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