The Plasma Membrane Flashcards
Cytology
The study of cells
Cell size
Measured in micrometers (mcm or μm)
Side note: 1 μm is one thousandths of a mm
Plasma Membrane
Barrier that separates inside & outside the cell
Nucleus
Largest structure, where genetic material (DNA) is stored
Plasma membrane Functions
- keeps cytosol inside
- keeps Interstitial fluid Outside
- selectively regulates movement of material in and out.
What does the plasma membrane let in?
Water, glucose and oxygen
Phospholipids
MAIN lipid of the membrane; forms bi later
Cholesterol
Stabilizes membrane during temp. change; keeps membrane “fluid”
Glycolipids
Part of the glycocalyx (“sugar coating”); cellular ID marker
Extra note: “Glyco” = sugar
Transport proteins
Allow certain substances to cross the membrane & move in or out the cell.
Microvilli
Increases the surface area of the plasma membrane. For absorption of nutrients/water
On intestinal cells/ kidney cells
Cilia
Moves material across the cell surface; sweep back and forth motion; like windshield wipers.
On respiratory tract cells and oviduct cells (fallopian tubes)- sweeps eggs around in the uterus
Flagellum
Moves in a whip like motion; like a tadpole tail
- propels the cell through its environment
- on sperm cells
Tights junction
Like a zipper or ziplock seal
Holds cells tightly together
Prevents leakage
Where are tight junctions located at?
On stomach cells, intestine cells, blood vessel cells and bladder cells
Desmosome
Like buttons or snaps b/tw 2 cells
Adds strength to tissue that are pushed or pulled on a lot.
Prevents neighboring cells from pulling apart.
Where are Desmosomes located ?
On skin cells
Gap junction
Like tunnels or connector pipes
-provides a direct passage for material to flow from cytolsol of one cell into the neighboring cells
- allows flows of ions/electrical signals
-
Where are gap junctions found ?
On heart cells
Passive Transport
Doesn’t require energy input
- generally moves substances w/their natural flow
Active Transport
REQUIRES energy input
- generally moves substances against their natural flow
Concentration Gradient
Difference in amount of a substance from one area to another
-Drives diffusion
Diffusion
Movement of solute molecules from an area of higher solute concentration to an area of lower concentration.
Passive transport: Facilitated Diffusion
Moves small charged or Polar solutes through the Plasma membrane
Facilitated Diffusion requires what type of transport ?
Transport Proteins; Channels or carriers
Channels: move ions
Carrier: move glucose
Simples Diffusion
Moves small non polar solutes straight through the Plasma membrane
- no transport protein required
What solutes does simple diffusion move?
Small lipids(fatty acids)
Respiratory gasses such as O2 (oxygen gas), CO2 (carbon dioxide),
Hint for remembrance: “Breathing is simple”
Leak channel
Always open to allow ions to flow through
Gates channels
Usually kept closed but can open temporarily in response to a certain stimulus (“a key”)
Osmosis
Movement of solvent (water) across a selectively permeable membrane from a solution w/ lower solute concentration to a higher solute concentration.
Tonicity
The ability of a fluid to cause water to move by osmosis
Isotonic solution
Solute concentration is equal outside the cell and inside the cell—> water won’t move
Hypotonic Solution
Solute concentration is lower outside of the cell than inside—> water will enter the cell (can swell up an burst “hemolysis”)
Hint for remembrance: “Hypo hippo” makes the cell big like a hippo.
Hypertonic solution
Solute concentration is higher outside the cell than inside—> water will leave the cell (cell shrivels)
Hint: “Hyper sucks”
Sucks the water out of the cell
Why can’t we drink salt water??
Seawater is hypertonic.
Our cells will shrivel.
Why can drinking too much water in a short period of time kill you?
Pure water is hypotonic to our cells.
Too much pure water will cause water to enter cells .
Our cells will swell.
Active Transport
Always requires energy input, b/c:
Primary and secondary active transport, always move substance against their concentration gradient.
Bulk/vesicular transport
Move substances too large for transport proteins.
Uses vesicles and ATP energy
Two types of vesicle, transport endocytosis and exocytosis
Primary active transport
Sodium potassium pump= constantly working (uses up to 30% of cells ATP) to maintain proper concentration gradient (homeostasis) and every cell in the body
How many sodium ions and potassium ions does the sodium potassium pump out and in?
Pumps, three sodium ions out of cell and pumps two potassium ions into cell
Resting membrane potential
Sodium potassium pump contributes to charge gradient across cell.
- (RMP)
-Measured as voltage
-80 mV in average cell
Critical for cells that respond to electrical stimulation .
Calcium ion pump:
Pumps calcium ions out of the RBCs (red blood cells) in neurons.
Secondary active transport
Uses kinetic energy of one substance, moving down its concentration gradient to provide energy for a second substance to move up (against) it concentration gradient.
Endocytosis
Moves, large material INTO cells
Two types of endocytosis
Phagocytosis: “cell eating” only certain immune system cells can do this ,they eat bacteria ,dead cells or cell fragments.
Pinocytosis: “cell drinking”
all cells do this. Cells drink interstitial fluid, and it dissolves solutes.
Exocytosis
Moves large material OUT of the cell.
Reverse process of endocytosis
