Chapter 8 – Cellular Transport

Plasma Membrane Selectively permeable Controls what passes through the membrane Made of: phospholipids, proteins, and cholesterol.

Diffusion Movement of molecules from a high concentration of molecules to a low concentration of molecules Brownian movement: molecules are moving all the time- (random movement)

Concentration Gradient Difference in the concentration of molecules across a space Molecules will move until the solute and solvent are mixed evenly

Dynamic Equilibrium When the concentration of the molecules are equally distributed There is no concentration gradient There will still be movement of particles, but no net change

Osmosis Diffusion of water molecules through a selectively permeable membrane (type of diffusion) High concentration to….. Low concentration

Osmosis: Diffusion of Water Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell.

Section 8.1 Summary – pages 195 - 200 What controls osmosis? Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. Before Osmosis After Osmosis Water molecule Sugar molecule Selectively permeable membrane Section 8.1 Summary – pages 195 - 200

3 type of solutions Isotonic Solution Hypertonic Solution Hypotonic Solution

Section 8.1 Summary – pages 195 - 200 Cells in an isotonic solution In an isotonic solution, the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell. H2O H2O Water Molecule Dissolved Molecule Section 8.1 Summary – pages 195 - 200

This means: The concentration of the water is the same inside the cell and outside the cell Dynamic Equilibrium has been reached

Cells in an isotonic solution In an isotonic solution, water molecules move into and out of the cell at the same rate, and cells retain their normal shape. H2O H2O Water Molecule Dissolved Molecule

Section 8.1 Summary – pages 195 - 200 Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution. Section 8.1 Summary – pages 195 - 200

Cells in a hypertonic solution In a hypertonic solution, there is a higher concentration of dissolved substances (solute) in the solution than the concentration inside the cell

The water concentration is lower outside the cell than inside the cell This means……. The water concentration is lower outside the cell than inside the cell

Section 8.1 Summary – pages 195 - 200 Cells in a hypertonic solution In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink. H2O H2O Water Molecule Dissolved Molecule Section 8.1 Summary – pages 195 - 200

Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall.

Cells in a hypotonic solution In a hypotonic solution, there is a lower concentration of dissolved substances (solute) in the solution than inside the cell

Water concentration is higher outside the cell than inside the cell This means….. Water concentration is higher outside the cell than inside the cell

Cells in a hypotonic solution In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. H2O H2O Water Molecule Dissolved Molecule

Section 8.1 Summary – pages 195 - 200 Cells in a hypotonic solution Plant cells swell beyond their normal size as pressure increases. Section 8.1 Summary – pages 195 - 200

Blood cell Plant cell

Review Hypotonic solution-hippo/hypo Water enters his mouth- looks like he is going to explode

Review Hyper kids rushing out of class after 2 hours in 104 degree classroom Hyper-Hypertonic- water leaves the cell

Types of Transport Passive Transport Active Transport

Passive Transport Movement of particles across membranes by diffusion - the cell uses NO energy to move the particles - particles move ALONG the concentration gradient

Passive Transport High Concentration to Low Concentration Diffusion Facilitated Diffusion Osmosis High Concentration to Low Concentration

Facilitated Diffusion Type of passive transport that uses transport proteins Doesn’t use energy

Active Transport Transport that requires energy Transport of materials AGAINST the concentration gradient High Concentration Low Concentration

Active Transport Endocytosis Exocytosis

Endocytosis Phagocytosis- cell engulfs particle with pseudopodia (cell eating) Pinocytosis-cell gulps/drinks extracellular fluid (cell drinking)

Section 8.1 Summary – pages 195 - 200 Transport of Large Particles Endocytosis is a process by which a cell surrounds and takes in material from its environment. Nucleus Wastes Digestion Endocytosis Exocytosis Section 8.1 Summary – pages 195 - 200

Section 8.1 Summary – pages 195 - 200 Transport of Large Particles The material is engulfed and enclosed by a portion of the cell’s plasma membrane. Nucleus Wastes Digestion Endocytosis Exocytosis Section 8.1 Summary – pages 195 - 200

Section 8.1 Summary – pages 195 - 200 Transport of Large Particles The resulting vacuole with its contents moves to the inside of the cell. Nucleus Wastes Digestion Endocytosis Exocytosis Section 8.1 Summary – pages 195 - 200

Section 8.1 Summary – pages 195 - 200 Transport of Large Particles Exocytosis is the expulsion or secretion of materials from a cell. Nucleus Wastes Digestion Exocytosis Endocytosis Section 8.1 Summary – pages 195 - 200

Transport of Large Particles Endocytosis and exocytosis both move masses of material and both require energy. Nucleus Wastes Digestion Endocytosis Exocytosis

Question 1 A. active transport The diffusion of water across a selectively permeable membrane is called __________. Water molecule Selectively permeable membrane Sugar molecule A. active transport B. endocytosis Section 1 Check

Question 1 The diffusion of water across a selectively permeable membrane is called __________. Water molecule Selectively permeable membrane Sugar molecule C. exocytosis D. osmosis Section 1 Check

The answer is D, osmosis. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within the cell. Before osmosis After osmosis Water molecule Selectively permeable membrane Sugar molecule Section 1 Check

Question 2 What is the expected result of having an animal cell in a hypertonic solution? A. The cell shrivels up. B. The plasma membrane shrinks away from the cell wall. C. The cell swells up. D. The cell retains its normal shape. Section 1 Check

The answer is A. In a hypertonic solution, cells experience osmosis of water out of the cell. Animal cells shrivel because of decreased pressure in the cells. H2O H2O Water molecule Sugar molecule Section 1 Check

Question 3 A grocer mists the celery display with water to keep it looking fresh. What type of solution is the celery now in? A. isotonic B. hypotonic C. hypertonic D. exotonic Section 1 Check

The answer is B. Plant cells contain a rigid cell wall and do not burst even in a hypotonic solution. Section 1 Check

Concentration gradient Question 4 Transport of materials across the plasma membrane that does not require energy from the cell but does use transport proteins is called __________. Channel proteins A. osmosis B. simple diffusion Concentration gradient Plasma membrane Section 1 Check

Concentration gradient Question 4 Transport of materials across the plasma membrane that does not require energy from the cell but does use transport proteins is called __________. Channel proteins C. facilitated diffusion Concentration gradient Plasma membrane D. active transport Section 1 Check

Concentration gradient The answer is C. Facilitated diffusion is a type of passive transport and requires no energy from the cell. Channel proteins Concentration gradient Plasma membrane Section 1 Check

End of Chapter 8 Show