B5 Biological Molecules and Enzymes T7-8 Flashcards
Biological molecules 2.7 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils) 2.8 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugars, protein from amino acids, and lipid from fatty acids and glycerol
What are carbohydrates made of chemically?
hydrogen, oxygen, carbon
What are the large molecules of carbohydrates in animals and plants?
animals+fungi -> glycogen
plants -> starch
What do the polymers of carbohydrates break down into?
glucose (sugars)
What does the body use glucose for?
release energy for respiration
What are proteins made of chemically?
hydrogen, oxygen, carbon, sulfur, nitorgen, phosphorus
What are the large molecules of proteins?
proteins
What do the polymers of proteins break down into?
amino acids
What does the body use amino proteins for?
growth + repair of cells
What are lipids made of chemically?
hydrogen, oxygen, carbon
What are the large molecules of lipids (fats)?
fat molecule = triglycerides
What do the polymers of lipidss break down into?
3 fatty acids + 1 glycerol
(3 points)
What are lipids/fats used for in the body?
- insulation - heat
- long term energy store
- make cell membranes
Practical: investigate food samples for the presence of starch
What is the food test for starch?
What solution is added?
1) Pipette the sample solution into wells or on a tile
2) Add drops of iodine solution and leave for 1 minute
3) Record any colour change
● If starch is present the solution will turn blue-black
● If starch is not present the solution will remain brown
orange -> blue black
IODINE
Practical: investigate food samples for the presence of glucose
What is the food test for glucose?
What solution is added?
1)Add the sample solution into a test tube
2) Add drops of Benedict’s solution into the test tube
3) Heat in a water bath at 60-70°C for 5 minutes
4) Take test tube out and record the colour
● If glucose is present the solution will turn brick red
● If glucose is not present that the solution will remain blue
blue -> brick red
BENEDICT
Practical: investigate food samples for the presence of proteins
What is the food test for proteins?
What solution is added?
Add the sample solution into a test tube
2) Add drops of Biuret solution into the test tube
3) Leave for 1 minute and then record the colour
● If protein is present the solution will turn purple
● If protein is not present that the solution will remain blue
blue -> purple
BIURET
Practical: investigate food samples for the presence of proteins
What is the food test for lipids?
1)Add 2cm3 of ethanol to the test solution
2) Add 2cm3 of distilled water
3) Leave for 3 minutes and then record the colour
● If fat is present a milky white emulsion will form
● If fat is not present that the solution will remain colourless
colourless -> milky white emulsion
ETHANOL
Define enzyme
biological catalyst
- speeds up a chemical reaction
Define catalyst
substance whih changes the rate of a chemical reaction without being changed itself
Explain the enzyme substrate complex
Each enzyme has a uniquely shaped active site where the substrate binds together
The substrate shape is complementary to the shape of the active site
Define activation energy
energy needed for a chemical reaction to take place
Explain how enzymes work
1) the active site is complementary to the substrate
2) the substrate and active site collide forming the enzyme substrate complex
3) enzyme breaks the substrate into products and they leave the active site, so the enzyme is reused
Optimum temperature for enzymes
(where enzymes work the fastest)
37°C (body temperature)
How temperature affects enzymes
The rate of reaction increases with an increase in temperature, molecules gain kinetic energy causing more successful collisions and a faster reaction rate.
Up tothe optimum, where it works the fastest
After optimum temperature,active site no longer complementary to substrate, enzymes DENATURES and eventually reaction stops.
What happens to enzymes when the temperature becomes too hot?
active site changes shape, substrate is not complementary so can’t fit in.
enzyme is denatured and can no longer work
[5 marks]
Practical: investigate how enzyme activity can be affected by changes in temperature
1) Starch solution is heated to set temperature
2) Amylase is added
3) Iodine is added to each well after a minute
4) Measure the time it takes until the iodine stops turning blue-black (this means that starch is not
present as amylase has broken the starch down into glucose)
5) Repeat the test with different temperature
SAFETY MEASURES
Practical: investigate how enzyme activity can be affected by changes in temperature
eye protection - safety
Optimum pH for enzymes
generally -> 7
stomach (acidic) -> 2
How pH affects enzymes
If the pH is too high or too low, the forces that hold the amino acid chains that make up the
protein will be affected
This will change the shape of the active site, so the substrate can no longer fit in
The enzyme is denatured and doesn’t work
CATALASE
Practical: investigate how enzyme activity can be affected by changes in pH
TRIPLE AWARD
1) catalase speeds up the breakdown of hydrogen peroxide -> oxygen + water
2) when reaction happens oxygen bubbles are given off -> hgiher the foam, faster the enzyme is working
Practical: investigate how enzyme activity can be affected by changes in pH
TRIPLE AWARD
Method:
1) Place 5cm3 buffer solution pH 2, 4, 6, 8 into boiling tubes
2) Add a potato chip - same size each rime
3) Add 1cm3 washing up liquid to each tube
4) Add 5cm3 H2O2
5) After 10 mins measure heignht of foam
Practical: investigate how enzyme activity is affected by changes in pH
dependent variable
TRIPLE AWARD
volume of oxygen produced
Practical: investigate how enzyme activity is affected by changes in pH
independent variable
TRIPLE AWARD
different pH levels
Practical: investigate how enzyme activity is affected by changes in pH
control variable
TRIPLE AWARD
boiled potato (denatured enzyme)
to show no oxygen produced
What does a buffer solution do
changes the pH
