AS biology

What molecules do carrier proteins move through the cell membrane and how?
They move large molecules by the molecule attaching to the protein causing it to change shape releasing the molecule on the other side of the membrane inside the cell.
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What molecules do channel proteins move across the membrane and how?
They move charged particles by acting as a channel allowing molecules to move through.
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What are isotonic/hypotonic/hypertonic solutions?
Isotonic=When 2 solutions have the same water potential as each other. Hypotonic=When solution has higher WP than the cell. Hypertonic=When the solution has a lower WP than the cell.
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How do you make serial dilutions?
1.Set up test tubes, one with 10cm3 of a 2M solution and 4 with 5cm3 of distilled water. 2.Use pipette to draw 5cm3 of 2M solution and put it into first test tube, mix it about then use pipette to do the same but using the mixed test tube before it.
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How does co transport of sodium and glucose work in the small intestine?
1.Active transport of sodium into blood by S-P pump to create conc. gradient of sodium. 2.Na+ diffuse from lumen to cells via Na-glucose transporter + carries glucose into cells with it. 3. High conc of glucose in cells cause it to move into blood.
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How does phagocytosis work?
1.Phagocyte recognises pathogen so moved cytoplasm around pathogen engulfing it. 2.Pathogen now in phagocytic vacuole which fuses with lysosome releasing lysozymes to destroy. 3.Phagocyte presents pathogens antigens to activate other immune cells.
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What is the role of T cells in the immune response and how are they activated?
Activated by: binding to complementary antigen displayed by phagocyte. Helper T cells release chemicals which stimulate phagocytes and B cells. Cytotoxic T cells kill abnormal/foreign cells.
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What is the role of B cells in the immune system?
They are covered in antibodies so when one of their antibodies binds to a complementary antigen along with chemicals secreted by T cells activate B cells causing them to divide into plasma cells-clonal selection.
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What is the role of plasma cells in the immune response?
Secrete loads of antibodies which are complimentary to the pathogen (monoclonal antibodies).
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What is agglutination and how does it happen?
When antibodies bind to 2 antigens at once causing them to clump together meaning that phagocytes phagocytose many pathogens at once leading to total destruction of the pathogen in the body.
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What is the humoral/cellular immune response?
Humoral=B-cells, clonal selection and production of monoclonal antibodies. Cellular=T-cells and what they interact with eg.phagocytes.
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What is herd immunity?
Vaccines reduce the occurrence of the disease as there are fewer people to catch it from so people are less likely to catch the disease giving people who aren't vaccinated protection.
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What ethical issues surround vaccinations?
1.Testing on animals. 2.Can come from animal based substances. 3.Testing on humans can be a risk as people this they are protected so put themselves at more risk of getting a disease. 4.In case of epidemic decisions on who gets them first are made.
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How does the direct ELISA test work?
1.Patients antigens bound to well.2.Complementary antibody to antigen added with enzyme attached.3.Antibody will bind if antigen of interest is present.4.Plate is washed and substrate solution added, if enzyme present substrate binds=colour change.
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How does indirect ELISA test work?
1.Desired antigen bound to well. 2.Blood sample added+well is washed out. 3.Antibody with specific enzyme attached added+well washed again. 4.Substrate solution added and if enzyme on antibody is present a colour change happens.
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How does someone develop AIDS when suffering from HIV?
HIV kills helper T cells and without these the immune system can't bring about an effective response to pathogens. When a patients helper T cell count is critically low they develop AIDS.
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Roughly what is the structure of HIV?
Spheical shape, core containing RNA and some proteins eg.reverse transcriptase, envelope made of previous host cells membrane and attachment proteins on surface to attach to host T-cells.
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How does HIV replicate?
1.Attaches to host T-cell and releases capsid which un-coats and releases RNA.2.Reverse transcriptase makes complimentary strand of DNA and inserts it into human DNA.3.Host cell enzymes make the viral proteins. which are made into new viruses and bud
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What does a dissociation curve show?
How saturated haemoglobin is with o2 at any given po2. Saturation affects affinity making it easier for o2 to bind when one molecule is already bound which is why it appears in a 's' shape.
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Where do the renal vein and renal artery carry blood to and from?
Renal artery=body to kidneys. Renal vein=from kidneys to vena cava.
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How is tissue fluid created?
The Hydrostatic pressure of capillary at artery end is high causing overall outwards pressure forcing fluid out of blood into space around cells. As fluid leaves hydrostatic pressure drops so at venal end is much lower so water moves in as low WP.
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How do you test for reducing sugars?
Add Benedicts reagent to a sample and heat in a water bath which has been brought to the boil, reducing sugar present is red precipitate forms.
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How do you test for non reducing sugars?
You need to break up monosaccharides so you add dill hydrochloric acid then heat in water bath, you then neutralise with sodium hydrogen carbonate then repeat the test for a reducing sugar and look for same results.
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What type of molecules are amylose and amylopectin (make up starch)?
Amylose is long unbranched chain of a-glucose which is coiled. Amylopectin is a long branched chain of a-glucose.
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What makes cellulose a song material?
It is two strands held together by hydrogen bonds forming microfibrils which are strong fibres.
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How do you test for a lipid in a solution?
Shake the sample with ethanol for around 1 minute then pour the solution into water, if a milky emulsion forms a lipid is present.
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What features do Phospholipids have making them useful in bilayer?
They have hydrophilic heads (point to outside) and hydrophobic tails (point to inside) which means water soluble substances can't pass through easily.
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What makes triglycerides good fat storage molecules?
Their tails contain energy which are released when broken down, they are insoluble so don't affect WP and bundle together to form droplets which is useful for storage.
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What happens during formation of primary structure of proteins?
Hydrogen bonds form between amino acids which makes the chain automatically coil into alpha helix or beta pleated sheet.
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What happens during formation of proteins tertiary structure?
More bonds form between different parts of chain including hydrogen bonds and ionic bonds. Disulphide bridges form if 2 molecules of cystine are close to each other as sulphur atoms bond to each other.
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How do you do the biuret test for proteins?
1.Add few drops of sodium hydroxide to make sample alkaline. 2. Add copper(II) sulphate solution. 3. If protein is present the solution will turn purple. If no protein the solution will stay blue.
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How can enzymes lower the activation energy needed for a reaction?
If 2 molecules need to join, being attached to the enzyme holds them closer together reducing repulsion between the molecules so they can join easier. Fitting into active site puts strain on bonds in substrate so substrate can be broken up easier.
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What was the lock and key model of enzymes?
Where the substrate fits into the enzymes active site the way a key fits into a lock, it suggests that the enzyme and substrate are unaffected after the reaction-scientists realised this was wrong.
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What is the indices fit model of enzymes?
Substrate doesn't have to the exact shape of the active site as it causes the active site to change shape in the right way. Changed the lock and key model when new evidence came about.
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Why can adding extra substrate when competitive enzyme inhibitors are present have an effect on reaction rate?
Because substrate and competitive inhibitors both bind to the active site of enzymes so adding more substrate makes it more likely to bind that the inhibitors.
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What does adding extra substrate when non competitive inhibitors are present have no effect on reaction rate?
As the inhibitors don't bind to the active site of the enzyme, they change shape of active site by binding to other part of the enzyme, adding more substrate won't make a difference as they won't fit into the active sites.
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What are the 2 measures of how fast the rate of enzyme controlled reactions are?
1.How fast the product of the reaction appears. 2. How fast the substrate is broken down.
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What is ATP used for in cells?
Provide energy for processes eg. active transport. To add phosphate to other molecules making them more reactive.
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How can you tell if an image has been produced by a SEM microscope?
It will be 3D.
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How do you calculate a % change?
Subtract the original value from the final value and divide by the original value then multiply by 100.
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How do you work out a % error?
Divide the uncertainty by the reading and multiply by 100.
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How do you work out the rate of reaction on a graph at a specific point?
You need to draw a tangent (straight line at desired point) you then need to turn the tangent into a triangle and measure the x side and the y side of the triangle. Then divide the length of the y side by x side to give reaction rate.
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How do you work out a percentage decrease?
You work out the difference between the two numbers then divide this increase by the original number and multiply this by 100.
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What statistical test would you use when working out if the difference between 2 means occurred due to chance?
Student T test.
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What statistical test would you use if you have categorical (grouped) data and you want to compare observed results to expected ones?
Chi squared test.
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What statistical test would you use when you need to work out to what degree two sets of data are correlated and the value given is between 1 and -1?
Spearmans rank correlation coefficient.
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What is genetic diversity?
The number of different alleles for a gene in a population or species.
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What is an adaptation?
A feature which helps an organism survive in a certain environment.
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What are the 3 types of adaptations that natural selection can lead to?
Behavioural (how they act). Physiological (processes within the body). Anatomical (structural features).
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What are the 5 useful properties of water?
Good solvent, metabolite, cohesive, high latent heat of vaporisation, high specific heat capacity.
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Wha does it mean for water to have high specific heat capacity?
Hydrogen bonds between water molecules means it takes a high amount of energy to raise 1 gram by 1 degree.
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In what order are cell organelles separated in cell fractionation?
Nuclei, Mitochondria,Lysosomes,ER,Ribosomes
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Why do electron microscopes have higher resolution than light microscopes?
They use a beam of electrons instead of light to form an image, electrons have a much shorter wavelength than light.
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Where is amylase released?
Salivary glands and the pancreas.
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What are the monosaccharides of sucrose and maltose?
Sucrose= glucose and fructose. Maltose= glucose and glucose.
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How do bile salts aid the digestion of lipids?
They cause lipids to form small droplets (emulsify) so now lipids have a larger surface area for the same volume. When broken down the monoglycerides stick with bile salts to form micelles which aid digestion.
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What are membrane bound disaccaridases?
Enzymes attached to the cell membranes of epithelial cells which help break down disaccharides into monosaccharides.
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Card 2

Front

What molecules do channel proteins move across the membrane and how?

Back

They move charged particles by acting as a channel allowing molecules to move through.

Card 3

Front

What are isotonic/hypotonic/hypertonic solutions?

Back

Preview of the front of card 3

Card 4

Front

How do you make serial dilutions?

Back

Preview of the front of card 4

Card 5

Front

How does co transport of sodium and glucose work in the small intestine?

Back

Preview of the front of card 5
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