Homeostasis/molecules of life: SHS 3.7.2, 3.1.2

*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