…and why are enzymes so important? What Happens to the Food You Eat?

n Bio = n Synthesis = –Biosynthesis is creating tissue, etc. from the foods/nutrients we eat n 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? n Decrease in blood nutrient levels is detected by HYPOTHALAMUS n Triggers release of digestive juices into stomach. n Feeling of hunger motivates you to find food!

“I Must Eat!!”

Steps In Human Digestion 1. MECHANICAL… Chewing Food a.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. M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? n Enzymes: proteins that speed up specific reactions IN THIS CASE---DIGESTION! n Enzymes act on substrates!

Enzymes n Complex molecules, proteins n Function: –Speed up chemical reactions that otherwise would take place slowly –Catalyst n Required in small amounts –Not used up n 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) H2OH2OO2O2 + (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 H2OH2OO2O2 + (substrate) (products)

5. Products are released. Products 4. Substrates are converted to products. 3. Active site can lower E A and speed up a reaction. 2. Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. 1. Substrates enter active site; enzyme changes shape such that its active site enfolds the substrates (induced fit). 6. Active site is available for two new substrate molecules.

Carbohydrates Q. Where are carbohydrates digested? Q. What is the enzyme that breaks carbohydrates down?

Proteins Q. Where are proteins digested? Q. What is the enzyme that breaks proteins down?

Lipids Q. Where are lipids digested? A. Pancreatic lipases Q. What is the enzyme that breaks lipids down?

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 of reaction without enzyme Free energy E A without enzyme E A with enzyme is lower Course of reaction with enzyme