Overview

• Photosynthesis is the process by which plants make their food from sunlight, using chloroplasts in the cells of leaves to convert carbon dioxide and water into glucose and oxygen.
• The light energy from sunlight is used to turn the reactants into the products in the word equation for photosynthesis: CO2 plus H2O makes C6H12O6 plus O2.
• The symbol equation for photosynthesis is: 6CO2 + 6H2O makes C6H12O6 + 6O2.
• To balance the equation, a 6 is placed in front of everything except the glucose.
• Glucose is the food that plants make from sunlight, which is important for the plant as it is the starting point to make lots of things that the plant needs.
• Glucose and oxygen can then be used in respiration.
• Photosynthesis is an endothermic reaction, as it takes energy in from the sun.
• Temperature, light, and carbon dioxide are limiting factors that can affect how fast or slow photosynthesis can happen.
• Stomata are tiny holes in plants that allow the gases and water to come in and out.
• Guard cells control the size of stomata by swelling up with water when they're open and shrinking when they're closed.
• The waxy cuticle protects the leaf by preventing water loss.
• The upper epidermis is completely see-through to allow light through.
• Palisade cells, packed with chloroplasts, are one of the most important types of cells in a plant as they do lots of photosynthesis.
• The spongy mesophyll is where all the gases can move about in the plant.
• The lower epidermis contains the stomata and their guard cells.
• Auxins make the shoots of a plant grow, causing them to be positively phototropic and grow towards light.
• Auxins collect on the shady side of a plant, making the shoots on the darker side grow faster.
• Auxins stop the roots of the plant from growing, causing them to be negatively phototropic and grow against gravity.
• Gibberellins control seed germination, causing the seed to begin turning into a plant when produced.
• Ethene controls the ripening of fruits, causing them to ripen faster when transported just before they're ready to sell.
• The temperature of the environment that the plant is in is a limiting factor, as if the plant is too cold the enzymes inside of it don't have enough energy to work, but if the plant is too hot the enzymes inside of it that control photosynthesis denature.
• Light is also a limiting factor, as if it's too dark and there's not enough light photosynthesis can't happen, as we need the light energy for photosynthesis to take place.
• The xylem is a tube within the plant that transports water up from the roots to the leaves.
• The cells in the xylem are completely dead, which might be because they're transporting water.
• The cell walls in the xylem break down to allow water to flow through the tube without getting stuck.
• The xylem also has a substance called lignin, which spirals along the edge of the tube to protect it if water's passing through at high pressure.
• The process of transporting water is called transpiration.
• The water enters through the roots at the bottom and moves up through the xylem to the leaves or the top of the flower where it's needed, creating a transpiration stream.
• The leaves need to draw more water up from the roots to use it again, creating a transpiration stream.
• Factors that can affect transpiration include temperature, wind, and light.
• The xylem is used to transport water, while the phloem is used to transport sugars.
• The sugars in the plant can move in both directions, up and then back down, because every single part of the plant needs to use the sugars, from the roots to the leaves to the flower at the top.
• The phloem cells are living, but they need companion cells to keep them alive because they have no structures themselves and no structures to make more of the sugars to be able to move through.
• The cells in the phloem are called sieve cells because they look like a sieve with these holes to allow the sugars to pass through.
• The process of transporting sugars is called translocation.
• The rate of photosynthesis increases as the light intensity increases, but as the carbon dioxide concentration increases, the rate of photosynthesis also increases, as more carbon dioxide means more reactants to turn into products.
• The inverse square law is about the intensity of light as it gets further away, as shown in the diagram with squares.
• Plants collect water with their roots.