Photosynthesis is how plants, algae and some bacteria make their own food. Inside chloroplasts, a green pigment called chlorophyll absorbs light energy. The plant uses that energy to combine carbon dioxide from the air with water from the soil, making glucose (a sugar) and releasing oxygen as a byproduct. In words: carbon dioxide plus water, with light energy, makes glucose plus oxygen. The glucose stores chemical energy the plant can use to grow, or that animals can use when they eat the plant.
The NGSS performance expectation MS-LS1-6 asks middle schoolers to explain the role of photosynthesis in cycling matter and moving energy into and out of organisms. That means tracking two things: the atoms (carbon, hydrogen and oxygen get rearranged, never created or destroyed) and the energy (light becomes chemical energy). Photosynthesis is also tied to cellular respiration, which releases that stored energy and gives back carbon dioxide and water. Answer each question below, then read the explanation to check your reasoning.
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Answer: C) Chloroplast
Chloroplasts contain chlorophyll and are where light energy is used to make glucose. Mitochondria carry out cellular respiration.
Answer: chlorophyll
Chlorophyll, found in chloroplasts, absorbs light energy and gives plants their green color.
Answer: B) Carbon dioxide
Carbon dioxide enters the leaf and supplies the carbon and some of the oxygen atoms used to build glucose.
Answer: glucose (also accepted: c6h12o6)
Photosynthesis makes glucose, C6H12O6, which stores chemical energy.
Answer: B) carbon dioxide + water → glucose + oxygen
The reactants are carbon dioxide and water; the products are glucose and oxygen. The first option is cellular respiration.
Answer: oxygen (also accepted: o2, oxygen gas)
Oxygen is released through the leaves. Much of the oxygen we breathe comes from photosynthesis.
Answer: A) Chemical energy
The energy is stored in the chemical bonds of glucose, so it is chemical energy.
Answer: stomata (also accepted: stoma, stomates, stomate)
Stomata are pores that open to let carbon dioxide in and oxygen and water vapor out.
Answer: D) The products of one are the reactants of the other.
Photosynthesis makes glucose and oxygen; respiration uses glucose and oxygen and gives back carbon dioxide and water. Together they cycle matter.
Answer: 6 (also accepted: six)
There are 18 oxygen atoms on the left (12 in CO2 plus 6 in H2O). Glucose uses 6, leaving 12 atoms, which make 6 O2 molecules.
Answer: B) It stops or nearly stops.
Without light there is no energy to drive photosynthesis, so it stops. The plant keeps respiring and uses up stored sugar.
Answer: producers (also accepted: producer, autotrophs, autotroph)
Producers (autotrophs) make their own food and form the base of food chains.
Answer: B) Carbon dioxide from the air
Most of a tree's dry mass is carbon compounds built from carbon dioxide taken in from the air. Sunlight is energy, not matter.
Plants take in water and minerals from soil, but they MAKE their food (glucose) through photosynthesis. Most of a plant's mass comes from carbon dioxide in the air.
Plants carry out cellular respiration all the time, day and night. Photosynthesis only happens when there is light.
Carbon dioxide and water go in; glucose and oxygen come out. Respiration is the reverse.
Light is energy, not matter. It powers the reaction but does not become atoms in the glucose.
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No. Photosynthesis needs light, so it stops in the dark. Cellular respiration continues day and night.