CHAPTER 8: CELLULAR TRANSPORT AND THE CELL CYCLE Do now: What is the function of the plasma membrane. What is diffusion ? copyright cmassengale

copyright cmassengale Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. copyright cmassengale

Osmosis: Diffusion of Water copyright cmassengale

In a cell, water always moves to reach an equal concentration on both sides of the membrane. The diffusion of water across a selectively permeable membrane is called osmosis. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell.

What controls osmosis? Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions.

Diffusion of H2O Across A Membrane The Plasma Membrane 1/18/2019 Diffusion of H2O Across A Membrane High H2O potential Low solute concentration Low H2O potential High solute concentration copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale Cells in an isotonic solution In an isotonic solution, the concentration of dissolved substances outside the cell is the same as the concentration of dissolved substances inside the cell. In an isotonic solution, water molecules move into and out of the cell at the same rate, and cells retain their normal shape. copyright cmassengale

Cell in Isotonic Solution The Plasma Membrane 1/18/2019 Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCL 90% H2O What is the direction of water movement? The cell is at _______________. equilibrium G. Podgorski, Biol. 1010

copyright cmassengale Cells in a hypotonic solution In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. copyright cmassengale

Cell in Hypotonic Solution The Plasma Membrane 1/18/2019 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale Cells in a hypertonic solution In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink. copyright cmassengale

Cell in Hypertonic Solution The Plasma Membrane 1/18/2019 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? copyright cmassengale G. Podgorski, Biol. 1010

Osmosis in Red Blood Cells The Plasma Membrane 1/18/2019 Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 1/18/2019 Cells in Solutions copyright cmassengale G. Podgorski, Biol. 1010

NO NET MOVEMENT OF H2O (equal amounts entering & leaving) The Plasma Membrane 1/18/2019 Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 1/18/2019 isotonic hypotonic hypertonic hypertonic isotonic hypotonic copyright cmassengale G. Podgorski, Biol. 1010

Types of Transport Across Cell Membranes The Plasma Membrane 1/18/2019 Types of Transport Across Cell Membranes copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 1/18/2019 Passive Transport 1) Simple Diffusion Doesn’t require energy Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out. copyright cmassengale G. Podgorski, Biol. 1010

2) Facilitated diffusion The Plasma Membrane 1/18/2019 Passive Transport 2) Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. copyright cmassengale G. Podgorski, Biol. 1010

Proteins Are Critical to Membrane Function The Plasma Membrane 1/18/2019 Proteins Are Critical to Membrane Function copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 1/18/2019 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 1/18/2019 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump copyright cmassengale G. Podgorski, Biol. 1010

Three Forms of Transport Across the Membrane The Plasma Membrane Three Forms of Transport Across the Membrane 1/18/2019 copyright cmassengale G. Podgorski, Biol. 1010

Moving the “Big Stuff” Exocytosis- moving things out. The Plasma Membrane Moving the “Big Stuff” 1/18/2019 Exocytosis- moving things out. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how many hormones are secreted and how nerve cells communicate with one another. copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 1/18/2019 Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating” copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 1/18/2019 Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell copyright cmassengale Cell environment G. Podgorski, Biol. 1010