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Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
Cells
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Cells

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  • 1. Cell Boundaries What are the main functions of the cell membrane and the cell wall?
  • 2.
    • When you study a country, you often begin by examining a map of its borders – where does it begin and where does it end?
    • This same principle applies to cells…the border of a cell is very important to understand.
  • 3. The Cell Wall
    • Cell walls lie outside the cell membrane in plants, algae, fungi, and many prokaryotes.
    • Most are porous enough to allow H 2 O, CO 2 , and O 2 to pass through easily.
    • Most are made from carbohydrate or protein fibers
    • The main function of the cell wall is to provide support and protection for the cell.
  • 4. The cell membrane regulates what enters and leaves the cell – also provides protection and support.
  • 5.
    • The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer .
    • Embedded into the bilayer are proteins, some of which are attached to a carbohydrate.
    • Carbohydrates are identification markers.
    • Proteins without carbohydrates often serve as channels and pumps that help move substances across the cell membrane.
  • 6.
    • Hydrophilic region – water ‘loving’ – mix easily with water
    • Hydrophobic region – water ‘hating’ – does not mix well with water
  • 7.
    • [What moves into and out of cells?]
    • In  food, carbohydrates (sugars), proteins, lipids, O 2 , H 2 O
    • Out  wastes (ammonia), CO 2 , H 2 O…
    • [What determines the rate and the direction of this movement across the membrane?]
    • Concentration gradient – the difference in concentration across a space…
    • ( solvent / solute )
    • Often the movement will continue until equilibrium is reached – equal concentrations on both sides of the membrane (equal movement in both directions)
  • 8. There are two main types of transport
    • Passive Transport – movement that does not require energy. The cell does not have to generate any energy to accomplish this type of movement.
    • The most well known example of passive transport is…
    • DIFFUSION – the movement of a substance from an area of high(er) concentration to an area of low(er) concentration.
    • When water moves, we call it…
    • OSMOSIS – the diffusion of water through a semi-permeable membrane
  • 9. Diffusion
  • 10. Osmosis
  • 11. How does OSMOSIS work?
    • Water will move into the cell . [When the surrounding fluid contains a lower concentration of dissolved materials than the cell does…]
    • … Water moves into the cell…Why?...
    • … The solution outside of the cell has a lower solute concentration than the cell itself.
    • The cell is in a hypotonic solution.
  • 12.
    • Water will move out of the cell . [When the surrounding fluid has a concentration of dissolved substances greater than the concentration within the cell…
    • Water moves out of the cell – Why?
    • The solution outside the cell has a higher solute concentration than the cell itself.
    • This cell is in a hypertonic environment.
  • 13.
    • Water moves both into and out of the cell equally . Water-to-solute concentrations are equal on both sides of the membrane.
    • This is an isotonic environment.
  • 14. The Effects of Osmosis on Cells
  • 15. Does my life depend on diffusion?
  • 16. Another example of passive transport is…
    • … Facilitated Diffusion . This is when membrane proteins chemically bind to a particle on one side of the membrane, carry it across the membrane, and release is on the other side moving WITH the concentration gradient.
    • No cellular energy is required since its moving ‘with the flow.’
  • 17.
    • New research has shown H2O enters the cell by facilitated diffusion. (Osmosis)
    • Why does water have a tough time passing through the cell membrane?
    • Many cells contain water channel proteins called aquaporins that allow water to pass right through them…
  • 18. Another application…
    • What disease does these people suffer from?
  • 19. Cystic Fibrosis
    • CF is an incurable genetic disease that affects 1 in every 3,000 Caucasian births.
    • It involves a chronic cough, lung infections, and digestion problems.
    • 25% of patients survive in their 30’s.
    • What causes it?
    • CF is caused by a mutation in the gene of a membrane protein (CFTR protein) – this protein is a part of the cell membrane and helps regulate the movement of chlorine ions (Cl - ) across the cell membrane.
  • 20.  
  • 21.
    • The inability to regulate the movement of Cl - ions results in an imbalance of water – a thick mucus builds up…
    • … on the cells of the lungs (this makes one vulnerable to lung infections)
    • … on cells in the digestive system (this blocks the release of digestive enzymes)
    • … on reproductive organs (infertility may be a problem – sperm can’t get to egg)
    • The POINT  Serious issues may arise when your cell losses its ability to regulate what substances can and can’t move across its membrane…
  • 22.
    • Active Transport - movement that does require energy. The cell plays an active role in accomplishing these particle movements.
    • Examples – All animal cells use the sodium-potassium pump to move Na + and K + across a membrane. [see next slide]
  • 23.  
  • 24.
    • Another example – proton pumps – hydrogen ions (protons) need to get moved across a membrane
  • 25. The movement of large particles into or out of cells…
    • Endocytosis (when materials are taken into the cell)
    • Phagocytosis – “cell eating” – the cell ingests large solid particles such as bacteria and food
    • Pinocytosis – “cell drinking” – the cell takes in dissolved materials
    • Receptor-mediated – specific molecules combine with receptor proteins in the membrane (this is the main way eukaryotic cells take in macromolecules)
    • Exocytosis (when materials are removed from the cell
  • 26.  
  • 27.  
  • 28. Transport Summary…

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