Enzymes + Food tests Flashcards
Why do we have enzymes?
to speed up the useful chemical reactions in our body
what are enzymes?
biological catalysts
what are catalysts?
a catalyst is a substance which increases the speed of a reaction without being changed or used up in the reaction
what are enzymes made of?
proteins which are made up of long chains of amino acids that are folded into unique shapes to do their job
What is the active site in an enzyme?
a unique shape that fits onto the substance involved in a reaction
Why won’t the reaction be catalysed if the substrate doesn’t fit the active site?
because for the enzyme to work, the substrate must fit into the enzymes active site.
what is the name of the diagram that shows catalyse reaction steps?
Lock and key diagram
what is a substrate?
the substance that an enzyme works on
what is it called when the substrate fits into the enzyme?
enzyme substrate complex
Why do enzymes have an optimum pH?
if pH is too high or too low, the pH interferes with the bonds holding the enzyme together which changes the shape of the active site causing the enzyme to denature.
what two things can denature an enzyme and why?
temperature - if temp too hot, bonds break changing shape of enzymes active site so substrate no longer fits and enzyme is denatured
pH - if too pH too high or too low, bonds holding enzyme together are broken and changes shape of active site which denatures enzyme
what pH do enzymes often work best at?
neutral pH 7
How can you test for sugar?
what colour does it go?
Benedict’s test
blue to brick red
how can you test for starch?
what colour will it turn?
iodine solution test
brown to black
how can you test for proteins?
what colour does it go?
biuret solution
blue to purple
how can you test for lipids?
what colour will it go?
emulsion test, milky white
sudan III test, red
how can you work out rate of reaction?
1000/time
how can you calculate how much something changes over time with rate of reaction?
amount it has changed over time/time taken
bile emulsifies fats, explain what this means and how it aids digestion
it breaks the fats down into tiny droplets to giving larger surface area for lipase enzyme to work upon. making digestion faster
what would you observe shaking Sudan III stain solution with a food sample containing lipids?
the mixture will separate into two layers, the top layer being red
what are the 3 jobs of enzymes?
chemical digestion (break down)
assimilation - building up new molecules
transforming molecules - used in metabolic pathways
catalyst - speeds up rate of reaction
state the steps of the Benedict’s test
1) prepare a food sample and transfer 5 cm3 to a test tube
2) prepare a water bath so that its set to 75 degrees Celsius
3) add some Benedict’s solution to the test tube (about 10 drops) using a pipette
4) place the tube in the water bath using a tube holder and leave it in there for 5 mins, make sure the tube is pointing away from you
5) if the food sample contains a sugar, the solution in the test tube will turn from blue to green, yellow or brick red depending on how much sugar is in the food.
name steps in the iodine test
1) make a food sample and transfer 5cm3 of your sample to a test tube
2) add a few drops of iodine solution and gently shake the tube to mic the contents. if sample contains starch, colour of solution will turn from brown to black
name steps of biuret test
prepare a sample of food and transfer 2cm3 of sample to a test tube
add 2cm3 of buret solution to the sample and mix the contents of the tube by gently shaking
if food contains solution will change from blue to purple
state steps of Sudan III test
prepare a sample of the food you’re testing, transfer 5cm3 into a test tube
use a pipette to add 3 drops of Sudan III stain solution to test tube and gently shake
Sudan III stains lipids, if sample contains lipids, mixture will separate into two layers, the top layer will be bright red
state the adaptations of the small intestine
large blood supply to maintain high concentration gradient
large surface area for maximum absorption
thin wall of villi for shorter diffusion
blood capillaries close to wall for shorter diffusion
what is the independent variable?
the one thing you change
what is the dependent variable!
the change that happens because of the independent variable
what is the controlled variable?
what stays the same (eg type of acid used)
