1. The Cell: Structure and Function

The cell is the basic structural and functional unit of all known living organisms. It comprises a cytoplasm enclosed within a plasma membrane, containing various organelles. Key organelles include the nucleus (containing genetic material), mitochondria (energy production), ribosomes (protein synthesis), endoplasmic reticulum (protein and lipid synthesis), and Golgi apparatus (protein modification and packaging). The intricate structure of each organelle is specialized for its specific function, collectively enabling the cell to perform life processes.

2. Biomolecules

Biomolecules are the organic molecules found in living organisms. Major classes include carbohydrates (energy source, structural components), lipids (energy storage, cell membranes), proteins (diverse functions including enzymes, structure, transport), and nucleic acids (DNA and RNA, carrying genetic information). These molecules interact in complex ways to carry out cellular activities, forming the basis of life's chemistry.

3. Cell Cycle and Cell Division

The cell cycle is the sequence of events a cell undergoes between one division and the next. It comprises interphase (growth and DNA replication) and the mitotic phase (cell division). Cell division, through mitosis (for growth and repair) or meiosis (for sexual reproduction), ensures the continuity of life by passing genetic material to daughter cells. Understanding cell division is fundamental to development, tissue regeneration, and the study of diseases like cancer.