Biology 207Spring 2004

Lecture 2: Cells

Reading: R-Campbell Chapter 7 or chapter on cell structure from any introductory biology textbook

Outline:

1. Plasma Membrane

2. Nucleus

3. Cytoplasm

4. Mitochondria

5. Cytoskeleton

6. Extracellular matrix/cell junctions

Lecture:

To understand what goes wrong in a cancer cell, we need to know more about the structure and function of normal cells. In today's class we will review some basic cell biology and point out some of changes that occur in cancer cells.

[Insert schematic diagram of a cell]

1. Plasma membrane

  • forms boundary of cell
  • critical for receiving signals from outside cell and deciding what enters cell
  • phospholipid bilayer
  • contains embedded proteins, such as receptors

Normal cell / Cancer cell
Let nutrients and oxygen in, wastes out / Same as normal cell
Receive/send signals to other cells / Incorrectly process signals/send wrong signals

Signals are sent and received by a cell usually via receptor proteins in the plasma membrane.

[diagram of receptor]

2. Nucleus

[diagram of cell illustrating structures in the nucleus]

nucleus=membrane bound organelle that contains the genetic material. Changes in appearance when cell divides.

Normal cell / Cancer cell
Nucleus contains genes / Some of the genes are "mutated"
Nucleus directs cell to make proteins
DNARNA protein / Mutated genes in the nucleus direct synthesis of altered proteins
Nucleus receives chemical signals from cytoplasm that alter gene expression / Cancer cell nucleus receives the wrong signals; tell cell to divide or to turn on inappropriate genes

Genes=segments of DNA that contain information to make RNA or proteins

Mutation=change in the base sequence of DNA

ACG TGC normal gene

ACG TGAmutated gene

Change DNA sequence change code for protein

3. Cytoplasm

Consists of fluid (cytosol), proteins, ribosomes (sites of protein synthesis), and membrane bound organelles

Organelles include

  • Mitochondria: Energy metabolism
  • Endoplasmic reticulum and Golgi body: Protein processing
  • Lysosomes: Degration of organelles and proteins

4. Mitochondria

mitochondria=organelles involved in energy metabolism and cell death

Normal cell / Cancer cell
Efficiently make ATP, the energy storing molecule / Hog ATP and starve out normal cells
Old cells receive a signal to die so they are replaced by new cells / Old cells not told to die; get too many cells cancer

5. Cytoskeleton

cytoskeleton=Network of fibers throughout the cytoplasm

  • Made of filamentous proteins: tubulin, actin, keratin
  • Provide structural support
  • Determine cell shape
  • Involved in cell movement
  • Anchor cell-cell connections
  • Move organelles around
  • Move chromosomes during cell division

Normal cell / Cancer cell
Predetermined cell shape / Become metastatic, able to change shape and migrate from original site
Divide in response to normal signals / Cell division not regulated

6. Extracellular matrix/cell junctions

ECM=material outside cell that holds cell in place yet allows for movement of nutrients, oxygen, and signaling molecules.

  • Includes a lot of "sticky proteins" (collagen, proteoglycan, fibronectin).

[diagram of cells adhering to basement membrane via ECM]

Normal cell / Cancer cell
Cells stay put / Cells migrate away
Cells anchored to ECM / Secrete enzymes that break down ECM

Intercellular junctions

  • Hold cells together
  • Some allow communication between cells
  • Some prevent fluid from seeping into tissues
  • Most common in epithelia

[diagram showing examples of cell junctions]

Normal cell / Cancer cell
Cells attached to each other / Cells lose their attachments
Cell communication good / Cell communication reduced

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