Homeostasis/molecules of life: SHS 3.7.2, *cell functions involve specific chemical reaction *homeostasis is the dynamic regulation and balance of an organisms internal environment to maintain condistions suitable for survival

Homeostasis: The ability the body has in regulating its internal environment despite any changes in the external environment The body uses different systems to monitor and maintain homeostasis-the brain and its neurons (nervous system) and our glands and their hormones (endocrine system) are main examples

Homeostatic example *An example would be your body temperature staying at 98.6˚ despite it being 30˚ outside. This is due to the “thermostat” in your brain detecting whether you need to shiver or sweat to heat or cool your body

Dogs and homeostasis Dogs pant to keep their bodies from overheating

Reptiles and homeostasis Reptiles lay in the hot sun to increase their body temperature

Cell transport and homeostasis Transport of substances across membranes is related to maintaining body homeostasis-red blood cells swell as water rushes in when placed in pure water. They shrink from water rushing out when placed in salt water (osmosis)

Molecules of Life Most molecules of a cell are carbon based Its basic structure is the foundation of the wide range of life’s molecules

Molecules of Life Monomers Small molecular unit that is the building block of a larger molecule Polymers Every living cell has thousands of polymers They are a chain of smaller molecular units (monomers)

Examples of monomers making a polymer Polysaccharides are made from monosaccharides Proteins are made from amino acids Nucleic acids (DNA and RNA) are made from nucleotides

Four main categories of large molecules 1. carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids

Carbohydrates Organic compound made of sugar molecules Main fuel supply for cellular work

Types of sugars Monosaccharide-simple sugars with only one sugar unit (glucose, fructose) Disaccharides-double sugar from two monosaccharides (sucrose) Polysaccharides-long chains of simple sugars monomers or complex carbohydrates (starch, glycogen, cellulose)

Lipids Water avoiding compound-hydrophobic- Known as fats and store energy in your body Examples: fats and steroids (cholesterol)

Proteins Polymer constructed from a set of 20 kinds of monomers called amino acids Responsible for all functions of an organism Form hair, fur, muscles, nutrient storage, defend body from microorganisms, convey messages from cell to cell

Enzymes Group of specialized proteins Cellular reactions depend upon catalysts to speed up chemical reactions Enzymes allow cells to perform reactions without raising their temperature to dangerous levels- enzymes lower the activation energy (energy to start a chemical reaction) for the reaction to take place

Enzymes cont. Enzymes act upon only specific reactions Their shape determines which reactant they act upon-its structure and shape determines its function-this is sensitive to changes in the environment