Topic 1-Biological molecules Flashcards
Explain how competitive inhibitors decrease the rate of an enzyme- controlled reaction. (3 marks)
1) Inhibitor the same/ similar shape to the substrate.
2) This fits/ binds to the active site
3) This prevents/ reduces enzyme- substrate complexes forming.
Describe how the structure of glycogen is related to its function.
(4 marks)
1) Helix/ coiled/ branched so it’s compact
2) Polymer of glucose so easily hydrolysed
3) Branched so more ends for faster hydrolysis
4) Glucose polymer so it provides respiratory substrate for energy release
5) Insoluble so not lost from cell
OR insoluble so water potential is not affected
Glycogen and cellulose are both carbohydrates.
Describe two structural differences between them.
(2 Marks)
- Cellulose is made of Beta glucose whereas glycogen is made up of alpha glucose.
- Cellulose molecule has a straight chain whereas Glycogen is coiled OR branched
- Glycogen has 1,4 and 1,6 glycosidic bonds whereas cellulose only has 1,4 glycosidic bonds
Describe and explain two features that make starch a good storage molecule.
(2 Marks)
- Insoluble so it does not affect water potential
- Coiled/branched spit makes the molecule more compact OR can fit many molecules in small area
- Polymer of alpha glucose so provides glucose for respiration.
- Large so doesn’t fit across the cell membrane
- Branched so more ends for faster breakdown.
How does glycogen act as a source of energy?
(2 Marks)
- Hydrolysed to glucose
- Glucose is used in respiration
Explain how cellulose molecules are adapted to 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 wall
Describe how a triglyceride molecule is formed.
(3 Marks)
- One glycerol and three fatty acids
- Condensation reactions and the removal of three water molecules
- Ester bonds are formed
Suggest and explain a procedure a researcher could use to stop a chemical reaction.
(3 Marks)
- Boil OR add strong acid/ alkali
- To denature the enzymes/ ATP synthase
- Put in ice/ fridge/ freeze
- Lower genetic energy so less enzyme- substrate complexes form
- OR add a high concentration of an inhibitor
- So enzyme substrate complexes do not form
A competitive inhibitor decreases the rate of enzyme- controlled reaction.
Explain why.
(3 Marks)
- Inhibitor has similar shape to the substrate.
- Fits/ binds to the active site
- Prevents/ reduces the enzyme substrate complexes forming
Describe how the structure of a protein is dependent on the amino acids it contains.
(5 Marks)
- The structure is dependent on the position of the amino acids/ R group
- The primary structure is the sequence/ order of animo acids.
- The secondary structure formed by hydrogen bonds between amino acids.
- Tertiary structure is formed by interactions between R groups.
- Creating an active site for enzymes
- Quaternary structure contains one or less polypeptide bond.
OR quaternary structure formed by reactions/ bonds between polypeptides.
Describe how amino acids join to form a polypeptide so there is always an amine group at one end and a carboxyl group at the other end.
(2 Marks)
- One amine group joins a carboxyl group to form a peptide bond.
- So in the chain there is a free amine group at one end and a free carboxyl group at the other end.
OR each amino acid is orientated in the same direction in the chain.
Explain how an enzymes active site causes a high rate of reaction.
(3 Marks)
- Lowers activation energy
- Induced fit causes active site to change shape.
- So enzyme substrate complexes cause bonds to break/ form.
Describe a biochemical test to confirm the presence of proteins in a solution.
(2 Marks)
- Add buried reagent OR sodium hydroxide solution and copper sulphate solution.
- A positive result would be purple.
A dipeptide consists of two amino acids joined by a peptide bond. Dipeptides may differ in the type of amino acids they contain.
Describe two other ways dipeptides are similar and one way they differ.
(3 Marks)
Similarities:
1. Amine groups at the end
2. Carboxyl groups at the end
3. Two R groups
4. All contain C,H,N and O
Differences:
1. Variable/ different R groups
Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction.
(3 Marks)
- Attaches to the enzyme at a site other than the active site.
- Changes the shape of the active site OR changes the territory structure of the enzyme.
- So the active site and substrate are no longer complementary so less/ no substrate can bind/ fit.
Describe the structure of DNA.
(5 Marks)
- Polymer of nucleotides.
- Each nucleotide is formed from: a nitrogenous base, deoxyribose and a phosphate group.
- Phosphodiester bonds between nucleotides.
- double helix/ 2 strands held together by hydrogen bonds.
- Hydrogen bonds/ pairing between adenine, thymine and cytosine, guanine.
Describe how a phosphodiester bond is formed between nucleotides within a DNA molecule.
(2 Marks)
- Condensation reaction/ loss of water.
- Between phosphate and deoxyribose.
- Catalysed by DNA polymerase.
Describe how separation between strands occurs in semi-conservative DNA replication.
(2 Marks)
- DNA helicase
- Breaks hydrogen bonds between base pairs.
OR breaks bonds between polynucleotide strands.
Describe the role of DNA polymers in the process of semi-conservative DNA replication.
(2 Marks)
- Joins adjacent DNA nucleotides.
- Catalyses condensation reactions.
- Catalyses formation of phosphodiester bonds between adjacent nucleotides.
Give two features of DNA and explain how each one is important in the semi-conservative replication of DNA.
(2 Marks)
- Weak hydrogen bonds between bases allows the two strands to separate.
- Two strands so they can both be used as a template.
- Complementary base pairing allows for accurate replication.
Describe how an ATP molecule is formed from its component parts.
(4 Marks)
1 and 2. (2 marks for 3 correct names):
Adenine, ribose/ pentose and 3 phosphate.
3. Condensation reaction.
4. ATP synthase.
Describe how ATP is resynthesised in cells.
(2 Marks)
- From ADP and an inorganic phosphate.
- By ATP synthase.
- During respiration/ photosynthesis.
Give two ways in which the hydrolysis of ATP is used in cells.
(2 Marks)
- To provide energy for other reactions.
- To add phosphate to other substances and to make them more reactive/ to change their shape.
Explain 5 properties that make water important for organisms.
(5 Marks)
- A metabolite in hydrolysis/ condensation/ photosynthesis/ respiration.
- A solvent so metabolic reactions can occur OR A solvent so allowing transport of substances.
- High specific heat capacity so buffers change in temperature.
- Large latent heat of vaporisation so provides a cooling effect through evaporation.
- Cohesion between water molecules supports columns of water in plants.
- Cohesion between water molecules produces surface tension to support small organisms.
