a. Outputs of Photosynthesis
Sugar (Glucose):
- Creation: During photosynthesis, plants convert carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) using sunlight as the energy source. This occurs during the Calvin Cycle (light-independent reactions) in the stroma of the chloroplasts. The energy from ATP and NADPH, generated in the light-dependent reactions, drives the conversion of CO2 into glucose.
- Fate: The glucose produced can be utilized immediately for energy through cellular respiration, stored as starch for later use, or used as a building block for other organic molecules like cellulose, which forms the structure of plant cell walls.
Oxygen:
- Creation: Oxygen is produced during the light-dependent reactions of photosynthesis. When light energy is absorbed by chlorophyll, water molecules are split (a process called photolysis) to release oxygen, protons, and electrons. The oxygen released is a byproduct of this reaction.
- Fate: The oxygen produced is released into the atmosphere and can be used by aerobic organisms (including humans) for cellular respiration.
b. Significance of Photosynthesis:
Photosynthesis is crucial because it is the primary means by which energy from sunlight is captured and transformed into chemical energy in the form of glucose, which serves as food for plants and other organisms. It also produces oxygen, which is essential for the survival of aerobic organisms. Moreover, photosynthesis plays a significant role in regulating atmospheric CO2 levels, thus impacting climate change and the global carbon cycle.
c. Photosynthesis and Chloroplasts:
Photosynthesis takes place in plant cell organelles called chloroplasts.
d. Identifying Photosynthesizing Parts of a Plant:
You can tell which parts of a plant are photosynthesizing by observing areas that are green, as green parts of the plant contain chlorophyll. Chlorophyll is the pigment required to capture sunlight energy.
e. Organelle Housing Chlorophyll:
The organelle that houses chlorophyll and where photosynthesis takes place is the chloroplast.
f. Complete Equation for Photosynthesis:
The complete equation for photosynthesis is:
\[ 6CO2 + 6H2O + \text{light energy} \rightarrow C6H12O6 + 6O2 \]
Collaborative Catch-up: Photosynthesis
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Deciduous trees are trees that lose their leaves in the fall. Chlorophyll production in deciduous trees decreases in the fall.
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The loss of leaves means that the level of photosynthesis in areas where this happens decreases significantly since the primary sites of photosynthesis (the leaves) are removed from the tree, limiting the tree’s ability to capture sunlight and produce glucose.
7. Living Organisms Extract Energy through Cellular Respiration
a. Fueling Actions - Cellular Respiration: i. Organisms: Many different organisms perform cellular respiration, including animals, plants, fungi, and many microorganisms, both aerobic and anaerobic.
ii. Purpose: Organisms perform cellular respiration to convert glucose into ATP (adenosine triphosphate), the energy currency necessary for cellular activities.
b. Location of Cellular Respiration: Cellular respiration primarily takes place in the mitochondria of eukaryotic cells.
c. Major Inputs and Outputs of Cellular Respiration:
- Inputs: Glucose (C6H12O6) and oxygen (O2)
- Outputs: Carbon dioxide (CO2), water (H2O), and ATP
The equation for cellular respiration is:
\[ C6H12O6 + 6O2 \rightarrow 6CO2 + 6H2O + \text{ATP} \]
d. Source of Exhaled CO2: The CO2 that you are exhaling right now comes from the breakdown of glucose during cellular respiration in your cells. When glucose is metabolized, carbon atoms are converted to CO2 as a waste product.
e. Plants' Use of CO2: The CO2 you are exhaling will soon be utilized by plants during photosynthesis. Plants will incorporate CO2 to produce glucose and oxygen, continuing the cycle of energy transformation and gas exchange in the ecosystem.
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