Active Transport

Requires use of energy because it does not happen naturally through diffusion or facilitated diffusion.

Requires a carrier protein* that uses energy from ATP molecules (Adenosine Tri-Phosphate, a nucleotide that stores energy and can release it when bonds are broken.)

Why? Moving stuff against the concentration gradient requires a “pump”.

ORFusing/rebuilding of cell membranes

Compare Membrane ProteinsActive Transport vs. Facilitated Diffusion :

Both use…. Carrier Proteins

But only active transport carrier proteins require…

ATPBecause they need energy to change their

shape!

ATP

Sodium – Potassium Pump

Phos

phol

ipid

B

ilaye

r

Na+

Phos

phat

es fr

om

ATP

brea

kdow

n

K+

Active Transport - Bulk Transport

One large or many small particles moved in or out of cell using membrane bubbles called vesicles that can fuse with the cell/plasma membrane

Exocytosis – materials moved out of cellEx.: secretion of tears & sweat

Active Transport - Bulk Transport

Endocytosis – materials moved into cell

Phagocytosis – “cell eating” solid particle(s) taken inEx.: phagocytes such as macrophages & other immune cells ingesting bacteria

Pinocytosis – “cell drinking” liquid/many small particle(s) taken inEx.: Cells “gulping up” plasma from blood, leaving RBCs in blood

08-19a-PhagocytosisAnim.mov

08-19b-PinocytosisAnim.mov

Endocytosis?

Exocytosis?

# 2

# 1

#3

Endocytosis

1. Pinocytosis

2. Phagocytosis

Contractile Vacuole‘Sump Pump’ in unicellular aquatic organisms

Environment is 99% Water

Cell is 95% Water

Active or Passive?