Flashcards
Biological Molecules - Exam Questions
Flashcards do conjunto (30)
- 1Maltose is hydrolysed by the enzyme maltase. Explain why maltase catalyses only this reaction. (3 marks)- Active site has a specific shape / tertiary structure / active site
complementary to substrate / maltose
- Only maltose can bind/fit
- To form an enzyme-substrate complex - 2Describe how a saturated fatty acid differs in molecular structure from an unsaturated fatty acid. (2 marks)Any 2 from:
- The absence of a double bond
- in the hydrocarbon chain
- unable to accept more hydrogen / saturated with hydrogen - 3Describe the role of DNA polymerase in DNA replication. (1 mark)- Joins nucleotides to form a new strand
- 4Describe how you would test a sample of food for the presence of starch. (2 marks)- Add iodine/potassium iodide solution to the food sample
- Blue / black / purple indicates starch is present - 5The concentration of glucose in the blood rises after eating a meal containing carbohydrates. The rise is slower if the carbohydrate is starch rather than sucrose. Explain why. (3 marks)- Starch digested to maltose / by amylase;
- Maltose digested to glucose / by maltase;
- Digestion of sucrose is a single step / only one enzyme/sucrase - 6Describe the structure of proteins. (5 marks)Any 5 from:
- A polymer of amino acids
- Joined by peptide bonds
- Formed by condensation
- Primary structure is order of amino acids
- Secondary structure is folding of polypeptide chain due to hydrogen bonding
- Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide
bonds;
- Quaternary structure is two or more polypeptide chains. - 7Explain one way in which starch molecules are adapted for their function in plant cells. (2 marks)- Insoluble
- Doesn't affect water potential
OR
- Helical;
- Compact;
OR
- Large molecule;
- Cannot leave the cell. - 8Explain how cellulose molecules are adapted for their function in plant cells. (3 marks)- Long and straight chains;
- Become linked together by many hydrogen bonds to form fibrils
- Provide strength to cell walls - 9Explain the difference in the structure of the starch molecule and the cellulose molecule. (2 marks)- Starch formed from α-glucose but cellulose formed from β-glucose;
- The position of hydrogen and hydroxyl groups on carbon atom 1 inverted. - 10The enzyme sucrase catalyses the breakdown of sucrose into monosaccharides. What type of reaction is this breakdown? (1 mark)- Hydrolysis
- 11Describe a biochemical test to find out if the solution collected from the apparatus contains the products of the hydrolysis of sucrose. (2 marks)- Heat with Benedict’s solution
- orange / brown / brick red / green / yellow colour or precipitate - 12Describe a biochemical test to find out if the solution collected from the apparatus contains the enzyme used. (2 marks)- biuret test / NaOH + CuSO4
- purple / violet / lilac / mauve colour - 13Some seeds contain lipids. Describe how you could use the emulsion test to show that a seed contains lipids. (3 marks)- Crush/grind
- With ethanol/alcohol
- Then add water / then add to water
- Forms emulsion / goes white/cloudy - 14The structure of a phospholipid molecule is different from that of a triglyceride. Describe how a phospholipid is different. (2 marks)- Phosphate / PO4;
- Instead of one of the fatty acids / and two fatty acids - 15In a piece of DNA, 34% of the bases were thymine. What are the names and percentages of the other bases. (2 marks)- Guanine 16%
- Adenine 34%
- Cytosine 16% - 16A polypeptide has 51 amino acids in its primary structure. What is the minimum number of DNA bases required to code for the amino acids in this polypeptide? (1 mark)- 153
- 17DNA helicase is important in DNA replication. Explain why. (2 marks)- Separates / unwinds / unzips strands / helix / breaks H-bonds
- So nucleotides can attach / are attracted / strands can act as templates - 18Name the monosaccharides of which the following disaccharides are composed: -Sucrose -Lactose (2 marks)- Sucrose: Glucose and Fructose
- Lactose: Glucose and Galactose - 19Explain what is meant by a polymer. (1 mark)- Chain of repeating units/monomers
- 20Complete the equation of the reaction: Lactose + ............... --> Glucose + ............... (2 marks)- Lactose + Water
- Glucose + Galactose - 21What bond holds cellulose molecules together side by side? (1 mark)- Hydrogen
- 22On each template strand, DNA polymerase works in opposite directions. Use your knowledge of enzyme action to explain why. (4 marks)- DNA is antiparallel
- The nucleotides are in different directions/positions
- Enzymes have a specific active site
- The active site of DNA polymerase can only bind with a complementary nucleotide - 23Write a simple equation to show how ATP is synthesised from ADP (1 mark)- ADP + Pi --> ATP + H2O
- 24Give two ways in which the properties of ATP make it a suitable source of energy in biological processes. (2 marks)Any 2 from:
- It releases energy in small, manageable amounts
- Releases energy from one reaction - quick and simple
- Soluble - 25Give and explain two properties of water that are important in the cytoplasm of cells. (4 marks)- Polar molecule
- Acts as a universal solvent
OR
- Universal solvent
- Reactions occur faster in solution
OR
- Reactive
- Takes place in hydrolysis/condensation reactions - 26Compare and contrast the processes by which water and inorganic ions enter cells. (3 marks)- Comparison: Both move down a concentration gradient
- Comparison: Both move through protein channels in the membrane
-Contrast: Ions can move against a concentration gradient by active transport - 27Name the two enzymes that play an important role in DNA replication. (2 marks)- DNA Polymerase
- DNA Helicase - 28Explain what effect phosphorylation has on a reaction. (1 mark)- Makes substrates more reactive / raises the substrates energy level / lowers activation energy for the reaction
- 29Describe how DNA is replicated (6 marks)- Strands separate / H-bonds break
- DNA helicase involved
- Both strands / each strand act(s) as (a) template(s)
- Free nucleotides attach
- Complementary / specific base pairing / AT and GC
- DNA polymerase joins nucleotides on new strand
- H-bonds reform
- Semi-conservative replication / new DNA molecules contain one old strand
and one new strand - 30Name the type of bond that joins amino acids together in a polypeptide. (1 mark)- Peptide
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- Descrição
- Exam questions and answers for the topic of biological molecules.
- Criado por
- Mia Weaver
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