A lipid bilayer that contains protein channels, enzymes, and receptors

  Cholesterol increases membrane fluidity

  Cells are negative inside compared to outside; based on Na/K ATPase (3 Na⁺ out/2 K⁺ in)

  The Na⁺ gradient that is created is used for co-transport of glucose, proteins, and other molecules

  Desmosomes/hemidesmosomes – adhesion molecules (cell–cell and cell–extracellular matrix, respectively), which anchor cells

  Tight junctions – cell–cell occluding junctions; form an impermeable barrier (eg epithelium)

  Gap junctions – allow communication between cells (connexin subunits)

  G proteins – intramembrane proteins; transduce signal from receptor to response enzyme

  Ligand-triggered protein kinase – receptor and response enzyme are a single transmembrane protein

  ABO blood-type antigens – glycolipids on cell membrane

  HLA-type antigens – glycoproteins (Gp) on cell membrane

  Osmotic equilibrium – water will move from an area of low solute concentration to an area of high solute concentration and approach osmotic equilibrium

CELL CYCLE

  G1, S (protein synthesis, chromosomal duplication), G2, M (mitosis, nucleus divides)

  G1 most variable, determines cell cycle length

  Growth factors affect cell during G1

  Cells can also go to G0 (quiescent) from G1

  Mitosis

•  Prophase – centromere attachment, spindle formation, nucleus disappears

•  Metaphase – chromosome alignment

•  Anaphase – chromosomes pulled apart

•  Telophase – separate nucleus reforms around each set of chromosomes

NUCLEUS, TRANSCRIPTION, AND TRANSLATION

  Nucleus – double membrane, outer membrane continuous with rough endoplasmic reticulum

  Nucleolus – inside the nucleus, no membrane, ribosomes are made here

  Transcription – DNA strand is used as a template by RNA polymerase for synthesis of an mRNA strand

  Transcription factors – bind DNA and help the transcription of genes

•  Steroid hormone – binds receptor in cytoplasm, then enters nucleus and acts as transcription factor

•  Thyroid hormone – binds receptor in nucleus, then acts as a transcription factor

•  Other transcription factors – AP-1, NF-κB, STAT, NFAT

  Initiation factors – bind RNA polymerase and initiate transcription

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