Chapter 4, Section 1Cell Processes and Energy PHOTOSYNTHESIS
KEY IDEAHow do cells obtainthe energy they needto carry out theirfunctions?
Photosynthesis • The process by which a cell captures energy in sunlight and uses it to make food • Nearly all living things depend on the energy of the sun
The Two Stages of PhotosynthesisSTAGE 1: Capturing the sun’s • The sun’s energy is taken in byenergy the leaves of a plant • This is done by the photosynthetic pigment, chlorophyll, in the chloroplasts Chloroplasts in a plant cell of the plant cell • CHLOROPHYLL gives plants their GREEN color • This energy is then used in the second step of photosynthesis
STAGE 2: Using energy to • The captured sun energy ismake food used to make sugars and oxygen from water and carbon dioxide. • The plant roots take in water (H₂O) from the soil • Tiny pores on the leaves, called stomata, take in carbon dioxide (CO₂) from the air • Once in the leaves, the H₂O and CO₂ move into the chloroplasts in the cells Magnified stomata in a pine needle Table Talk: What do stomata remind you of in the human body?
Table Talk: Summarize the two stages of photosynthesis
What happens to the • Plants use some of it forsugar produced in foodphotosynthesis? • Some sugar molecules are converted into other compounds such as cellulose, which is used to form the plant cell wall • Other sugar molecules are stored in the plant’s cells for later use • When we eat fruits and vegetables, we are eating the plant’s stored energy
QUICKWRITE: SUMMARIZE In your own words, write a short paragraph describing the process of photosynthesis. Include and underline the following words: Carbon dioxide Water sugar Oxygen Photosynthesis Sunlight Chloroplasts stomataSee BrainPop, “Photosynthesis” end