Cellular Level of Organization

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Cellular Level of Organization

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Introduction

• Two types of cells
• Sex cells (haploid)
• Somatic cells (diploid)

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Cell Membranes

• 4 main functions

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1. Physcial Isolation

• Separates inside of cell from outside

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2. Selectively Permeable Membrane

• Regulates exchange with the environment

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3. Sensitivity

• Contains receptors

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4. Structural Support

• The cell membrane can connect to other cells or
  extracellular proteins

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Cell Membrane Structure

• Hydrophilic head
• Hydrophobic tails

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Cell Membrane Structure

• Ions and water soluble compounds cannot cross the
  membrane

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Cell Membrane Structure

• This separates the extracellular fluid from the
  cytosol which is important for homeostasis

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What are in membranes?

• 1. Cholesterol

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What are in membranes?

• Integral proteins

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What are in membranes?

• Enzymes
• Catalyzes reactions

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What are in membranes?

• Receptor proteins
• Protein lock
• Ligand - key

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What are in membranes?

• 5. Carrier Protein
• Transports things across the membrane

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What are in membranes?

• Channels
• Allows continuous movements of ions and water
  soluble materials

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What are outside cell membranes?

1. Peripheral proteins
2. Glycoproteins
3. Glycolipids

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Glycoprotiens and glycolipids

• Can tell if certain cells are normal or abnormal
  by their glycoproteins and glycolipids

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Organelles

• Components of cells

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1. Cytoskeleton

• Strength and flexibility
• Composed of 3 main structures
• Microfilaments ( actin )
• Intermediate filaments ( collagen )
• Microtubules ( tubulin )

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2. Microvilli

• Increase surface area
• Finger-shaped projections of cell membranes

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3. Centrioles

• Their involved in cell division
• Not found in RBC, skel. muscle cells, cardiac
  muscle cells, and neuron cells

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4. Cilia

• Long slim extensions of the cell membrane
• Found in trachea

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5. Ribosomes

• Synthesize proteins
• Composed of two subunits ( one small and one
  large)
• Free ribosomes
• Fixed ribosomes

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6. Endoplasmic Reticulum

• Network within the cytoplasm attached to the
  nucleus

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6. Endoplasmic Reticulum

• Two types
• SER
• RER

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6. Endoplasmic Reticulum

• SER
• Detoxifies drugs or toxins
• Synthesizes lipids and carbs

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6. Endoplasmic Reticulum

• RER
• Transports materials and synthesizes proteins

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7. Golgi Apparatus

• Proteins come from the ER into the golgi for
  modification

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8. Lysosome

• Breaks down and recycles organelles
• Breaks down bacteria and foreign material

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9. Peroxisomes

• Breaks down fatty acids and organic compounds

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10. Mitochondria

• Powerhouse of the cell
• Produces ATP energy
• Contains two membranes (outer and inner)

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11. Nucleus

• Chromosomes are stored here
• Composed of DNA

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Membrane Transport

• Membranes are selectively permeable

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Membrane Transport

• Passive processes do not require energy

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Membrane Transport

• Active processes require energy

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Membrane Transport

• 3 major ways in which materials are transported
• Diffusion
• Carrier-mediated transport
• Vesicular transport

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Diffusion

• Hypotonic solution less concentrated

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1. Diffusion

• Hypertonic more concentrated

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1. Diffusion

• Isotonic solutions equal concentration

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1. Diffusion

• Solutes move from hypertonic solution to
  hypotonic solution

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Ions and Water

• Remember ions and water must pass through channels

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Lipid Soluble Substances

• Alcohol, fatty acids, and steroids are lipid
  soluble

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O2 and CO2

• O2 and CO2 pass easily

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Glucose

• Glucose to big to cross cell membrane

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2. Carrier-Mediated Transport

• Can be passive or active

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2. Carrier-Mediated Transport

• Proteins carry substances across

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2. Carrier-Mediated Transport

• Sometimes carries two things at once (cotransport)

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2. Carrier-Mediated Transport

• Sometimes carries to things in opposite
  directions (countertrasnport)

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2. Carrier-Mediated Transport

1. Fascilitated Diffusion
2. Active Transport
3. Secondary Active Transport

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Facilitated Diffusion

• Passive

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Facilitated Diffusion

• Carries substances such as glucose and amino acids

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Facilitated Diffusion

• Goes down conc. Gradient but limited to number of
  carrier proteins

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Active Transport

• Requires energy

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Active Transport

• Not dependent on concentration gradient

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Active Transport

• Ion pumps use active transport

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Active Transport

• Exchange pumps move two kinds of ions in
  different directions
• Example Na/K Pump

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Na/K Pump

• Na higher in concentration outside cell
• K higher in cell

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Na/K Pump

• Sometimes Na diffuses into cell and K leaves
  through leaky channels

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Na/K Pump

• Na/K pump puts things back into order

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Na/K Pump

• Ejects on average 3Na and bringing in 2K ions

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Secondary Active Transport

• Does not require energy

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Secondary Active Transport

• Goes down a conc. gradient

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Secondary Active Transport

• It uses the concentration gradient of a molecule
  as the driving force to move another molecule
  against the concentration gradient

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3. Vesicular Transport

• Requires energy

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3. Vesicular Transport

1. Endocytosis
2. Exocytosis

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Endocytosis

• Imports substances into the cell

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Endocytosis

1. Receptor mediated endocytosis
2. Pinocytosis
3. Phagocytosis

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Receptor Mediated Endocytosis

• Extremely selective

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Receptor Mediated Endocytosis

• Plasma membrane proteins bind only with certain
  substances

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Pinocytosis

• Cell drinking

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Pinocytosis

• Dissolved proteins gather on the external surface
  of the plasma membrane, causing the membrane to
  invaginate and to incorporate a droplet of fluid

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Phagocytosis

• Cell eating

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Phagocytosis

• Parts of the plasma membrane flow around a
  relatively large or solid material and engulf it.

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Exocytosis

• Expels material out of the cell