Unit 2 Flashcards
Prokaryote
-No nucleus
-DNA in nucleoid
-cytosol
-ribosomes
-small
-primitive
-ex: bacteria, archaea
Eukaryote
-Nucleus
-cytosol
-membrane bound organelles
-larger
-more complex
-ex: plant, animal
Surface area to volume ratio
Cells must maintain a large surface area to volume ratio. Allows increased rate of diffusion between cell and environment.
Plasma membrane is
selectively permeable
selectively permeable
small, nonpolar molecules can easily pass through
Fluid mosaic model
membrane is held together by weak interactions.
membrane is composed of phospholipids, proteins, and carbs
Phospholipids
Amphipathic: hydrophilic heads (polar), hydrophobic tails (nonpolar)
membrane fluidity
Saturated: straight tails tightly packed together = less fluid
unsaturated: double bonds create kinks, prevent tight packing = more fluid
cholesterol
acts as a buffer for fluidity
limit fluidity at high temps
hinders close packing at low temps preventing solidification.
Passive transport
Diffusion occurs without energy. molecules move from high to low.
Passive transport: simple diffusion
movement of small, nonpolar molecules across the membrane
Passive transport: Facilitated diffusion
movement of polar (hydrophilic) molecules through transport proteins.
Down Concentration Gradient
High to low
Up Concentration Gradient
Low to High, requires ATP
Osmosis
water moves through membrane in response to solute concentration differences
Isotonic
solute concentration is equal
Hypertonic
higher solute concentration outside the cell. Causes water to diffuse out of the cell.
Hypotonic
Lower solute concentration outside the cell. Causes water to move into the cell.
channel proteins
during facilitated diffusion, these proteins provide a hydrophilic channels for polar molecules to pass through
carrier proteins
during facilitated diffusion, these proteins carry the molecules across the membrane
Aquaporin
channel protein that allows the passage of water
Active Transport
Requires energy (ATP). Proteins transport molecules AGAINST the concentration gradient. (low to high)
Sodium Potassium Pump
To keep the inside of the cell negative and out the cell positive, the sodium potassium pump moves Na+ and K+ against their concentration gradient. 3 Na+ are pumped out, 2 K+ are moved in.
cotransport
membrane protein enables “downhill” diffusion of one solute to drive “uphill” transport of the other
