Eukaryotic cells

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Eukaryotic cells
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Structure of Eukaryotic cells

• Nucleus - contains DNA
• Membrane bound organelles p64
• Larger than prokaryotic cells
• Divided into 5 categories
• Nucleus and ribosomes
• Organelles of the endomembrane system
• Peroxisomes and vacuoles
• Energy related organelles
• cytoskeleton

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Nucleus

• Nucleus contain chromatin material
• Nucleoplasm semifluid matrix
• RNA produced in nucleus
• Nucleolus dark region of chromatin, rRNA
  produced and forms ribosomes
• Nuclear envelope double membrane with nuclear
  pores (allow mRNA and ribosomes out)

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Ribosomes

• Non-membrane bound, protein synthesis
• Composed of 2 subunits
• Polyribosomes group of ribosomes
• Cytoplamsic ribosomes and ER ribosomes produce
  their own proteins

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Endomembrane System

• Nuclear envelope
• membranes of ER
• golgi apparatus
• vesicles
• Compartmentalizes the cell
• Page 72

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Endoplasmic reticulum

• Physical continuous with the nuclear envelope
• Rough studded with ribosomes synthesizes
  proteins
• Forms vesicles that transport large molecules
  usually to cell membrane or Golgi apparatus
• Smooth continuous with rough, contain gland
  cells that synthesize lipids

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Golgi Apparatus

• Stack of curved, flattened sacs, face ER and cell
  memebrane
• Receives vesicles from ER
• Sorts and packages proteins and lipids, some are
  lysosomes, others exit through exocytosis.

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Lysosomes

• Membrane vesicles produced by GA
• contain hydrolytic digestive enzymes
• Recycle cellular material.
• Tay-Sachs disease result of missing enzyme that
  digests a fatty substance that helps insultate
  nerve cells.
• Apoptosis programmed cell death

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Peroxisomes

• Vesicles that enclose enzymes whose action
  results in hydrogen peroxide
• Hydrogen peroxide is broken down to water and
  oxygen by catalase.

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Vacuoles

• Membranous sacs larger than vesicles
• Usually store substances
• Central vacuole filled with cell sap that give
  support to cell and stores nutrients and waste
  products, plants do not have an excretory system.
• Functions as lysosomes in plants, old organelles
  fuse with vacuole and get broken down.

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Chloroplasts

• Use solar energy to synthesize carbohydrates
• A type of plastid (double membrane organelle that
  contains a series of internal membranes/vesicles
  and DNA)
• ex. Chromoplasts, leucoplasts.
• Stroma (space), Thylakoid (disk), granum (stack
  of disks)

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Mitochondria

• Double membrane, outer and inner (cristae)
• Cristae are folded to increase surface area
• Matrix contains mtDNA and ribosomes
• Produce ATP

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Cytoskeleton

• Maintains shape of cell and allows organelles to
  move.
• Contains actin filaments, intermediate filaments
  and microtubules.

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Actin filaments

• Long, thin flexible fibers
• Structural role, just under cell membrane
• Together with myosin, move the cell and its
  organelles.

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Intermediate filaments

• Ropelike assembly of fibrous polypeptides.
• Roles include supporting nuclear envelope, plasma
  membrane and/or cell to cell junctions.

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Microtubules

• Small, hollow cylinders
• Made of tubulin, small globular protein
• During cell division, disassemble and reassemble
  as spindle fibers, and back again.

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Centrioles

• 9 0 microtubule triplets
• In animal cells, contained in the centrosome
• - main microtubule organizing center for the
  cell
• Involved in the process of microtubule assembly
  and disassembly?
• In cell division, aid in mitotic spindle
  organization?
• Give rise to basal bodies in cells with cilia and
  flagella?

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Cilia and Flagella

• Hair-like projections used for locomotion
• Membrane bound, 92 pattern
• Basal body in cytoplasm at base