Transport across cell membranes

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Define diffusion.
the net movement of particles down a concentration gradient from an area of high concentration to an area of low concentration
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What type of process is diffusion?
A passive process.
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What is strange about water and the phospholipid bilayer?
Water is able to move through the bilayer even though its polar. (It's small enough to fit through.)
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Give some of the factors affecting rate of diffusion
the concnetration gradient (steeper concentration gradient, faster diffusion), thickness of the exchange surface, surface area and the temperature.
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why is diffusion faster under hot temperatures?
due to particles having more kinetic energy meaning that they can move faster (e.g. from one end of the gradient to the other)
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what is facilitated diffusion?
The process in which some larger molecules, ions and polar molecules are able to diffuse across the phospholipid bilayer.
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what type of process is facilitated diffusion?
It is a passive process.
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What molecules does facilitated diffusion use?
It uses carrier proteins and channel proteins.
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What type of molecules do carrier proteins transport?
They transport large molecules in and out of the cell down the concentration gradient.
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Give the steps to facilitated diffusion with carrier proteins.
The large molecule attaches to the carrier protein in the plasma membrane. The protein then changes shape- this releases the molecule on the opposite side of the membrane.
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what type of molecules does a channel protein transport?
It transports charged molecules via diffusion down the concentration gradient.
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What do channel proteins form to allow the diffusion of particles across phospholipid bilayer?
They form pores in the membrane.
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What is active transport?
The process in which molecules and ions move across the membrane against the concentration gradient.
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What type of process is active transport?
It is an active process (requires energy)
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Give the steps in which active transport occurs.
The molecule attaches to the carrier protein, the protein changes shape and the molecule moves across the membrane and is released on the other side of the membrane.
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What is endocytosis?
The process in which molecules too big to taken through the cell can be taken through the cell.
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Give the steps of endocytosis.
The cell surrounds the substance with a section of plasma membrane. The membrane pinches off to form vesicle inside the cell which contains the substance.
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Give an example of endocytosis
a white blood cell taking in a pathogen
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what type of process is endocytosis?
An active process (uses ATP for energy)
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what is exocytosis?
The process in which some of the substances that are produced by the cell leave the cell
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give the steps in which exocytosis occurs
vesicles containing the substance pinch off from sacs in the golgi apparatus. Then they move to the plasma membrane. Vesicles then fuse with the plasma membrane, releasing contents into plasma membrane- e.g. proteins- and outside cell
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What type of process is exocytosis?
Active (uses ATP as an energy source)
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define osmosis
the diffusion of water molecules across a partially permeable membrane down a concentration gradient, from high concentration to an area of lower concentration.
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define water potential
the potential of water molecules to diffuse out into a solution
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what has the highest water potential?
pure water. Thus all other solutions have lower water potential.
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what controls how much water will move in or out of a solution?
The water potential of surrounding solution
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what is the net movement of water when the solution has a higher water potential than the cell?
into the cell, meaning cell will burst
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what is the net movement of water when the solution has the same water potential of the cell?
the water molecules pass in and out of cell in equal amounts; cell stays the same
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what is the net movement of water when the solution has a lower water potential than the cell
net movement out of the cell; cell shrinks
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what is the movement of water when a plant is placed in hyptonic solution
net movement of water into cell; vacuole swells and vacuole and cytoplasm push against cell wall (doesn't break due to cell wall). Cell becomes turgid
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what is the movement of water when a plant is placed in isotoic solution
cell stays same
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what is the movement of water when a plant is placed in hypertonic solution
cell shrinks as net movement of water out of cell
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Other cards in this set

Card 2

Front

What type of process is diffusion?

Back

A passive process.

Card 3

Front

What is strange about water and the phospholipid bilayer?

Back

Preview of the front of card 3

Card 4

Front

Give some of the factors affecting rate of diffusion

Back

Preview of the front of card 4

Card 5

Front

why is diffusion faster under hot temperatures?

Back

Preview of the front of card 5
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