Question

Compare the structure of chloroplasts (described in Chapter 7 ) to that of mitochondria, and describe how the similarities in structure relate to similarities in function.

Short answer

Both chloroplasts and mitochondria are double-membraned organelles with their own DNA, ribosomes, and enzymes. Chloroplasts, responsible for photosynthesis, have thylakoids within the stroma, while mitochondria, responsible for cellular respiration, have cristae in the matrix. These structures enhance their respective functions. Both organelles are involved in energy transformation by moving electrons across an electron transport chain, creating a proton gradient used to generate ATP via chemiosmosis. Their structural similarities relate to their functional similarities in ATP production.

Step-by-step solution

Structure of Chloroplasts

Chloroplasts are responsible for photosynthesis in plant cells. They are organelles with a double-membraned structure, containing an inner and outer membrane. Inside the inner membrane, there is a fluid called the stroma, which contains circular DNA, ribosomes, and other enzymes. Suspended within the stroma is a network of flattened membranous sacs called thylakoids, arranged in stacks called grana. These thylakoids contain chlorophyll and other pigments required for photosynthesis. The process of photosynthesis uses light energy to convert carbon dioxide and water into glucose and oxygen.

Structure of Mitochondria

Mitochondria are the powerhouse of cells and are responsible for producing energy in the form of ATP through the process of cellular respiration. They are also double-membraned organelles with an outer and inner membrane. The inner membrane is folded into cristae to increase the surface area for chemical reactions to take place. The space enclosed by the inner membrane is called the matrix, which contains circular DNA, ribosomes, and enzymes needed for cellular respiration.

Structural Similarities

Both chloroplasts and mitochondria have a double-membrane structure, with an intermembrane space between the inner and outer membranes. They both contain their own DNA (circular), ribosomes, and enzymes needed for their respective processes (photosynthesis in chloroplasts and cellular respiration in mitochondria). Also, both organelles have specific structures within their innermost compartment (thylakoids in chloroplasts and cristae in mitochondria) that enhance their performance of their respective functions.

Similarities in Function

The similarities in structure point to some similarities in the function of chloroplasts and mitochondria. Both organelles are involved in energy transformation processes. Chloroplasts convert light energy into chemical energy, while mitochondria convert chemical energy stored in glucose into usable energy (ATP) for the cell. These processes involve moving electrons across an electron transport chain located within the membranes of the organelles, which creates a proton gradient. This gradient is then used to generate ATP via a process called chemiosmosis, where an enzyme called ATP synthase drives the formation of ATP using the energy stored in the proton gradient. In conclusion, chloroplasts and mitochondria share similarities in their structures, such as their double-membrane organization and presence of specific components like thylakoids and cristae. These structural similarities are related to their similar functions of energy transformation, where both organelles use an electron transport chain and chemiosmosis processes to produce ATP.