Macromolecules

Objectives

· Summarize and describe the basic molecular structure and primary functions the four macromolecules (carbohydrates, lipids, proteins, and/or nucleic acids.

· Create 3D models of each of the biological macromolecules

· Match the structure of a macromolecule to its correct function.

· Identify the primary functions of carbohydrates, lipids, proteins, and/or nucleic acids in organisms.

· Compare and contrast the importance of the different biological macromolecules in an organism

2.1 The Nature of Matter

Atoms

The atom is the basic unit of matter, made up of three subatomic particles.

• Protons have a positive charge and neutrons carry no charge. Strong forces bind protons and neutrons together in the nucleus.

• An electron is a negatively charged particle that has only about 1/1840 the mass of a proton. Electrons constantly move around the space surrounding the atom’s nucleus.

• Because an atom has the same number of protons and electrons, if it is electrically neutral.

Elements and Isotopes

A chemical element is a pure substance that consists entirely of one type of atom.

• Atoms of the same element that differ in the number of neutrons are called isotopes. Isotopes are identified by their mass number, the total number of protons and neutrons in the nucleus. Because they have the same number of electrons in each atom, all isotopes of an element have the same chemical properties.

• Radioactive isotopes have unstable nuclei and break down at a constant rate.

Chemical Compounds

A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed. Scientists use formulas to show the ratio of elements that make up a compound.

Chemical Bonds

The atoms in compounds are held together by chemical bonds. Electrons that are available to form bonds are called valence electrons.

• An ionic bond forms when one or more electrons are transferred from one atom to another, forming ions. An atom that loses electrons becomes positively charged. An atom that gains electrons becomes negatively charged.

• A covalent bond forms when electrons are shared rather than transferred. The structure formed by atoms joined by covalent bonds is called a molecule. The molecule is the smallest unit of most compounds.

• When molecules are close together, a slight attraction can form between the oppositely charged portions of nearby molecules. These intermolecular forces of attraction are called van der Waals forces.

2.3 Carbon Compounds

The Chemistry of Carbon

Organic chemistry is the study of compounds with bonds between carbon atoms. Carbon atoms have four valence electrons, allowing them to form strong covalent bonds with many other elements, including hydrogen, oxygen, phosphorus, sulfur, and nitrogen. Living organisms are made up of molecules made of carbon and these other elements.

• One carbon atom can bond to another to form chains and rings.

• Carbon can form millions of different large and complex structures.

Macromolecules

Many of the carbon molecules in living things are so large they are called macromolecules. Macromolecules form by polymerization, in which smaller units called monomers join together to form polymers. Biochemists sort the macromolecules in living things into groups based on their chemical composition.

Practice Problems