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41 Cards in this Set
- Front
- Back
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What are Prokaryotes? |
-single celled organisms with a simple structure -have a single undivided internal area- the cytoplasm |
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What are Eukaryotes? |
-make up multicellular organisms -have a much more complicated internal strucure- containing membrane bound nucleus and cytoplasm which contain many membrane bound cellular components (organelle) |
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What do organelles do? |
-allow reactions of metabolism to be compartmentalised, departed by selectively permeable membranes |
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What is cytoplasm composed of? |
-cytosol which is made up of water, salts and organic molecules |
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The nucleus |
-contains DNA -DNA dictates what proteins are reguired and then made -DNA is packaged with histone to make chromatin -chromatin is coiled and superwired into chromosomes -controls the cells activities
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The nuclear envelope |
-is a double membrane -1/3 of the surface has nuclear pores that allow molecules to move into and out of the nucleus |
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The nucleolus |
-an area within the nucleus -responsible for producing ribosomes -composed of proteins and RNA -RNA is used to produce ribosomal RNA (rRNA) which combines with proteins to form ribosomes |
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Mitochondrion |
-site of aerobic respiration -lots in active cells and makes ATP -can produce their own enzymes and reproduce themselves-> evolved by endosymbiosis -oval shaped -have a double membrane, the inner one is foleded into cristae -inside is the matrix which contains enzymes involved in respiration |
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Vesicles |
-are membrane bound sacs that have storage and transport roles -transport materials/substances inside the cell -single membrane with fluid inside -secretory vesicles- if the proteins are destined to leave the cell |
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Lysosomes |
-specialised forms of vesicles that contain hydrolytic enzymes -responsible for breaking down the waste material in cells like old organelles and ingesting pathogens -play an important role in programed cell death (apoptosis) -stays inside cell |
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Centioles |
-found in all eukaryotic cells apart from flowering plants and fungi -barrel shaped arrangements of microtubules -organise the spindle fibres that organise chromosomes in cell division |
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Flagella |
-used for movement -stick out from cell surface and are surrounded by the plasma membrane - 9+2 arrangement of microtubules -microtubules contract to make flagella move -are like outboard motors |
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Cilia |
-small, hair like structures - 9+2 arrangement of microtubules -waft/beat to create a current which causes fluid/objects to move |
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Rough endoplasmic reticulum |
-network if membranes enclosing flattened sacs called cisternae -surface is covered with ribosomes -responsible for proteinsynthesis and the transport of proteins |
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Smooth endoplasmic reticulum |
-no ribosomes -responsible for lipid and carbohydrate synthesis and storage -cisternae are more tubular |
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Ribosomes |
-small organelle that ks either free floating in the cytoplasm or attached to RER -made of RNA and proteins -site of proteinsynthesis |
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Golgi apparatus/body |
-stack of flattened sacs -modifies proteins, carbs and lipids that are delivered in vesicles to cis-face from ER - after modification they are packaged into vesicles/lysosomes on the trans face |
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What is in an animal cell? |
-nucleus -ribosomes -mitochondria -cytoplasm -RER -vesicles -SER -cell membrane -nuclear membrane |
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What is in a plant cell? |
Everything in an animal cell plus some extras: -vacuole -cell wall -chlorplasts |
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Vacuole |
-contains all the sap -separated from the cytoplasm by the membrane of the vacuole, called the tonoplast -tonoplast is selectively permeable so some small molecules can pass through it but not others -acts as a resevoir, supports cell when turgid |
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Cell wall |
-made of cellulose -made of long, strong straight fibres -function: 1-freely permeable 2-provides strength and shape to cell 3- prevents cell from bursting 4- defence mechanism against invading pathogens |
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Chloroplasts |
-responsible for photosynthesis -a small flattened structure with a double membrane -contains internal thylakoid membranes that stack up to form grana which are linked together by lamellae -thylakoid is the site of chlorphyll absorbing light -stroma is the fluid enclosed in chlorplasts, contains enzymes for photosynthesis -can make their own proteins due to having DNA and ribosomes |
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Cytoskeleton |
-is a network of fibres that provide shape and stability of a cell |
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Microfilaments |
-contractile fibres formed from the protein actin -responsible for cell movement and cytokinesis (cell division) |
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Microtubules |
-polymers of globular tubulin that forms a scaffold like structure that determines the shape of a cell -acts like tracks for the movement of organelles |
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Intermediate fibres |
-gives mechanical strength to cells -helps maintain their integrity |
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What is the structure of a membrane? |
-formed from a phospholipid bilayer -hydrophilic head -hydrophobic tail (line up together) -unsaturated fatty acids make the membrane more flexible and fluid |
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Membrane history (1972) |
-Singer and Nicoleson proposed the 'fluid mosaic model' of membrane structure -phospholipids are free to move within the layer (they're fluid) giving membrane flexibility |
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Intrinsic proteins - channel |
Channel proteins: have a hydrophilic channel to allow passage of polar molecules/ions/water down a concentration gradient
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Intrinsic proteins- carrier |
-can change shape when they bind with the transported substance; can be passive (down a concentration gradient) or active transport (against concentration gradient) |
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Intrinsic proteins - glycoproteins |
-are embedded in the cell surface membrane -made of proteins and carbs -involved in cell adhesion and cell signalling 1 -neurotransmitters at synapses 2- peptide hormones e.g insulin (into cells) and glucagon (low blood sugar, move sugar out of cell) |
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Intrinsic proteins - glycolipids |
-made of lipids and carbs -they are cell markers or antigens that are recognised by the immune system as self (of the organsim) or non self (belonging to another organism) |
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Extrinsic proteins |
-have hydrophilic groups that interact with polar heads of the phospholipids or with intrinsic proteins -act as receptors or for mechanical support -can be present in either layer and some move between layers |
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Cholesterol |
-a lipid with hydrophilic and hydrophobic ends that is positioned between the phospholipids -adds stability without making them too rigid -found in all cell membranes (except bacteria) -cholesterol molecules prevent the membrane becoming too solid by stopping the phospholipid molecules from grouping too closely and crystalising |
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What effect does temperature have on cell membranes? |
When the temperature is increased the phospholipids will have more kinetic energy and will move more. This makes the membrane more fluid and it begins to lose its strucure. If temperature continues to increase the cell will eventually break down completely. The loss of this structure increase the permeability of the membrane, making it easier for particles to cross it |
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The effect of temperature on intrinsic proteins |
Intrinsic proteins (channel and carrier) will denature at higher temperatures, so membrane permeability will also be affected ad they are involved in the transport of substances across the membrane |
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What is the effect of solvents on membranes? |
-organic solvents will dissolve membranes, disrupting cells -very strong alcohol solutions are toxic as they destroy cells in the body -less concentrated solutions of alcohols will not dissolve membranes but they still cause damage -when the membrane is disrupted it becomes more fluid and more permeable |
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Definition of diffusion |
The net movement of particles from an area of high concentration to an area of low concentration |
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Diffusion |
-is a passive process so does not require an input of energy, it will continue until there is a concentration equilibrium (particles are evenly distributed in both directions) -it happens because particles move randomly so some will go where there are less particles |
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What are the factors that affect diffusion? |
1: concentration gradient- the greater the difference, the greater the rate of diffusion 2: temperature- the higher the temperature the higher the rate of diffusion (more kinetic energy) 3: thickness of membrane- the thinner the exchange surface, the higher the rate of diffusion 4: surface area- the larger the area of exhange surface, the higher the rate of diffusion
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What is Fick's law? |
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