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Cell Membranes & Movement Across the Membrane
SC.912.L.14.2 Cell Membranes & Movement Across the Membrane Relate structure to function for the components of plant and animal cells. Explain the role of cell membranes as a highly selective barrier (passive and active transport).
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Title: L.14.3 Cell Membrane Guided notes
Cell Membranes Left Side Right Side We do Activity Osmosis & Diffusion Title: L.14.3 Cell Membrane Guided notes Attach the guided notes to the right side of your notebook and complete the blanks.
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Bell Ringer #1 Look at the cross section of a cell membrane of a eukaryotic cell. H ions are being pumped from an area of low concentration to an area of high concentration. How do you describe this type of transport across the cell membrane? A. active transport B. passive transport C. facilitated diffusion D. co-transport
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Bell Ringer #2 Joy took the notes shown below while learning about cells; • Forms boundary between a cell and the outside environment • Controls the movement of materials into and out of the cell • Consists of double layer of phospholipids She forgot to write the name of the cell structure that her class was studying that day. What structure is described in her notes? A. endoplasmic reticulum B. cell membrane C. cell wall D. nucleus
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Cell (plasma) membrane
Cells need an inside & an outside… separate cell from its environment cell membrane is the boundary IN food - sugars - proteins - fats salts O2 H2O OUT waste - ammonia - salts - CO2 - H2O products - proteins cell needs materials in & products or waste out
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Remember: oil & water don’t mix!!
Building a membrane How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? FATS LIPIDS Remember: oil & water don’t mix!! What substance do you know that doesn’t mix with water?
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Structure of the Cell Membrane
Membrane is made of special kind of lipid phospholipids Membrane is a double layer phospholipid bilayer lipid phosphate “attracted to water” inside cell outside cell “repelled by water”
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Semi-permeable membrane
Cell membrane controls what gets in or out Need to allow some materials — but not all — to pass through the membrane semi-permeable = only some material can get in or out So what needs to get across the membrane? sugar lipids aa O2 H2O salt waste
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Crossing the cell membrane
What molecules can get through the cell membrane directly? fats and oils can pass directly through lipid inside cell outside cell salt waste but… what about other stuff? sugar aa H2O
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Protein channels Proteins act as doors in the membrane allowing other molecules through. channels to move specific molecules through cell membrane HIGH Donuts! Each transport protein is specific as to the substances that it will translocate (move). For example, the glucose transport protein in the liver will carry glucose from the blood to the cytoplasm, but not fructose, its structural isomer. Some transport proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel through the membrane -- simply provide corridors allowing a specific molecule or ion to cross the membrane. These channel proteins allow fast transport. For example, water channel proteins, aquaprorins, facilitate massive amounts of diffusion. LOW
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Diffusion Move from HIGH to LOW concentration diffusion of water
passive transport no energy needed diffusion of water diffusion osmosis
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Simple Diffusion Move from HIGH to LOW Directly through the membrane
Which way will fat move? fat fat fat inside cell fat fat fat LOW HIGH fat outside cell fat fat fat fat fat fat fat
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Facilitated Diffusion
Move from HIGH to LOW through a channel sugar sugar sugar sugar inside cell sugar sugar LOW Which way will sugar move? HIGH outside cell sugar sugar sugar sugar sugar sugar sugar
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Osmosis Movement of Water Across Cell Membrane
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Osmosis Water is very important, so we talk about water separately
Osmosis: diffusion of water from HIGH concentration of water to LOW concentration of water across a semi-permeable membrane
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Osmosis Terms Isotonic – “same strength” on both sides
Hypertonic – “above strength” More concentrated Hypotonic – “below strength” Less concentrated A B C C Use the figure below the definitions to help students understand vocabulary. LH side – how will you remember what each word means? Picture or analogy to represent vocab.
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Keeping water balance Cell survival depends on balancing water uptake & water loss freshwater balanced saltwater
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Keeping right amount of water in cell
1 Keeping right amount of water in cell Hypotonic Solution (Freshwater ) a cell in fresh water high concentration of water around cell cell gains water example: Paramecium problem: cells gain water, swell & can burst (water continually enters Paramecium cell) solution: contractile vacuole (pumps water out of cell) KABOOM! freshwater What does a plant cell have that does not allow it to burst? Cell wall No problem, here
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Review - You tell me! Effect of Cells in a Hypotonic Solution
Water Moves In Less Solute Hypotonic Solution Normal Red Blood Cell
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Controlling water Contractile vacuole in Paramecium
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Keeping right amount of water in cell
2 Keeping right amount of water in cell Hypertonic Solution (Saltwater) a cell in salt water low concentration of water around cell cell loses water example: shellfish problem: cell loses water in plants: plasmolysis in animals: shrinking cell solution: take up water I’m shrinking, I’m shrinking! saltwater I will survive!
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Effect of Cells in a Hypertonic Solution
Review – You tell me! Effect of Cells in a Hypertonic Solution Water moves out More Solute Hypertonic Solution Normal Red Blood Cell
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Keeping right amount of water in cell
3 Keeping right amount of water in cell Isotonic Solution (Balanced conditions) no difference in concentration of water between cell & environment cell in equilibrium example: blood problem: none -water flows across membrane equally, in both directions -volume of cell doesn’t change That’s better! balanced I could be better…
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Review - You tell me! Effect of Cells in a Isotonic Solution
Equal Solute Isotonic Solution Normal Red Blood Cell
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Effect of Osmosis on Animal Cells (red blood cells)
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Cells may need molecules to move against concentration “hill”
Active transport Cells may need molecules to move against concentration “hill” need to pump “uphill” from LOW to HIGH using energy protein pump requires energy = ATP Plants have nitrate & phosphate pumps in their roots. Why? Nitrate for amino acids Phosphate for DNA & membranes Not coincidentally these are the main constituents of fertilizer. ATP
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Transport summary simple diffusion facilitated diffusion
ATP active transport
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We Do DRAW an ARROW to indicate the direction that the solution will flow AND DRAW an ARROW with a “W” to indicate the direction that the water will flow. Answer the questions that follow. Below are two examples:
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Bell Ringer Re-Try Look at the cross section of a cell membrane of a eukaryotic cell. H+ ions are being pumped from a low concentration to a high concentration. How do you describe this type of transport across the cell membrane? A. active transport B. passive transport C. facilitated diffusion D. co-transport
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Bell Ringer Re-Try Joy took the notes shown below while learning about cells. Forms boundary between a cell and the outside environment Controls the movement of materials into and out of the cell Consists of double layer of phospholipids She forgot to write the name of the cell structure that her class was studying that day. What structure is described in her notes? A. endoplasmic reticulum B. cell membrane C. cell wall D. nucleus
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You Do The following questions can be projected when an instructor reaches the “You Do” or an instructor can use the handout.
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You Do #1 A person with swollen gums rinses his mouth with warm salt water, and the swelling decreases. Which of the following has occurred? The swollen gums have absorbed the saltwater solution. The saltwater solution lowers the temperature of the water in the gums. The salt in the solution has moved against the concentration gradient. The water in the gums has moved out due to the high concentration of salt in the solution.
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You Do #2 Look at the diagram of a cross-section of a cell membrane below. The cell membrane controls movement of materials into and out of the cell. The following particles are moving from high concentration to low concentration and are using a carrier protein. How would you describe this type of movement across the membrane? simple osmosis active transport simple diffusion facilitated diffusion
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You Do #3 The cell membrane of the red blood cell will allow water, oxygen, and carbon dioxide to pass through. Because other substances are blocked from entering, this membrane is called perforated semi-permeable non-conductive permeable
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You Do #4 Placing a grape in a concentrated syrup solution will cause it to shrivel. Which statement best describes what is occurring? Water left the grape cells by osmosis. Osmosis caused sugars to enter the grape cells. Water entered the cells of the grape by osmosis. Sugars in the grape caused water to leave the cells by osmosis.
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You Do #5 The diagram below represents a cell in water. Formulas of molecules that can move freely across the cell membrane are shown. Some molecules are located inside the cell and others are in the water outside the cell. Based on the distribution of these molecules, what would most likely happen after a period of time? The concentration of O2 will increase inside the cell. The concentration of CO2 will decrease outside the cell. The concentration of CO2 will remain the same inside the cell. The concentration of O2 will remain the same outside the cell.
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You Do #6 The U-tube in the figure below is divided in the middle by a membrane that is impermeable to starch but permeable to water. A 10% starch solution is put into the right-hand half of the tube and an equal amount of 6% starch solution is put into the left-hand half of the tube In this situation: water will move from the left to the right starch will move from the right to the left water will move in both directions, but more from left to right than right to left water will move in both directions, but more from right to left than left to right
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