Carbohydrate Absorption

1. Starch is broken down into glucose by digestion

2. Sodium ions are actively transported out of epithelial cells by the sodium potassium pump into the blood through one type of carrier protein

3. There is a higher concentration of sodium ions in the lumen of the intestine than in the epithelial cells.

4. Therefore, sodium ions diffuse into the epithelial cells down a concentration gradient through a different carrier protein by co-transport

5. As they come back through a second carrier protein they couple with glucose molecules which are carried into the cell with them

6. The glucose passes into the blood plasma by facilitated diffusion

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1. Most of Cholera bacterium is killed by acidic conditions in the stomach

2. Surviving bacteria in small intestine use their flagella to propel themselves through the mucus lining of the small intestine

3. Part of the toxin enters the epithelial cells - this causes the ion channels of the cell-surface membrane to open, releasing chloride ions to flood into the lumen of the small intestine from cells

4. Loss of chloride ions from epithelial cells raises their water potential. Increase of chloride ions in the lumen decreases its water potential. Water flows into lumen from surrounding cells by Osmosis

5. Loss of ions from epithelial cells establishes a concentration gradient. Ions move by diffusion into epithelial cells from surrounding tissues due to a water potential gradient

6. Loss of water from blood into intestine causes diarrhoea

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Oral Rehydration

  • Contains sodium and glucose salts
  • Brings in glucose and sodium by co-tranport from the lumen into the epithelia cells in the small intestine in large amounts
  • More sodium makes negative water potential in epithelial cells
  • Therefore water moves into cells from cells by Osmosis (due to decreased water potential gradient)
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1. Plasmid is cut a specific region by a protein called relaxosome

2. Accessory proteins of the relaxosome are released but relaxase remains attached to the DNA

3. DNA-relaxase complex is reconigsed by a coupling factor and transported to the exporter

4. Exporter pumps DNA-relaxase complex into recipient

5. Once molecule is transported, relaxase joins the ends to make a circular DNA molecule. As it is transferred, it is replicated to become double stranded

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Carbohydrate digestion

1. Food is chewed and broken down - large surface area

2. Saliva contains amylase - converts starch in mouth to maltose

3. Also maintains mineral salts to maintain the pH

4. Oesophagus - acidic - denatures the amylase and prevents further hydrolysis

5. Small intestine - pancreatic juice contains pancreatic amylase.This continues hydrolysis to maltose

6. Alkaline salts produced by pancreas and intestinal wall maintain pH 

7. Muscles in intestinal wall push food along small intestine 

8. Epithelial lining produces the enzyme maltase

9. The maltase hydrolyses the maltose into a-glucose

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Things to remember

  • Small sample sizes - not very reliable
  • Non-comparible units for varibles
  • Precision of measing equipment - standards as a qualatitive comparison as can be measured to half a pH
  • Anything quantative will be more precises and the more decimal places the more precise is it
  • Line of best fit/ joining up the points - Not enough points for a line of best fit
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Why is colormetry is more precise than colour stan

  • Colormetry gives you a qualatative value - porportional to the density/depth of colour in a solution
  • Deeper colour = higher concentration = more light will be absorbed and less passed through to detector on another side
  • Allows you to plot a graph of absorbance against conc - can be used to calculate quantative value
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How does Colormetry work?

  • Light is shone through a solution
  • The higher the concentration of H+ ions the more of the light (transmittance) will be absorbed
  • Thus, less light will be passed through to a receptor on the other side
  • Beers law - To obtain a Beer’s law curve, several standards (solutions of known concentration) are prepared and their absorbance values are determined using a Colorimeter. A graph of absorbance vs. concentration is then plotted
  • A solution of unknown concentration is placed in the colorimeter and its absorbance measured. 
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Cell Fractionation


  • Cells are broken up
  • Releases organelles from the cell
  • Resultant fluid = homogenate


1. Filtrate placed in ultracentrifuge and spun at a slow speed

2. Heaviest organelles are forced to the bottom of the tube

3. Supernatent (fluid) is removed

4. Supernatent is spun at faster speed

5. Heavier organelles - mitocondria - forced to bottom of tube

6. At each increase of speed - heaviest organelle is sedimented and seperated out

Nuclei - Mitocondria - Lysosomes - Ribosomes

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