BIOLOGICAL MOLECULES Flashcards
(7 cards)
HOW to undertake a food test
1) prepare food sample: grind up food with pestle and mortar, transfer to test tube, add distilled water, mix food by stirring, filter mixture, collect solution
2) add specific solution (+ heat in boiling water bath for 5 minutes if glucose test)
3) observe colour change
Colour changes for all tests
GLUCOSE: Benedict’s: blue to brick red
STARCH: iodine: orange-brown to blue-black
PROTEIN: Biuret: blue to purple/lilac
LIPIDS: Ethanol : cloudy emulsion
LIPIDS test
1) prepare food sample
2) add ethanol (5 cm cubed) to food sample
3) shake vigorously
4) strain solution and collect in another test tube
5) add distilled water in equal volume
6) observe cloudy emulsion forming or colourless
HAZARDS of food tests:
-always wear goggles, biuret solution contains dangerous copper sulfate + iodine is irritant to eyes
-sodium hydroxide in biuret is corrosive
-ethanol is highly flammable, keep away from Bunsen burner
How do enzymes speed up a chemical reaction?
-enzymes act as BIOLOGICAL CATALYSTS that speed up the rate of a chemical reaction without being changed or used up
-enzymes are all specific to one particular substrate , as the active site of the enzyme is complementary to the shape of the substrate
1) enzymes and substrates move around randomly in solution
2) when enzyme and substrate collides, the active site and complementary substrate shape attach and join like a “lock and key”, forming an enzyme-substrate complex
3) the reaction occurs
4) products formed are released from the active site- which remains unchanged
5) the enzyme continues to catalyse other reactions
FACTORS that affect enzyme action:
TEMPERATURE:
-a higher temperature increases the kinetic energy of the molecules, meaning they move faster and there is a higher rate of collisions, therefore the rate of reaction is increased
-at the optimum temperature (37 in humans), the enzymes are working at their highest rate
-however, beyond the optimum, the high heat temperatures can cause the bonds that hold teh enzyme together to be broken, ad the enzyme will begin to lose it’s shape
-the active site will therefore no longer be complementary to teh substrate, and cannot fit, as it’s active site shape has been lost,
-causing activity to decrease and eventually stop as DENATURATION is irreversible
-at low temperatures, the enzyme rate is just slower as there is less kinetic energy in the molecules
PH:
-if the pH is too high or too low, the bonds that hold the enzyme together can be disrupted/destryoed
-changing the shape of the active site, so the substrate can no longer fit and they ar eno longer complementary
-rate of activity will decrease and eventually stop as DENATURATION is irreversible
-optimum pH of most enzymes is 7, however if produced in some acidic conditions (STOMACH, optimum pH is 2) produced in alkaline conditions such as (duodenum, optimum pH is 8/9)
Practical: INVESTIGATING TEMPERATURE EFFECT ON RATE OF AMYLASE
1) LABEL 6 test tubes A-F + put 1 cm cubed of amylase in each
2)Label another 6 test tubes 1-6 + put 5 cm cubed of starch solution in each
3) prepare 6 spotting tiles, and place a drop of iodine solution in each well
3) prepare 6 water baths of temperatures increasing in ten degree intervals from 10-60 degrees
4) group test tube A with 1, B with 2 etc. and place A1 in the ten degrees water, B2 in the 20 degrees water and so on
5) leave test tubes to incubate in water baths for 5 minutes + test for temperature with a thermometer
6) add the starch solution into the amylase solution in each water baths, shake well , immediately starting the stopwatch
70 at every 2 minutes interval, use a dropper to place a drop of the solution into a well on the spotting tile, continue until the iodine solution no longer has a colour change- this indicates that the reaction is complete
8) stop the timer and record time taken
9) continue this process for all 6 temperatures,
10) repeat the entire practical 3 times for increased reliability
11) average data from 3 repeats and present data in a table
CONTROL: we will make sure we control the volume and concentration of iodine, starch and amylase solutions + control temperature of the room
