cell movement

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the passage of water from a region of high to low water potential through a partially permeable membrane

turgid- cell wall in a plant cell prevents it from bursting when water enters the cell but an animal cell will burst

plasmolysed- the membrane in a plant cell pulls from the cell wall; an animal cell cannot function as the surface area has changed

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1. active transport pushes sodium out of cell and potassium enters at capillaries, low concentration of sodium inside

active transport- movement of a substance from a low to high concentration region, requires energy (ATP)

2. sodium at top comes in at with glucose as facilitated diffusion using co-transport; high concentration inside

facilitated diffusion- presense of a protein carier molecule to allow the passive movement of substances across plasma membranes

3. glucose pushes through using facilitated diffusion using carrier proteins

carrier molecule- a protein on the surface area of a cell that helps to transport molecules and ions across plasma membrane

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structure of epithelial cell

nucleus envelope- double membrane
outer membrane-RER, controls entry and exit of materials, contains reactions taking place inside
nucleus pores- allows passage of large molecules (mRNA)
nucleoplasm- granular and jelly like, makes up bulk of nucleus
chromatin- DNA found in nucleoplasm, manufactures RNA

Mitochondria- double membrane surrounding organelle
inner- cristae- provides large SA for attachment of enzymes in respiration
matrix- semi-rigid, enzymes found here, controls own production of proteins, lipids and DNA

Endoplasmic Reticulum-
RER- ribosomes present- provide large SA for synthesis of proteins- provide pathway
SER- tubular, synthesise, store and transport lipids and carbohydrates

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structure of epithelial cell

Golgi Apparatus- contains vesicles
proteins and lipids pass onto golgi in a sequence to be modified- adding non-protein components; sorts and orders to be sent to correct destination;
transports through vesicles, which mvoe to cell surface where they fuse with membrane to be released out of cell; form lysosomes; secrete carbohydrates to be joined with proteins and lipids

Vesicles- stacked membranes with small, hollow structures

Lysosomes- formed in vesicles; store and release enzymes
break down materials ingested by phagocytic cells
digest worn out organelles so chemicals can be re-used
break down cells when they have died-autolysis

Ribosomes- cytoplasmic granules found in all cells- cytoplasm or RER
80S- eukaroytic 70S- prokayotic
contains ribosomal RNA and protein- important in protein synthesis

Microvilli- increase surface area

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villis role in absorption in the small intestine

glucose is absorbed through the wall of the small intestine

they have small thin walls which are lined with epithelial cells- rich network of capillaries- reduce length of diffusion pathway

increase SA to increase rate of diffusion

situated between the lumen, blood and tissues

blood is carried away taking the glucose with it- this maintains the concentration gradient

contains muscles that contract and relax to mix the contents of small intestine

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role of diffusion in the absorption of glucose in

diffusion- net movement of molecules or ions from high to low concentration

greater concentration of glucose withing small intestine than in the blood

glucose diffuses into blood along the concentration gradient

glucose absorbed is constantly removed as cells use it for respiration- maintains concentration gradient

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role of active transport in the absoprtion of the

not all available glucose cam be absorbed in diffusion due to equilibrium being reached
some pass pass out of the body
active transport can go against the concentration gradient so glucose is absorbed into the blood
glucose is absorbed into the small intestine- co-transport
glucose is drawn into cells along with sodium ions that have been actively transported out using sodium-potassium pump

1. sodium ions transported out of epithelial cells into blood- carrier proteins- cell-surface membrane
2. higher concentration of sodium ions in lumen than inside the cells
3. sodium ions diffuse into epithelial cells through co-transport|
sodium ions go back through this second carrier protein
couple with glucose which are carried into the cell
4. glucose passes into blood plasma by facilitated diffusion using another protein carrier

both move into cells- sodium goes along concentration gradient- glucose goes against it

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characteristics of lipids

contains carbond, hydrogen and oxygen

proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates

insoluble in water

soluble in organic solvents- alcohol, acetone

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role of lipids

plasma membranes- adds flexibility
transfer lipid-soluble substances across membrane
insoluble so good for waterproofing
energy source- twice as much than in carbohydrates
insulation- fats are slow conductors of heat
protection- stored around delicate organs
glycerol + 3 fatty acids = triglyceride + 3 02 - condensation reaction
70 fatty acids- all have carboxyl group with hydrocarbon attaches
single double bond- mono-unsaturated
more than one double bond- polyunsaturated
single bond- saturated

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one fatty acid is replaced by a phosphate molecule

phosphates are attached to water- hydrophillic head

fatty acids repel water- hydrophobic tail


form bilayer sheet- poles force the layers to point into the centre- protected from water on both sides

fluid mosaic model

fluid- phospholipids move relative to one another to give flexibility

mosaic- proteins in variety of sizes and shape

model- not a certain idea

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test for lipids

emulsion test

cloudy-white liquid if limit is present

any lipid in sample being finely dispersed in water form an emulsion

lightly passing through emulsion is refracted as it passes from oil to water droplets

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proteins in bilayer

extrinsic- on surface or partly embedded in bilayer

mechanical support to membrane

work in conjuntion with glycolipids as cell receptors - hormones

intrinsic- span from one side of bilayer to other

transports water-soluble materials across membranes

provide structural support

allows active transport across the membrane by forming ion channels

form reconition sites by identifying cells- enzymes

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magnification- size image/ size object

light microscope- low resolution due to large wavelength; can use live speciment; 2-D image

resolution- distinguishing between two objects

electron transmission microscopes- vacuum conditions, magnetic and beam used
thin specimen needed- preparation time
2-D image which is black and white

electron scanning microscope- uses beams from above to give a 3-D image
preparation time is needed
has lower resolution than TEM

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separating organelle for microscopes

cel fractionation- cells broken up and separated
buffer used- maintain pH
isotonic- stop osmosis affecting organelles
cold- reduce enzyme activity

homogenation- organelles released from cell
blender and filter

process using spinning
spun slow- large organelles separated from supernatent
remove organelle and spin again
spun fast- small organelle separated
nuclei- mitochondria- lysosomes- ribosomes

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