III. Chemistry, Lipid structure, and Cell Boundaries Chemistry – study of the composition, properties, & changes of substances. Inorganic Chemistry – study of all compounds that don’t contain carbon. -Inorganic compounds don’t contain carbon, ex : H 2 O, NaCl, etc. -2 exceptions : CO 2 & CaCO 3 (in rocks) Organic Chemistry – study of all compounds that contain carbon. -Organic compounds contain carbon, ex : CH4.

A. The Chemistry of Carbon 1. Carbon has 4 valence electrons for bonding. 2. Carbon can bond with other carbon atoms to form carbon chains. 3. Carbon can form large, complex molecules, ex : Chains form rings.

B. Macromolecules : “Giant molecules” -Living cells contain large molecules known as macromolecules or giant molecules. -Are formed by polymerization – process of building large compounds by joining smaller ones together. Monomer – small units that can join together to form polymers. Polymer – large compound formed from combinations of monomers.

C. Lipid structure Recall : Lipids – macromolecules made mainly from carbon made mainly from carbon & hydrogen atoms & & hydrogen atoms & glycerol; includes fats, oils, glycerol; includes fats, oils, waxes, phospholipids, & waxes, phospholipids, & steroids. steroids.

Body Use of Lipids The body uses lipids to : The body uses lipids to : Get extra fuel 9 kcal/gram. Get extra fuel 9 kcal/gram. Build cell membrane parts. Build cell membrane parts. Provide insulation for the winter Provide insulation for the winter or cold environments. or cold environments. Give padding to organs. Give padding to organs. Waterproof the skin, ears, etc. Waterproof the skin, ears, etc. Make hormones. Make hormones. -Can be found in : meats, oils, milk, nuts, and egg yolks.

Saturated vs. Unsaturated Fats *Lipids include 2 types of fats : Saturated vs. Unsatured. Saturated – having all single carbon to carbon bonds in the fatty acid (C – C). Is bad fat that is solid at room temperature and tends to be room temperature and tends to be stored in animals, ex : butter. *These stored in animals, ex : butter. *These build up in our bodies & are solids that increase cholesterol.* Unsaturated – having 1 or more pairs of carbon to carbon double or triple bonds in the fatty acid. This is healthier fat that tends to by liquid at room temperature, ex : olive oil.

Polyunsaturated Fats Polyunsaturated – having more than 1 double or triple bond in the fatty acid. -Lipids also include cholesterol, which is made by the liver and can accumulate, leading to heart attacks if over 200. What is the correct amount of lipids that the body needs? Answer : 30% of diet.

D. Cell Boundaries *Cell borders separate the cell from its environment. May be : Cell membrane – a thin, flexible barrier found around all cells. Cell wall – a strong supporting layer around cell membranes in plant cells. 1. The Cell Membrane -Cell membranes regulate what enters & leaves the cell (selectively permeable). It also provides protection/support. -Is made up of a double-layered sheet called a lipid bilayer (2 layers of flexible lipids). Mostly lipids & proteins.

Structure of the Cell Membrane -Proteins are found embedded in the lipid bilayer, some with carbohydrate chains attached. -The bilayer contains phospholipids, molecules with a phosphate head & a lipid tail. -The phosphate head is hydrophilic (water-loving) & the lipid tail is hydrophobic (water fearing).

Cell Membrane : Fluid Mosaic Model -Cell membranes are fluid : proteins & lipids are constantly in motion. -Because cell membranes are fluid & have patterns (mosaics) of proteins & other molecules in them, scientists refer to the structure of the cell membrane as the Fluid mosaic model.

2. Cell Walls Main function : to provide support & protection for the cell. -Found in plants, algae, fungi, & some prokaryotes. -Are made mostly of cellulose, a tough carbohydrate fiber.