Biology Test 303

Complex IV is reduced by cyt c not oxidised 

Chlorophyll a plays a crucial role in photosynthesis by absorbing sunlight and converting it into chemical energy. This process is fundamental to the primary reaction of photosynthesis, where light energy is transformed into chemical or electrical energy, enabling the synthesis of ATP and NADPH. Interesting fact: Chlorophyll a is considered the universal photosynthetic pigment because it is found in all photosynthetic plants, highlighting its essential role in the energy conversion process.

Moll's half-leaf experiment clearly demonstrated that CO₂ is required for photosynthesis. In this experiment, a part of a leaf enclosed in a test tube with KOH (which absorbs CO₂) did not show starch formation, indicating no photosynthesis occurred in the absence of CO₂. This experiment underscores the importance of carbon dioxide in the photosynthetic process. Interesting fact: This experiment elegantly shows the necessity of CO₂ for photosynthesis, reinforcing our understanding of plant biology.

Carotenoids play a supportive role in photosynthesis by absorbing light energy and transferring it to chlorophyll a. They are considered accessory pigments and help broaden the spectrum of light that can be used for photosynthesis, making the process more efficient. Interesting fact: Carotenoids also protect chlorophyll a from photo-oxidation, ensuring the longevity and effectiveness of the photosynthetic machinery.

Mitosis is crucial for the growth and repair of tissues in multicellular organisms. It ensures that each daughter cell receives an exact copy of the parent cell's DNA, maintaining the chromosome number and allowing the organism to grow and replace damaged cells. This process is essential for the overall maintenance and health of an organism. An interesting fact is that mitosis is so precise that even a minor error in chromosome distribution can lead to diseases such as cancer.

DNA replication occurs during the S (Synthesis) phase of the cell cycle. This phase is characterized by the doubling of the DNA content in the cell, from 2C to 4C, although the chromosome number remains unchanged. This ensures that each daughter cell receives a complete set of chromosomes during cell division. DNA replication is a critical step for cell division, providing a foundation for genetic continuity between generations.

The centrosome plays a pivotal role in spindle formation during mitosis. It duplicates during the S phase of interphase and moves to opposite poles of the cell during prophase, facilitating the organization of spindle fibers that are crucial for the segregation of chromosomes into daughter cells. The spindle apparatus is essential for ensuring that each daughter cell receives an identical set of chromosomes. The centrosome's role in this process underscores its importance in cellular division and genetic stability.