Biology

BIOLOGY B7

• Equation for photosnthesis 6CO₂ + 6H₂O > C₆H₁₂O₆ + 6O_2.
• _{Light energy is absorbed by chlorophyll in green plants it isint used in the process, and it isint a reaction.}
• _{Within the chlorophyll molecule the light energy is used to rearrange the atoms of} CO₂ and H₂O to make glucose (A sugar)
• Oxygen is made as a waste product it leaves the plant via leafs it can be reused by the plant during respiration.
• Glucose can be converted into chemicals needed for plant growth for example. Carbohydrates-cellulose and starch, proteins and chlorophyll.
• Glucose is soluble chemical can be stored in plant as an insoluble long-chained molecule called starch. Long chained molecules that are made up of many copies of the same unit are called polymers.
• Cellulose is need to build call walls similar structure to statch but the long chains are cross-linked to form a mesh.
• Glucose with nitrates absorbed by the soil can be converted into amino acids. Amino acids can be linked together in different combinations to form proteins which is an example of a polymer.
• Cells contain H₂O. If glucose dissolves in the cell water, it changes the osmotic balanceof the cell to favour net water movement out of the cell.
• If a plant does not contain any dissolved glucose water moves in and out at the same rate so it is osmotically balanced.
• If a plant cell does not contain any dissolved glucose, the less-concentrated water outside the cell will flow into the cell by osmosis. This causes the cell to swell (become turgid) The cell is not osmotically balanced.
• Starch is an insoluble chemical so it does not alter the osmotic balance within a cell. This makes starch a better storage molecule than glucose. The starch is stored in the cells in the form of starch grains.