BMS100 Chapter 3 Outline, Part One
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A typical cell includes a cell membrane, cytoplasm (with organelles), and a nucleus.
Movements Through Cell Membranes (p. 59)
The cell membrane is selectively permeable. The ability of a particle to pass through the membrane is based mainly on the size of the particle.
  1. Passive mechanisms such as diffusion do not require cellular energy.
    1. Diffusion is the movement of molecules or ions from regions of higher concentration toward regions of lower concentration
    2. diffusion occurs "down" or "with" the gradient)            
    3. Diffusion of oxygen: from air in lungs to blood to cell interiors
    4. Diffusion of carbon dioxide: from cells to blood to air in lungs
    5. Facilitated diffusion - example: glucose diffuses into cells via transporter made of protein
  2. Active transport
    1. moves molecules or ions from regions of lower conc. toward regions of higher conc. ("up" or "against" the gradient)            
    2. requires 1) carrier molecules in the cell membrane and 2) cellular energy from ATP
    3. example: sodium/potassium pump            
    4. Answer the following questions about ions in body fluids.
      1. Active transport results in the transport of sodium ions (choose one) into cells or out of cells?
      2. In most human tissues, the concentration of sodium ions inside cells is _?_ the concentration of sodium ions outside cells.  
      3. Diffusion results in the movement of sodium ions into cells or out of cells?
      4. Active transport results in the transport of potassium ions (choose one) into cells or out of cells?
      5. In most human tissues, the concentration of potassium ions inside cells is _?_ the concentration of potassium ions outside cells.  
      6. Diffusion results in the movement of potassium ions into cells or out of cells?
Animations (available at BMS 100 Web Site): Diffusion | Sodium Potassium Pump
Chapter 3 Questions at Online Learning Center – 2, 3, 4, 7, 8, 9, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 25, 26, 29, 31, 33, 34, 35, 36, 38, 41, 43, 44

BMS100 Chapter 3 Outline, Part Two: The Nucleus, DNA, Genes and Chromosomes

Four major points for today’s class:
  1. The structure/function of protein molecules is critical.
    • active transport - Ions are pumped into or out of cells.
    • Examples: Na gets pumped out of cells; chloride also gets pumped out of cells (by a separate pump).
    • The "pump" molecules are made of protein.
    • 20 amino acids are found in protein molecules; each protein typically consists of hundreds of amino acids
    • Primary structure of a protein = the sequence of amino acids
    • tertiary structure (“3D shape”) - is critical for normal function; is dependent on primary structure
    • cystic fibrosis (CF) - thick mucus “clogs” lungs and pancreatic ducts
    • CF is caused by a defective Cl pump
    • Chloride pump normally contains 1,480 amino acids. In cystic fibrosis, one amino acid is missing. Defective gene leads to defective protein.
    • Sickle cell anemia: abnormal hemoglobin, causes cells to “sickle” and block blood vessels

  2. The information needed to produce “correct” proteins is stored in DNA (genes) in the nucleus.
    • chromatin contains DNA
    • 1869 - Miescher isolated a slightly acidic substance from the nuclei of white blood cells - “nucleic acid”
    • Percentages of bases (A, T, G, & C) in DNA: for each species, %A very close to %T, %G very close to %C
    • Watson & Crick deduced the double helix structure of DNA (1953)
    • Base Pairing Rules: G & C fit together, A & T fit together
    • The bases are held weakly together by H bonds.
    • Information is stored in the sequence of bases.
    • A gene is a segment of a DNA molecule. Each DNA molecule (chromosome) contains thousands of genes.

  3. Genetic information in must be available to the cytoplasm.
    • Central Dogma - describes the flow of information: DNA to RNA to protein.
    • Part One: process of transcription transfers information to messenger RNA (p. 84)
      • DNA double helix “unzips,” loose individual bases assemble according to base pairing rules; the bases are linked into a messenger RNA (mRNA) molecule.
      • The mRNA is a “transcript” of the original gene.
      • The DNA re-zips returns to its original state.
      • Messenger RNA leaves the nucleus and goes to the cytoplasm (Fig. 4.13)
    • Central Dogma, Part Two - process of translation: mRNA carries a “message” to build a protein with a certain primary structure
    • In cystic fibrosis and sickle cell disease, the _?_ is defective. Choose one or more.
      1. information in DNA (the gene)
      2. process of transcription
      3. information in RNA (the messenger)
      4. process of translation
      5. primary structure of the protein (the gene product)

  4. If a cell divides, genetic information must be transmitted to the daughter cells.
    • Cell cycle (Fig. 3.21) - needed during embryonic development and in adults (cells in bone marrow divide and produce more than 2 million new blood cells per second)
    • Cell cycle begins with one cell, results in two “daughter cells.” Each daughter cell has a complete set of genes (46 chromosomes).
    • Mice have been grown from individual stem cells from skin (they contained all mouse genes)
    • Major parts of cell cycle:
      1. Interphase – DNA “copies itself”
        1. double helix “unzips”
        2. loose bases enter & “pair up” (A’s & T’s, G’s & C’s)
        3. loose bases are linked together
        4. result: two molecules of double stranded DNA, each “half old, half new”
      2. Mitosis – DNA is directed to daughter cells
        1. DNA “coils up” into a chromosome (prophase); each chromosome consists of two identical DNA molecules (“chromatids”) attached to each other
        2. Chromosomes “line up” on equator (“metaphase”)
        3. microtubules attach to chromatids and cause them to move apart (“anaphase”)
        4. Once the chromatids are pulled apart, two nuclei begin to appear (“telophase”).
        5. At the end of the cell cycle, there will be _?_ (how many) daughter cells, each with _?_ (how many) chromosomes.
        6. There are approximately six feet of DNA per cell. Why do we need chromosomes?
    • Stem cell - undergoes mitosis - one daughter cell becomes a skin cell, blood cell, etc.; other daughter cell remains a stem cell (so we never “run out of” stem cells)
Animations: Cell Cycle | Mitosis
Chapter 3 Questions at Online Learning Center – 2, 3, 4, 7, 8, 9, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 25, 26, 29, 31, 33, 34, 35, 36, 38, 41, 43, 44
also do these Questions from Chapter 4 - 17, 18, 19, 24, 25, 27
BMS100 Outlines | BMS100 Home
Fall 2011