biological molecules Flashcards
Topic 2C
what elements do carbohydrates contain (3)
hydrogen and oxygen and carbon
a monosaccharide is a
simple sugar (eg. glucose)
a disaccharide is made when
2 monosaccharide join together (eg. maltose)
a polysaccharide is formed when
lots of monosaccharides join together ( eg. starch, glycogen)
are polysaccharides insoluble
yes
carbohydrates are made up of
simple sugars
proteins are made up of
amino acids
long chains of amino acid
proteins contain (atoms)
carbon, hydrogen, oxygen and nitrogen
examples of protein (2)
haemoglobin and enzymes
how are different proteins formed (amino acid arrangement)
as amino acids can be arranged in any order, it results in hundreds of different proteins
lipids are made from
3 fatty acids bonded to 1 glycerol molecule
lipids contain (atoms)
carbon, hydrogen and oxygen
lipids are divided into (2)
fats (solids at room temp)
oils ( liquids at room temp)
how do you prepare a food sample
1- get a piece of food and break it up using pestle and mortar
2- transfer to test tube and add distilled water
3- mix with glass rod to dissolve some of the food
4- filter the mixture using funnel and filter paper to get rid of solid bits of food.
test for glucose ( sugar) name
benedicts test
benedicts test
- add benedict’s solution to sample solution in a test tube
- heat in a boiling water bath for 5 mins
- take out and observe colour
- if there is glucose colour will have changed from blue to orange/brick red
if glucose is present what will the colour change be
blue to orange/ brick red
test for starch name
iodine test
iodine test
- add drops of iodine to food sample
- if colour changes from orange to blue black then starch is present
colour change for starch
orange/brown to blue/black
protein test name
biurets test
Biurets test
- add drops of biuret solution to food sample
- colour change will be from blue to violet/purple if protein is present
colour change for protein
blue to violet / purple
name for test for lipids
ethanol test
ethanol test
- mix food sample with 4cm³ of ethanol and shake
- allow time for food sample to dissolve in ethanol
- strain ethanol solution into another test tube
- add ethanol solution to 4cm³ of cold distilled water
- positive test will show milky, cloudy emulsion forming
colour change for ethanol test
colourless to cloudy, milky
what is a catalyst
a catalyst is a substance which increases the rate of reaction without chemically being used up
enzymes are
proteins that act as biological catalysts
what do enzymes do
act as biological catalysts to speed up rate of chemical reactions without being changed or used up
why are enzymes necessary to all living organisms
they maintain reaction speeds of all metabolic reactions at a rate that can sustain life
enzymes work fastest at
their optimum temperature
optimum temperature for enzymes in the human body
37º
what happens to an enzyme if temperatures go beyond optimum
the enzyme will denature and so the bonds that keep it together will break and it will lose its shape
what happens if an enzyme is denatured
substrate cannot fit into active site and so it doesn’t work anymore
can denaturisation be reversed
no, once an enzyme has been denaturedd, they cannot regain their shape
effect of temperature on an enzyme
- Increasing the temperature towards the optimum increases the activity of enzymes as the more kinetic energy the molecules have the faster they move and the number of collisions with the substrate molecules increases, leading to a faster rate of reaction
- This means that low temperatures do not denature enzymes, they just make them work more slowly due to a lack of kinetic energy
practical for investigating temp can affect enzyme activity
- add 5cm³ starch solution to a test tube and heat in water bath
- at the same time add 2cm³ of amalyse in a test tube and heat that in a water bath as well
- add a drop of iodine to each of the wells of a spotting tile
- mix the starch and amylase together
- every minute, transfer a droplet of solution to a new well of iodine solution ( which turns blue-black) until colour stops changing
- record time taken for colour change
- repeat with range of temperatures
optimum pH for most enzymes
7
if the pH is too high or too low,
the bonds holding the amino acid chain can be destroyed so the enzyme is denatured.
the active site changes shape and substrate no longe fits meaning activity stops
practical of how pH affects enzyme activity
Add a drop of iodine to each of the wells of a spotting tile
Use a syringe to place 2 cm3 of amylase into a test tube
Add 1cm3 of buffer solution (at pH 2) to the test tube using a syringe
Use another test tube to add 2 cm3 of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette
Every 10 seconds, transfer a droplet of the solution to a new well of iodine solution (which should turn blue-black)
Repeat this transfer process every 10 seconds until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch)
Record the time taken for the reaction to be completed
Repeat the investigation with buffers at different pH values (ranging from pH 3.0 to pH 7.0)
