Aim: How does the cell membrane function to maintain homeostasis? Do Now: Describe what homeostasis is. Homework: Vocab: Homeostasis, equilibrium, concentration gradient, diffusion, carrier protein, osmosis, hypertonic, hypotonic, isotonic, semi permeable Read pp. 178 183 P. 183 # 2, 3, 4 Quiz Friday on Parts of cell & Cell Membrane Function Dec 7 10:47 AM Dec 7 11:24 AM Cell Membranes: Gatekeepers of the cell * Substances must be able to move in and out of the cell A. Passive Transport Def: Substances cross the cell membrane down the concentration gradient; from an area of higher concentration towards an area of lower concentration Concentration Gradient when one area has a higher concentration gradient than another Equilibrium when two areas have the same concentration or are filled evenly 1. Simple Diffusion when small molecules can pass directly through the lipid bilayer 2. Facilitated Diffusion molecules that require the assistance of proteins to pass through the lipid bilayer of the cell membrane a. Channel Proteins create a pore or tunnel through the CM; each tunnel is specific to a certain substance Ex: sugars, amino acids b. Carrier Protein transports substances that fit at their binding site on one side of cell membrane protein changes shape once the substance binds substance moves across the membrane Dec 7 11:24 AM Dec 7 10:53 AM Four Different Ways for Substances to Move Across a Cell Membrane Dec 8 8:52 AM Dec 8 8:47 AM 1
Phospholipid molecules (cutaway view) of Cell Membrane Transport Across Cell Membranes Importance All cells acquire the molecules and ions they need from their surrounding extracellular fluid (ECF). There is an unceasing traffic of molecules and ions in and out of the cell through its plasma/ cell membrane Examples: glucose, Carbohydrates, Na+ (sodium), Ca2+ (calcium) In eukaryotic cells, there is also transport in/ out of membrane bounded intracellular organelles such as the nucleus, endoplasmic reticulum, Protein, and mitochondria Two problems to be considered: 1. Relative concentrations Molecules and ions move spontaneously down their concentration gradient (i.e., from a region of higher to a region of lo concentration) by diffusion. Molecules and ions can be moved against their concentration gradient, but this process, called active transport, requir the expenditure of energy (usually from ATP). Dec 8 8:41 AM Jan 3 8:02 PM Transport across a Membrane Two problems to be considered: 1. Relative concentrations Molecules and ions move spontaneously down their concentration gradient: (i.e., from a region of higher to a region of lower concentration) by diffusion. Molecules and ions can be moved against their concentration gradient, but this process, called active transport, requires the expenditure of energy (usually from ATP). 2. Lipid bilayers are impermeable to most essential molecules and ions. The lipid bilayer is permeable to water molecules and a few other small, uncharged, molecules: oxygen (O2) and carbon dioxide (CO2) diffuse freely in and out of the cell. Osmosis the diffusion of water across a membrane such an important process to the cell that it has a special name Lipid bilayers are not permeable to: ions such as: K +, Na+, Ca2+,Cl, HCO3 small hydrophilic molecules like glucose macromolecules like proteins and RNA Jan 3 8:12 PM Dec 8 8:48 AM Class Notes 12/7/09 LE 5 n Dec 8 8:51 AM Dec 7 11:48 AM 2
Solving these problems Mechanisms by which cells solve the problem of transporting ions and small molecules across their membranes Facilitated diffusion: Transmembrane proteins create a water filled pore through which ions and some small hydrophilic molecules can pass by diffusion. The channels can be opened (or closed) according to the needs of the cell. Active transport Transmembrane proteins, called transporters, use the energy of ATP to force ions or small molecules through the membrane against their concentration gradient. 1/5/11 Aim: What are hypertonic, hypotonic, & isotonic solutions? Do Now: 1. Explain what a concentration gradient is? 2. What is diffusion? Is energy required? Homework Rd pp. 179-183 P. 183 Copy & Answer # 1, Vocabulary: Solvent, Solute,osmosis, extracellular,intracellular, endocytosis, exocytosis, vesicle Jan 3 8:33 PM Dec 9 8:24 AM Jan 5 10:15 AM Jan 5 10:21 AM Osmosis the diffusion of water across a membrane moves passively across a membrane in the direction of high concentration to low concentration. EXAMPLE: A red blood cell is placed into a dish of distilled water (has NO solutes). What direction will water flow in? Into or out of cell? (Hint: Where is water less concentrated?) Jan 5 6:51 AM Jan 3 7:59 PM 3
CellMembranePassive_ActiveTransport2010.notebook Jan 3 7:59 PM Jan 3 7:59 PM Vesicle Mediated Transport (Passive Transport) Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Required due to the size of the molecule- like proteins or bacteria Exocytosis is the term applied when transport is out of the cell. Endocytosis is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle, bringing substances into cell Dec 13 11:28 PM Isotonic Solution Dec 13 11:36 PM LE1 1/6 Isotonic Solution 1/6/2011 LE3 A solution that has the same salt concentration as the normal cells of the body and the blood. A solution that has the same salt concentration as the normal cells of the body and the blood. When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic Dec 7 11:33 AM Dec 7 11:33 AM 4
CellMembranePassive_ActiveTransport2010.notebook Isotonic Solution 1/6/2011 LE3 A solution that has the same salt concentration as the normal cells of the body and the blood. When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic Dec 7 11:33 AM LE 3 1/6 Hypertonic Solution Hypertonic solution contain a high concentration of solute in relation to the solution within the cell (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel up. Dec 7 11:29 AM Hypertonic Solution LE1 1/6 Hypertonic solution contain a high concentration of solute in relation to the solution within the cell (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel up. Dec 7 11:29 AM Hypotonic Hypotonic LE3 1/6 A hypotonic solution contain a solution with a lower salt concentration than in normal cells When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode. Dec 7 11:30 AM LE3 1/6 Hypotonic LE1 1/6 A hypotonic solution contain a solution with a lower salt concentration than in normal cells A hypotonic solution contain a solution with a lower salt concentration than in normal cells When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode. When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode. Dec 7 11:30 AM Dec 7 11:30 AM 5
Cell membranes are permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell. * A substance must be in solution in order to Pass through a membrane Jan 3 8:40 PM Dec 7 11:26 AM Cell membranes are permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell. Dec 7 11:26 AM Jan 3 7:53 PM Aim: Reviewing osmosis and diffusion between cells and its environment Do Now: Begin to work on the review sheet on your desk. Homework 1. Complete review sheet 2. Read pp. 182 183 3. p. 183 #3, 4 QUIZ tomorrow on Cell parts & Diffusion Jan 6 8:56 AM Jan 3 7:55 PM 6
Osmosis & Diffusion Review Sheet Name: Fill in the Blank away low high hypertonic hypotonic diffusion molecules osmosis vacuole water solute permeable towards semi permeable concentration gradient 1. The cell membrane regulates and controls what kind of ** move in & out of the cell. 2. When molecules spread from an area of high to low concentration to, it is called **. 3. As molecules diffuse, they create a **, which is a difference in concentrations across space. 4. Cell membranes are **. This means that they only allow certain things to pass through. 5. A membrane that would allow ANYTHING to pass through it would be called **. 6. Diffusion is the movement of molecules. Osmosis is the diffusion of **. 7. ** is the process of water molecules moving across a cell membrane. 8. The direction that water molecules move is determined by the difference in the concentration of ** dissolved in the solvent inside outside the cell. 9. Osmotic pressure, or osmosis, pushes water molecules ** the area of greater solute concentration. 10. Water molecules are pulled ** from areas of lower solute concentration. 11. The word hypertonic means ** concentration of solutes. 12. The word hypotonic means ** concentration of solutes. 13. A plant cell undergoes plasmolysis, or shrinking of the cell membrane, when it is placed in a solution with a HIGH concentration solute. What type of solution causes plasmolysis? ** 14. An animal cell undergoes cytolysis, or stretching of the cell membrane, when it is placed in a solution with a very LOW concentr solute. What type of solution causes cytolysis? ** 15. Turgor pressure is the flow of water into a plant cell that causes the cell membrane to be pushed up against the cell wall and cau sac in a plant cell to expand. What is this sac that holds this water from the turgor pressure? ** Isotonic Solutions 16. ** The concentration of the solutes inside the cell is to the concentration outside the cell. (A) less than (B) greater than (C) equal to 17. ** Water molecules will move: (A) into the cell faster than out of the cell (B) out of the cell faster than they will move into the cell (C) in and out of the cell at the same rate 18. ** Turgor Pressure is the pressure that water places on the inside of a PLANT cell. An increase in turgor pressure can cause t membrane to press up against the cell wall and a decrease in turgor pressure can cause the cell membrane to shrivel. If the turgor is kept constant, the cell membrane will maintain its shape. In an isotonic solution, the turgor pressure is: (A) normal (B) decreasing (C) increasing Using the terms... " This solution is hypertonic as compared to solution 2." " Blood 19. ** In animal cells, the cell membrane will: (A) shrivel up (B) be normal (C) expand & possibly burst 20. ** In the picture to the right, the movement of water across the membrane will be (A) mostly out (B) mostly in (C) in and out equally Hypotonic Solutions 21. ** The concentration of the solutes inside the cell is to the concentration outside the cell. (A) less than (B) greater than (C) equal to 22. ** Water molecules will move: (A) into the cell faster than out of the cell (B) out of the cell faster than they will move into the cell (C) in and out of the cell at the same rate 23. ** Turgor Pressure is the pressure that water places on the inside of a PLANT cell. An increase in turgor pressure can caus membrane to press up against the cell wall and a decrease in turgor pressure can cause the cell membrane to shrivel. If the turg is kept constant, the cell membrane will maintain its shape. In a hypotonic solution, the turgor pressure is: (A) normal (B) decreasing (C) increasing 24. ** In animal cells, the cell membrane will: (A) shrivel up (B) be normal (C) expand & possibly burst 25. ** In the picture to the right, the movement of water across the membrane will be (A) mostly out (B) mostly in (C) in and out equally Hypertonic Solutions 26. ** The concentration of the solutes inside the cell is to the concentration outside the cell. (A) less than (B) greater than (C) equal to 27. ** Water molecules will move: (A) into the cell faster than out of the cell (B) out of the cell faster than they will move into the cell (C) in and out of the cell at the same rate 28. ** Turgor Pressure is the pressure that water places on the inside of a PLANT cell. An increase in turgor pressure can ca membrane to press up against the cell wall and a decrease in turgor pressure can cause the cell membrane to shrivel. If the tu is kept constant, the cell membrane will maintain its shape. In a hypertonic solution, the turgor pressure is: (A) normal (B) decreasing (C) increasing 29. ** In animal cells, the cell membrane will: (A) shrivel up (B) be normal (C) expand & possibly burst 30. ** In the picture to the right, the movement of water across the membrane will be (A) mostly out (B) mostly in (C) in and out equally Jan 6 8:57 AM Jan 3 7:46 PM Aim: What is active transport? Do Now: A red blood cell is 3 different solutions: #1 solution is 3% salt, a second is 10% salt and a third has 0% salt in it. 1. Describe the relationship between them using iso, hyper & hypo tonic vocabulary. 2. Show with arrows the direction of the net flow of water Dec 8 8:46 AM Dec 11 11:11 AM Active Transport of Sodium ions The Gate opens for Na+ (sodium ions) only after the carrier protein channel has energy (Green Glucose/ ATP). Na+ is moving against the concentration gradient Active Transport A. Purpose in order for cell to function correctly 1. Occurs across a cell membrane 2. Goes from low concentration to high concentration this is against concentration gradient 3. Requires energy from the cell (ATP) 4. Uses carrier proteins EX: Sodium Potassium Pump Endocytosis a cell uses a vesicle to move material into the cell Exocytosis cell uses a vesicle to move materials (Ex. wastes, pathogens, proteins) out of the cell Dec 13 11:21 PM Dec 11 11:14 AM 7
Active Transport Across the Cell Membrane: Step by Step Dec 10 9:40 AM Dec 13 11:13 PM Compare & Contrast Passive & Active Transport Dec 11 11:20 AM 8