Cells

1
Cells

• Cell theory All living things are cellular.
• Challenged in 20th century.
• Viruses non-cellular.
• Exception not important here.

2
Cell

• Components of a cell
• Plasma (cell) membrane
• Cytoplasm
• Nucleus

3
Plasma membrane

• Fluid mosaic model
• Fluid mosaic of phospholipid and protein,
  resembles soap bubble.
• Phospholipid has polar and non-polar ends.
• Cell lives in aqueous (polar) environment.
• Phospholipids spontaneously form bilayer.
• Polar heads to aqueous internal and external
  fluids
• Non-polar tails to inside of membrane

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Plasma membrane
5
Organelles

• Nucleus
• Ribosomes
• Endoplasmic reticulum
• Golgi apparatus
• Lysosomes

• Peroxisomes
• Mitochondria
• Centrioles
• Cytoskeleton
• Cilia/flagella

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CELLULAR REPRODUCTION

• Reproduction is characteristic of life.
• Reproduction of individuals depends on
  reproduction at cellular level.

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CELLULAR REPRODUCTION

• When cells reproduce, new cells (daughter cells)
  must be exact copies of mother cell!!
• Genomes must be identical!
• Anything else leads to chaos.
• Cell with incomplete genome (missing genes) would
  be inviable or non-functional.
• Cell with extra (too many) genes could also be
  abnormal.
• Trisomy-21 (Down syndrome)

8
Life cycle of a cell the Cell Cycle.

• G1 first gap phase
• cell growth, normal metabolism.
• S synthesis phase
• replication, synthesis of new DNA and chromosome
  material
• G2 second gap phase
• production of enzymes and other proteins for
  mitosis
• Mitosis normal, ordinary nuclear division.

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Cell Cycle

• Interphase
• G1
• S
• G2
• Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase

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Phases of Mitosis

• from end of "interphase" (end of G2)
• PROPHASE
• nucleolus and nuclear envelope disappear
• chromosomes coil, shorten, thicken to become
  visible
• chromosome 2-stranded, held together at
  centromere
• chromosomes move toward cellular "equator"
• centrioles move apart toward poles, beginning of
  mitotic spindle

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PROPHASEearly late
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Phases of Mitosis

• METAPHASE
• 2-stranded chromosomes arrive at "equator"
• spindle fibers pull on centromeres

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Phases of Mitosis

• ANAPHASE
• centromeres split,
• each strand 1-strand chromosome
• 1-strand chromosomes move apart toward centrioles

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Phases of Mitosis

• TELOPHASE (prophase in reverse)
• chromosome movement ends
• mitotic spindle disassembles
• chromosomes uncoil, lengthen, become invisible
• nucleolus and nuclear envelope reappear, reform

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Cytokinesis

• division of cytoplasm
• usually simultaneous with telophase
• not in skeletal muscle??
• Some cells in animals, plants, fungi, amoebae
  have multinucleate cells
• mitosis without cytokinesis

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Lab drawings

• Measure 1 inch (2.5 cm) from 4 edges of paper
• Fold in half to find center
• Vertical
• Draw within margins
• Print labels
• Extend pointers all the way to objects.
• Number, Title, and magnification on title line.