Exam Questions Flashcards
What is a monomer?
A smaller repeating unit from which larger molecules (polymers) are made.
Describe the chemical reactions involved in the conversion of polymers to monomers and monomers to polymers.
A condensation reaction joins monomers together and forms a bond and releases water.
A hydrolysis reaction breaks a bond between monomers and uses water.
Suggest a method other than using a colorimeter to measure the quantity of reducing sugar in a solution.
Filter and dry the precipitate.
Find mass.
Why would the use of a colorimeter improve the repeatability of results?
Colour change is subjective.
Describe two differences between the structure of cellulose and glycogen.
Cellulose is made up of beta glucose. Glycogen is made up of alpha glucose.
Glycogen has 1,4 and 1,6 glycosidic bonds. Cellulose only has 1,4 glycosidic bonds.
What are two features of starch that make it a good storage molecule?
Starch is insoluble in water so it doesn’t affect the water potential.
Starch is a large molecule so it can’t cross the cell membrane.
Describe the structure of glycogen.
Glycogen is a polymer of alpha glucose and is joined by glycosidic bonds.
How does glycogen act as a source of energy?
It is hydrolysed into glucose and glucose is used in respiration.
Explain the difference between starch and cellulose.
Starch is formed from alpha glucose. Cellulose is formed from beta glucose.
The positions of hydrogen and hydroxyl on carbon 1 are inverted.
Explain how cellulose molecules are adapted for their function in plant cells.
They are long and straight chains. They’re linked together by many hydrogen bonds to form fibrils. Thus they can provide strength to the cell wall.
Describe how a triglyceride molecule is formed.
One glycerol and three fatty acids. There are condensation reactions and the removal of 3 water molecules. Ester bonds are formed.
How is an ester bond formed in a phospholipid molecule?
Condensation reaction between glycerol and fatty acid.
What type of bond is between glycerol and fatty acid?
Ester bond.
Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst.
Substrate binds to the active site of the enzyme and enzyme-substrate complex forms.
Active site changes shape slightly so it is complementary to the substrate.
This reduces activation energy which speeds up a reaction.
How does a competitive inhibitor decrease the rate of an enzyme-controlled reaction?
Inhibitor is similar in shape to the substrate. It binds to the active site. Prevents enzyme-substrate complexes from forming.
How does the structure of a protein depend on the amino acids it contains?
Structure is determined by the position of the amino acid. The primary structure is the sequence of amino acids. The secondary structure is formed by hydrogen bonding. The tertiary structure is formed by hydrogen bonds, ionic bonds and disulfide bridges. This creates the active site in enzymes.
Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end.
One amine group joins to a carboxyl group to form a peptide bond. There is a free amine group at one end and a free carboxyl group on the other.
How does the active site of an enzyme cause a high rate of reaction?
It lowers activation energy. The induced fit causes the active site to change shape. So enzyme-substrate complex causes bonds to form/break.
Describe two other ways in which all dipeptides are similar and one way in which they might differ.
Similarities - NH2 group at one end.
COOH group at one end.
Difference - Different R groups.
Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction.
Attaches to the enzyme at a site other than the active site.
Changes shape of the active site.
Substrate is no longer complementary so enzyme-substrate complexes can’t form.
How is the secondary structure of a polypeptide produced by bonds between amino acids?
Hydrogen bonds between NH and C=O group forming beta pleated sheets or alpha helix shapes.
How can two proteins with the same number and type of amino acids have different tertiary structures?
Different sequence of amino acids can lead to ionic bonds, hydrogen bonds and disulfide bridges being formed in different places.
How does the formation of an E-S complex increase the rate of reaction?
Reduces activation energy due to bending bonds.
In what two ways are starch and cellulose similar?
They both have glycosidic bonds.
They are both polymers of monosaccharides.
