B3

• Give two reasons why we can't just make our cells even warmer to increase the rate of reactions

  higher temperatures would speed up non-useful reactions

  higher temperatures could damage our cells
• Explain how increasing the temperature can cause an enzyme to denature

  High temperatures start to break the bonds holding the enzyme together. This causes the enzyme and it's active site to change shape.

  This means the enzymes active site will no longer be complementary to the substrate.
• photosynthesis word equation

  carbon dioxide + water -> glucose + oxygen
• photosynthesis symbol equation

  6CO2 + 6H2O ➔ C6H12O6 + 6O2
• What can the glucose made during photosynthesis be used for?

  stored as starch for later

  respiration
• How do plants get the carbon dioxide required for photosynthesis?

  it diffuses from the air into the leaves via the stomata
• How do plants get the water required for photosynthesis?

  it diffuses from the soil into the root hair cells via osmosis
• What makes starch a useful long term storage molecule?

  it is compact

  it is insoluble in water

  it can be easily broken down when needed
• What are the main uses of glucose in plants? 

  cellular respiration

  to make cellulose

  make starch

  make amino acids

  make lipids
• factors which affect the rate of photosynthesis

  amount of chlorophyll

  temperature

  carbon dioxide concentration

  light intensity
• which photosynthesis factor would give this graph?

  temperature

  
• which variables could be on the x axis?

  light intensity

  carbon dioxide concentration

  
• what is the limiting factor on this graph?

  carbon dioxide concentration

  
• what could be limiting the rate of photosynthesis?

  temperature, carbon dioxide concentration

  
• Describe and explain how the rate of photosynthesis varies with temperature

  At first the rate of photosynthesis rises with temperature as the particles have more energy and move more quickly. This means they can react more quickly and so the rate is higher.

  However, as temperature rises above the optimum temperature for the enzymes involved, the enzymes may start to break down. This decreases the rate until it falls to zero (when the enzymes are denatured).
• diffusion

  net movement of particles from a high concentration to a low concentration
• Which molecules are able to diffuse into and out of cells?

  water

  amino acids

  glucose
• List three factors that affect the rate of diffusion

  temperature

  surface area

  distance to diffuse across
• Why does a higher temperature increase the rate of diffusion?

  Higher temperatures mean particles have more energy and therefore can move faster, causing them to diffuse quicker.
• osmosis

  net movement of particles across a partially permeable membrane from an area of higher water concentration to a region of lower water concentration
• active transport

  movement of molecules across a membrane, from a region of lower concentration to a region of higher concentration. this requires energy from respiration.
• The four levels of plant organisation

  cells

  tissues

  organs

  organ systems
• what part of the leaf is this?

  waxy cuticle

  
• what part of the leaf is this?

  palisade mesophyll layer

  
• what part of the leaf is this?

  spongy mesophyll layer

  
• what part of the leaf is this?

  lower epidermis

  
• what part of the leaf is this?

  guard cells

  
• what name is given to these openings?

  stomata

  
• The upper epidermis is transparent so that light can pass through it. This means that as much light as possible can reach the palisade mesophyll cells below, and be used in photosynthesis. 
• If there is plenty of water in the leaf, guard cells become turgid, which opens the stomata. This allows carbon dioxide to enter the leaf, but also allows water to escape. 
• Meristem tissue is made up of plant stems cells. It's found in the growing parts of the plant such as the tips of shoots and roots. 
• translocation

  movement of cell sap up and down the plant via phloem
• transpiration

  the evaporation of water from the leaves
• Which substance are xylem cells reinforced with to make them stronger

  lignin
• Which mineral ions are needed for chlorophyll in plants?

  magnesium
• Why do plants need nitrate ions?

  to produce amino acids
• Explain why plants need nitrate ions, and what will happen if they don't get enough

  Nitrates contain nitrogen which is needed to make amino acids

  This is needed to make proteins, which is used for growth

  So deficiency leads to stunted growth
• A habitat is the place where an organisms lives. 
• A population refers to all of the organisms of a particular species that live in the same habitat. 
• A community refers to all the populations of different species that live together in a habitat