cell transport notes. all cells have a cell membrane made of proteins and lipids cell membrane lipid...
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Cell Transport
Notes
•All cells have a cell membrane made of proteins and lipids
Cell Membrane
lipid bilayer
protein channel
protein pump
Layer 1
Layer 2
Cell Membrane
Function of Cell Membrane• Cell membrane separates the components of a cell from its
environment—surrounds the cell
• “Gatekeeper” of the cell—regulates the flow of materials into and out of cell—selectively permeable
• Cell membrane helps cells maintain homeostasis—stable internal balance
Cell Membrane Structure
Phospholipids• Lipids (fatty acid) with a phosphate group attached. • Polar head and non-polar tails• Hydrophilic (likes water) head and hydrophobic
(afraid of water) tail
Tail
Hydrophilic and Hydrophobic
Hydrophilic: “likes water”
Hydrophobic: “fears water” - repels water
Transport Proteins• Found in plasma membrane (also known as
transport proteins)• Allows larger substances to move through the
plasma membrane.
Cholesterol molecule
• Helps stabilize the phospholipids
• Prevents the fatty acid chains of the phospholipids from sticking together
Passive TransportMovement of material down the
concentration gradient, requires NO energy from the cell
Diffusion…going with the flowDiffusion: The random movement of
molecules from an area of high concentration to an area of low concentration.
Osmosis
Osmosis: The movement of water across a semipermeable membrane due to differences in the solute on each side.
Facilitated DiffusionPassive Transport by Proteins
(NO energy required)
• Channel proteins – form channels to allow specific molecules to flow through
• Carrier proteins – change shape to allow a substance to pass through the membrane.
outside of cell
inside of cell
Glucose molecules
Active TransportMovement of material through a membrane
against a concentration gradient, requires energy from the cell
outside of cell
inside of cell
Carbon Dioxide molecules
Transport of Large Particles
1. Endocytosis – the process by which a cell surrounds and takes in material from its environment. (engulfed)
2. Exocytosis – the expulsion or secretion of materials from a cell.
Same Conc. Lower Conc. Higher Conc.
Effect of concentration
Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel.
Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode.
Isotonic Solutions: contain the same concentration of solute as another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.
HYPOTONIC HYPERTONIC
ISOTONIC