4.1 Biological Molecules (Cambridge (CIE) O Level Biology): Flashcards
Exam code: 5090
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Which chemical elements are found in carbohydrates?
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Cards in this collection (22)
Which chemical elements are found in carbohydrates?
Carbon, hydrogen and oxygen.
Which chemical elements does a protein contain?
Carbon, hydrogen, oxygen and nitrogen (some proteins also contain small amounts of sulfur).
As well as carbon, hydrogen, oxygen and nitrogen, DNA also contains the element .
As well as carbon, hydrogen, oxygen and nitrogen, DNA also contains the element phosphorus.
Which four main types of molecule in living organisms all contain carbon?
Carbohydrates
Proteins
Lipids
DNA
What are the smaller units (monomers) that make up proteins?
Amino acids — there are about 20 different ones.
Starch, glycogen and cellulose are all made from many molecules.
Starch, glycogen and cellulose are all made from many glucose molecules.
Define a triglyceride.
A lipid made of one glycerol molecule bonded to three fatty acid chains.
What is formed when two glucose molecules join together?
Maltose (a disaccharide).
Define a nucleotide.
The individual repeating unit that joins together to make up DNA.
All amino acids share the same basic structure but differ in their group.
All amino acids share the same basic structure but differ in their R group.
True or False?
A small change in the order of amino acids produces a different protein.
True.
Even a small difference in the order of amino acids results in a different protein being formed.
What are lipids (fats and oils) made from?
One glycerol molecule bonded to three fatty acids.
What reagent tests for starch, and what is a positive colour change?
Iodine solution: changes from orange-brown to blue-black.
What reagent tests for glucose (a reducing sugar), and what is a positive colour change?
Benedict's solution, heated at 60–70 °C for ~5 minutes: changes from blue to orange / brick red.
What reagent tests for protein, and what is a positive colour change?
Biuret solution: changes from blue to violet / purple.
Describe the ethanol emulsion test for lipids and its positive result.
Mix the sample with ethanol and shake, then add to an equal volume of cold water; a cloudy white emulsion shows lipid is present.
A positive iodine test for starch changes colour from orange-brown to .
A positive iodine test for starch changes colour from orange-brown to blue-black.
The test for glucose must be heated in a water bath to show a colour change.
The Benedict's test for glucose must be heated in a water bath to show a colour change.
True or False?
The Benedict's test for glucose gives a positive result at room temperature without heating.
False.
The sample must be heated (60–70 °C) for the colour change to occur.
Biuret solution turns from blue to when protein is present.
Biuret solution turns from blue to purple (violet) when protein is present.
When describing a food test in an exam, what two things must you always give?
The starting colour and the colour it changes to for a positive result.
Define the emulsion test.
The food test for lipids, using ethanol and water to produce a cloudy white emulsion if lipid is present.
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