Denature proteins Enzymes & Digestion Page 48, 99-105 662-670
Jan 21, 2016
Denature proteinsEnzymes
&
Digestion Page 48, 99-105
662-670
Protein structure (review)
amino acid sequence
peptide bonds
1°
determinedby DNA R groups
H bonds
R groupshydrophobic interactions
disulfide bridges(H & ionic bonds)
3°multiple
polypeptideshydrophobic interactions
4°
2°
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
Sickle cell anemia
I’mhydrophilic!
But I’mhydrophobic!
Just 1out of 146
amino acids!
Protein denaturation• Unfolding a protein
– 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
In Biology,size doesn’t matter,
SHAPE matters!
•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.mcgraw-hill.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,sucrase,lactase
Breaks down carbohydrates(disaccharides into monosaccharides)
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 hoursmechanical 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
maltasesucraselactase
Obtaining Macromolecules thru the Food Pyramid