Movement of Materials Across a Membrane Passive and Active Transport

Concentration Gradient The difference in the amount of a substance in two different places

The Goal! To reach EQUILIBRIUM between the cell and its environment Equilibrium an equal concentration of substances on both sides of a membrane

2 Types of Transport in Cells 1.Passive Transport - movement of substances across a membrane from a region of high concentration to a region of low concentration With the concentration gradient No energy needed Ex: Diffusion and Osmosis

Types of Passive Transport Diffusion - molecules move from an area of higher conc. to an area of lower conc. until equilibrium is reached. Facilitated Diffusion – molecules that are too large to pass directly through phospholipid bilayer go through channel proteins instead. (no energy needed) Ex. Sugars, Amino Acids

Types of Passive Transport Osmosis - Diffusion of water across a semi-permeable membrane. The water is the substance that moves across the membrane.

Osmosis Solute (particles of stuff) is too large to move across membrane. Equilibrium must be reached by the movement of water instead.

Types of Solutions Three types of solutions: Hypertonic Hypotonic Isotonic

Hypertonic Solution Solution outside of cell has a higher concentration of solute and a lower concentration of water than the solution inside the cell. Hyper = above/elevated “More Stuff, less Water”

Hypotonic Solution Solution outside of cell has a lower solute concentration and a higher water concentration than the solution inside the cell. Hypo = below/lowered “Less Stuff, More Water”

Isotonic Solution Solutions outside and inside cell have equal solute concentrations. Isos = equal “Same amount of Stuff and Water”

Effect of Solutions on Living Animal Cells Hypertonic- cells shrink because of osmosis, “Crenation”, water leaves the cell. Hypotonic- cells swell because of osmosis, “Lysis”, water rushes into the cell. Isotonic- no change in cell size.

Isotonic Hypertonic Hypotonic (no change) (Crenation) (Lysis)

Effect of Solutions on Living Plant Cells Plants become wilted in isotonic environment. Plasmolysis – plant in hypertonic environment causes cell water loss, cell shrivels and the cell membrane pulls away from cell wall and can kill the cell.

Effect of Solutions on Living Plant Cells Turgor – plant in hypotonic environment causes water to enter cell, swell the vacuole, and push the cell membrane against the cell wall. Ex. Lettuce and celery become crisp when put in fresh water

Effect of Solutions on Living Plant Cells

If the fluid outside the cell has less water than is present inside the cell Then the outside fluid is: Hypertonic Water moves: Out of the cell Effect on the cell: Shrinking

If the fluid outside the cell has more water than is present inside the cell Then the outside fluid is: Hypotonic Water moves: Into the Cell Effect on the cell: Swelling and bursting of the cell

If the fluid outside the cell has same amount of water as inside the cell Then the outside fluid is: Isotonic Water moves: Into and out of the cell at the same rate Effect on the cell: none

2 Types of Transport in Cells 2. Active transport - movement of substances across a membrane from a region of low concentration to a region of high concentration Against the concentration gradient Requires Energy (ATP) Ex: Endocytosis and Facilitated Diffusion

Active Transport the movement of a substance against the concentration gradient. (from low concentration to high concentration) Used for substances that the cell needs an abundance of Active transport requires the cell to USE ENERGY (ATP)

Types of Active Transport Sodium Pump- carrier protein transports three sodium ions out of the cell and two potassium ions into the cell (Both are against the concentration gradient)

Types of Active Transport Endocytosis- the movement of a substance into the cell by a vesicle. Exocytosis- the movement of a substance out of the cell by a vesicle.

Types of Endocytosis Phagocytosis- cytoplasm of cell surrounds and engulfs particle Ex. ameba and white blood cell

Types of Endocytosis Pinocytosis- “Cell Drinking” - cell membrane "pinches in" to take in fluids or molecules too large for diffusion

Review Questions Pg 197-198: #1-8, 19, 21-23, 26-28 Please answer on a separate sheet of paper and hand in.