Osmosis/Water Potential/Membranes ch 7.

what does "random but directional" mean in the context of diffusion

random bc no real plan for where the specific molecules will go

directional because general trend will always be [high]->[low]

the rate of diffusion is determined by ____

concentration

do substances diffuse independent or dependent of each other

substances diffuse independent of each other

osmosis

diffusion of water through a selectively permeable membrane

aquaporin

A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane

diffusion

movement of molecules from an area of higher concentration to an area of lower concentration

is atp required for diffusion

no

can molecules of sugar, salts, etc move through membranes by themselves

no, they require transport proteins

tonicity

measure of osmotic pressure; ability of the surrounding solution to cause a cell to gain/lose water

hypertonic solution

solution of the environment has a greater concentration of solutes compared to the cell

what happens in a hypertonic solution

water moves out of the cell, cell shrinks

what is the condition of the cell if the solution is considered hypertonic

cell is hypotonic

hypotonic solution

solution has a lower concentration of solute compared to the cell

what happens in a hypotonic solution

water moves into the cell, cell swells

what role do cell walls play when a cell is in a hypotonic solution

cell walls prevent lysis

water flows from ______ (hypotonic/hypertonic) solutions to ______ (hypotonic/hypertonic) solutions

water flows from hypotonic solutions to hypertonic solutions

isotonic solutions

same solute/water concentration as inside cells; water moves in and out

water potential

the potential energy of a volume of water, expressed as a pressure

units for water potential

megapascals (MPa)

water potential equation

Ψ = Ψs + Ψp

water passes across a membrane from (high/low) water potential to (high/low) water potential

water passes across a membrane from high water potential to low water potential

explain high water potential in terms of solutes

high water potential means fewer solutes (less negative value)

as concentration increases, water potential _____

decreases

3 types of passive transport

diffusion, osmosis, facilitated diffusion (channel proteins, carrier proteins)

does passive transport take energy

yes

is cellular ATP needed for passive transport

no

what kind of molecules can pass through a bilayer with diffusion

small uncharged molecules like water, CO2, O2

facilitated diffusion

uses transport proteins to move other ions and small molecules across the plasma membrane using a concentration gradient

do channel proteins physically transport molecules

no

how do channel proteins work

gated channels open in response to an environmental gradient

do carrier proteins physically transport molecules

yes

how do carrier proteins work

- A large molecule attaches to a carrier protein in the membrane.

- The protein changes shape.

- This releases the molecule on the opposite side of the membrane.

rate of transport depends on

- solution/electrical gradient

- number of transfer proteins

active transport

uses cellular ATP to pump molecules across a membrane against a concentration/electrical gradient

electrogenic pump

An active transport protein that generates voltage across a membrane while pumping ions.

how does the cell use energy stored through the electrogenic pump

cell uses energy stored in the electrical change gradient to drive cellular work

Na K pump

major electrogenic pump of animals; used to build up an electrical/chemical gradient used to drive other transport processes in the cell

does the cytoplasm favor + or -? does the extracellular fluid favor + or -?

The cytoplasm is - so favors +

the extracellular fluid is + so favors -

explain how the Na/K pump works

Sodium-Potassium (Na-K) - By using Phosphate from ATP, the shape of the protein changes. This change in shape changes the affinity for (Na) or (K). The difference in number of charged ions gives a different charge.

proton pump

major electrogenic pump of plants, fungi, bacteria

does the proton pump use ATP?

yes: used to split h2O and release h+

explain how the proton pump works

energy is used to pump h+ out, causing a + charge on one side of the membrane and a - charge on the other side. this electrochemical gradient (+/-) can be used to do work

co-transport

The transport of one substance coupled with the transport of another substance across a plasma membrane in the same direction through the same protein carrier.

Sucrose/H+ pump

1. pumps h+ through membrane proteins (proton pump)

2. h+ return through other protein carriers which also bring in a needed second molecule, like sucrose

cytosis

large biological molecules (proteins, polysaccarides, etc) enter or leave a cell enclosed in a lipid bilayer (vesicle) plasma membrane

does cytosis require atp?

yes

exocytosis and its steps

Process by which a cell releases large amounts of material

1. vesicles from golgi moves via cytoskeleton to plasma membrane

2. vesicle and plasma membrane fuse, releasing contents outside of plasma membrane

endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

types of endocytosis

phagocytosis, pinocytosis, receptor-mediated endocytosis

phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells

pintocytosis

the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.

receptor-mediated endocytosis

The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.

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