Unit 3:CELLS

Cellular Energy

Carbon Compounds

Objective• What are the functions of each

group of organic compounds?

• Most of the compounds that make up living things contain carbon. In fact, carbon makes up the basic structure, or “backbone,” of these compounds. Each atom of carbon has four electrons in its outer energy level, which makes it possible for each carbon atom to form four bonds with other atoms.

• As a result, carbon atoms can form long chains. A huge number of different carbon compounds exist. Each compound has a different structure. For example, carbon chains can be straight or branching. Also, other kinds of atoms can be attached to the carbon chain.

Section 2-3

Interest Grabber

Life’s backbone

Methane Acetylene Butadiene Benzene Isooctane

Macromolecules “giant molecules”

• Formed by a process called polymerization

Monomers• Smaller units

Polymers• Linked up monomers

Carbohydrates• Compounds made up of carbon,

hydrogen, and oxygen atoms usually in a ratio of 1:2:1

• Main source of energy

• The monomers of starch are sugars

• Single sugar molecules are called monosaccharides

• The large macromolecules formed from monosaccharides are known as polysaccharides

Starch

Glucose

Lipids• Made mostly from carbon and

hydrogen atoms

• Used to store energy

Lipid Glycerol

Fatty Acids

Proteins• Macromolecules that contain

nitrogen as well as carbon, hydrogen, and oxygen

• Proteins are polymers of molecules called amino acids

Amino Acids

General structure Alanine Serine

Carboxyl group

• More than 20 different amino acids, can join to any other amino acid

• The instructions for arranging amino acids into many different proteins are stored in DNA

• Each protein has a specific role• The shape of proteins can be very

important

Proteins

Amino Acids

Nucleic Acids• Macromolecules containing hydrogen,

oxygen, nitrogen, carbon, and phosphorus

Double Helix

Nucleotides• Consists of 3 parts: 5-carbon sugar,

phosphate group and nitrogen base

Nitrogen Base

5-Carbon Sugar

Phosphate group

2 kinds of nucleic acids• RNA (ribonucleic acids) –

contains sugar ribose

• DNA (deoxyribonucleic acid) – contains sugar deoxyribose

Homework

1. Name four groups of organic compounds found in living things

2. Describe at least one function of each group of organic compounds

3. Compare the structures and functions of lipids and starches

Chemical Reactions and Enzymes

Objectives• What happens to chemical bonds

during chemical reactions?

• How do energy changes affect whether a chemical reaction will occur?

• Why are enzymes important to living things?

The Big Idea• Living things are made up of

chemical compounds

• Everything that happens to an organism is based on chemical reactions

Chemical Reactions• A process that changes or

transforms one set of chemicals into another

Reactants• Elements or compounds that

enter into a reaction

Products

• Elements or compounds produced by a chemical reaction

Example Reaction: Getting rid of carbon dioxide

• In the blood

• In the lungs

CO2 + H20 H2CO3 (carbonic acid)

H2CO3 CO2 + H2O

Released as you breathe

Energy in reactions Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Products

Activation energy

Activation energy

Reactants

Reactants

Activation Energy• The energy that is needed to get

a reaction started

Enzymes• Some chemical reactions are too

slow or have activation energies that are too high to make them practical for living tissue

• These chemical reactions are made possible by catalysts

Catalyst• Substance that speeds up the

rate of chemical reactions

• Work by lowering a reactions activation energy

Enzyme• Biological catalysts

• Speed up reactions in cells

• Very specific

• Named for the reaction is catylzes

• Enzyme names always end in -ase

Reaction pathwaywithout enzyme Activation energy

without enzyme

Activationenergywith enzyme

Reaction pathwaywith enzyme

Reactants

Products

Substrates• The reactants of enzyme

catalyzed reactions

• The active site of the enzyme and the substrate have complementary shapes

• Fit like a lock and key

Enzyme Action

Enzyme – substrate complex

Glucose

Substrates

ATP

Substratesbind toenzyme

Substratesare convertedinto products

Enzyme-substratecomplex

Enzyme(hexokinase)ADP

Products

Glucose-6-phosphate

Productsare released

Active site

Regulation of Enzyme Activity

• Enzymes are affected by any variable that affects chemical reactions

1. pH

2. Temperature

3. Concentration

of enzyme

Homework

1. What happens to chemical bonds during chemical reactions

2. Describe the role of energy in chemical reactions

3. What are enzymes, and how are they important to living things?

4. Describe how enzymes work, including the role of the enzyme substrate complex

5. A change in pH can change the protein. How might a change in pH affect the function of an enzyme such as hexokinase (hint: think about the analogy of the lock and key)