Monday, October 12 th What are some materials that you think a cell needs to obtain to fuel the processes that support life?

Monday, October 12 th What is your favorite organelle? Explain why.

B-2.5Explain how active, passive, and facilitated transport serve to maintain the homeostasis of the cell. Passive Trnasport Diffusion Osmosis Facilitated Diffusion Active Transport

Cell Transport & Homeostasis All organisms have processes and structures which respond to stimuli in ways that keep conditions in their bodies conducive for life. Homeostasis depends in part on appropriate movement of materials across the cell membrane.

How does cellular transport support life? Materials needed for cellular processes must pass into cells so they can be utilized. –For example, oxygen and glucose are continuously needed for the process of cellular respiration. Waste materials from cellular processes must pass out of cells as they are produced. –For example, carbon dioxide is continuously produced within the cell during the process of cellular respiration.

Cell Membrane The cell membrane regulates the passage of material into and out of the cell. Depending on the needs of the cell, excess substances must move out of the cell and needed substances must move into the cell. Each individual cell exists in a fluid environment, and the cytoplasm within the cell also has a fluid environment. The presence of a liquid makes it possible for substances (such as nutrients, oxygen, and waste products) to move into and out of the cell. A cell membrane is semipermeable (selectively permeable), meaning that some substances can pass directly through the cell membrane while other substances can not.

Passive Transport NO ENERGY REQUIRED to move substances across membrane -- water, lipids, and other lipid soluble substances. Types: –Diffusion –Osmosis –Facilitated Diffusion

Diffusion The spreading out of molecules across a cell membrane until they are equally concentrated. It results from the random motion of molecules and occurs along a concentration gradient. Molecules move from an area of higher concentration to an area of lower concentration Substances that are able to pass directly across the cell membrane can diffuse either into a cell or out of a cell.

Diffusion Molecules move down the concentration gradient until there are equal numbers of molecules on both sides ~ dynamic equilibrium.

 Diffusion is controlled by  Temperature  Pressure  Concentration

Dynamic Equilibrium Molecules continue to move randomly, but the overall concentration remains the same.

Osmosis Diffusion of water from an area of greater concentration of water to an area of lesser concentration of water -- across a semipermeable membrane. Isotonic Solutions Hypertonic Solutions Hypotonic Solutions Three Types of Solutions

Isotonic Solution Iso=Same Concentration of solutes in the solution is the same as inside the cell. Cell is in dynamic equilibrium, i.e., no net gain or loss of water. Blood Cell Plant Cell

Hypotonic Solution Concentration of solutes is higher inside of the cell Net movement of water will be INTO the cell. Blood Cell Plant Cell 13,000x

Hypotonic Solution Plant Cell Turgor Pressure -- This is why grocery stores spray vegetables -- crispness! Animal Cell Cytolysis -- Animal cell bursts.

Hypotonic Solutions

Hypertonic Solution Concentration of solutes is greater outside of the cell Net movement of water will be OUT OF the cell. Plant Cell Blood Cell 13,000x

Facilitated Diffusion Movement across the membrane with the help of transport proteins. No energy required Some substances have chemical structures that prevent them from passing directly through a cell membrane. Ex. Glucose The cell membrane is not permeable to these substances.

Transport Proteins –Types: Carrier protein - its shape fits certain molecules. Channel protein - molecules diffuse through channel.

Active Transport Transport of materials against (low to high) a concentration gradient –REQUIRES ENERGY! One process of active transport happens when cells pump molecules through the cell membrane. Calcium, potassium, and sodium ions are examples of materials that must be forced across the cell membrane using active transport

Active Transport Sodium-Potassium Pump –transports sodium ions out of cell, potassium ions into cell. Low Sodium K+K+ Na + High Potassium High Sodium Low Potassium

Cellular Structure and Function Endocytosis -Process by which the cell takes particles into the cell Exocytosis -Secretion of material out of the plasma membrane Large Molecules When molecules are too large to pass through a cell membrane even with the aid of proteins then vesicles are used to help them through the membrane.

Review Types of Cellular Transport Passive (No Energy Required) –Diffusion: Movement of solute (high to low) –Osmosis: Movement of water (high to low) Hypotonic, Isotonic, and Hypertonic –Facilitated Diffusion: Carrier and channel proteins Active (Requires Energy) Endocytosis,, Exocytosis, Some Carrier Molecules Sodium-Potassium Pump