Learning Outcomes
i. Define mitochondria and chloroplasts.
ii. Describe the external and internal structures of mitochondria and chloroplasts.
iii. Link the structures of mitochondria and chloroplasts with their respective functions in cellular respiration and photosynthesis.
i. Mitochondria: Mitochondria are organelles that are found in the cytoplasm of eukaryotic cells. They are known as the "powerhouses of the cell" because they are responsible for producing energy in the form of ATP.
External structure of mitochondria: Mitochondria are oval-shaped organelles that are surrounded by a double membrane. The outer membrane is smooth, while the inner membrane is folded into cristae. The cristae increase the surface area of the inner membrane, which allows more ATP to be produced.
Internal structure of mitochondria: The interior of the mitochondrion is filled with a gel-like substance called the matrix. The matrix contains a variety of enzymes that are involved in cellular respiration.
ii. Function of mitochondria: Mitochondria are responsible for cellular respiration, which is the process of breaking down glucose to produce ATP. Cellular respiration occurs in three stages: glycolysis, the Krebs cycle, and oxidative phosphorylation.
Glycolysis: Glycolysis occurs in the cytoplasm and does not require oxygen. It breaks down glucose into two molecules of pyruvate and produces a small amount of ATP.
Krebs cycle: The Krebs cycle occurs in the mitochondrial matrix and requires oxygen. It breaks down pyruvate into carbon dioxide and water and produces ATP.
Oxidative phosphorylation: Oxidative phosphorylation occurs on the inner mitochondrial membrane and requires oxygen. It uses the energy released from the Krebs cycle to produce ATP.
iii. Chloroplasts: Chloroplasts are organelles that are found in the cytoplasm of plant cells and some algae. They are responsible for photosynthesis, which is the process of using sunlight to convert carbon dioxide and water into glucose and oxygen.
External structure of chloroplasts :Chloroplasts are oval-shaped organelles that are surrounded by a double membrane. The outer membrane is smooth, while the inner membrane is folded into thylakoids. The thylakoids are arranged in stacks called grana.
Internal structure of chloroplasts: The interior of the chloroplast is filled with a gel-like substance called the stroma. The stroma contains a variety of enzymes that are involved in photosynthesis.
iv. Function of chloroplasts: Chloroplasts are responsible for photosynthesis, which is the process of converting carbon dioxide and water into glucose and oxygen using sunlight energy. Photosynthesis occurs in two stages: the light-dependent reactions and the Calvin cycle.
Light-dependent reactions: The light-dependent reactions occur in the thylakoids and use sunlight energy to split water molecules into hydrogen and oxygen. The hydrogen atoms are used to produce NADPH, while the oxygen is released as a byproduct.
Calvin cycle: The Calvin cycle occurs in the stroma and uses the NADPH produced in the light-dependent reactions to convert carbon dioxide into glucose.
v. Relationship between structure and function in mitochondria and chloroplasts
The structures of mitochondria and chloroplasts are well-suited to their respective functions. The cristae in mitochondria increase the surface area of the inner membrane, which allows more ATP to be produced. The thylakoids in chloroplasts are arranged in stacks, which increases the efficiency of the light-dependent reactions.
Mitochondria and chloroplasts are essential organelles that play vital roles in cellular respiration and photosynthesis, respectively. Their structures are well-suited to their respective functions. Understanding the structures and functions of these organelles is essential for understanding cell biology and plant biology.
