aos 1b

Question 1

photosynthetic autotrophs

Answer 1

• plants and photosynthetic phytoplankton (algae)
• use energy from sunlight to produce food (glucose)
• majority of autotrophs use photosynthesis

Question 2

chemosynthetic autotrophs

Answer 2

• obtain energy from inorganic chemical reactions
  e. g. ammonium ions into nitrite, sulphide ions into sulphate ions
• prokaryotes
• often seen as the basis of light deep under the ocean living off chemicals released by volcanic vents

Question 3

heterotrophs

Answer 3

• can’t make own food, must consume other organisms (or their products) to survive
• herbivores: eat plants
• carnivores: eat other animals
  
  • insectivores: eat insects
• omnivores: eat both plants and animals
• saprotrophic heterotrophs: fungi etc, digest food outside of themselves then absorb the digested material

Question 4

light dependent reactions

Answer 4

• requires light to occur
• light energy absorbed by chlorophyll is used to photolyse (break) water molecules into H+ ions and oxygen gas
• occurs in the thylakoid
  light
  water ——-> hydrogen ions + oxygen + ATP
  chlorophyll

Question 5

light independent reactions

Answer 5

• occurs in the stroma
• does not need light
• hydrogen and ATP from the first stage, plus CO2 are used to make glucose and water
  hydrogen + ATP + carbon dioxide —–> glucose + water + ADP

Question 6

balanced equation for the process of photosynthesis

Answer 6

sun energy
CO2 + H2O ———> C6H12O6 + O2
carbon water chlorophyll sugars oxygen
dioxide

Question 7

aerobic respiration

Answer 7

• oxygen present
• mitochondria:
  
  • cristae = infoldings of the inner membrane
  • matrix = region enclosed by the inner membrane
• once in the mitochondria, pyruvate is broken down in a series of enzyme reactions
• two steps:
  
  • Krebs cycle (occurs in the matrix)
  • Electron transport chain (occurs over cristae membrane)
• C6H12O6 + 6O2 —-> 6H2O + 6CO2 + 36ATP
• also occurs in cytosol
• energy efficiency = 2 ATP from glycolysis, 34-6 from aerobic respiration
• speed = slow
• other products = CO2, H2O

Question 8

anaerobic respiration

Answer 8

• in plants, yeast and some bacteria Pyruvate is converted into Ethanol and CO2
• in animals Pyruvate is converted to Lactic Acid
• difference in products due to different enzymes found in the organisms
  glucose —-> ethanol + carbon dioxide + adenosin triphosphate
• location = cytosole
• no O2 required
• energy efficiency = 2 ATP from glycolysis, 0 anaerobic respiration
• speed = fast
• other products = plants: Ethanol, CO2, animals : Lactic Acid

Question 9

glycolysis

Answer 9

• occurs in cytoplasm
• breakdown of glucoes (6C) into two molecules of Pyruvate (3C)
• 2 ATP generated
• process is anaerobic (no O2 required)
• Pyruvate is then either transported to the mitochondria or continues to be metabolized to the cytoplasm.