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Active Transport

Active Transport Unlike passive transport, active transport requires energy

– movement is against the concentration gradient (from low to high)

– Energy required is cellular energy, aka ATP

2 methods of Active Transport 1. Via membrane proteins (pumps)

2. Change in the cell membrane (endocytosis, exocytosis)

Active Transport Pumps: • Requires a membrane protein called a “pump”

• Pump directly uses ATP to transport substances against concentration gradient.

• Active transport pumps are specific to the substance it transports.

• Like “lock and key”

Active Transport Pumps:

Examples of active transport pumps:

– Proton pump transports hydrogen ions

• Sodium (Na+) / Potassium (K+) Pump

– 3 Na+ pumped out

– 2 K+ pumped in

http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

Examples of active transport pumps:

Why are pumps necessary?

• Nerve cells need a difference in ions (charge) on either side of the membrane so they can fire.

• Which side of the cell membrane will have a more “+” charge???

3 Na+ out

2 K+ in

Change in cell membrane (2nd type of active transport process)

• Cell membrane will change its shape to take in or release larger substances that cannot pass through membrane proteins

• Involves vesicles

• Endocytosis moving materials into cell

• Exocytosis moving materials out of cell

Endocytosis “in” – Takes in (engulfs) larger substances that

cannot pass through membrane proteins

–Cell membrane folds in until it forms a vesicle

– There are two types of endocyotosis: pinocytosis and phagocytosis

Phagocytosis: • “Cell Eating”

–Pseudopods engulf material with extensions of the cell membrane.

– Ex. White blood cell taking in foreign material for destruction.

Phagocytosis:

Pinocytosis: • “Cell Drinking”

–Membrane sips in substance and pinches membrane off into a vesicle.

Pinocytosis:

Exocytosis: (OUT) • Vesicle fuses with cell membrane, releasing

contents to outside of cell.

– ex. Waste

– ex. Digestive enzymes

RNA

Rough ER

Golgi apparatus

Plasma membrane

Exocytosis: (OUT)

Protein in vesicle

Figure 7.14 The formation and functions of lysosomes (Layer 1)

Figure 7.14 The formation and functions of lysosomes (Layer 2)

Figure 7.14 The formation and functions of lysosomes (Layer 3)