Cell Membrane Transport

GPS StandardsSAP1. Students will analyze anatomical

structures in relationship to their physiological functions.d. Relate cellular metabolism and transport to

homeostasis and cellular reproduction.

Learning Goals

By the end of this section, you will be able to: Describe the components of the cell

membrane and their functions. Relate cellular transport to homeostasis. Differentiate between passive transport

processes and active transport processes.

Medical Terminology

Use prefixes, suffixes, and roots sheet to define the following:• bi-• endo-• exo-• extra-• hydro-• inter-• intra-• phago-• pino-• trans-• -osis• -philic• -phobic• cyt• integral• peripheral

Use prefixes, suffixes, and roots to define the following:

• transport

• bilayer

• extracellular

• endocytosis

• exocytosis

• hydrophilic

• hydrophobic

• integral protein

• intracellular

• peripheral protein

• phagocytosis

• pinocytosis

prefix suffix root

The Cell Membrane

The cell membrane is a selectively permeable membrane that determines which molecules can come into the cell and which molecules can leave the cell.

Nucleus

Cell Membrane

Transverse Section of the cell

membrane

The Cell Membrane

Cell Membrane Components

1. Phospholipid bilayer– Made up of

• Hydrophilic head• Hydrophobic tail

– Allows small molecules, like water and gases, to pass through the membrane easily

Cell Membrane Components Continued

2. Proteins– Integral proteins

• Permanently imbedded in the membrane• Used as carrier proteins for large molecules

– Peripheral proteins• Loosely bonded to the internal and external

surfaces of the membrane• Mainly used in cell to cell communication and the

immune response

Passive Transport

• A process that moves molecules across the cell membrane without energy from the cell

• Moves molecules from high to low concentrations

• Like riding a bike downhill

• Processes– Diffusion– Osmosis– Facilitated Diffusion

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration.

Diffusion

Osmosis

• The diffusion of water across a selectively permeable membrane.

• Osmotic solutions can be– Hypotonic (hypo- means “less than”)

– Isotonic (iso- means “the same”)

– Hypertonic (hyper- means “more than”)

Hypertonic Isotonic Hypotonic

Osmosis

Cells in Osmotic Solutions

Facilitated Diffusion

The diffusion of molecules across a membrane with the help of transport molecules imbedded in the cell membrane.

Facilitated Diffusion

Facilitated Diffusion

Active Transport

• A process that drives large molecules across the cell membrane from a region of lower concentration to a region of higher concentration

• Like riding a bike uphill

• Processes– Endocytosis– Exocytosis– Ion Pumps

Endocytosis

• Molecules are brought into the cell by vesicles formed from the cell membrane

• Processes– Pinocytosis. The cell takes tiny droplets

from its surroundings into tiny vesicles. – Phagocytosis. The vesicle engulfs food

particles that are digested by lysosomes.

Endocytosis

Exocytosis

• Molecules are forced out of the cell by vesicles made by the Golgi apparatus

Exocytosis

Exocytosis

Ion Pumps

Ion pumps use integral proteins and energy (ATP) to transport ions, such as sodium (Na) and potassium (K) across the membrane.