Chapter 12 Pt 2 Flashcards
Upper limit to cell size
Cell needs a high enough surface area to volume ratio to meet its metabolic requirements
Why is controlling cell division particularly important for multicellular organisms
Crucial for proper development and maintenance of a healthy organism
Cell division rates vary with cell types
- skin cells divide frequently
- liver cells only decide when a need arises
- nerve cells and muscle cells do not divide
Cell cycle checkpoints
Control points in the cell cycle where “stop” and “go” signals can regulate the cycle
-can be internal or external
G1 checkpoint (most important)
Cell can exit or enter the cell cycle
-G0 phase: non diving state of cell
Growth factors
Proteins released by certain cells that stimulate other cells to divide
-affect different cell types
What are PDGFs? Why are they important?
Blood platelets release PLATELET DERIVED GROWTH FACTOR, which stimulates fibroblast cells to divide
Anchorage dependence
Most cells must be attached to a surface to divide
Density dependent inhibition
Cells stop dividing when they come into contact with one another
-in tissue culture cells grow to a single layer thick
Cancer cells
Cancer cells are no longer controlled by signals that regulate the cell cycle in normal mammalian cells
-cancerous cells divide uncontrollably
Tumor
Masses of uncontrollably dividing cells
Benign tumors
Remain at original site
-can be completely removed by surgery and do not cause serious problems
Malignant tumors
Can invade surrounding tissues
- can impair one or more organs
- more difficult to treat (chemotherapy)
What happens to the surface to volume ratio as cells grow?
As cells grow, the volume increases at a greater rate than surface area
-surface area to volume ratio decreases
