Cell Cycle, Division, Differentiation & Signaling (BEB-102, Autumn 2024) PDF

Cell Cycle, Cell Division, Cell Differentiation & Cell Signaling BEB-102, Autumn 2024 1  Learning Objectives By the end of this section, you will learn about: Cell Cycle Cell Division Cell Differentiation Cell Signaling...

Cell Cycle, Cell Division, Cell Differentiation & Cell Signaling BEB-102, Autumn 2024 1  Learning Objectives By the end of this section, you will learn about: Cell Cycle Cell Division Cell Differentiation Cell Signaling 2  Cell Cycle Cell Cycle refers to the entire sequence of events that a cell goes through from one division to the next. It includes growth, DNA replication, and preparation for division. The cell cycle is made up of interphase (G1, S, G2 phases) and mitotic phase (M phase, which includes mitosis and cytokinesis). 3  Cell Division: Interphase Interphase is the longest part of the cell cycle (95% of the cycle) and consists of three distinct stages: G1 (Gap 1), S (Synthesis), and G2 (Gap 2). 1.G1 Phase: 1. During G1, the cell grows in size, produces new proteins, and builds up energy reserves. 2. It also performs regular cellular functions and prepares for DNA replication. 3. This phase is critical for ensuring the cell is ready to replicate its DNA in the next stage. 2.S Phase: 1. The primary event in the S phase is DNA replication, where each chromosome duplicates to form sister chromatids. 2. The cell also begins replicating its centrosomes, which are important for later stages of cell division. 3. At the end of this phase, the cell has double the amount of DNA, preparing for mitosis. 3.G2 Phase: 1. In G2, the cell continues to grow and produces proteins necessary for cell division. 2. This phase includes critical checkpoints to ensure DNA has been replicated correctly and repairs any damage before entering mitosis. 3. By the end of G2, the cell is fully prepared to enter mitosis, where it will divide. 4  Cell Division: Mitotic Phase The mitotic phase is when the cell divides into two identical daughter cells. It has two main parts: 1.Mitosis (nuclear division), with four stages: 1. Prophase: Chromosomes condense; nuclear envelope breaks down; spindle forms. 2. Metaphase: Chromosomes align at the center; spindle fibers attach to centromeres. 3. Anaphase: Sister chromatids are pulled apart to opposite poles. 4. Telophase: New nuclear envelopes form; chromosomes de-condense. 2.Cytokinesis (cytoplasmic division): The cytoplasm splits, completing cell division and forming two identical daughter cells. 5  Cell Differentiation Cell differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation is guided by: 1.Gene Expression: Specific genes are turned on or off, directing cells to produce proteins that define their structure and function. 2.Signaling Molecules: External signals from the cell's environment, such as growth factors, hormones, and neighboring cells, influence its differentiation path. 3.Epigenetic Modifications: Chemical changes to DNA or histones can regulate gene activity without altering the genetic code, supporting specialized cell functions. 6 Cell Differentiation: Stages 7 Stem cell potency Unipotent T cell 8  Stem Cell: Types There are three main types of stem cells, classified by their origin and potency: 1.Embryonic Stem Cells (ESCs): 1. Derived from early-stage embryos (blastocysts). 2. Pluripotent: Can become any cell type in the body. 2.Adult (Somatic) Stem Cells: 1. Found in specific tissues (e.g., bone marrow, skin). 2. Multipotent: Limited to forming certain cell types related to their tissue of origin (e.g., hematopoietic stem cells produce blood cells). 3.Induced Pluripotent Stem Cells (iPSCs): 1. Created by reprogramming adult cells to an embryonic-like state. 2. Pluripotent: Can differentiate into any cell type in the body, similar to ESCs. 3. Used in research and regenerative medicine due to ethical advantages over ESCs.9  Differentiation: Hematopoietic Stem Cell As cells differentiate, they can become progressively more specialized. A stem cell might first become a precursor cell (like a hematopoietic stem cell that can become a red blood cell or a white blood cell), and then a fully differentiated cell type (like a red blood cell). 10 Cell Signaling 11