Sac revision Flashcards
Simple diffusion
a type of diffusion in which the molecule can pass directly through the lipid bilayer
Facilitated diffusion
a type of diffusion in which a carrier or channel protein is needed because the molecule cannot pass the lipid bilayer directly
Osmosis
movement of water which occurs from a low concentration of solution to a high concentration of solution
Active transport
movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Requires energy
Bulk Transport
Bulk transport is the movement of large molecules, those that are too large for facilitated diffusion.
Factors which affect diffusion across a membrane
size tonicity temperature hydrophobic/hydrophilic polarity
Hypertonic
Higher solute, Lower water
decreased weight because water moves out of the cell
Hypotonic
Lower solute, Higher water
increase in the weight of cell because water has moved in
Isotonic
when the concentration of two solutions is the same
hydrophilic
Water loving
passive transport
the movement of substances across a cell membrane without the use of energy by the cell
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extracellular
outside the cell
intracellular
within the cell
solute
A substance that is dissolved in a solution.
solution
mixture of two or more substances in which the molecules of the substances are evenly distributed
Function of the plasma membrane- Transport
A plasma membrane is permeable to specific molecules that a cell needs. Transport proteins in the cell membrane allow for selective passage of specific molecules from the external environment. Each transport protein is specific to a certain molecule
Function of the plasma membrane- Communication
Your cell membrane plays an integral role in cellular communication because it holds the proteins, carbohydrates, and other molecules that are essential to cellular communication. These communications may come from signalling molecules sent by other cells, from cell-to-cell interactions, or from within the cell itself.
Function of the plasma membrane- Retain contents
The cell membrane, therefore, has two functions: first, to be a barrier keeping the constituents of the cell in and unwanted substances out and, second, to be a gate allowing transport into the cell of essential nutrients and movement from the cell of waste products.
Function of the plasma membrane- Surround organelles
provides protection for a cell, transport nutrients into the cell and also to transport toxic substances out of the cell.
Phospholipids
Phospholipids are a class of lipids whose molecule has a hydrophilic “head” containing a phosphate group and two hydrophobic “tails” derived from fatty acids, joined by an alcohol residue. 0==
Lipid bilayer
The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. (plasma membrane)
Carrier and channel proteins
Channel proteins are proteins that have the ability to form hydrophilic pores in cells’ membranes, transporting molecules down the concentration gradient. Carrier proteins are integral proteins that can transport substances across the membrane, both down and against the concentration gradient.
Cholesterol
mainly functions to prevent the phospholipids from packing in too tightly and becoming stiff. Cholesterol is not present in plant cell membranes.