Plasma Membrane-Gateway to the Cell

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Slide 42

Carrier Proteins

Other carrier proteins change shape to move materials across the cell membrane

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Active Transport

Requires energy or ATP

Moves materials from LOW to HIGH concentration

AGAINST concentration gradient

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Active transport

Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients.

Called Na+-K+ Pump

Slide 45

Sodium-Potassium Pump

3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential

Slide 46

Moving the “Big Stuff”

Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.

Exocytosis- moving things out.

This is how many hormones are secreted and how nerve cells communicate with one another.

Slide 47

Exocytosis

Slide 48

Moving the “Big Stuff”

Large molecules move materials into the cell by one of three forms of endocytosis.

Slide 49

Pinocytosis

Most common form of endocytosis.

Takes in dissolved molecules as a vesicle.

Slide 50

Pinocytosis

Cell forms an invagination

Materials dissolve in water to be brought into cell

Called “Cell Drinking”

Slide 51

Example of Pinocytosis

pinocytic vesicles forming

mature transport vesicle

Transport across a capillary cell (blue).

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Receptor-Mediated Endocytosis

Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.

Slide 53

Receptor-Mediated Endocytosis

Slide 54

Slide 55

Endocytosis – Phagocytosis

Used to engulf large particles such as food, bacteria, etc. into vesicles

Called “Cell Eating”

Slide 56