-
Phospholipids form a bilayer which is like a "lake" in which a variety of proteins "float." This model is known as the __
fluid mosaic model
-
Membranes may vary in __. Phospholipids vary in __
lipid composition; fatty acid chain length
-
2 types of membrane proteins:
- peripheral: lack exposed hydrophobic groups & do not penetrate the bilayer
- integral: penetrate the bilayer
(page 8 on slide)
-
Membranes have carbs on the outer surface that serve as __
recognition sites for other cells & molecules
- glycolipids (carb + lipid)
- glycoproteins (carb + protein)
(page 8 on slide)
-
Cells arrange themselves in groups by __ & __
cell recognition; cell adhesion
-
cell junctions
specialized structures that hold cells together
- tight junctions
- desmosomes
- gap junctions
-
form a "quilted" seal, barring the movement of dissolved materials & bacteria through the space between epithelial cells. helps ensure directional movement of materials
tight junctions
(page 11 on slide)
-
link adjacent cells tightly but permit materials to move around them in the intercellular space, has intermediate filaments
desmosomes
(page 12 on slide)
-
let adjacent cells communicate
gap junctions
(page 13 on slide)
-
Membranes have __ permeability, meaning __
selective; some substances can pass through, but not others
-
passive transport
no outside energy required (diffusion)
-
active transport
energy required
-
random movement toward equilibrium (particles continue to move, but there is no change in distribution)
diffusion
(page 16 on slide)
-
For passive transport, net movement is directional until __ is reached.
equilibrium
-
Diffusion is the net movement from regions of __ concentration to regions of __ concentration
greater/higher; lesser/lower
(page 17 on slide)
-
Diffusion rate depends on:
- diameter of the molecules or ions
- temperature of the solution
- concentration gradient
-
Simple diffusion: __ molecules pass through the lipid bilayer. __ molecules can diffuse across the membrane. __ molecules can NOT pass through easily.
- Small;
- Water & lipid-soluble;
- Electrically charged & polar
-
osmosis
the diffusion of water
-
Osmosis depends on __, NOT __
- the # of solute particles present;
- the type of particles
-
For osmosis, water will diffuse from the region of __ concentration to the region of __ concentration.
- higher water (lower solute);
- lower water (higher solute)
-
There are concentrated solutes outside of the cell & more water inside the cell. The outside of the cell is __ and water will flow __ the cell.
hypertonic; out of
(page 21 on slide)
-
There is equivalent solute concentration both inside & outside the cell.
isotonic
- Our plasma is isotonic & the red blood cell has a biconcave shape.
(page 22 on slide)
-
There are dilute solutes outside of the cell & more water inside. The outside of the cell is __ and water will flow __ the cell.
hypotonic; into
(page 23 on slide)
-
proteins involved in passive transport
- channel proteins
- carrier proteins
-
proteins that have a central pore lined with polar amino acids
channel proteins
-
membrane proteins that bind some substances & speed their diffusion through the bilayer (facilitated diffusion)
carrier proteins
-
There is more K+ in the cell than outside, so the __ force is __
chemical driving; outward
(page 25 on slide)
-
There is more Na+ outside the cell than inside, so the __ force is __
chemical driving; inward
(page 26 on slide)
-
If there is more + ions outside the cell & more - ions inside the cell, the + ions will flow __ & - ions will flow __. This is called the __ force.
inward; outward; electrical driving
(page 27 on slide)
-
specific channel proteins w/ hydrophilic pores
ion channel
-
For ion channels, rate & direction of ion movement through channels depends on __
the concentration gradient & the distribution of electrical charge (electrical gradient)
(page 29 on slide)
-
2 types of ion channels
- leakage channels (K+, always open)
- voltage-gated (Na+, can be closed or open to ion passage)
(page 30 on slide)
-
Carrier proteins transport polar molecules such as glucose across membranes in both directions. This is called __
facilitated diffusion
(page 31 on slide)
-
The more glucose concentration outside of the cell, the rate of diffusion would be __
into the cell
(page 32 on slide)
-
moves substances against a concentration and/or electrical gradient - requires energy
active transport
-
The energy source for active transport is __
ATP (adenosine triphosphate)
-
3 kinds of proteins for active transport
- uniporters (1 ion goes in)
- symporters (2 ions go in same direction)
- antiporters (2 ions go in/out opposite direction)
(page 35)
-
primary vs secondary active transport
- primary: requires direct hydrolysis of ATP
- secondary: Energy comes from an ion concentration gradient that is established by primary active transport.
-
The Na+/K+ pump is an __ protein and uses __ transport.
- integral membrane (antiporter);
- primary active
(page 37 on slide)
-
In secondary active transport, energy can be "regained" by __
letting ions move across a membrane with the concentration gradient.
-
Secondary active transport aids in uptake of __ & uses __ (proteins)
- amino acids & sugars;
- symporters (Na+ & glucose) & antiporters (K+ & Na+)
ex. Na+ brings glucose in (as energy)
(page 40 on slide)
-
Macromolecules that are too large to cross the membrane can be taken in or secreted by means of __
membrane vesicles
Large molecules include:
- proteins
- polysaccharides
- nucleic acids
-
processes that bring molecules into a eukaryotic cell. The plasma membrane folds in or invaginates around the material, forming a vesicle.
endocytosis
(page 42 on slide)
-
material in vesicles is expelled from a cell
exocytosis
- Indigestible materials are expelled.
- Other materials leave cells such as digestive enzymes & neurotransmitters.
(page 43 on slide)
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