Biology- Cells

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  • Created by: FireDwarf
  • Created on: 10-09-13 18:41
Cell membrane
The cell membrane is a partially permable wall which holds the cell together and exerts control over what enters and leaves the cell. It consists of the phospholipid bilayer with embedded proteins
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Golgi Body
The golgi body is made of stacks of membrane bound sacs in the cytoplasm. Their function is to recieve synethsised protiens from the ER and prepare them for secretion from the cell.
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The lysome is a vesicle which contains digestive enzymes. Its role is to destroy worn-out organelles and digesting unnneeded contents of vaccuoles.
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Has a hard outer membrane and a inner one which is folded to form cristea. Cotains ribosomes, DNA and enzymes.Its role is to carry out the production of ATP for a cell by carrying out aerobic resperation.
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Has two membranes. Has a matrix called the stroma which has a system of membranes running through it. The stroma cotains ribosomes, DNA and starch grains. Pigment captures sunlight and transfers it to chemical energy.
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Whats the ER?
Endoplasmic Reticulum
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Endoplasmic Reticulum - Rough
The Endroplasmic recticulium's function is to transfer material throughout the cell. They transfer diffrent material to places such as the cell membrane or the golgi body.
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In addition, they have ribsomes attached to them. They are able to synestsis protiens in their sacs.Made of interconnected sacs called cisternae.
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These also transfer materials around the cell. However, they do not synethsise protien, but instead synthesise steroids and lipids.
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The vaccuole provides support to the cell. It contains a variety of substances such as cell waste or cell related products.
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Ribosomes synthesis protiens. A small organelle not bound by a membrane. Made of protien.
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What is a Eukaryotic cell?
It means " true nucleus" and is a cell which contains a nucleus, organelles all enclosed in a cell membrane.
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What type of things have Eukaryotic cells?
Animal cells, plant cells, fungi cells
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What is a Prokaryotic cell?
Means "Before nucleus" and is a cell where the DNA is not enclosed by a membrane.
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What type of things have a Prokaryotic cell?
Bacteria, blue-green bacteria?
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How do you know its an animal cell?
First its a eukaryotic cell because it has organelle and a cell membrane bound nucleus and its not plant cause 1) No cell wall, cell membrane 2) No chloroplasts
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Genetic Material
Where the DNA is stored and is not contained in a cell membrane.
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also known as?
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Used for locomotion (movement)
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Cell wall- NOT SAME AS Eukaryota
Thick and made of polysaccharides and polypeptides- Mechanical support and holds structure
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Acts as a layer of slime which protects the cell from the hosts immune system
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Cell surface membrane
Emits control over what enters and leaves the cell.
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Hairs- used to stick to other things
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Circular piece of DNA which allows for reproduction independently of the genetic material.
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What are the two types of microscope?
Electron Microscope and Compound light microscope
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Compound light microscope- How does the light work?
Light passes through the spectrum and passes through 2 glass lens, the objective lens and the eyepiece (ocular) piece
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How does it work?
Light refracts to give a magnified image of the object
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How can the image be shown?
Directly into the observors eyes or can be printed onto photographic film. This is called phototomicmicrograph or light micro graph.
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What if the magnification is too high?
Image becomes blurred.
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What is the limit of effection magnification called?
The resolution
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0.2 micrometer is what?
Its resolution
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Magnification formula?
I= M x O
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I = Image , M= Magnification and o= Object
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What process breaks cells up?
Cell fractionation
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What does it involve?
Proccess where cells are broken up and the diffrent organelles are seperated out
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Why do we do it?
We do it to gain large numbers of diffrent organelle to be able to anaylse them.
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What do we need to do before we can complete cell fractionation?
we ensure the solution is cold (reduce enzyme activity which would break down the organelles), isotonic (prevent organelles shirviling/bursting. Buffered (PH)
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What are the two stages of cell frationation?
Homogenation and Ultracentrifugation
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What is Homogenation?
Cells are broken up via a homogeniser. This releases the organelles from the cell. The resultant fluid, the homogenate, is then filtered to remove any large pieces pf debris and complete cells.
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What is Ultracentrifugation?
Proccess where fragments in the homogenate are seperated in a machine called a ultracentrifuge. This spins the tubes of homogenate at high speeds to create a centrifugal force.
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Describe the Proccess;
- Spun at low speeds. Heaviest organelles (nuclei) are forced to the bottom and form a pellet. -Fluid then removed which just leaves the nuclei (fluid = supernatant) - Supernatant transfered to another tube
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and spun in the centrifuge at a faster speed then before. - Mitochondria then forced to bottom to force a pellet. - Proccess continued and at each increase of speed, the next heaviest organelle forms a pellet.
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Cell surface membrane- whats it made of?
Phospholipid bilayer with embedded protiens
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Whats the most common lipid in living organisms?
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What is a triglyceride made up of?
a kolecule of glycerol and 3 fatty acid molecules
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General formula for a fatty acid molecule?
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What does saturated and unsaturated mean?
Saturated- No double bond
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How does a triglyceride form?
Via condensation between the glycerol and the 3 fatty acid molecules (condensation is when a bond is formed when water is formed seperatly and removed from the te
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Lipid test?
Emulsion Test- disolve substance by shaking it with ethanol- pour into water- + result- white emulsion
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What is a phospholipid?
A class of lipids which is simular to triglyceride but contains a phosphate group rather then a fatty acid
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What does it often get described as?
Head and tail- Head (glyercol) Tail ( Long chains of hydrogen and carbon atoms)- fatty acids
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What is special about them?
Head - hydrophilic and tail - hydrophobic
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What does this mean?
When mixed with water they form a double layer with the hydrophilic head facing outwards and the hydrophobic tail facing inwards.
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What is the Fluid Mosaic model?
A model which explains the structure and functions of the cell membrane.
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Why is it only a model?
The cell membrane cannot be observed with a TEM and therefore the model cannot be proven.
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Why is it called Mosaic? Why is it called fluid?
Mosaic- How the molecules of the diffrent substances are arranged in a mosaic pattern, Fluid because the molecules are moving around.
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What molecules can pass through the phsopholipid bilayer?
small molecules that can dissolve in lipids/non-polar can easilly pass through the bilayer
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What do polar/water soluble do?
They pass through the pores in the protien molecules embedded.
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What is the phospholipid bilayer therefore?
A selective barrier.
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What can the protiens do? Are they attached or not?
Some attached to the membrane and some not
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What role do they have as well as being a barrier? (Protiens)
Enzymes (eg: digest carbohydrates in cell surface membrane of the the epithermial cell of small intestine CONC
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Carrier Protiens, Receptors for hormones
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What else does the fluid mosaic model have?
polyshaccharide attached to protien (glycoprotien) and lipids, to allow cells to reconise each other.
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Definition of Diffusion
Passage of ions or atoms or molecules that make up a substance, from where they are in high concentration to where they are in low concentration. They therefore move down the concentration gradient.
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How do the partials move? What makes them move?
Randomly. The kinetic energy
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What 4 factors effect the rate of diffusion?
Surface area, thickness of the wall, conc gradient, temperture
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Surface area
Increased area- more particals in collission with the exchange surface- more movement of particals- more diffusion
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More kinetic energy- particals move more and faster- can tavel to the lower side faster- faster diffusion
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Thin walls
Decreases the distance travelled in surface area- faster diffusion- faster rate
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Conc gradient
higher gradient- faster rate
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What is osmosis?
The movement of water molecules from an area of high water potential to an area of low water potential and across a partially permable membrane.
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What is water potential measured in? What unit?
Like a scale sign, psi, and in kilopascals (kpa).
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What is water's water potential?
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What happens when you add more solute to the solution?
Water potential decreases
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What is the water potential of any solution compared to water?
Lower (- then 0)
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Test to find out the WP of solutions?
Place them in another solution with diffrent water potenitals. When there is no movement of water molecules between the two substances, then their WP is equal.
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How does osmosis occur?
Water molecules are moving randomly. The partially permable membrane will only allow the passage of water molecules. These water molecules will move from an area of high Wp to low WP. Therefore, they will move from one side to another untill the WP
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on each side becomes equal, therefore reaching equlibrium.
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why do solutes lower the WP?
The water molecules bind to the solute molecules, stoppin them moving across the gradient.
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What else effects WP?
Pressure, greater pressure, higher value of WP.
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Cell wall example of how pressure helps.
Cell wall excerts pressure of the cytoplasm, causing an increase in WP .
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Equation for WP?
WP= Solute potenial + Pressure potential
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Effect on plant cells of diffrent WP's?
The WP is same as outside as inside- no movement of water molecules- isotonic. WP outside cell lower then inside- water moves out of cell- plasmolysed. Cytoplasm retracts.
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WP is higher outside then inside, causes water to move in, turgid.May burst.
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No movement (WP equal)- isotonic, WP is higher inside then outside, crenation, hyper-tonic solution, WP is higher out then in, haemolysis.
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What is Facilitated diffusion?
Passive proccess that is simular to diffusion, but requires the assistance of protiens to pass across the membrane.
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What are the two types of protiens that can facilitate?
Carrier and channel protiens.
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Allow water-soluble molecules to pass across the membrane. Channels are selective and only open for certian molecules (remain closed if not present)
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Carrier protiens?
When a molecule of a specific shape occupies the bind site on the protien, it binds, causinf a shape change in the carrier protien and allowing the molecule to be released into the membrane.
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What is active transport?
Movement of molecules or ions agianst a conc gradient, from an area of low conc to an area of high conc, using energy and carrier molecules.
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How does it differ from passive diffusion?
Goes agianst a conc gradient, requires ATP, Requires carrier protiens (as a pump), proccess is selective
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How does it use ATP?
Directly to provide energy to move the molecules, using a conc gradient that has already been established (co-transport)
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What is direct active transport?
Carrier protien acceps the molecule , binds to receports, ATP then binds to the protien causing it to break ( ADP and phosphate) therefore changing shape and opening up the other side of the membrane. Molecule released.
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And then the ADP and phosphate are recombined to form ATP during resperation. Causes protien to revert back to original shape.
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What is special about a sodium potassium pump?
It has two diffrent directions of ative-transport occuring in the same place, at the same time. Sodium are being removed from the cell and potassium are being taken in from the surroundings. Imporant in nerve impulses.
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why is active transport better then diffusion at absorbing more?
Glucose can only at best absorb 50% of the molecule, as the equlibrium is reached, but active transport is able to absorb it all.
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How is glucose therefore abosrbed?
Glucose is facilitated with the pressence of the sodium, where it couples with the sodium and uses the sodium conc gradient to facilitate diffuse into epithemal cells.. Glucose then uses a diffrent carrier to get into the blood. Sodium leaves
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epththemcal cells via the sodium potassium pump into the lumen.
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What s cholera?
A water born bacteria caused by Vibrio cholerae.
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What type of cell is it therefore?
Prokaryotic cell.
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Why are bacteria successful?
Small size ( 0.1-1um).
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How do bacteria store food reserves?
glycogen granulles and oil droplets.
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How do we get cholera?
Ingestion of water, or rarely food, that has been contaminated with facal material containing the pathogen.
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Main symptoms?
diarrhoea & dehydration
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How does it occur?
Ingested by humans, most destroyed by acid in stomch but some survive. Surviving bacteria reaches small intestine and use flagella to propel through the mucus of intestine.
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protduce toxic protien, choloragen, which binds to the specific carbohydate receptors on the cell surfance membrane of the epithemal cells.
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The other, toxic, part enters the epithemal cell and causes the ion channels to open, and chorine ions to flood out of the epidermal cell into the lumen.
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wp IN EPITHEMAL CELLS becomes higher, lumen becomes lower. Water flows out of epithemal cells into lumen.
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ions move therefore into epithemal cells and water then moves frm blood and surrounding tissues into the intestine
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What causes diarroea?
Loss of microvilli from toxins, damage to eptihemal cells lining the intestine, exsessive secrtion of water
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What is oral rehydration therapy?
There is more then one type of carrier protien in the cell surface membranes of the epithemal cells. Trick, use sodium ions to use these alternative paths and therefore lowering WP of the epithemal cells and causes the water to move back in (osmosis)
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Why is drinking water just ineffective?
Water is not being absorbed and doesnt replace the ions lost from the epithemal cells.
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Use a drop to replace water and ions
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What does the ORT contain?
Water- rehydrate tissue, sodium ions, replace those lost and to increase optium of alternative sodium-glucose carrier protiens., glucose- stimulate uptake of sodium, pot- replace lost pot ions and increase appitite, electrodes, stop imbalance.
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Why is ORT good?
Cheap, easy to adminster, increased access therefore. Bad? Was tested on from children as they are the main sufferers.
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alternative with starch? whys it better?
Because starch is being broken down via hydrolysis in the SI. Using diffrent amounts of starch, we can find an opimum glucose amount that is taken up as produced, therefore not effecting the WP.
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Names of the two types of protien embedded in the phospholipid bilayer?
Extrinsic and intrinsic
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Extrinsic protien?
Occurs on the surface of the bilayer or only partially embedded but never spans the entire distance of the the bilayer. Either provide mechanical support or as cell receptors for hormones.
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Completly span the phospholipid bilayer. Some act as carriers to transport water-soluble materials acrpss the membrane while others act as enzymes.
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Golgi Body


The golgi body is made of stacks of membrane bound sacs in the cytoplasm. Their function is to recieve synethsised protiens from the ER and prepare them for secretion from the cell.

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