Biology - Membranes

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State 5 roles of membranes within cells and at the surface of cells
Separates cell from environment, cell to cell attachment, control what leaves and enters cell/organelle, attachment of ribosomes, folding to increase surface area
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Define the term 'compartmentalisation'
The formation of separate membrane-bound areas in a cell
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Why is compartmentalisation useful to cells?
It means reactions are contained in separate parts of the cell, so the conditions required for each can be maintained
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Define the term 'partially permeable'
Lets some molecules pass through but not others
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Define the term 'cell signalling'
The process of a chemical binding to a receptor, causing a response from the cell (could be a direct response or a cascade of others)
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Define the term 'phospholipid bilayer'
Made up of 2 layers of phospholipis, with hydrophobic tails pointing inwards and hydrophilic heads pointing outwards
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Explain what is meant by 'fluid' in the 'fluid mosaic model of membrane structure'
The different components of the membrane can move about
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Explain what is meant by 'mosaic' in the 'fluid mosaic model of membrane structure'
It is made up of lots of different components
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Define the term 'glycoprotein'
Carbohydrate attached to protein
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Define the term 'phospholipid'
component with hydrophilic head and hydrophobic tail
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Define the term 'cholesterol'
A lipid with a hydrophilic head and hydrophobic tail
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Define the term 'glycolipid'
Carbohydrate attached to lipid
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Define the term 'channel protein'
Intrinsic protein that allows passive movement across a membrane
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Define the term 'carrier protein'
Intrinsic proetin that allows passive and active transport across a membrane
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Define the term 'intrinsic protein'
Protein embedded through both layers of bilayer
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Define the term 'extrinisc protein'
Protein present in one side of bilayer
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Define the term 'receptor protein'
Extrinsic glycoprotein that binds chemical signals, triggering a response
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State the role of phospholipids in the membrane
Act as a partially permable membrane
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State the role of cholesterol in the membrane
REgulates membrane fluidity by stabilising membrane
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State the role of glycoproteins in the membrane
Act as receptors, act as antigens, bind cells together, attach to water to stabilise membrane
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State the role of glycolipids in the membrane
Act as receptors, act as antigens, attach to water to stabilise membrane
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State the role of proteins in the membrane
Form channels or act as carriers to transport substances across membranes, may be enzymes
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Define the term 'cell adhesion'
Binding cells together
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Explain how cholesterol affects fluidity and stability of membranes
Cholesterol molecules are positioned between phosphlipids, with their hydrophilic end interacting with the heads and vice versa - they prevent membranes becoming too solid by stopping phospholipid molecules from grouping too closely and crystalising
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Explain the importance of membrane bound proteins in chemical reactions
Proteins have to be in particular positions for chemical reactions to take place - for example, the elctron carriers and the enzyme ATP synthase have to be in the correct positions within the cristae for the production of ATP in respiration
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Explain how the binding of a molecule to a membrane bound glycoprotein can cause effectes within a cell
Examples: receptors for neurotransmitters at nerve cell synapses - the binding of neurotransmitters triggers/ prevents impulses in the next neurone; receptors for peptide hormones, which affect the amount of glucose; some drugs bind to cell receptors
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Describe the effect of changing temerature on the permeability of cell membranes
As temperature incresaes, the permeability of the cell membrane increases, and vice versa
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Explain the effect of changing temperature on the permeability of cell membranes
As temperature increases, the phospholipids will have more kinetic energy, and will move more, so the membrane will begin to lose its structure, making it it easier for particles to move across it - carrier and channel proteins will also denature
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Describe the effect of solvent concentration on the permeability of cell membranes
If a solvent is used, the membrane becomes more permeable,and the higher the concentration, the more permeable it will be
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Explain the effect of solvent concentration on the permeability of cell membranes
The solvent particles will disrupt the phospholipid bilayer, so the membrane will become more fluid and permeable
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Define the term 'simple diffusion'
The movement of molecules from a region of high concentration of that molecule to a low concentration, down a concentration gradient - no ATP is required
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Define the term 'facilitated diffusion'
The movement of molecules from a region of high concentration of that molecule to one of low concentration, using carrier and channel proteins - no ATP is required
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Define the term 'osmosis'
The movemnet of water molecules from an area of high water potential to one of low water potential, where water moves through the bilayer or through specific protein channels called aquaporins - no ATP is required
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Define the term 'passive transport'
The movement of molecules that utilise enrgy from the natural motion of particles, rather than energy from another source
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Define the term 'active transport'
The movement of molecules or ions across a membrane in the opposite direction to the concentration gradient, using intrinsic carrier proteins in the membrane as pumps - energy input from ATP is required
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Define the term 'endocytosis'
The bulk transport of materials into cells, where the membranes can form vesicles which can break off from the plasma membraneto allow this transport - energy input from ATP is required
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Define the term 'exocytosis'
The bulk transport of materials out of cells, where the membranes can form vesicles which can fuse with the plasma membrane - energy input from ATP is required
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Define the term 'pinocytosis'
Endocytosis of liquids
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Define the term 'phagocytosis'
Endocytosis of solids
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Explain the difference between a channel protein and a carrier protein and link this to their functions
Channel proteins simply provide an easier route through, and can be gated, so only help with passive movement. Carrier proteins often change shape, so are open to one side of the membrane, so can help with ac
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Explain the importance of the structure of ATP in active transport
ATP binds to carrier protein and is hydrolysed into ADP + phosphate, changing the shape of the protein, releasing the molecule/ion - then the phosphate is released and recombines with ADP to form ATP, so the carrier protein returns to original shape
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List the factors affecting the rate of diffusion of a molecule
Temperature, concentration gradient, surface area and thickness of membrane
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State which types of molecule can move across a membrane by simply diffusion
Gases such as oxygen and carbon dioxide, small molecules and lipid-based molecules
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Identify which transport mechanisms require an input of energy from ATP
Active transport, exocytosis and endocytosis
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Other cards in this set

Card 2

Front

Define the term 'compartmentalisation'

Back

The formation of separate membrane-bound areas in a cell

Card 3

Front

Why is compartmentalisation useful to cells?

Back

Preview of the front of card 3

Card 4

Front

Define the term 'partially permeable'

Back

Preview of the front of card 4

Card 5

Front

Define the term 'cell signalling'

Back

Preview of the front of card 5
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