THE PLASMA MEMBRANE Structure and Function PLASMA MEMBRANE

THE PLASMA MEMBRANE Structure and Function

PLASMA MEMBRANE Function: Maintains homeostasis by controlling substances entering & leaving the cell.

THINK-PAIR-SHARE WHAT KINDS OF SUBSTANCES MIGHT NEED TO ENTER OR LEAVE THE CELL?

A cell must take in and keep needed materials, such as glucose, while maintaining a balance with its surroundings.

A cell must remove wastes and keep harmful substances from entering.

SELECTIVE PERMEABILITY The property of a membrane that allows some materials to pass through while keeping others out.

STRUCTURE OF THE PLASMA MEMBRANE

outside cell cytoplasm

1) CHOLESTEROL Stabilizes the membrane by preventing phospholipids from sticking together

2) TRANSPORT PROTEINS help move large molecules across the membrane

3) Carbohydrates are used for cell recognition and attachment

4) PHOSPHOLIPIDS

PHOSPHOLIPIDS Phosphate head Phosphate “attracted to water” Phosphate + glycerol hydrophilic “attracted to water” 2 Fatty acid tails hydrophobic “repelled by water” Fatty acid “repelled by water”

Phospholipids are arranged in a bilayer Hydro________ HYDRO______ __

Phospholipids are arranged in a bilayer

PHOSPHOLIPIDS MOVE AROUND The phospholipids can move sideways through their layer, but not from one layer to the other.

Name given to this model of the plasma membrane. Fluid because the phospholipids are free to move within the membrane. Mosaic because of the pattern it produces when viewed from above.

Plasma Membrane TALK TO A PARTNER Carbohydrates, transport proteins, cholesterol, phospholipids, bilayer, cytoplasm, outside cell

QUESTIONS? ? ?

WHAT DOES IT MEAN THAT A CELL MEMBRANE HAS A LIPID BILAYER?

WHAT IS THE FUNCTION OF THIS STRUCTURE?

DESCRIBE THE 2 COMPONENTS OF THIS STRUCTURE

Which of the following best describes the plasma membrane's mechanism in maintaining homeostasis? A. protein synthesis B. selective permeability C. fluid composition D. structural protein attachment

Why do the phosphate heads point outward and the fatty acid tails point inward? Phospholipid molecule Nonpolar tails (fatty acids) Polar head (includes phosphate group)

Explain why the model of the plasma membrane is called the fluid mosaic model.

CORNELL SUMMARY