2.5 enzymes key concept enzymes are protein catalysts

2.5 Enzymes

KEY CONCEPTEnzymes are Protein Catalysts

2.5 Enzymes

A catalyst lowers activation energy.

• Catalysts are substances that speed up chemical reactions in 2 ways:– decrease activation energy needed to start the reaction– increase the speed of the reaction

2.5 Enzymes

A catalyst lowers activation energy.

Chemical reactions have 2 sides:

Reactants -----------------> Products

“hydrogen peroxide yields water and oxygen gas”

H2O2 --------------------> H2O + O2

2.5 Enzymes

First Five 10/29

1. Do you think enzymes can ever run out? Why or why not?

Schedule1.First Five2.Notes enzymes3.Play dough demo

HW: BioChem Review – Due Thurs. 10/31Test Packet – Due Friday 11/1Catalase lab – Due Friday

GQ: How do enzymes work?

2.5 Enzymes

Enzymes allow chemical reactions to occur safely and rapidly in all living cells.

Examples:

Enzyme names: What it speeds up:

Lactase breaks down lactose (a sugar)

Amylase breaks down amylose (a starch)

Peptidase breaks down polypeptides (proteins)

2.5 Enzymes

-An enzyme’s function depends on its protein structure.

-Changes in temperature and pH can denature enzymes.

-When its shape is lost it loses the active sites and it can’t work.

Remember-

2.5 Enzymes

Enzyme structure fits a specific molecule the way a key fits a specific lock.

2.5 Enzymes

1. The lock-and-key model shows an enzyme making a bigger molecule.

– substrates brought together at the active sites– bonds in substrates weaken, new bonds form in

product.

Substrates bind to anenzyme at certain places called active sites.

The enzyme bringssubstrates together and weakens their bonds.

The catalyzed reaction formsa product that is releasedfrom the enzyme.

Enzyme/substrate complex

2.5 Enzymes2. Induced Fit Model of an Enzyme that catalyzes

reactions to split larger molecules into smaller molecules.

Enzyme changes shape slightly to fit the substrate as it binds at active sites.

Bonds break in the substrate and products are released.

2.5 Enzymes

Induced Fit Enzyme Model for Monday’s Lab

H2O2 ----------> H2O + O2

Catalase enzyme puts stress on H2O2 so less energy is needed to break its bonds.

2.5 Enzymes

Pineapple and Gelatin