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Description
Flashcards by Mia Weaver, updated more than 1 year ago
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Created by Mia Weaver
about 5 years ago
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| Question | Answer |
| Maltose 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 |
| Describe 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 |
| Describe the role of DNA polymerase in DNA replication. (1 mark) | - Joins nucleotides to form a new strand |
| Describe 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 |
| The 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 |
| Describe 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. |
| Explain 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. |
| Explain 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 |
| Explain 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. |
| The enzyme sucrase catalyses the breakdown of sucrose into monosaccharides. What type of reaction is this breakdown? (1 mark) | - Hydrolysis |
| Describe 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 |
| Describe 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 |
| Some 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 |
| The 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 |
| In 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% |
| A 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 |
| DNA 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 |
| Name the monosaccharides of which the following disaccharides are composed: -Sucrose -Lactose (2 marks) | - Sucrose: Glucose and Fructose - Lactose: Glucose and Galactose |
| Explain what is meant by a polymer. (1 mark) | - Chain of repeating units/monomers |
| Complete the equation of the reaction: Lactose + ............... --> Glucose + ............... (2 marks) | - Lactose + Water - Glucose + Galactose |
| What bond holds cellulose molecules together side by side? (1 mark) | - Hydrogen |
| On 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 |
| Write a simple equation to show how ATP is synthesised from ADP (1 mark) | - ADP + Pi --> ATP + H2O |
| Give 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 |
| Give 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 |
| Compare 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 |
| Name the two enzymes that play an important role in DNA replication. (2 marks) | - DNA Polymerase - DNA Helicase |
| Explain what effect phosphorylation has on a reaction. (1 mark) | - Makes substrates more reactive / raises the substrates energy level / lowers activation energy for the reaction |
| Describe 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 |
| Name the type of bond that joins amino acids together in a polypeptide. (1 mark) | - Peptide |
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