Summary Questions

• What are four features that animal and plant cells have in common?

  Both have a cell membrane, cytoplasm, ribosomes, and genetic material.
• What are four sub-cellular structures present in prokaryotic cells but not eukaryotic cells?

  Plasmids, flagella, pili, and a capsule.
• How have electron microscopes increased our understanding of sub-cellular structures?

  They provide higher resolution images than light microscopes, allowing for detailed observation of structures.
• Why is it important to take a thin slice of a sample before viewing it under a light microscope?

  A thin slice allows light to pass through, enabling clearer visibility of the structures within the sample.
• How can you calculate the magnification of an image if you don’t know which lenses were used?

  Magnification can be calculated by dividing the size of the image by the size of the real object.
• What are the initials of the four bases present in DNA?

  A, T, C, and G.
• Describe the structure of a nucleotide.

  A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.
• What is a gene?

  A gene is a segment of DNA that codes for a specific protein or trait.
• What is a triplet code?

  A triplet code is a sequence of three nucleotides that corresponds to a specific amino acid in protein synthesis.
• What is the process of making mRNA from DNA called?

  Transcription.
• In what part of a cell are amino acids joined together to form a protein?

  In the ribosomes.
• Draw a diagram to show how the ‘lock and key’ mechanism of enzymes works.

  Enzymes have a specific active site that fits a specific substrate, similar to a key fitting into a lock.
• What does it mean when an enzyme has been ‘denatured’?

  It means the enzyme's structure has changed, rendering it inactive and unable to catalyze reactions.
• Sketch a graph to show how substrate concentration affects the rate of an enzyme-controlled reaction.

  The graph typically shows an increase in reaction rate with substrate concentration until a maximum rate is reached.
• Give two things that you could measure when investigating the rate of an enzyme-controlled reaction.

  You could measure the amount of product formed or the time taken for the reaction to complete.
• Give two variables that need controlling when investigating the effect of pH on an enzyme-controlled reaction.

  Temperature and substrate concentration.
• What is respiration?

  Respiration is the process of converting glucose and oxygen into energy, carbon dioxide, and water.
• Is respiration an exothermic or an endothermic reaction?

  Exothermic.
• Name the type of respiration that requires oxygen.

  Aerobic respiration.
• Give an example of when lactic acid would be produced as a product of respiration.

  During intense exercise when oxygen levels are low.
• Which form of respiration transfers more energy per glucose molecule?

  Aerobic respiration transfers more energy than anaerobic respiration.
• Briefly describe an experiment to show that carbon dioxide is a product of respiration.

  One could use a respirometer to measure the amount of carbon dioxide produced by a respiring organism.
• What type of polymer do you get when you join together simple sugars?

  Polysaccharides.
• Name the basic units that lipids are made from.

  Fatty acids and glycerol.
• What can you conclude if a test sample turns a blue-black colour when iodine is added?

  It indicates the presence of starch in the sample.
• How would you test for lipids in a sample solution?

  You can use the emulsion test, where the sample is mixed with ethanol and then water is added to observe a milky emulsion.
• In what part of a cell does photosynthesis take place?

  In the chloroplasts.
• Give three factors that can limit the rate of photosynthesis.

  Light intensity, carbon dioxide concentration, and temperature.
• Describe how you could investigate the effect of CO₂ concentration on the rate of photosynthesis.

  You could use aquatic plants and measure the rate of oxygen production at different CO₂ concentrations.