Chapter 3 Cell Structure

Chapter 3A Cell Membranes

A. Describing Cell Membranes I. Cell Membranes A. Describing Cell Membranes

Cytology The study of cells

A. Describing Cell Membranes 1. Outer boundary of the cell 2. Senses and responds to changes in the environment

A. Describing Cell Membranes Protects cell from harmful substances Porous - allows needed materials into the cell

A. Describing Cell Membranes 3. Fluid mosaic model Phospholipids Hydrophilic Hydrophobic Lipid bilayer “bi-” means two

A. Describing Cell Membranes 4. Selectively Permeable

Selectively Permeable A selectively permeable membrane allows certain molecules to pass through the membranes and others to not pass through

B. Transport Across the Membrane I. Cell Membranes B. Transport Across the Membrane

B. Transport Across the Membrane Passive transport a) moves substances through a membrane without the use of the cell’s own energy.

B. Transport Across the Membrane Passive transport b) 2 types * diffusion

Diffusion The movement of molecules from a place where there are many of those molecules to a place where there are few of them

Diffusion

B. Transport Across the Membrane Passive transport b) 2 types * diffusion * osmosis

Osmosis The diffusion of water through a selectively permeable membrane

Osmosis

B. Transport Across the Membrane 2. Active transport a) requires the cell to use its own energy to move substances through a membrane.

Transport Comparison Passive Transport Active Transport Molecules move from higher to lower concentration Does not require the cell to use energy Molecules move from lower to higher concentration Requires the cell to use energy