cell transport notes. all cells have a cell membrane made of proteins and lipids cell membrane lipid...

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