Cellular Transport: Cell Membrane How Molecules Are Transported Across The Cell Membrane.

Essential Questions How do cells maintain homeostasis? How are cell membranes (plasma membranes) selectively permeable (semi-permeable)? Why is it important that cells are able to transport molecules with (active transport) and without (passive transport) energy?

Cell Membranes Functions: a.Controls what enters and exits the cell to maintain homeostasis b.Provides protection and support for the cell TEM picture of a real cell membrane.

What is the purpose of cellular transport? Homeostasis depends upon appropriate movement of materials across the cell membrane. The cell membrane regulates the passage of materials into and out of the cell. –Needed (required) materials move in Ex. Oxygen and glucose –Excess materials or wastes move out Ex. The CO 2 produced as waste product of cellular respiration

How? A cell membrane is semi-permeable (selectively permeable) – means some substances can pass directly through cell membrane while other substances can not. Materials enter or exit through the cell membrane either passive transport or active transport.

What is a membrane made of? Phospholipid – lipid made of a phosphate group and 2 fatty acids. –1 polar head – phosphate group Hydrophilic -loves water – 2 non-polar tails - fatty acids Hydrophobic -hates water Draw in Journal

Lipid bilayer – double layer of phospholipids –polar head of one faces outside and other faces inside of cell –Non-polar tails face towards each other inside bilayer Draw in Journal

Membrane Proteins – allows large substances in cell –located in lipid bilayer –made of amino acids which contain polar and non-polar sides Non-polar repelled by water on both sides of bilayer, this holds proteins in place. – proteins able to move along bilayer

Phospholipids and proteins in plasma membrane can move (drift lateally) within bilayer This ability for the cell membrane to be fluid is called the Fluid Mosaic Model Membrane movement animation Fluidity of Membranes