Chapter 2: How Cells Function 2.1: Chemical reactions take place inside cells 2.2: Cells capture and release energy 2.3: Materials move across the cell’s membranes Will learn: -About the types of elements found in all cells -the functions of the large molecules in the cell -Why water is important to the activities of the cell Have already learned: -All living things are made of cells -Cells need energy to sustain life -Plant and animal cells have similarities and differences

Warm-up Questions True for animal cells, plant cells, or both? They need energy to sustain life They have organelles They have cell walls

All cells are made of the same elements The matter that makes up the cell itself is too small for a light microscope All matter broken down into elements, each with own characteristics Example: Oxygen, on Earth, found as colorless odorless gas 25 elements (of ~100 on Earth ) are essential for life 6 elements account for about 99% of the mass of our bodies! Oxygen: 65%, Carbon: 18.5%, Hydrogen: 9.5%, Calcium: 1.5%, Phosphorus: 1.0%, all other 19: 1.2%

Elements Smallest unit of an element: atom In our body: RANK- simple to complex: cell, atom, molecule Smallest unit of an element: atom In our body: mostly in the form of compounds – atoms of two or more elements chemically bonded O + O = O2 C + O + O = CO2 Most cellular activities: atoms and molecules interacting via chemical reactions (bonds broken and formed to make new molecules) Need and release energy! Chemical energy!

Large molecules for cell function 1) Carbohydrates 2) Lipids 3) Proteins 4) Nucleic Acids ALL have carbon atoms Work together in a cell

Carbohydrates Provide the cell with energy Also structure Breaking the bonds within the cell releases energy Simple carbohydrates – carbon, oxygen, hydrogen Complex carbohydrates – simple linked into chains: starch, cellulose, glycogen Plants: energy not used makes starches and cellulose (cell wall) Animals eat plants and get energy http://www.npr.org/templates/story/story.php?storyId=130731888

Lipids Fats, oils, and waxes Similar to carbohydrates, also made of carbon, oxygen, and hydrogen Cells use lipids for energy and making structures Atoms arranged differently than carbohydrates Do not dissolve in water! Cannot mix with water (important for cell membranes…)

Proteins Made of amino acids Carbon, oxygen, hydrogen, nitrogen, and sometimes phosphorus and sulfur Linked into long chains, folded into 3-D shapes Structure and function determined by type, number, and order of the amino acids We get amino acids from food: meats, eggs, cheese, beans, or created by body Different types: enzymes (control chemical reactions in cells), others support growth and repair, muscle movement, fight infections, deliver oxygen, form part of the cell membranes

Nucleic Acids Hold instructions for the maintenance, growth , and reproduction of a cell DNA – Deoxyribonucleic acid RNA – Ribonucleic acid Both made of carbon, oxygen, hydrogen, nitrogen, and phosphorus. Subunits called nucleotides DNA: information used by the cell for making all the protein the cell needs Nucleotide pattern in DNA is copied to RNA, which delivers information into the cytoplasm…where it controls chemical reactions and form structures.

Two thirds of all cells is water All chemical reactions inside the cell take place in water Water makes up: 46% of body’s mass inside cells 23% outside cells in body fluids Polar: slight positive charge near hydrogen atoms, slight negative near oxygen Attract opposite charges, repel like Many substances dissolve in water

Water & Cells Most lipids do NOT dissolve in water Cell membrane is made of a double layer of lipids Head is polar, tail is not polar Cell membrane is a boundary, keeping the inside of a cell separate from the outside Water-hating tails repel water