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Worksheet 5

membranes, diffusion and membrane transport.

QuestionAnswer
plasma membrane forms the outer boundary of a eukaryotic cell. illustrates a fluid-mosaic nature.
phospholipid most abundant molecule in the plasma membrane. it has hydrophilic head and hydrophobic tail region.
what is the role of cholesterol in the plasma membrane> maintaining its fluidity and stability across different temperatures, essentially acting as a "buffer" to prevent the membrane from becoming too fluid at high temperatures or too rigid at low temperatures
The lipids account for the fact that the membrane is like a fluid, explain why the inner layer and outer layer of the lipid are mostly water and hydrogen bonds with water to stabilize the basic structure [hydrogen bond=weak and transient]
identify carbohydrates and protein in the membrane they transport molecules across the cell membrane through channel and pores, facilitating cell to cell recognition, transmitting signals, maintaining cell shape.
integral proteins permanently embedded within the cell membrane
peripheral proteins are attached to the surface of the membranes at different times.
why is the membrane called mosaic figure due to membranes being diverse molecules embedded within the phospholipid bilayer, creating a pattern across the membrane surface performing different specific functions.
membrane permeability refer to? the ease with which a substance passes through a cells plasma membrane.
define diffusion the net spreading of particles in a mixtures or solution from an area of high concentration to an area of low concentration until uniformly distributed.
identify features that influence the rate of diffusion primarily influenced by: concentration gradient, temperature molecular size [mass], surface are, distance traveled and properties of the medium.
how does passive transport move within the cell? from high concentration to low concentration and particles down and with their gradient. this move does not require energy.
how does active transport move within the cell? from low to high concentration, particles up and against their gradient. This movement requires energy.
simple diffusion small uncharged substances such as oxygen and carbon dioxide and hydrophobic molecules such as lipids, to pass thru.
channel-mediated diffusion movement of substances thru protein from high to low concentration. small hydrophilic and particular ionic substances can pass thru. [selective]
leakage channel it is always open and particles can flow thru by diffusion.
gated channel can be open or closed conformation. [selective]
3 categories of gated channel voltage [changes in electrical charge], Ligand [BINDING by a signal molecule], and mechanically [movement].
concept of saturation in carrier-mediated diffusion the number of particles they can translate at a limited given time.
osmosis the diffusion of water through a semipermeable membrane down its concentration gradient
osmotic pressure force associated with the osmotic flow. IN AND OUT
hydrostatic pressure common forces to resist osmotic flow.
osmolarity property of a solution that is independent in any membrane
tonicity property of a solution reference to a particular membrane
hypertonic environment loses its function. [crenation=shrivel]
isotonic environment equal to the osmolarity of the cell [lysis=rupture]
hypotonic environment lysis. lower concentration of osmolarity outside.
pump proteins uses ATP or another cellular energy source to move particles.
Sodium-potassium exchange pump. transport sodium ions out of the cell and potassium ions into the cell.
primary active transport direct pumping of an ion or ions.
exocytosis Vesicles form from/fuse with plasma membrane by turning themselves inside out to release content.
endocytosis Vesicles form from/fuse with plasma by pulling material into cell as they form. [with coated protein]
Pinocytosis pulls inward to engulf fluid and dissolved particles into cells.
phagocytosis the cells extends sections of membranes to engulf large, solid particles outside the cell.
Created by: Alexa Bales
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