Photosynthesis

• Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light.
• Stencil supplies heat energy for enzymes to work and is a limiting factor with a number 17.
• Proteins are a leaf containing yellow areas which lack chlorophyll.
• Starch is an independent variable which controls rate of photosynthesis with a number 16.
• Variegated Leaf is partly covered in foil, excluding light from covered areas.
• Oxygen increases light energy and is a limiting factor with a number 14.
• Temperature is made from sugars and nitrates and is needed for plant growth with a number 18.
• The need for light in photosynthesis is demonstrated in an experiment where a potted plant kept in darkness for at least 48 hours has its leaves tested for starch.
• The need for chlorophyll is demonstrated in an experiment where a potted plant having variegated leaves is tested for starch.
• Add iodine solution to the leaf: blue-black colour is positive, starch is present.
• Spread the leaf out on a white tile to make it easy to see the result.
• The need for carbon dioxide in photosynthesis is demonstrated in an experiment where two potted plants kept in darkness for 48 hours have their leaves tested for starch.
• Light energy is absorbed by chlorophyll, a green pigment found in chloroplasts in green plant cells and algae.
• Absorbed light energy is used to convert carbon dioxide (from the air) and water (from the soil) into the sugar glucose.
• Oxygen is released as a by-product of photosynthesis.
• In land plants, water is absorbed from the soil by the roots and carried in the xylem vessels of the vascular bundles.
• The experiment was done under water to prevent the gas from escaping.
• The results of the experiment indicate that light and photosynthesis are necessary for the plant.
• The palnt was destarched before the beginning of the experiment to ensure that no starch was present.
• Experiment No.5 showed that oxygen is produced during photosynthesis.
• The experiment has no control.
• In Experiment No.3, it was determined that carbon dioxide is not necessary for photosynthesis.
• In Experiment No.4, it was determined that chlorophyll is not necessary for photosynthesis.
• One part of the leaf was left uncovered to allow for photosynthesis.
• Carbon dioxide is absorbed from the air through the stomata (pores in the leaf).
• In the leaf cells, the CO2 and H2O are combined to make sugar.
• The energy for this reaction comes from sunlight that has been absorbed by the green pigments chlorophyll.
• Chlorophyll is able to absorb energy from light and use it to split water molecules into hydrogen and oxygen.
• The oxygen escapes from the leaf and the hydrogen molecules are added to carbon dioxide molecules to form sugar.
• In this way, the light energy has been transferred into the chemical energy of carbohydrates as they are synthesised.
• The glucose made in photosynthesis has multiple fates: used by the plant in respiration to release energy needed to drive other chemical reactions such as the building up of proteins, converted to sucrose for translocation in the phloem, converted to starch for long-term energy storage, used for the synthesis of other molecules such as cellulose for the cell walls, lipids for cell membrane, proteins for the cytoplasm and pigments for flower petals.
• Chlorophyll is required because it helps absorb the “light” required.
• CO2 is important because it is converted into the sugar, glucose.
• Light is important because it provides the energy to drive the reaction.
• Investigations can be used to find out what factors (CO2, light, chlorophyll) are needed for photosynthesis.
• Plants must be de-starched before carrying out the investigation.
• When the algae die they are decamped by decomposers (bacteria) which respire using O2 and creating anoxic conditions, resulting in the death of aquatic animals from lack of O2.
• To test a leaf for starch, drop it into boiling water in a water bath for about 30 seconds, remove it, dip it into alcohol, and then dip it into water again to soften it.
• The word equation for photosynthesis is: Carbon dioxide + Water + Light Energy → Glucose + Oxygen.
• Chlorophyll is found inside mitochondria in leaf cells.