Chapter 3: Cellular Level of Organization

Introduction Smallest unit performing vital physiological functions Sex Cells Somatic Cells Homeostasis maintained at cellular level

Fluid Mosaic

Membrane Flow Continuous movement and exchange across membrane Change in response to environmental changes Membranes are Green!

Membrane Transport

Why is membrane transport important? How does membrane transport happen?

Membrane Permeability Selectively permeable Passive diffusion Facilitated diffusion Active Transport Endocytosis and exocytosis

Diffusion Even distribution of molecules Movement from high to low concentration Enfluencing factors: Distance Molecule size Temperature Gradient size Electricle forces

Passive Diffusion Movement of molecules down the gradient Small lipid soluable molecules Gases, steroid hormones, chemotherapy drugs, alcohol No energy is needed

Facilitated Diffusion Integral membrane proteins Uniporters Molecules are transported down the gradient No energy is needed Specific Saturation limits

Active Transport Primary Active Transport Pumps Energy (ATP) is needed Secondary Active Transport Carriers Channels

Active Transport: Pumps Small ions and molecules Use ATP Transportation is against the gradient Saturation limits Na+/ K+ Pump Maintain proper ion concentrations Electrochemical gradient

Active Transport: Carriers Transport ions and small molecules Specific and have saturation limits Use gradient created by pumps Movement with gradient Secondary Active Transport Cotransport of molecules Symporters Antiporters

Osmosis

Animation Endocytosis and Exocytosis

Animation Summary Plasma membrane is semipermeable Pumps use ATP as an energy source to establish concentration gradients Channels and carriers need concentration gradient created by pumps to transport Membrane Transport is important in order to maintain proper concentrations of ions and molecules Endocytosis and exocytosis move very large molecules into and out of the cell

Electro-Chemical Gradient

Membrane Receptors Chemical (Ligand) Gated Mechanically Gated Voltage Gated G-Protein Coupled

Cell Environment Interactions It is important for cells to interact with their environment Cell Adhesion Molecules (CAMS) Anchor to surrounding tissue Allow cell to “walk” ( ) Signal other cells ( ) Sensors

Life Cycle of the Cell