The Cell

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The Cell

• JP Slovak
• TAMU-Commerce

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Cells

• Cell theory
• basic unit of life
• all organisms are made of cells
• All cells rise from preexisting cells
• every cell must carry ou its own functions

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Cells

• General Characters
• complex organization
• CHON
• length - 2 micrometers to 1 meter
• different shapes - round, disc, branching

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Cells

• Generalized cell
• nucleus
• cytoplasm
• plasma membrane

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Cells

• Plasma membrane (fig. 3.2)
• fluid mosaic model
• phospholipid bilayer
• hydrophilic heads
• hydrophobic tails
• integral proteins - transmembrane proteins
• peripheral proteins - not embedded in lipid

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Cells

• Microvilli
• finger like extensions - absorptive cells
• Membrane Junctions
• tight junctions - form impermeable junctions that
  encircle cell. Bladder and intestines
• desmosomes - anchoring junctions - found in
  tissues that are streched
• gap junctions - allow chemicals to pass from cell
  to cell. connexons. cardiac cells

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Cells

• Membrane transport
• diffusion - tendency of molecules to scatter
  evenly throughout the environment
• passive diffusion - must be lipid soluble and
  small
• facilitated - passive, but requires carrier
  molecule

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Cells

• Osmosis
• water is polar, does not passively diffuse
• differences in solute concentration
• be concerned with of solutes, not the type

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cells

• tonicity
• isotonic - no net loss or gain of water
• hypertonic - net loss of water by cells (crenate)
• hypotonic - net gain of water by cells

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Cells

• Active transport
• require carrier molecules
• against concentration gradient
• ATP used

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Cells

• Vesicular transport
• exocytosis- out of the cell
• endocytosis - enter the cell
• phagocytosis - cell eating
• pinocytosis - cell drinking
• receptor mediated endocytosis - receptors and
  ligand are endocytosed. EX. lipoprotein
  receptors

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Cells

• Role of membrane receptors
• contact signaling - recognition of other cells.
  Immune system
• electrical signaling - open and close ion gates
• chemical - most receptors involved in this form
  of signaling. ligand/receptor complex
• second messengers - cAMP

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Cells

• Cytoplasm
• inside plasma membrane and outside nucleus
• most cellular activities occur here
• cytosol
• organelles

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Cells

• Organelles
• Mitochondria
• sausage shaped
• energy production (ATP)
• consists of 2 membranes. outer and inner
• has own DNA

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Cells

• Peroxisomes
• sac like
• detoxify harmful substances
• free radicals

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Cells

• Ribosomes
• site of protein synthesis
• free or bound to endoplasmic reticulum
• free - make proteins for cytosol
• RER - proteins for membrane or export

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Cells

• Endoplasmic Reticulum
• rough and smooth
• rough - site of protein synthesis
• smooth - continuation of RER and synthesis of
  steroids and lipid metabolism

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The Cell Cycle

• Mitosis and Cytokinesis
• G1
• S phase
• G2

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Mitosis

• Prophase
• appearance of chromosomes
• nuclear envelope disappears
• microtubules form and associate with centrioles
  and chromosomes
• have sister chromatids joined to a centromere

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Mitosis

• Metaphase
• Spindle fibers attach to centromeres of
  chromosomes
• Chromosomes line up along the equator of the cell

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Mitosis

• Anaphase
• centromeres separate
• now are considered separate chromosomes
• spindle fibers shorten

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mitosis

• Telophase
• chromosomes complete migration to the centrioles
• Nuclear envelope reforms around each set of
  chromosomes
• Microtubules disassemble

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