Download Cellular Transport Notes

Cellular Transport
Cell Borders
1. Cell Wall – Provides support and protection.
(In plants!)
• Made of cellulose – a tough carb
2. Cell Membrane – Controls what enters and
leaves cell. (In ALL cells!)
Cell Membrane
• Its function is to maintain a balance called
homeostasis within the cell.
• Remember that the cell membrane is semipermeable or selectively permeable. It controls
how, when, and how much stuff enters and leaves
the cell. It is picky.
Cell Membrane Structure
• Phospholipids: arranged in a bilayer with polar
phosphate heads out and non-polar fatty-acid tails
in (allows the cell to easily separate the outside
environment from the inside environment)
Cell Membrane Structure
• Transport Proteins: move needed substances into
and out of the cell that will not easily pass through
the phospholipids
Cell Membrane Structure
• Cholesterol: keeps the fatty-acid tails from sticking
together and adds to the fluidity of the membrane
• Carbohydrate chains: defines cells characteristics
and helps to read chemical signals
How is a window screen like a cell
membrane?
• What are some things that can pass through a
window screen?
• What are some things that cannot?
• Why is it important for a cell membrane to regulate
what moves into and out of a cell?
Fluid Mosaic Model
Solutions and Cellular Transport
• Solution: a mixture formed when one substance is dissolved into
another substance; ex: Kool-Aid, Jell-o
• Solute: the substance being dissolved; ex: Kool-Aid mix, Jell-o mix
• Solvent: the substance doing the dissolving; ex: water
• Concentration Gradient: the difference in concentrations of
solute between two areas
• There is a concentration gradient across the cell membrane.
Essential Questions
• What are the processes of diffusion, facilitated
diffusion, and active transport?
• What is the effect of a hypotonic, hypertonic, or
isotonic solution on a cell?
• How do large particles enter and exit cells?
2 Ways to Cross the Membrane
• Passive Transport – NO energy is required to move a substance across
the membrane.
• Movement of solute along/with the gradient; ex: floating in the lazy
river
• Active Transport – Energy IS REQUIRED to move a substance across the
membrane.
• Movement of solute against the gradient; ex: trying to swim
upstream or against the current
Passive Transport - Diffusion
• Diffusion - movement of particles from areas of high concentration of
solute to areas of low concentration of solute.
(water, oxygen, carbon dioxide)
• When the concentration is the same throughout, equilibrium is reached.
• Temperature and size of molecule affect the rate of diffusion.
Passive Transport - Diffusion
Passive Transport - Osmosis
• Osmosis – the diffusion of water particles across a membrane.
• *****Water moves from low solute to high solute.*****
• Why is osmosis important for cells?
How Osmosis Works in the Cell
• Hypotonic - Concentration of solutes outside is lower than it is inside
the cell.
• Water in
How Osmosis Works in the Cell
• Hypertonic - Concentration of solutes outside are higher than inside
of the cell.
• Water out
How Osmosis Works in the Cell
• Isotonic – Concentration of solutes outside and inside cell are equal.
• Equilibrium – water moves in and out at the same rate
Passive Transport:
Facilitated Diffusion
• Facilitated Diffusion – Larger molecules (like glucose, sodium ions, and
chloride ions) move across the membrane with the help of protein
channels.
• Moves from high concentration of solutes to low concentration of
solutes– no energy required.
Active Transport
• Large molecules (glucose) and ions (Na+, K+, Ca+2) pass
across the membrane using proteins and ATP ENERGY
when moving from low to high concentrations.
Active Transport:
Exocytosis - Wastes and products are packaged in vesicle by the
Golgi and sent OUT of cell
Active Transport:
Endocytosis – cell membrane forms vesicle and brings things
INTO the cell.
Types of Endocytosis
• Phagocytosis – engulfs by surrounding
membrane around solids.
• “Phago-” means “to eat”
• Pinocytosis – pinches membrane and brings in
liquids.
• “Pino-” means “to pinch”
Odd Man Out
• Osmosis
• Diffusion
• Cell membrane
Odd Man Out
• Semi permeable
• Cell membrane
• Phospholipid
• Hydrophillic
• Protein Channels
• Diffusion
• Osmosis
• Passive Transport
• Active transport
• Facilitated Diffusion
• ATP
• Passive Transport
• Solute
• Water
• Solvent
• Osmosis
• ATP
• Active transport
• Homeostasis
• Hydrophillic
• Protein Channels
• Solvent
• Isotonic Solution
• Hypotonic Solution
• Isotonic solution
• Hypertonic solution
• Semi Permeable