cell movement
- Created by: bethany cracknell
- Created on: 03-05-13 17:32
osmosis
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
co-transport
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
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
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
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
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
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
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
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
phospholipids
one fatty acid is replaced by a phosphate molecule
phosphates are attached to water- hydrophillic head
fatty acids repel water- hydrophobic tail
polar
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
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
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
microscopes
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
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
ultracentrifugation
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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