BIOLOGY 2020

• What is the word equation for photosynthesis?

  Carbon Dioxide + Water = Glucose + Oxygen
• How do plants gain energy for the photosynthesis reaction?

  Light is absorbed by chlorophyll in chloroplasts
• How do you calculate the mean value X from the numbers 18.5, 19.3, and 19.5?

  $X =$$\frac{18.5 + 19.3 + 19.5}{3} =$$19.1$
• What is one possible cause of an anomalous result in an experiment?

  The scale was misread
• How did the students deal with the anomalous result?

  They did not use it in the calculation
• What factor should have been kept constant in the investigation?

  Light intensity
• Why did the rate of photosynthesis decrease from 35 °C to 45 °C?

  Enzymes lose the shape of the active site
• What is meant by the term diffusion?

  Movement of molecules from an area of higher concentration to an area of lower concentration
• Which two changes will increase the rate at which carbon dioxide diffuses into the mesophyll cells?

  Increased carbon dioxide concentration in the air and increased number of stomata that are open
• How are the human lungs adapted for efficient gas exchange by diffusion?

  • Many alveoli provide a larger surface area
  • Capillaries are thin, providing a short diffusion path
  • Breathing mechanism moves air in and out to maintain a concentration gradient
  • Large capillary network around alveoli removes oxygenated blood quickly
• What process allows water molecules to enter the root hair cell?

  Osmosis
• What method is used to transport nitrate ions into the root hair cell?

  Active transport
• Why is energy needed to move nitrate ions into the root hair cell?

  Because they move from a lower concentration in the soil to a higher concentration in the root
• What are two similarities between prokaryotic and eukaryotic cells?

  • Both have cytoplasm
  • Both have a cell membrane
  • Both contain DNA
  • Both have ribosomes
• What are three differences between prokaryotic and eukaryotic cells?

  • Prokaryotic cells are smaller
  • Prokaryotic cells have no mitochondria
  • Prokaryotic cells have no nucleus
• How do you calculate the ratio of the size of a bacterial cell to the size of a mesophyll cell?

  The ratio is $1 \mu m : \text{size of mesophyll cell}$
• What type of cell division produces genetically identical body cells for growth and repair?

  Mitosis
• What percentage of the time for one cell cycle is represented by stage 2 and stage 3 together?

  35%
• What happens during each stage of the cell cycle?

  • Stage 1: Chromosomes duplicate
  • Stage 2: One set of chromosomes is pulled to each end of the cell
  • Stage 3: The cytoplasm and cell membrane divide to form two cells
• What two products are formed when lipids are broken down?

  • Fatty acids
  • Glycerol
• What is the ‘lock and key theory’ of enzyme action?

  Enzyme binds to the substrate because they are complementary shapes, breaking down the substrate into products so products are released
• Why does each different type of lipase act on only one specific type of lipid molecule?

  Each active site has a specific shape that only fits one type of lipid molecule
• How would students find out if the liquid from the leaf contained glucose?

  Add Benedict’s solution to the liquid and heat; if glucose is present, the blue color changes to yellow/green/orange/brown/brick red
• How would students find out if the liquid from the leaf contained starch?

  Add iodine solution to the liquid; if starch is present, it changes color to blue/black from yellow/orange/brown
• Why did the leaf in the light for four days contain both glucose and starch?

  Glucose from photosynthesis is converted to starch as excess
• Why did the leaf left in a cupboard with no light for two days contain glucose but not starch?

  Starch stores were converted to glucose for respiration since there was no light to make new glucose
• How could students develop the investigation to find out more about glucose and starch production in plants?


  Test roots in the light and dark
• What type of defense response are thorns?

  Mechanical
• How do thorns defend the gorse plant?

  To prevent animals from damaging it
• What type of defense response are poisonous berries?

  Chemical
• What are two possible reasons for yellow leaves and stunted growth?

  Lack of magnesium ions so not enough chlorophyll for efficient photosynthesis so not enough glucose to make proteins for growth.

  infection by pathogen so leaves become discoloured so less photosynthesis so not enough glucose to make proteins for growth
• How does a lack of magnesium ions affect plant growth?

  Not enough chlorophyll for efficient photosynthesis leads to insufficient glucose for growth
• How does infection by a pathogen affect plant growth?

  Leaves become yellow, leading to less photosynthesis and insufficient glucose for growth
• Suggest how the nodules benefit the bacteria

  bacteria obtain glucose from the plant

  glucose used for respiration for making other named substances
• How do nodules benefit bacteria?

  Bacteria obtain glucose from the plant
• How do nodules benefit the gorse plant?


  The gorse plant obtains nitrate ions needed for amino acids
• What plant material was chewed as a painkiller?

  Willow bark
• What are two factors that scientists would have controlled in their investigation?

  Smoking habits and diet
• How do you calculate the percentage decrease in relative risk of developing cirrhosis of the liver for this woman?

  $\frac{2.55 - 1.60}{2.55} \times 100 =$$37\%$
• How do you calculate the relative risk of developing cirrhosis of the liver for this woman?

  $12 \times 2 \times 7 =$$168$