- Use the following terms in the same sentence: photosynthesis, light reactions, pigment, and photosystem.
- Choose the term that does not belong in the following group, and explain why it does not belong: electron transport chain, chemiosmosis, Calvin cycle, and photosystem II.
- Word Roots and Origins The prefix chloro- is derived from the Greek word that means “green.” Using this information, explain why the chlorophylls are well named.
- Distinguish between autotrophs and heterotrophs.
- Identify the primary source of energy for humans.
The Correct Answer and Explanation is :
- During photosynthesis, the light reactions occur in the photosystems within the chloroplasts, where pigments absorb light energy and convert it into chemical energy.
- The term that does not belong is the Calvin cycle. It differs from the other terms because the electron transport chain, chemiosmosis, and photosystem II are all part of the light reactions of photosynthesis, which occur in the thylakoid membrane. The Calvin cycle, on the other hand, is part of the dark reactions or light-independent reactions, which take place in the stroma of the chloroplast and are responsible for carbon fixation and the production of glucose, not the conversion of light energy into chemical energy.
- The chlorophylls are well named because the prefix chloro-, derived from the Greek word for “green”, reflects their green color. Chlorophylls are the primary pigments involved in the absorption of light during photosynthesis, and their green color is due to their ability to absorb mostly red and blue wavelengths of light while reflecting green wavelengths. This green reflection gives plants their characteristic color, and it is a key feature for photosynthesis because chlorophyll plays an essential role in capturing light energy.
- Autotrophs are organisms that produce their own food through processes like photosynthesis or chemosynthesis, using sunlight or chemicals to synthesize organic compounds from inorganic materials. Examples include plants, algae, and some bacteria. Heterotrophs, on the other hand, are organisms that cannot produce their own food and must obtain organic compounds by consuming other organisms. This includes animals, fungi, and many bacteria.
- The primary source of energy for humans is glucose, a simple sugar that is derived from the food we eat. Humans obtain glucose from carbohydrates found in a variety of foods like fruits, vegetables, grains, and legumes. Once consumed, glucose is absorbed into the bloodstream and transported to cells, where it is used to produce ATP (adenosine triphosphate) through cellular respiration. ATP is the energy currency of cells and powers various cellular functions, such as muscle contraction, active transport, and biosynthesis.
In the process of glycolysis, glucose is broken down into smaller molecules, releasing energy that is used to form ATP. This occurs in the cytoplasm of the cell. The energy stored in glucose can also be processed through the citric acid cycle and the electron transport chain within the mitochondria, where even more ATP is generated. Oxygen is required for the most efficient production of ATP in these latter stages, which is why humans need to breathe oxygen.
Glucose is crucial because it is not only the immediate source of energy but also can be stored as glycogen in the liver and muscles for later use. When glucose levels drop, glycogen can be broken down to release glucose back into the bloodstream. This ability to store and mobilize energy ensures that the body has a continuous supply of fuel for essential processes, particularly during periods of physical activity or fasting.