Cells: Function


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  • Often in biology, structure determines function and vice versa. clockwise: muscle tissue, red blood cells, bacteria on smoked salmon, nerve cells,
  • This is an actual microscopic image. Colors are added digitally to enhance the different parts.
  • This is an actual microscopic image. Colors are added digitally to enhance the different parts.
  • Cells: Function

    1. 1. Cells: FunctionThe Inner Workings of Life Heartlife 2012-2013 Teacher: Julie Pen Harvard Cell Video
    2. 2. Plasma Membrane• Made of a phospholipid bilayer• Semi-permeable: like a screen - some things pass while others cannot
    3. 3. Selectively Permeable Membrane
    4. 4. Transport Across Membranes• Passive Transport: small, uncharged molecules move freely across the plasma membrane• Active Transport: Larger, charged molecules need help to get across – requires energy
    5. 5. Passive Transport• Passive Transport: – Small, uncharged molecules move in and out of a cell • water, carbon dioxide, ammonia, oxygen, fatty acids – Molecules move both directions across the plasma membrane – Net movement is down the concentration gradient • Simple Diffusion – directly through the phospholipid bilayer • Facilitated Diffusion – with the help of channel or carrier proteins – proteins only let certain molecules through
    6. 6. Active TransportActive Transport• Larger, charged molecules need the help of transport proteins to get across• Can go against concentration gradient• Requires energy Transport Animations
    7. 7. Exocytosis
    8. 8. Endocytosis EndocytosisExocytosis
    9. 9. Nucleus• Surrounded by a double membrane – called the nuclear envelope• Contains chromatin – loose DNA strands that form chromosomes – DNA & RNA hold "blueprints" that build/regulate proteins • direct all cell functions• Pores in membrane allow material to enter and leave the nucleus
    10. 10. Nucleolus• Dense mass of RNA and proteins inside the nucleus• NOT bound by membrane• Ribosomes are made here• Sometimes more than one
    11. 11. Ribosomes• Ribosomes build proteins in a process called translation – Two subunits (parts) work together – mRNA feeds through, directing the sequence of amino acids – amino acid are joined to form a polypeptide chain Protein Synthesis Video
    12. 12. Ribosomes• Build proteins by connecting amino acid chains• mRNA gives instructions for specific amino acid sequences• tRNA pieces hold amino acids and match up with mRNA to build the protein chain
    13. 13. Rough Endoplasmic ReticulumRough ER• studded with ribosomes• Sorts & transports proteins• connected to nuclear envelope• Vesicles are pinched off to transport contents to Golgi or outside of cell
    14. 14. Smooth Endoplasmic ReticulumSmooth ER• Makes lipids – steroids, hormones• Breaks down carbohydrates, lipids and toxins• Vesicles pinch off – transport contents to Golgi or outside cell• Liver, ovaries & testes have LOTS of smooth ER
    15. 15. Golgi Apparatus• Looks like a stack of pancakes• Stores, sorts, modifies and packages proteins• Molecules transported to and from the Golgi by means of vesicles
    16. 16. Lysosomes• Garbage disposal of the cell• Contain hydrolytic enzymes that break down wastes (old cell parts as well as invaders)
    17. 17. Mitochondria• Site of Cellular Respiration (O2 is used, CO2 is given off)• Food molecules (fats, protein, carbs) are converted into ATP • Folds called cristae increase surface area & efficiency of chemical reactions • Inner fluid is called the matrix • Has its own DNA and ribosomes
    18. 18. Cell Wall• Found in bacterial and plant (as well as algae) cells• Located outside of the cell membrane
    19. 19. Cell Wall• Rigid, protective barrier composed of strong cellulose fibers (polysaccharides) and proteins• Outermost lamella is a gluey layer between adjacent cells
    20. 20. Chloroplasts• Contain chlorophyll (green pigment)• Inside the double membrane, granum are formed from stacks of thylakoids (membrane-bound disks) – this is where photosynthesis occurs (solar energy converted into carbs) • Contains own DNA and replicates independently from the rest of the cell
    21. 21. Week 7 Lab ReviewMicroscope Lab: plant vs. animal cells
    22. 22. Intercellular Junctions• Tight junctions bind cells together and prevent certain fluids and molecules from crossing the membrane.• Desmosomes (plasmodesmata) are strong anchors between cells. – made from folds of both cells’ intertwined membranes• Gap junctions are formed from proteins embedded in the cell membrane. – allow substances (and electrical charges) to flow in and out between cell.
    23. 23. PlasmodesmataGaps in a plant/bacterial cell wall that allow for transportation of substances between cells
    24. 24. Peroxisomes• Small sacks enclosed in a single membrane• Contains enzymes that break down alcohol & fatty acids• Formed from pinching off from the ER• Found mostly in kidney and liver cells
    25. 25. Cytoskeleton• Microfilaments – thin, contractile (stretchy) filaments – help muscles cells contract – pinches cells in two during cytokinesis – provide strength, elasticity and support to the cell’s cytoskeleton• Microtubules – tiny, tube-like structures – form centrioles – give rise to cilia and flagella – limited transport capabilities – give shape and support to cell’s cytoskeleton
    26. 26. Centrioles• Only in animal cells• Hang out near the nucleus• Made from microtubules• Help divide chromosomes during cell division.
    27. 27. Cilia & Flagella• Hair or tail-like structures that provide motility• Formed from microtubules that arrange themselves into a cylindrical shape• Centrioles form basal bodies that provide the framework for each cilium or flagellum• Generally occur only in animal cells
    28. 28. Flagellum