Biological molecules

what chemical elements are in carbohydrates?

carbon, hydrogen and oxygen

what chemical elements are in proteins?

carbon, hydrogen, oxygen and nitrogen

what chemical elements are in lipids?

carbon, hydrogen, oxygen (may contain phosphorus or nitrogen)

what are carbohydrates made from?

monosaccharides- glucose, fructose, galactose

disaccharides- maltose, sucrose, lactose

polysaccharides- starch, glycogen, cellulose

what are proteins made from?

amino acids

what are lipids made from?

glycerol and fatty acids

1 glycerol molecule with three fatty acids

explain how to conduct the benedict’s test

add benedict’s solution to a food sample

heat in a water bath (80°C) for a few mins

brick red—> orange—> yellow—> green—> blue (decreasing glucose concentration)

explain how to conduct the iodine test

add a few drops of iodine to food sample

blue-black—> starch present

orange-brown—> starch not present

explain how to conduct the biuret test

add sodium hydroxide to a sample

add a few drops of copper sulfate

lilac/purple—> protein oresent

blue—> protein not present

explain how to conduct the ethanol emulsion test

add ethanol to sample and shake

pour into water

milky white emulsion—> fat present

clear—> fat not present

why is heating needed for benedict’s test?

to provide the activation energy required for the chemical reaction to occur between the reducing sugar and the benedict’s reagent

what is the role of enzymes?

biological catalysts that increase the rate of chemical reactions in living organisms without being changed or used up in the process

how does temperature change affect enzyme function?

At optimum temperature:

More kinetic energy

More frequent successful collisions

More enzyme-substrate complexes form

At high temperatures:

Enzyme denatures

Active site changes shape

Substrate no longer fits → reaction stops

what is the method for investigating the effect of temperature on enzyme activity?

Set up water baths at different temperatures

Add amylase solution to a test tube and starch solution to another test tube

Place both in the water bath for a few minutes (to equilibrate)

Mix the amylase and starch together

Start a timer and every 10–20 seconds, take a drop of the mixture

Place it onto iodine on a spotting tile

Record the time when iodine stays orange-brown (no blue-black)

what does it mean if there is a shorter time in the starch-amalyse experiment?

there is a faster enzyme activity

what are the control variables in the starch-amylase experiment?

pH (keep constant with buffer)

volume of enzyme/substrate

concentration of enzyme/substrate

what is the method for investigating the effect of pH on enzyme function?

Prepare buffer solutions of different pH values

Add amylase to a test tube and a buffer solution

Add starch solution

start timing immediately and every 10–20 seconds:

Take a drop of the mixture

Place onto iodine on a spotting tile

Record the time when iodine stays orange-brown (no blue-black)

how does pH affect enzyme activity?

At optimum pH:

Active site has correct shape

Substrate fits perfectly → many enzyme-substrate complexes

At extreme pH (acidic or alkaline):

Bonds in enzyme break

Active site changes shape

Substrate no longer fits

Denaturation occurs

What are some improvements you could make to the experiment investigating pH on enzyme activity?

Repeat and calculate mean

Use smaller pH intervals

Keep temperature constant (water bath)