bio 4

• The Human Body is composed of roughly 37 trillion cells
• Cells


  Microscopic, Eukaryotic cells (10-100 mm)

  
• Human egg cell is barely visible to the naked eye
• Plasma membrane

  • Surrounds the cell
  • Regulates what goes in and out of the cell
  • It is semi-permeable
• Cytoplasm


  • Contains the cellular contents between the plasma membrane and the nucleus
  • Cytosol is the watery environment within the cell
• Nucleus


  • Largest organelle in humans
  • Contains chromosomes (linear pieces of DNA that code for genes)
  • Controls cell structure and function (activities)
• Organelles


  • Found in the cytoplasm
  • Small membrane bound structures
  • Specialized compartments that have specific roles in the cell

  
• Cytoskeleton

  • Network of interconnected protein filaments in the cell
  • The "cell's skeleton"
  • A dynamic network of protein fibers found in the cytoplasm

  
• Types of cytoskeleton fibres

  • Microtubules
  • Microfilaments
  • Intermediate filaments
• Microtubules


  Hollow tubes made from tubulin monomers (thickest)
• Microtubules


  • Cell shape
  • Organelle movement
  • Chromosome movement
  • Cell motility (cilia and flagella)

  
• During cell division, microtubules form mitotic spindles
• Microfilaments


  Solid rods made from actin protein monomers (thinnest)

  
• Microfilaments


  • Cell shape
  • Muscle contraction
  • Cell motility (pseudopodia)
  • Cell division (cleavage furrow)
  • Cytoplasmic streaming
• Intermediate filaments


  Solid rods made from keratin proteins (various types)

  
• Intermediate filaments


  • Cell shape
  • Fixes organelle location
  • Nucleus shape and rigidity (nuclear lamina)

  
• Ribosomes


  • Complexes of rRNA and ribosomal proteins
  • Synthesize proteins from mRNA
• Types of ribosomes


  • Free ribosomes
  • Bound ribosomes
• Free ribosomes


  • Found in the cytoplasm
  • Synthesize cytosolic proteins
  • Proteins used in the cell

  
• Bound ribosomes


  • Bound to the endoplasmic reticulum
  • Synthesize membrane-bound and secreted proteins

  
• Endoplasmic reticulum (ER)


  Extensive membranous network of tubules and sacs continuous with the nuclear envelope

  
• Types of Endoplasmic Reticulum (ER)


  • Smooth ER
  • Rough ER

  
• Smooth ER


  • Lacks ribosomes
  • Synthesizes lipids (ex. steroids like testosterone in the testes)
  • Participates in carbohydrate metabolism
  • Drug and poison detoxification
  • Stores Calcium (Ca2+) in muscle cells
• Rough ER


  • Has ribosomes on its surface
  • Synthesis of secreted proteins and proteins destined for insertion into biological membranes
  • Produces

  
• Ribosomes


  Complexes of rRNA and ribosomal proteins that synthesize proteins from mRNA

  
• Types of ribosomes


  • Free ribosomes (found in cytoplasm, synthesize cytosolic proteins)
  • Bound ribosomes (bound to endoplasmic reticulum, synthesize membrane-bound and secreted proteins)

  
• Endoplasmic reticulum (ER)


  Extensive membranous network of tubules and sacs continuous with the nuclear envelope, within the cytoplasm

  
• Types of Endoplasmic Reticulum (ER)

  • Smooth ER (lacks ribosomes, synthesizes lipids, participates in carbohydrate metabolism, detoxifies drugs/poisons, stores calcium in muscle cells)
  • Rough ER (has ribosomes on its surface, synthesizes secreted proteins and proteins destined for biological membranes, produces membrane for its own structure)

  
• Protein production and secretion outside of the cell


  1. Protein synthesis begins on free ribosome

  2. Signal peptide synthesized, ribosome moves to RER and becomes bound

  3. Protein synthesis continues on bound ribosome

  4. Protein enters RER

  5. Protein leaves RER via transport vesicle

  6. Transport vesicle fuses with cis side of Golgi

  7. Protein processed, sorted and delivered to trans side of Golgi

  8. Protein leaves trans side of Golgi in secretory vesicle

  9. Secretory vesicle fuses with plasma membrane

  10. Protein released outside cell by exocytosis

  
• RER makes its own membrane
• Mitochondria


  Powerhouse (power plant) of the cell, site of cellular respiration to produce ATP
• Structure of mitochondria


  • Double phospholipid bilayer forming two fluid-filled spaces
  • Outer membrane is smooth and highly permeable
  • Inner membrane is extensively folded to increase surface area
  • Inner membrane contains enzymes involved in cellular respiration
  • Matrix contains DNA, ribosomes and enzymes

  
• Peroxisomes


  Surrounded by single phospholipid bilayer, contain enzymes for detoxification and breakdown of fatty acids
• Lysosomes


  Membrane-enclosed sacs of hydrolytic enzymes with very acidic pH, produced by Golgi apparatus
• Lysosome function


  • Carry out intracellular digestion by fusing with food vacuoles
  • Digest damaged organelles and macromolecules, release monomers for recycling
  • Break down and destroy things to protect cell, for maintenance, and to recycle components
• The nucleus


  Membrane-bound organelle containing DNA (genes)

  
• What happens in the nucleus

  1. DNA replicates to make copies

  2. DNA directs synthesis of RNA through transcription
• Nuclear envelope/membrane


  • Double phospholipid bilayer with nuclear pores for passage of large molecules
  • Has nuclear lamina network of proteins to maintain nuclear shape

  
• DNA


  Disorganized form is called chromatin, nucleolus is site of rRNA synthesis
• Cell types and organelles

  • B cells (antibody-secreting) - ribosomes, ER, Golgi
  • Liver cells - peroxisomes
  • Muscle cells - mitochondria, ribosomes
  • White blood cells - lysosomes, cytoskeleton
  • Beta cells in pancreas - ribosomes, ER, Golgi