
Endergonic vs. Exergonic reactions
exergonic endergonic- energy released- digestion
- energy invested- synthesis
-G
G = change in free energy = ability to do work
+G
Energy Changes• Some reactions release energy and some
absorb energy
• Activation Energy: the energy required to start a reaction
Speeding up Reactions• Slow reactions or reactions with high activation energies
need a catalyst
• Catalyst = any substance that lowers the activation energy of a reaction to “speed it up”
• Enzymes are proteins which act like a catalyst to speed up reactions. (found in the body, plants, animals, food, etc.
Where are enzymes?
• Enzymes are found in all cells
• Mostly in the stomach and intestines
Enzymes - Introduction
Enzymes• Enzymes provide a site where reactants can be
brought together to react. • In an enzyme-catalyzed reaction, the reactants
are called substrates (the starting substance – found in the same place you would find the enzymes – binds to the enzyme and is than made into a product).
• Each enzyme has a specific shape and a specific portion called the
active site, where substrates
bind.
• The substrates must fit exactly into the active site. This is called the lock and key model.
• The active site changes shape slightly to hold the substrate – induced fit
• Once the reaction is complete, the enzyme releases the products of the reaction.
• Enzymes can join or break substrates into products.
Joining 2 Substrates into 1 Product
Roles of Enzymes:1) regulating chemical pathways2) making materials3) releasing energy4) transferring info
So, if changing the shape of the active site keeps the enzyme from working, what else might keep it from working?
COFACTORS = non-protein enzyme helpers
• EX: Zinc, iron, copper
COENZYMES = organic enzyme helpers
• Ex: vitamins
http://www.wissensdrang.com/media/wis9r.gif
http://www.elmhurst.edu/~chm/vchembook/595FADcoq.html
COMPETITIVE inhibitor REVERSIBLE; Mimics substrate and competes with substrate for active site on enzyme
ENZYMEANIMATION
Enzyme Inhibitors
Enzyme InhibitorsNONCOMPETITIVE inhibitors bind to another
part of an enzyme, causing the enzyme to change shape and making the active site less effective
ENZYMEANIMATION
Digestive enzymes names match the foods they help react
Lactase helps break down
lactose.
Each enzyme is specially designed to react a certain
molecule
Lactase is just one enzyme that breaks down lactose but there are many
different enzymes at work in your body.
What happens if we don’t have them?
• Example: Lactose – Lactase
• We can’t convert it fast enough
into glucose So it builds up..
• Since our body can’t get rid of it..
• We feel sick.
(nauseous, throwing up)
More enzymes that break things down in your body…
Sucrose = Glucose + Fructose
Sucrose is table sugar!
AMYLASE: breaks down starch in your mouth and stomach
LIPASE: breaks down fats
PEPSIN: breaks down proteins
Factors affecting enzyme function
• Enzyme concentration – as enzyme = reaction rate
• more enzymes = more frequently collide with substrate
– reaction rate levels off• substrate becomes limiting factor• not all enzyme molecules can find substrate
enzyme concentration
reac
tio
n r
ate
Factors affecting enzyme function
substrate concentration
reac
tio
n r
ate
• Substrate concentration – as substrate = reaction rate
• more substrate = more frequently collide with enzyme
– reaction rate levels off• all enzymes have active site engaged• enzyme is saturated• maximum rate of reaction
TEMPERATURE & ENZYME ACTIVITYEach enzyme has an optimal temperature at which it
can function (Usually near body temp) Optimum T°
greatest number of molecular collisions human enzymes = 35°- 40°C
body temp = 37°C Heat: increase beyond optimum T°
denaturation = lose 3D shape (3° structure) Cold: decrease T°
molecules move slower
http://www.animated-gifs.eu/meteo-thermometers/001.htm
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