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Cell membranes
- 1. CellMembranes & Movement Across Them
- 2. All cells live in a liquid environment to survive One of the most important functions of a cell membrane is to regulate the movement of dissolved molecules from the liquid on one side of the membrane to the liquid on the other side.
- 3. Cell (plasma) membrane • Cells need an inside & an outside… – separate cell from its environment – cell membrane is the boundary between the inside & outside of cell OUT: IN: food Waste or - sugars products - proteins - ammonia - fats - salts salts - CO2 &H2O O2& H2O - proteins cell needs materials in & products or waste out
- 4. 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?
- 5. Lipids of cell membrane • Membrane is made of special kind of lipid: phospholipids Polar side is – “split personality” “attracted to water” • Membrane is a double layer – phospholipidbilayer: polar on outsides phosphate – Non-polar on the inside inside cell lipid Non-polar side is outside cell “repelled by water”
- 6. Semi-permeable membrane • only some material can get in or out • Cell membrane controls what gets in or out • Need to allow some materials — but not all — to pass through the membrane So what needs to get across the membrane? sugar lipids aa O2 H 2O salt waste
- 7. Quiz Time! Q) A non-polar molecule • A) is hydrophobic. • B) is hydrophilic. • C) is covalent. • D) is ionic.
- 8. Crossing the cell membrane • What molecules can get through the cell membrane directly? – fats and oils can pass directly through lipid inside cell waste salt but… sugar aa H 2O what about outside cell other stuff?
- 9. Cell membrane channels • Need to make ―doors‖ through membraneprotein channels allow substances in &out specificchannels allow specific material in & out • H2O channel, salt channel, sugar channel, etc. inside cell H 2O aa sugar waste salt outside cell
- 10. How do you build a semi- permeable cell membrane? • Channels are made of proteins – proteins both “like” water & “like” lipids bi-lipid protein channels membrane in bi-lipid membrane
- 11. Protein channels • Proteins act as doors in the membrane – channels to move specific molecules through cell membrane HIGH LOW
- 12. Q) Cell membranes are constructed mainly of: • A) lipid layers. • B) protein pumps. • C) carbohydrate gates. • D) free-moving proteins.
- 13. Movement through the channel • Why do molecules move through membrane if you give them a channel? ? HIGH ? LOW
- 14. Molecules are constantly moving. • They collide w/ one another and tend to spread out randomly. As a result… ? HIGH ? LOW
- 15. molecules move from high to low concentration. • Diffusion : movement from HIGH to LOW concentration
- 16. Q) Diffusion occurs because • A) molecules constantly move and collide with one another. • B) the concentration of a solution is never the same throughout a solution. • C) the concentration of a solution is always the same throughout the solution. • D) molecules never move or collide with one another.
- 17. Diffusion • Move from HIGH to LOW concentration –is passive transport –requires no energy diffusion of water diffusion osmosis
- 18. Simple Diffusion • Move from HIGH to LOW concentration fat fat fat Which way inside cell will fat move? fat fat fat LOW HIGH fat outside cell fat fat fat fat fat fat fat
- 19. Facilitated Diffusion • Move from HIGH to LOWconcentrationthrough 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
- 20. Diffusion Movement from HIGH to LOW concentration 1) directly through membrane *simple diffusion *no energy needed 2) help through a protein channel *facilitated diffusion (with help) *no energy needed HIGH LOW
- 21. Diffusion When the concentration of the substance on both sides of the cell are the same, particles will continue to move across the membrane in both directions, but in equal numbers. HIGH LOW
- 22. Simple vs. facilitated diffusion simple diffusion facilitated diffusion lipid inside cell inside cell H 2O protein channel H 2O outside cell outside cell
- 23. Q) A substance that moves across a cell membrane without using the cell’s energy tends to move • A) away from the area of equilibrium. • B) away from the area where it is less concentrated. • C) away from the area where it is more concentrated. • D) toward the area where it is more concentrated.
- 24. Q) A substance that moves across a cell membrane without using the cell’s energy tends to move • A) away from the area of equilibrium. • B) away from the area where it is less concentrated. • C) away from the area where it is more concentrated. • D) toward the area where it is more concentrated.
- 25. Q) Which of the following is a function of the cell membrane? • A) breaks down lipids, carbohydrates, & proteins from foods • B) stores water, salts, proteins, & carbohydrates • C) keeps the cell wall in place • D) regulates which materials enter & leave the cell
- 26. Active transport • Cells may need molecules to move against concentration “hill” – need to pump “uphill” • from LOW to HIGHusing energy – protein pump – requires energy • ATP ATP
- 27. Transport summary simple diffusion facilitated diffusion active ATP transport
- 28. Osmosis: Movement of Water Across Cell Membrane 2006-2007
- 29. 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
- 30. Keeping water balance • Cell survival depends on balancing water uptake & water loss freshwater balanced saltwater
- 31. Keeping right amount of water in 1 cell • Freshwater – a cell in fresh water KABOOM! freshwater – high concentration of water around cell • cell gains water • example: Paramecium • problem: cells gain water, swell & can burst No problem, –water continually enters here Paramecium cell • solution: contractile vacuole –pumps water out of cell
- 32. Controlling water • Contractile vacuole in Paramecium
- 33. Keeping right amount of water in 2 cell • Saltwater – a cell in salt water I’m shrinking, saltwater I’m shrinking! – low concentration of water around cell • cell loses water – example: shellfish – problem: cell loses water • in plants: plasmolysis I will survive! • in animals: shrinking cell – solution: take up water
- 34. Keeping right amount of water in 3 cell • Balanced conditions – no difference in That’s balanced concentration of water better! between cell & environment • cell in equilibrium • example:blood • problem: none –water flows across I could membrane equally, be better… in both directions –volume of cell doesn’t change
- 35. Ice Fishing in Barrow