2.5 Biological Membranes

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what is one of the main functions of the cell membrane
the cell membrane forms the barrier and separates the cell contents from the cell's exterior environment, or separates the organelles from cytoplasm
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why is the cell membrane described as partially permeable
some very small molecules simply diffuse through the cell membrane, n between the structural molecules. some substances dissolve in the lipid layer and pass through, other substances pass though special proteins channels. they are partially permeable as t
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what are the roles of the plasma membrane
separates the cell's components from external environment, regulates transport of materials into and out of the cell, may contain enzyme involved in specific metabolic pathways, has antigens so that organisms immune system can recognise the cell as being
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what is the role of the plasma membrane within cells
mitochondria have folded inner membranes, cristae which give a large surface area for reactions, the inner membranes of chloroplasts
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what is the fluid mosaic model
theory of cell membrane structure with proteins embedded in a sea of phospholipids
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why is the cell surface membrane referred to as the 'fluid mosaic model'
proposed by Singer and Nicolson and said that the fabric of the membrane consisted of a phospholipid bilayer with proteins floating in it, making up a mosaic pattern, and the lipid molecules can change places with each other some proteins may move which m
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what are the components of the 'fluid mosaic model'
it contains the phospholipid bilayer, with carrier proteins, channel proteins, peripheral and integral proteins, glycoproteins, glycolipids, glycocalyx and cholesterol
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what is an example of not all cell membranes not having the same composition
pg 129
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what is diffusion
the movement of molecules from an area of high concentration of that molecule to an area of low concentration. it may or may not be across a membrane, and does not involve metabolic energy (ATP)
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what the factors that affect the rate of diffusion
Temperature, Diffusion distance, surface area, size of diffusing molecule, concentration gradient
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how is the concentration gradient maintained inside of the plant cell during diffusion
oxygen diffusing into the cytoplasm of respiring cells then diffuses into mitochondria and used for aerobic respiration. CO2 diffusing into the palisade mesophyll cells of plant leaf will then diffuse into chloroplasts and used for photosynthesis
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what is facilitated diffusion
movement of molecules from an area of high concentration of that molecule to an area of low concentration across a partially permeable membrane via protein channels or carries and does not involve metabolic energy
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what is osmosis
the net diffusion of water molecules from a region of low water potential to an area of high water potential across a partially permeable membrane
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how does osmosis differ from diffusion
osmosis only involves water molecules
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what is the definition to water potential
measure of the tendency of water molecules to diffuse from one region to another. Pure water has the highest water potential
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what is the active transport
the movement of substances against their concentration gradient from low to high concentration of that substance across a cell membrane, using ATP and protein carries.
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what are carrier proteins
these membrane proteins have specific region, or sites that combine reversible wit only certain solute molecules or ions. They also have regions that binds to and allows the hydrolysis of a molecule of ATP to release energy
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what is bulk transport
some cell need to transport large molecule and particles that are too large to pass through the plasma membrane, in or out. They do this by bulk transport, a process that requires ATP
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what is endocytosis
bulk transport of molecules into the cell as a segment of of the plasma membrane surrounds and encloses the particle and brings it into the cell enclosed in a vesicle.
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what is exocytosis
bulk transport of molecules out the cell as a segment of of the plasma membrane surrounds and encloses the particle and is exported out of the cell enclosed in a vesicle.
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what is the difference between endocytosis and exocytosis
endocytosis is inside the cell and exocytosis is outside the cell
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what factors affect the membrane structure and permeability
temperature and solvents
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what happens to the phospholipid bilayer when the temperature drops
pg 138
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what happens to the phospholipid bilayer when the temperature rises
pg 138
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what happens to the proteins and temperature
pg 138
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what is the role of cholesterol
controls the fluidity of the membrane when the temperature increases or decreases
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effect of solvents on phospholipids
pg 139
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why is the cell membrane described as partially permeable

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some very small molecules simply diffuse through the cell membrane, n between the structural molecules. some substances dissolve in the lipid layer and pass through, other substances pass though special proteins channels. they are partially permeable as t

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what are the roles of the plasma membrane

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Card 4

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what is the role of the plasma membrane within cells

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what is the fluid mosaic model

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