Biology Unit Three Part II - Cells Mrs. Pearson’s First Semester Biology *For those watching by recording, watch for questions on the slides throughout the presentation. Email me the answers to the questions within two days of the lesson being presented in order to receive credit for watching the recording.

Biology Olympics Context Clues: Use the picture, the word parts, and the paragraph to determine what “semipermeable” means. Outdoor clothing is often made of semipermeable fabric. The material is waterproof yet breathable. Molecules of water vapor from sweat are small enough to exit the fabric, but water droplets are too large to enter.

Biology Olympics Semipermeable is a property of an object which allows some materials to pass through but stops others from passing. What are some ways, other than semipermeable clothing, in which this property could be useful?

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

Lesson Objectives Describe the structures and functions of the cell membrane.

Pearson’s Perfectly Pleasant Prefixes and Parts Inter – Intra – Bi – Semi – Hyper – Hypo – Passive Active Endo – Ecto – Cyto -

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. What do you think those functions are? cell membrane outside cell inside cell

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. forms a boundary between inside and outside of the cell controls passage of materials cell membrane outside cell **Those watching by recording, include in your email the two major functions of the cell membrane. inside cell

Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer. There are other molecules embedded in the membrane. Theorize what the other molecules in the membrane do. cell membrane protein cholesterol carbohydrate chain protein channel

Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. What does that mean? **Those watching by recording, include in your email the definition of selectively permeable.

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor What does Intra- mean?

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor membrane receptor

3.4 Diffusion and Osmosis KEY CONCEPT Materials move across membranes because of concentration differences.

3.4 Diffusion and Osmosis Passive transport does not require energy input from a cell. Molecules can move across the cell membrane through passive transport. There are two types of passive transport. diffusion osmosis Water moves freely across the cell membrane Describe the direction that the molecules move (not left or right or up or down).

3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. Molecules diffuse down a concentration gradient.

3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. Osmosis is the diffusion of water molecules across a semipermeable membrane. It helps keep all of the other “stuff” in the same concentrations inside and outside of the cells. When we describe a solution, we look at how much of something is dissolved in the water. So this solution has a higher concentration of “stuff” than the other solution.

3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. If we wanted to make the concentrations the same but we couldn’t change the number of stars BUT we could change the amount of water, what would we do? When we describe a solution, we look at how much of something is dissolved in the water. So this solution has a higher concentration of “stuff” than the other solution.

3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. There are three types of solutions. isotonic hypertonic hypotonic **Those watching by recording, include in your email the difference between isotonic, hypertonic, and hypotonic solutions.

3.4 Diffusion and Osmosis Some molecules can only diffuse through transport proteins. Some molecules cannot easily diffuse across the cell membrane. Facilitated diffusion is diffusion through transport proteins.

3.5 Active Transport, Endocytosis, and Exocytosis KEY CONCEPT Cells use energy to transport materials that cannot diffuse across a membrane.

3.5 Active Transport, Endocytosis, and Exocytosis Active transport requires energy input from a cell and enables a cell to move a substance against its concentration gradient. Passive transport requires no energy from the cell. Active transport is powered by chemical energy (ATP). Active transport occurs through transport protein pumps. Cells use active transport to maintain homeostasis.

3.5 Active Transport, Endocytosis, and Exocytosis A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis. Cells use energy to transport material in vesicles. Endocytosis is the process of taking material into the cell. If “endo-” means “in” and “exo-” means “out”, what do you think happens with exocytosis? **Those watching by recording, include in your email a description of the endocytosis process.

3.5 Active Transport, Endocytosis, and Exocytosis A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis. Cells use energy to transport material in vesicles. Exocytosis is the process of expelling material from the cell.

Review The cell membrane forms a boundary and controls the movement of particles into and out of the cell The cell membrane is selectively permeable. Chemical signals are transmitted across the cell membrane Substances move across the cell membrane through active and passive transport Solutions around a cell can be isotonic, hypertonic, or hypotonic.

Questions?