Cell Transport
Essential Standard
Bio.1.2 Analyze the cell as a living system.
Cell Transport
• Movement of materials across cell membrane
• 2 Types:
• Passive Transport
• Active Transport
Passive Transport
• Movement of substances across membrane without
input of energy until equilibrium is reached
• With concentration gradient; high to low
concentration
• 4 Types
• Diffusion
• Osmosis
• Facilitated Diffusion
• Ion Channels
Active Transport
• Movement of substances across membrane requiring
input of energy
• Against concentration gradient; low to high
concentration
• 3 Types
• Protein Pumps
• Endocytosis
• Exocytosis
Passive Transport - Diffusion
• Movement of molecules
• Molecules are in constant motion
• Moves “down” concentration gradient
• Rate of diffusion depends on
• Size of molecule
• Type of molecule
Passive Transport - Osmosis
• Diffusion of water
• Direction of osmosis depends on concentration of
solutes on both sides of membrane
• Hypotonic solution
• Cytolysis
• Hypertonic solution
• Plasmolysis
• Isotonic solution
Osmosis Problems
• A cell which is 98% water is placed into a solution of
10% sucrose. What is the direction of the water
movement?
Osmosis Problems
• A cell has 45% sodium concentration and is placed in a
solution of 55% water concentration. What is the
direction of the water movement?
Passive Transport – Facilitated Diffusion
• Diffusion of larger molecules
• Use carrier proteins (integral)
• No energy required
Passive Transport – Ion Channels
• Regulate flow of ions across membrane
• Ion-specific!
• Ions requiring ion channels: Na+, K+, Ca+, Cl-
Active Transport – Protein Pumps
• Carrier protein that transports molecules against
concentration gradient
Active Transport - Endocytosis
• Large particles are engulfed into the cell
• Pinocytosis – “cell drinking”
• Phagocytosis – “cell eating”
Active Transport – Exocytosis
• Large particles exit the cell