Plant Structures and their Functions

• why are photosynthetic organisms producers of biomass?

  Because they use sunlight energy through photosynthesis to create their own food (glucose) from carbon dioxide and water.
• Substances produced by glucose and what are their roles?

  • Starch - a complex carbonhydrate used by the plants to store energy and broken down into glucose when needed
  • Glycogen - excess glucose stored in the liver or muscles
  • Fatty acids - When glucose is abundant, and stored for long periods of time
  • Amino acids - glucose is used to synthesise amino acids, the building blocks of proteins.
• What happens in photosynthesis?

  • Photosynthetic organisms (green plants and algae) use energy from the sun to make glucose
  • Some glucose is used to make larger, complex molecules that plants need to grow. Making up the organisms biomass
  • The energy stored goes through the food chain as animals eat them and each other.
  • Photosynthesis happens inside the chloroplast - they contain chlorophyll, which absorbs light. Energy is transferred to the chloroplast by light.
• Why is photosynthesis an endothermic reaction?

  As energy is taken in during the reaction
• How are a leaf and its cells adapted for photosynthesis?

  • have a large surface area for sunlight
  • contain openings called the stomata
  • The cells inside the leaf have water on their surface
  • coated in a waxy cuticle—to stop water vapour escaping
• What is the equation for photosynthesis?

  6CO2 + 6H2O -> C6H12O6 + 6O2

  Carbon dioxide + water = glucose + oxygen
• What is meant by the rate of reaction?

  How quickly a reaction takes place by looking at how the amount of products or reactants changes.
• What are the effects of temperature?

  Denaturation (45 degrees celcius), enzyme activity (if the limiting factor), and metabolic rate.
• What are the effects of light intensity?

  • Not enough light slows down the rate of photosynthesis
  • As the light level is raised, the rate of photosynthesis increases steadily only up to a certain point where either the temperature or the CO2 level needs to be increased.
• What is the light intensity equation?

  The inverse square law:

  A) Light intensity

  B) distance (d)^2

  
• What are the effects of carbon dioxide concentration?

  • Increasing the CO2 concentration increases the rate of photosynthesis up to a point. It then flattens out as CO2 is no longer the limiting factor, and either the light or temperature needs to be increased.
• Why is the rate of photosynthesis is inversely proportional to the distance of a light source

  The distance away from a light source increases becoming spread over a wider area.
• How are root hair cells adapted to taking in water and mineral ions?

  • Large surface area; as the cells on the surface of plant roots grow into 'hairs', sticking out into the soil
  • Each branch of a root will be covered in millions of microscopic hairs
  • The concentration of mineral ions is higher in the root hair cells than in the soil around them, so ions are absorbed by active transport.
  • Water is absorbed by osmosis.
• What is diffusion?

  The spreading out of particles from an area of higher concentration to an area of lower concentration
• What is osmosis?

  The movement of water molecules from an area of lower water concentration to an area of higher water concentration across a semi-permeable membrane.
• What is active transport?

  Active transport is the movement of molecules or ions across a cell membrane against their concentration gradient (high to low), requiring energy transferred during respiration.
• What is meant by a concentration gradient?

  When there is a region of high concentration leading to a region of low concentration
• Why is active transport needed to transport some molecules?

  Because it allows movement against a concentration gradient
• How do molecules move by osmosis?

  Water molecules will flow from an area of high concentration (the solution that doesn't contain any sugar) to the area of lower water concentration (the solution that contains sugar)

  Trying to equalise the solute concentration on both sides of the membrane.
• How is the xylem tissue adapted to its function?

  • The xylem tube takes water up.
  • Xylem tubes are made up of dead cells joined end to end with no end walls between them and a hole down the middle.
  • strengthened by lignin.
  • They carry water and mineral ions from the roots to the stem and leaves.
  • The movement of water from the roots out of the leaves is called the transpiration stream.
• How is the phloem tissue adapted to its function?

  • The phloem tubes are made out of columns of elongated living cells with small holes in the end walls to allow stuff to flow through
  • They transport food substances (sucrose) made in the leaves to the rest of the plant for immediate use or for storage.
  • The process is called translocation and it requires energy from respiration
  • The transport goes in both directions
• How does transiration occur?

  • Is caused by the evaporation and the diffusion of water from the plant's surface (mostly the leaves)
  • The loss of water creates a shortage of water from the leaf, so more water is drawn up from the rest of the plant through the xylen vessels to replace it.
  • Meaning more water is drawn up from the roots, resulting in a constant transpiration stream of water through the plant.
  • The transpiration stream carries mineral ions along with it.
• How does translocation occur?

  • Through the movement of dissolved food substances
  • Sucrose, from the source to the sink (where it is used or stored) through the phloem tissue, a living tissue with specialized cells called sieve tubes
  • Which allows for the transport of these substances throughout the plant
• What is photosynthesis?

  Process where plants make glucose using sunlight
• Why are photosynthetic organisms crucial in food chains?

  They are the main producers of food
• What do green plants and algae use to make glucose?

  Energy from the Sun
• What is biomass in the context of plants?

  The mass of living material in organisms
• How does energy stored in biomass move through the food chain?

  As animals eat plants and each other
• Where does photosynthesis occur in plants?

  Inside chloroplasts
• What role does chlorophyll play in photosynthesis?

  It absorbs light energy
• What is the equation for photosynthesis?

  6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
• What type of reaction is photosynthesis?

  Endothermic reaction
• What factors affect the rate of photosynthesis?

  Light intensity, CO₂ concentration, temperature
• What happens if temperature is the limiting factor for photosynthesis?

  Enzymes work more slowly at low temperatures
• At what temperature do enzymes for photosynthesis denature?

  About 45°C
• How does light intensity affect the rate of photosynthesis?

  Increases steadily until a limiting factor occurs
• What is the inverse square law in relation to light intensity?

  Light intensity decreases with the square of distance
• If the distance from a lamp is doubled, how does light intensity change?

  It becomes four times smaller
• How do you calculate light intensity using the inverse square law?

  Use the formula 1/d²
• What happens to the rate of photosynthesis if CO₂ concentration is low?

  It slows down the rate of photosynthesis