Week 3 - Plasma Membrane Transport & Mitosis Flashcards
What is plasma membrane in terms of transport?
- Both a barrier and gateway between cytoplasm and extracellular fluid
- Some molecules pass easily through, others do not (selectively permeable)
- Atoms and molecules use Passive or Active processes
What is passive transport?
- No ATP required
- Molecules moves DOWN their concentration gradient (from high to low)
What is simple diffusion?
Non-polar, fat-soluble (hydrophobic) molecules diffuse through phospholipid bilayer
(e.g., oxygen (O2) into a cell)
What is facilitated diffusion?
- Polar (electrolytes), fat-insoluble / water-soluble (hydrophilic) molecules
- Carrier or channel protein (e.g., glucose)
What is osmosis?
- Simple diffusion of H2O across a selectively permeable membrane
- Between the phospholipids or Aquaporins (channels)
What is osmolarity?
- Concentration of solute particles (stuff) in solution
- When solutions of different osmolarity are separated by a plasma membrane, osmosis occurs
- Water moves DOWN its concentration gradient
- Until water concentration same on both sides (equilibrium)
What happens when osmosis occurs?
- Water enters or leaves a cell
- Changing cell volume disrupts cell function
What is tonicity?
The ability of a solution to cause a cell to shrink or swell
What is hypotonic?
Hypotonic solution has a lesser solute concentration (thus more water) than cell.
What is isotonic?
Isotonic solution has same solute concentration (thus water concentration) as that of cell.
What is hypertonic?
Hypertonic solution has a greater solute concentration (thus less water) than cell.
What is active transport processes?
- Molecules moves UP their concentration gradient (from low to high)
- ATP (energy) required
What is vesicular transport?
- Requires ATP
- Large molecules in vesicles (Sacs)
- Vesicle phospholipids merge with phospholipids of plasma membrane or other
membranous structures
What is exocytosis?
Secrete molecules out of cell
What is endocytosis?
Bring molecules into cell
What is the cell life cycle?
- Many cells have a limited lifespan and need to be replaced e.g., gut lining, wound healing
- Life cycle length variable between cells
What is interphase?
- Housekeeping e.g., protein synthesis
- DNA replicated to make enough chromosomes for two new cells
What is mitosis?
One pre-existing cell divides into two new identical cell
What is DNA replication?
- DNA untwisted to expose the two nucleotide strands (polymers)
- Each strand used as a template by DNA polymerase to build a new complementary
strand - Forty-six chromosomes replicated in 6-8 h by thousands of DNA polymerases
What happens at the end of DNA replication?
- Each chromosome now composed of two identical chromatids held together at
centromere - 46 chromosomes = 92 chromatids
- Ready for mitosis (mechanical process)
State the steps of the mitosis process?
- Prophase
- Metaphase
- Anaphase
- Telophase
(IPMAT)
What is prophase?
- Chromosomes compacted
- Nuclear envelope disintegrates
- Centrioles sprout microtubules (spindles) which push centrioles to each pole of cell
- Some microtubules attach the centromeres
What is metaphase (middle)?
Forty-six chromosomes lined up at cell equator by microtubules (Metaphase plate)
What is anaphase (apart)?
- Centromeres split separating the sister chromatids
- Chromosomes (single chromatids) pulled toward poles
