Denature proteins
Enzymes
&
Digestion
Page 48, 99-105
662-670
Protein structure (review)
R groups
hydrophobic interactions
disulfide bridges
(H & ionic bonds)
3°
multiple
polypeptides
hydrophobic
interactions
1°
amino acid
sequence
peptide bonds
determined
by DNA
4°
2°
R groups
H bonds
Primary (1°) structure
• Order of amino acids in chain
– amino acid sequence determined
by gene (DNA)
– slight change in amino acid
sequence can affect protein’s
structure & its function
• even just one amino acid change can
make all the difference!
lysozyme: enzyme
in tears & mucus
that kills bacteria
Just 1
out of 146
amino acids!
Sickle cell anemia
I’m
hydrophilic!
But I’m
hydrophobic!
In Biology,
Protein denaturation
size doesn’t matter,
• Unfolding a protein
SHAPE matters!
– conditions that disrupt H bonds, ionic bonds,
disulfide bridges
• temperature
• pH
• salinity
– alter 2° & 3° structure
• alter 3-D shape
– destroys functionality
• some proteins can return to their functional shape after
denaturation, many cannot
•A.Enzymes work best within a certain environment
•B. Denaturation-Enzymes can be permenantly
destroyed by changing their shape!
•Denaturation is caused by:
• High temperatures
• Acidity (pH changes)
• Solvents (alcohols, like rubbing alcohol)
• Other chemicals that break the bonds inside the
protein that help it keep its shape
What role do enzymes play in living things?
 some important chemical reactions are
too slow or have a high activation energy
(require too much energy to start the reaction)
 catalysts – substances that speed up the
rates of chemical reactions
 enzymes are proteins that act as natural
catalysts
 enzymes are very SPECIFIC, catalyzing
only 1 chemical reaction.
 enzyme-substrate complex  where
reactant (substrate) meets enzyme &
enough energy is provided to start the
reaction
 substrate (reactant) binds to active site
on specific enzyme (complimentary fit –
like a lock & key)
 enzymes remain unchanged
Enzyme-substrate Complex
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html
Examples of Enzymes in the Digestive System
amylase
breaks down carbohydrates
(starch into disaccharides)
pepsin
breaks down proteins
lypase
breaks down fat
maltase,
Breaks down carbohydrates
sucrase, (disaccharides into monosaccharides)
lactase
Regulation of Enzyme Activity
 enzymes can be affected by
temperature and pH
 enzymes produced by human cells work
best at normal human body temperature
 stomach enzyme pepsin works best in
acidic conditions
•
•1.
.Concentration of substrate:
•2. Concentration of enzyme
• Harder for the substrate to
randomly find the active site on
the enzyme
•3.Temperature
• At higher temperatures molecules
move faster, so the substrate has
a better chance of finding the
active site.
• Like bumpercars—more collisions
when you hit the gas!
Digestive System
 food travels through many organs of the
digestive system
 broken down into usable nutrients
mouth: 1 minute
 mechanical digestion via teeth
 chemical digestion via amylase
esophagus: 2-3 seconds
 tube that leads to the stomach via
peristalsis
amylase
pepsin
stomach: 2-4 hours
mechanical digestion via muscle churning
 chemical digestion via pepsin
small intestine: 3-5 hours
 bile (made by liver & stored in gall bladder)
chemically breaks down fat along with lipase
 enzymes maltase, sucrase, and lactase
break down carbs
large intestine: 10 hrs – several days
 absorbs H2O and eliminates wastes
Lipase
maltase
sucrase
lactase
Obtaining Macromolecules thru the Food Pyramid