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CELLS

CELLS. Structure of Cells. All start out life with : Plasma membrane 2. Region where DNA is stored 3. Cytoplasm. Two types: Prokaryotic Eukaryotic . Eukaryotic Cells. Have a nucleus and other organelles Eukaryotic organisms Plants Animals Protistans Fungi. Cell Diversity.

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CELLS

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  1. CELLS

  2. Structure of Cells All start out life with: • Plasma membrane 2. Regionwhere DNA is stored 3. Cytoplasm Two types: • Prokaryotic • Eukaryotic

  3. Eukaryotic Cells • Have a nucleus and other organelles • Eukaryotic organisms • Plants • Animals • Protistans • Fungi

  4. Cell Diversity Figure 3.8c

  5. Cell Diversity Figure 3.8a–b

  6. Cell Diversity Figure 3.8d–e

  7. Cell Diversity Figure 3.8f–g

  8. Cytoplasmic Organelles Figure 3.4

  9. List of Cell Organelles/Particles See your text for more complete list. Plasma Membrane Microvilli Lysosomes and Peroxisomes Centrioles Nucleus Nucleolus Mitochondria Ribosomes RER ane SER Golgi

  10. TERMS YOU SHOULD KNOW Hydrophobic: “water–hating” Hydrophilic: “ water – loving” Amphiphilic:These molecules have both a hydrophobic and a hydrophilic side. Ex. Phospholipids.

  11. Phospholipids

  12. The Plasma Membrane MAJOR FUNCTIONS : • Serves as a barrier, while maintaining integrity of cell contents, • Allows for selective transport of molecules across it…into and out of cell for purpose of ingestion and excretion and allowing important electrolytes in and out. • Play a major role in cell to cell communication as receptors are bound externally here on hormones and specialized white blood cells etc.

  13. Components of the Cell Membrane

  14. Examples of Membrane Proteins • Carriers- Membrane Proteins that bind to glucose, electrolytes, and transfer them to other side of membrane: use ATP • Channels- allow hydrophilic solute through membrane. Some channels have gates in response to various stimuli: ligand-regulated, voltage regulated and mechanically regulated. • Receptors-These proteins are specific for one substrate to enter the membrane ie a hormone.

  15. A Word About Receptors • Found on plasma membrane. • Involved w/ chemical signaling • The receptor site is specific for a molecule or “pathogen” which when bound ..activates the receptor. • Molecule or pathogen is called a LIGAND • Receptors are usually transmembrane proteins: nerve- muscle junctions where ligand is neurotransmitter ( acetylcholine)

  16. Fluid Mosaic Model • Membrane is a mosaic of • Phospholipids • Glycolipids • Sterols • Proteins • Most phospholipids and some proteins can drift through membrane

  17. “Fluid-Mosaic Model”: Membrane has a Mixed Composition; Various Types of proteins are dispersed throughout the phospholipidbilayer

  18. Active Vs. Passive Transport Passive Transport- Substances ( Molecules, ions, move with the concentration gradient and/or with a carrier molecule; NO ENERGY on the part of cell, is required. ( ex. Diffusion, Osmosis, Facilitated Diffusion) Active Transport- Molecules move against the concentration gradient ENERGY (ATP) REQUIRED.

  19. When Are Transmembrane Proteins Used To Transport? When substances are: 1) charged Or 2) too large

  20. Different Methods of Transport Through the Plasma Membrane: Some Involve TM Proteins Figure 3.10

  21. Facilitated Diffusion • Here the molecules use a carrier or channel protein even though they are traveling with the concentration gradient. • Molecules may either be too large or charged.

  22. Na-K Pump: How it Works • A type of active transport. • 3 sodium ions move out of cell • 2 potassium ions move into cell. • ATP is needed as each of these ions are moving against their conc. gradient. • Mostly used in cardiac muscle and nervous tissue. Maintains Na+K gradient concentration. • Huge amount of ATP goes into this NaK pumps!

  23. Sodium –Potassium Pump Figure 3.11

  24. Sodium-Potassium Pump A molecule of ATP is used with each “swap of Na/K ions

  25. INSIDE-0UT!!!GO!!! • The sodium-potassium pump (using a carrier protein) perpetuates this “flip-flopping” of charges or what is known as the “action-potential” that causes a nerve impulse.

  26. Adenosine Triphosphate (ATP) Figure 2.19a

  27. Nerves Impulse Conduction on Neuron

  28. BULK TRANSPORT METHODS • These include: Exocytosis, Endocytosis ( Phagocytosis is an example), Pinocytosis and Receptor-Mediated Endocytosis • They all are method of ACTIVE TRANSPORT ( use ATP)

  29. Endocytosis (phagocytosis) • This is Vessicle transport during which the entire plasma membrane folds inward allowing large particles into the cell. • Ex; the cell is ingesting microbes , perhaps?

  30. Exocytosis • The opposite of ENDOcytosis. Large particles are leaving the cell. (digested microbes for example).

  31. Receptor- Mediated Endocytosis Viruses are species –specific , and receptor specific, transmitted via receptor-mediated endocytosis.

  32. The Nucleus • Control center of the cell • Contains genetic material (DNA) • Three regions • Nuclear membrane • Nucleolus • Chromatin • Some cells , like skeletal muscle are multinucleate. Figure 3.1b

  33. Nucleolus • Dense mass of material in nucleus • May be one or more • Cluster of DNA and proteins • Materials from which ribosomal subunits are built (rRNA)stands for ribosomal RNA • Subunits must pass through nuclear pores to reach cytoplasm

  34. Cellular Respiration: Where Does it Take Place in the Cell?

  35. Double membrane Cristae

  36. Mitochondria • Several of the steps in cellular respiration occur in the matrixdue to its high concentration of enzymes.

  37. WHERE ARE PROTEINS MADE?

  38. RIBOSOMES • RIBOSOMES ; THE details called TRANSLATION, IS THE SUBJECT OF the next lesson . • For today, some basics: 1. they are the SITE of protein synthesis, that is where the polypeptide chain is arranged from DNA message. • 2. Ribosomes are “particles”, composed of 2 subunits; NOT membrane-bound organelles! • 3. After ribosomes get the polypeptide chain produced, some stay in cytoplasm to be modified but many go to the ER. Which ones ? ……..

  39. THEY ARE: Endoplasmic reticulum (ER) Golgi bodies Vesicles

  40. Endomembrane System • Group of related organelles in which 1. lipids are assembled and new polypeptide chains are modified • In otherwords they serve a similar function:(2 things) • 2. Products are sorted and shipped to various destinations

  41. Rough ER • Arranged into flattened sacs • Ribosomes on surface give it a rough appearance • Some polypeptide chains enter rough ER and are modified • Cells that specialize in secreting proteins have lots of rough ER

  42. Endoplasmic Reticulum

  43. Smooth ER • A series of interconnected tubules • No ribosomes on surface • Lipids assembled inside tubules • Smooth ER of liver inactivates wastes, drugs • Sarcoplasmic reticulum of muscle is a specialized form

  44. What is the Job of The Rough ER? A nascent protein chain will enter on the cisternal side WHY??? YOU ASK? ROUGH ……. is for bumpy…..this means there are little bitty … RIBOSOMES. Site of initial modification of protein for proteins that are to be either 1. Secreted,2. membrane-bound OR3. destined to be part of the plasma membrane. OK….

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