Passive and Active Transport

Passive and Active Transport

FOS 3 Infectious Disease Unit

FOS 3 Infectious Disease Unit

Homeostasis When organisms adjust internally to

changing external environments One way to maintain homeostasis is by

controlling the movement of substances across the cell membrane.

Transport Across Membranes

Active transport is pumping against the concentration gradient

3 types of Passive TransportDiffusion, Osmosis and Facilitated Diffusion

Diffusion Diffusion is movement from an area of high

concentration to low concentration Diffusion is passive transport: NO energy is

required!

Passive Transport- Diffusion Oxygen, Carbon

dioxide, water and amino acid molecules are small enough to diffuse.

Proteins, carbohydrates, and other ions are too large to diffuse.

Passive Transport-Diffusion

Passive Transport

Simple Diffusion Across Bilayers

Pas

sive

Tra

nsor

t- O

smos

isMore water

Less water

Osmosis: Water down Conc. Gradient

Tonicity

More solute in than out

Passive Transport- Facilitated Diffusion

Some ions diffuse through channel proteins. The pores can always be open or open in response to a stimulus. No energy is required so this is still passive transport.

Passive Transport- Facilitated Diffusion

Passive Transport- Facilitated Diffusion

Passive Transport- Facilitated Diffusion Transport of substances through the cell

membrane down a concentration gradient aided by carrier or channel proteins.

Active Transport Transport against the concentration

gradient that requires energy

Active Transport: Sodium-Potassium Pump

Electrochemical Gradient An electrochemical gradient is a

concentration gradient with ions: These ions want to move down their

concentration gradient These ions also want to move towards the

opposite charge found on the other side of the membrane.

This attraction for the other side of the membranes (membrane potential) can be harnessed to do work.

Active Transport- Electrogenic Pump

Active Transport- Cotransport

Movement “Across” Membrane

Endocytosis and Exocytosis These are mechanisms that involve

movement into and out of the lumen of the endomembrane.

NOT movement directly across the membrane

Substances enter the endomembrane system but not the cytoplasm!

Endocytosis Phagocytosis

Taking up solids Allows digestion in confined space

Phagocytosis Pictures

Exo

cyto

sis

Hormones Chemicals secreted by cells that act to

regulate the activity of other cells in the body.

Four Functions: Regulate processes, like growth and

development Coordinate production, use and storage of

energy. Maintaining Homeostasis React to stimuli outside the body

Hormones Two types:

Amino Acid Hormones Steroid Hormones

Lipid hormones

Hormones- Amino Acid How they work:

Bind to a receptor protein on the Cell Membrane, the receptor membrane changes shape

The shape changes causes a second messenger which causes a change in the target cell

Hormones-Steroid Hormones How it works:

Steroid Hormone is release, it diffuses through the cell membrane

There is a hormone receptor in the cytoplasm. The hormone and receptor bind

The hormone receptor complex enters the nucleus and either activates or inactivates transcription of a gene.