Eukaryotic Cells

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Eukaryotic Cells

• Eukaryotic cells are characterized by having
• DNA in a nucleus that is bounded by a membranous
  nuclear envelope
• Membrane-bound organelles
• Cytoplasm in the region between the plasma
  membrane and nucleus
• Eukaryotic cells are generally much larger than
  prokaryotic cells

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Plasma Membrane

• The plasma membrane is a selective barrier that
  allows sufficient passage of oxygen, nutrients,
  and waste to service the volume of every cell
• The general structure of a biological membrane is
  a double layer of phospholipids

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Surface Area to Volume

• The logistics of carrying out cellular metabolism
  sets limits on the size of cells
• As the surface area increases by a factor of n2,
  the volume increases by a factor of n3
• Small cells have a greater surface area relative
  to volume ratio

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Surface Area to Volume
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Nucleus

• Contains most of the DNA in a eukaryotic cell
• Ribosomes use information from DNA to make
  proteins
• Nucleus contains most of the cells genes and
  usually most conspicuous organelle
• Nuclear envelope encloses the nucleus, separating
  it from cytoplasm
• Nuclear membrane is double membrane each
  membrane consists of lipid bilayer

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Nucleus

• Pores regulate entry/exit of molecules
• Shape maintained by the nuclear lamina composed
  of protein
• DNA and proteins form genetic material called
  chromatin
• Chromatin condenses to form chromosomes
• Nucleolus located within nucleus is site of
  ribosomal RNA (rRNA) synthesis

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Ribosomes

• Ribosomes made of ribosomal RNA and protein
• Ribosomes carry out protein synthesis in two
  locations
• In the cytosol (free ribosomes)
• On outside of endoplasmic reticulum or nuclear
  envelope (bound ribosomes)

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Ribosomes
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The Endomembrane System

• Endomembrane system regulates protein traffic
  and performs metabolic functions in cell
• Components of endomembrane system
• Nuclear envelope
• Endoplasmic reticulum
• Golgi apparatus
• Lysosomes
• Vacuoles
• Plasma membrane
• Components are continuous or connected via
  vesicles

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Endomembrane System

• The endomembrane system is a complex and dynamic
  player in the cells compartmental organization

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The endoplasmic reticulum

• Endoplasmic reticulum (ER) accounts for more than
  half of total membrane in many eukaryotic cells
• The ER membrane is continuous with the nuclear
  envelope
• Two distinct regions of ER
• Smooth ER, lacks ribosomes
• Rough ER, ribosomes studding its surface

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Smooth VS Rough ER

• Smooth ER
• Synthesizes lipids
• Metabolizes carbohydrates
• Detoxifies poison
• Stores calcium
• Rough ER
• Bound ribosomes, secrete glycoproteins (proteins
  covalently bonded to carbohydrates)
• Distributes transport vesicles, proteins
  surrounded by membranes
• Membrane factory for the cell

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Golgi

• Golgi apparatus aflattened membranous sacs
  called cisternae
• Functions
• Modifies products of the ER
• Manufactures certain macromolecules
• Sorts and packages materials into transport
  vesicles

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The Golgi
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Lysosome

• Lysosome membranous sac of hydrolytic enzymes
• Can digest macromolecules
• Lysosomal enzymes can hydrolyze
• Proteins
• Fats
• Polysaccharides
• Nucleic acids

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Cell Digestive Stuff

• Some types of cell can engulf another cell by
  phagocytosis this forms a food vacuole
• A lysosome fuses with food vacuole and digests
  molecules
• Lysosomes also use enzymes to recycle cells own
  organelles and macromolecules, a process called
  autophagy

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Concept Check

• Main difference between phagocytosis and
  autophagy?
• Why are prokaryotic cells so impressive when
  compared to eukaryotic cells?
• What are the components of the endomembrane
  system?
• Whats the deal with skinny jeans on dudes these
  days?

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Vacuoles

• A plant cell or fungal cell may have one or
  several vacuoles
• Food vacuoles are formed by phagocytosis
• Contractile vacuoles, found in many freshwater
  protists, pump excess water out of cells
• Central vacuoles, found in many mature plant
  cells, hold organic compounds and water

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Mitochondria Chloroplasts

• Mitochondria are the sites of cellular
  respiration, a metabolic process that generates
  ATP
• Chloroplasts, found in plants and algae, are the
  sites of photosynthesis
• Peroxisomes are oxidative organelles

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Mitochondria Chloroplasts

• Mitochondria and chloroplasts
• Are not part of the endomembrane system
• Have a double membrane
• Have proteins made by free ribosomes
• Contain their own DNA