Unit 1: Wellness and Homeostasis Cells and Homeostasis Unit 1: Wellness and Homeostasis

Life Processes Complex organisms need to carry out the following (six) life processes: Obtain food Convert Energy Eliminate wastes Reproduce Grow & Repair Transport Substances Individual cells must also carry out ALL of these life processes

The Cell Theory The modern cell theory has three main principles: 1. All organisms are composed of one or more cells. 2. Cells are the basic unit of structure and organization of organisms. 3. Cells arise by the division of pre-existing cells.

Two Basic Cell Types: 1. Prokaryotic Cells No true nucleus Lacks (membrane-bound) organelles E.g. Bacteria

Prokaryotic Cell

Two Basic Cell Types: 2. Eukaryotic Cells Have a true nucleus Contain membrane-bound organelles, therefore, cell functions are separated into distinct compartments and can be carried out simultaneously. E.g. Fungus, Plants, Animals **We will focus on humans, therefore, eukaryotic cells.

Eukaryotic Cell

Cell/Plasma Membrane We will be only focusing on this part of the cell

Overview… Four Main Functions of Cell Membrane: 1. Thin, molecular layer that surrounds all living cells 2.  Separates the cell from its external environment 3. Protects the cell from changes in the chemical and physical environment

Overview… 4. Regulates the traffic of molecules into and out of the cell: Prevents unwanted materials from entering Transports raw materials into cell Transports manufactured products and wastes out of cell - Prevents escape of matter needed to perform cellular functions

Overview… Composed primarily of two types of molecules: LIPIDS – fatty & oily molecules PROTEINS

Structure The basic structure of the membrane is formed by two sheets of lipids (phospholipids), each sheet a single molecule thick. Hydrophilic Head (water loving) Hydrophobic Tails (water fearing) Hydrophilic Head (water loving) Phospholipids are the most abundant lipids in most membranes due to its possession of both hydrophilic and hydrophobic ends

Fluid Mosaic Model In the Fluid Mosaic Model, the cell membrane is composed of a double layer (bilayer) of phospholipids into which protein molecules are embedded. Proteins are responsible for: -Transporting substances across the membrane -Aiding communication between cells. -Carrying out chemical reactions.

Fluid Mosaic Model It is “fluid” because it is flexible – the phospholipids and proteins move within the membrane It is “mosaic” because the proteins create a ‘pattern’ on the membrane surface You Tube: Fluid Mosaic Model: http://www.youtube.com/watch?v=ULR79TiUj80