…and why are enzymes so important?

What Happens to the Food You Eat?

Bio = Synthesis =

– Biosynthesis is creating tissue, etc. from the foods/nutrients we eat

Digestion is breaking down food– So that our bodies can utilize the nutrients

and molecules

Biosynthesis & Digestion

life

make

How does your body know when it is hungry? Decrease in blood nutrient levels is

detected by HYPOTHALAMUS

Triggers release of digestive juices into stomach.

Feeling of hunger motivates you to find food!

“I Must Eat!!”

Steps In Human Digestion

1. MECHANICAL…

Chewing Fooda. Surface area of food increases

b. Moistens food with saliva

c. Saliva contains the enzyme AMYLASE that breaks down the carb MALTOSE into the simple sugars (GLUCOSE) (this stage in chemical)

Food passes through esophagus into stomach. Moves via peristalis.

Break it down!!

CHEMICAL Enzymes break food down

Mouth enzymes called amylase break down carbohydrates into glucose

Stomach enzymes called PEPSIN break down proteins into amino acids.

Final Absorption…

3. Food enters small intestine. a. Carbs broken down by pancreatic amylase into simple sugars b. Proteins broken down by pancreatic proteases into amino acids c. Fats broken down by pancreatic lipases into simple fats/lipids d. Most absorption of nutrients takes place

here.

Elimination

4. Undigested food that cannot pass through walls of small intestine enters the Large Intestine.

a. Water is absorbed by cells

b. Body eliminates the compacted

solid waste!

How are large molecules broken down into small ones?

Enzymes: proteins that speed up

specific reactions

IN THIS CASE---DIGESTION!

Enzymes act on substrates!

Enzymes Complex molecules,

proteins Function:

– Speed up chemical reactions that otherwise would take place slowly

– Catalyst Required in small

amounts– Not used up

Naming enzymes– Usually end in -ase– Combine the name of

substrate with -ase– Examples

• Substrate Sucrose , enzyme sucrase

• Substrate Lactose, enzyme lactase

• Exception: Substrate hydrogen peroxide, enzyme catalase

“Lock and Key” or Induced Fit Enzymes are substrate specific…only certain enzymes will work on any given substrate

Enzyme

Substrate

Enzyme Function

(Hydrogen Peroxide)

H2O O2

+

(Products)

What happens to the enzyme?What happens to the substrate?

What is the relationship of substrate and product?

Catalase

Hydrogen Peroxide --> Water and Oxygen

H2O O2

+

(substrate) (products)

5. Products arereleased.

Products

4. Substrates areconverted toproducts.

3. Active site can lower EA

and speed up a reaction.

2. Substrates held in active site by weakinteractions, such as hydrogen bonds andionic bonds.

1. Substrates enter active site; enzyme changes shape such that its active siteenfolds the substrates (induced fit).

6. Activesite is

availablefor two new

substratemolecules.

Carbohydrates

Q. Where are carbohydrates digested?

Q. What is the enzyme thatbreaks carbohydrates down?

Proteins

Q. Where are proteins digested?

Q. What is the enzyme thatbreaks proteins down?

LipidsQ. Where are lipids digested?

A. Pancreatic lipases

Q. What is the enzyme thatbreaks lipidsdown?

Important Terms• A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction• An enzyme is a catalytic protein• The reactant that an enzyme acts on is called the enzyme’s substrate • The active site is the region on the enzyme where the substrate binds• The enzyme binds to its substrate, forming an enzyme-substrate complex• Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction

Progress of the reaction

Products

Reactants

Change in free energy

(∆G ) is unaffected

by enzyme

Course ofreactionwithoutenzyme

Fre

e en

erg

y

EA

withoutenzyme EA with

enzymeis lower

Course ofreactionwith enzyme