Chapter 3

Cells Lecture B

Membrane Transport: Active Processes

Two types of active processes

Active transport Vesicular transportActive Transport

Sodium-potassium pump

Vesicular Transport

Functions:

Exocytosistransport out of cell

Endocytosistransport into cell

Phagocytosis, pinocytosis, receptor-mediated endocytosis

Endocytosis

Phagocytosis Pinocytosis

Receptor-mediated endocytosisExocytosis

Cell-Environment Interactions

Cells interact directly or indirectly by responding to extracellular chemicals

Always involves glycocalyx

Cell adhesion molecules (CAMs)

Plasma membrane receptors

Voltage-gated channel proteins

Roles of Cell Adhesion Molecules

Thousands on approximately every cell in body

Anchor to extracellular matrix or each other

Assist in movement of cells past one another

Attract WBCs to injured or infected areas

Stimulate synthesis or degradation of adhesive membrane junctions

Transmit intracellular signals to direct cell migration, proliferation, and specialization

Roles of Plasma Membrane Receptors

Contact signalingtouching and recognition of cells; e.g., in normal development and immunity

Chemical signalinginteraction between receptors and ligands (neurotransmitters, hormones, and paracrines) to alter activity of cell proteins (e.g., enzymes or chemically gated ion channels)

Same ligand can cause different cell responses

Response determined by what receptor linked to inside cell