Eat like a birdYou hear it about people who don’t eat much. People say they “eat like a bird.” Yet birds eat a larger proportion of their weight every day than even the heartiest human eaters.

Birds eat a high-energy diet of seeds, fruit, worms, insects, fish or meat---maximum energy, minimum bulk. Digestion is fast and thorough.

Food energy is spent in flight, in keeping warm-----in simply being a bird.

What is the relationship between an animal’s metabolism and the amount of food it eats? Use a comparison between birds and humans in your answer. (look in your glossary for the word metabolism)

Macromolecule Review

• 4 major groups

• Monomers & Polymers

• Functions

Concept: Enzymes

• Lesson Essential Question: How would a change in enzyme activity affect a living system?

• To understand enzymes, we have to understand basic chemistry including chemical reactions and how living things use macromolecules to chemically obtain energy for life’s functions.

Chemical Reactions & Energy

• Energy is stored or released by chemical reactions

• Bonds are broken and new bonds formed between atoms

• Different substances can be produced• Reactants are the starting materials for

chemical reactions• The newly formed substances are called

products.

Chemical Reactions

• Chemical reactions are summarized by chemical equations

• Example: 6CO2 +6H2O+sunlight energyC6H12O6 + 6O2

Reactants Products

• Arrow is read as “yields” or “forms”

Chemical Reactions

• Chemical reactions can release energy or absorb energy (also see fig. 6-15 & 6-16 in text)

Example: fossil fuel burning, respiration

Example: photosynthesis

Chemical Reactions & Life

• Metabolism is all of the chemical reactions that occur within an organism.

• Your cells get energy needed for metabolism from the food you eat.

• Chemical energy is converted into a useable form.

Chemical Reactions

• Energy is needed to start chemical reactions; we call this activation energy

• STOP: SUMMARIZE CHEMICAL REACTIONS in “Note Making” by yourself, then SHARE WITH LAB PARTNER

Enzymes

• All reactions need energy to start…called activation energy

• Catalysts are substances that speed up the rate of chemical reactions

• Enzymes are proteins that act as biological catalysts, greatly speeding up reactions in cells.

• Allows reactions to occur at much lower temperatures than normal…important for living things!

Enzymes

Enzymes, cont.

• Enzymes work because they provide a site where reactants can interact.

• The reactants in this case are called substrates• Figure 6.18 in text show how substrates bind to

the active site on the enzyme, react and then the products are released.

• Released products are things cells need to function… molecules big and small, regulating metabolism, releasing energy, etc.

Enzyme Action