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chapter 5.1-5.9 biology
Terms in this set (29)
fluid mosaic model
a flexible layer made of phospholipid molecules and is interspersed with large protein molecules that act as channels through which other molecules enter and leave the cell
polarity, size, and electric charge of molecules
what determines whether a molecule can pass through a membrane?
no energy required
energy is required
the formation of membrane enclosed collections of molecules
what was a critical step in the evolution of the first cells?
what is the key ingredient of biological membranes?
the movement of molecules from an area of high concentration to an area of low concentration
the tendency of particles to spread out evenly in an available space (random collision between molecules occur)
particles diffuse down their concentration gradient, which requires no energy
what happens in diffusion?
diffusion across a cell membrane, does not require energy
diffusion down concentration gradients
how does oxygen enter your cells and carbon dioxide pass out of cells?
the diffusion of water across a selectively permeable membrane
must pass through water channels called aquaporins
what must water do because it is a polar molecule?
the water molecules will move to the area where there is a higher concentration of solute in order to try and reach equillibrium
what will happen if there is a selectively permeable membrane separating two substances and one has a higher concentration of solute?
a term that describes the ability of a surrounding solution to cause a cell to gain or lose water
concentration of solutes relative to the concentration of solutes inside the cell
what does the tonicity of a solution mainly depend on?
the concentration of solute is the same on both sides of a membrane, and the cell volume will not change
the solute concentration is lower outside the cell, water molecules move into the cell, and the cell will expand and may burst
the solute concentration is higher outside the cell, water molecules move out of the cell, and the cell will shrink
what substances easily diffuse across a cell membrane?
polar or charged substances
what substances do not easily cross cell membranes?
the process in which polar or charged substances do not easily cross cell membranes and move across membranes with the help of specific transport proteins
does not require energy and relies on the concentration gradient
a cell must expend energy to move a solute against its concentration gradient
what energy molecule supplies the energy for most active transport?
exocytosis and endocytosis
what two mechanisms do cells use to move large molecules across membranes?
used to export bulky molecules, such as proteins or polysaccharides; molecules exit from the cell
used to take in large molecules; molecules enter the cell
the engulfment of a particle by the cell wrapping cell membrane around it, forming a vacuole (type of endocytosis)
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