CELLS

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CELLS

• Basic unit of life
• Cell theory
• Cytology study of cells
• Accomplished by LM, SEM, TEM

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CELL MEMBRANE

• Selectively permeable
• Physical isolation
• Regulation of exchange with environment
• Sensitivity
• Structural support

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MEMBRANE STRUCTURE

• Phospholipids (phosphate group bonded to a
  diglyceride) form a bilayer
• Cholesterol (lipid)
• Proteins partially embedded (peripheral) or
  totally spanning (integral)
• Carbohydrates glycocalyx act as adhesive,
  receptor area, ID system

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MEMBRANE PROTEINS

• Receptors receive chemicals at binding site
  triggers change in cell activity
• Channel allow H2O to get through lipid bilayer
• Carrier transport solutes across membrane
• Enzymes
• Anchor attach stabilize cell membrane
• Identifier identifies cell as self

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MEMBRANE TRANSPORT

• Can be passive or active

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PASSIVE TRANSPORT

• No energy requirement
• DIFFUSION
• The net movement of molecules from gt to lt
• Determined by lipid solubility (alcohol, fatty
  acids, steroids, O2, CO2)
• Molecules move DOWN their concentration gradient

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2. OSMOSIS

• Diffusion of H2O across a membrane
• H2O moves from areas of high H2O to low H2O
• OR low solute to high solute
• Isotonic
• Hypotonic (hemolysis results)
• Hypertonic (crenation)

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3. FILTRATION

• H2O and small molecules forced across membrane by
  hydrostatic pressure, along a pressure gradient
• EX. Movement of water, nutrients, and gases
  through a capillary wall formation of kidney
  filtrate

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4. FACILITATED DIFFUSION

• Transported molecule binds to receptor site,
  protein carrier (integral protein) undergoes a
  conformational change, allowing molecule to enter
  cell
• Carriers are specific
• EX glucose into cell

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ACTIVE TRANSPORT

• Requires ATP
• Moves a substance (molecule, ion) against its
  concentration (or electrochemical) gradient
• Requires a carrier protein

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1. SOLUTE PUMPING

• Against concentration gradient
• Movement of most amino acids and ions
• Requires a carrier protein (specific)
• EX. Na/K pump (exchange pump)

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2. EXOCYTOSIS

• Secretion of substances from cell
• Substance is enclosed in a membranous vesicle
  which fuses with the CM
• EX. Neurotransmitters, hormones, mucus, etc
  ejection of cell waste

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3. PHAGOCYTOSIS

• Type of endocytosis
• cell eating
• Large external particle (proteins, bacteria, dead
  cell debris) surrounded by a pseudopod and
  becomes enclosed in a membranous sac
• EX. WBCs and macrophages

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4. PINOCYTOSIS

• Type of endocytosis
• cell drinking
• CM surrounds an external droplet containing small
  solutes membrane edges fuse, forming a fluid
  filled vesicleEX. Absorptive cells of the
  intestines and kidneys

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5. RECEPTOR MEDIATED ENDOCYTOSIS

• External substances bind to specific membrane
  receptors and form a coated pit
• EX. Intake of some hormones, cholesterol, iron
  and others