3.3 Cell Membrane KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

3.3 Cell Membrane

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

3.3 Cell Membrane

I can describe the structure of the cell membrane.

I can summarize how chemical signals are transmitted across the cell membrane.

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane has two major functions.

cell membrane

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane has two major functions.

– forms a boundary between inside and outside of the cell

cell membrane outside cell

inside cell

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane has two major functions.

– forms a boundary between inside and outside of the cell

– controls passage of materials

cell membrane outside cell

inside cell

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.

3.3 Cell Membrane

cell membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is made of a phospholipid bilayer.

3.3 Cell Membrane

cell membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is made of a phospholipid bilayer.• There are other molecules embedded in the membrane.

protein

cholesterol

proteincarbohydratechain

protein channel

3.3 Cell Membrane

cell membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is made of a phospholipid bilayer.• There are other molecules embedded in the membrane.• The fluid mosaic model describes the membrane.

protein

cholesterol

proteincarbohydratechain

protein channel

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is selectively permeable.

Some molecules can cross the membrane while others cannot.

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is selectively permeable.

Some molecules can cross the membrane while others cannot.

3.3 Cell Membrane

Chemical signals are transmitted across the cell membrane.• Receptors bind with ligands and change shape.• There are two types of receptors.

3.3 Cell Membrane

Chemical signals are transmitted across the cell membrane.• Receptors bind with ligands and change shape.• There are two types of receptors.

– intracellular receptor

3.3 Cell Membrane

Chemical signals are transmitted across the cell membrane.• Receptors bind with ligands and change shape.• There are two types of receptors.

– intracellular receptor– membrane receptor

3.3 Cell Membrane

1. Cholesterol is located between the fatty acid chains in the phospholipid bilayer. Do you think cholesterol is polar or nonpolar? Explain

2. Describe a semipermeable membrane with which you are already familiar.

3. How do intracellular receptors differ from membrane receptors?

4. Insulin helps cells take up sugar from the blood. Explain the effect on blood sugar levels if insulin receptors stopped working.