Stem cells

• Adult stem cells are found in various tissues and can differentiate into a limited range of cell types.
• To calculate cell surface area and volume, use the formulas:

  • Surface Area = 6 x (side length)^2 for a cube
  • Volume = side length^3 for a cube
• To determine the surface area to volume ratio (SA:V), divide the surface area by the volume
• The ratio that is most efficient and ideal for cells is a higher surface area to volume ratio. This is because it allows for more efficient exchange of materials with the environment
• Cells divide for growth, repair, and reproduction
• The cell cycle is the series of events that take place in a cell leading to its division and duplication of its DNA to produce two daughter cells
• Phases of the cell cycle:

  • Interphase: Growth and DNA replication
  • Prophase: Chromosomes condense
  • Metaphase: Chromosomes align in the middle
  • Anaphase: Chromatids separate and move to opposite poles
  • Telophase: Chromosomes decondense and nuclear envelopes reform
  • Cytokinesis: Division of the cytoplasm
• Mitosis and Cytokinesis diagrams show the different stages of cell division
• Cytokinesis in plant cells involves the formation of a cell plate, while in animal cells, it involves the formation of a cleavage furrow
• DNA exists in different forms depending on the phase of the cell cycle:

  • Chromatin: DNA in a loosely packed form during interphase
  • Chromosomes: DNA in a condensed form during cell division
  • Chromatids: Two identical copies of a chromosome after replication
  • Sister chromatids: Two chromatids joined at the centromere
• Differentiation is the process by which cells become specialized for specific functions
• Apoptosis is programmed cell death and is important for removing damaged or unnecessary cells
• Cell cycle regulators are proteins that control the progression of the cell cycle
• The most important cell cycle regulator is the cyclin-dependent kinase (CDK)
• A kinase is an enzyme that adds phosphate groups to other proteins, regulating their activity
• CDK-cyclin complexes regulate the cell cycle by phosphorylating target proteins that drive the cell cycle forward
• Checkpoint events in each phase of the cell cycle:

  • G1 Checkpoint: Checks for cell size and DNA damage
  • S Checkpoint: Ensures DNA replication is complete and accurate
  • G2 Checkpoint: Verifies DNA replication and checks for damage
  • Mitotic Checkpoint: Ensures all chromosomes are properly attached to the spindle
• Uncontrolled cell division is caused by mutations in genes that regulate the cell cycle
• Mutated proto-oncogenes cause uncontrolled cell growth and division
• Mutated tumor suppressor genes cause a loss of control over cell division, leading to cancer
• The two main causes of gene mutations are environmental factors (such as radiation or chemicals) and genetic factors (inherited mutations)
• Characteristics of cancer cells include uncontrolled growth, evasion of cell death, and the ability to spread to other tissues (metastasis)
• Tumors are abnormal growths of cells. The two types are benign tumors (non-cancerous) and malignant tumors (cancerous)
• Common cancer treatments include surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy
• Stem cells are undifferentiated cells that can differentiate into specialized cell types
• Cells become specialized through a process called cell differentiation, where specific genes are turned on or off to give cells specific functions
• Types of stem cells:

  • Embryonic stem cells: Derived from embryos and can differentiate into any cell type
  • Adult stem cells: Found in various tissues and can differentiate into a limited range of cell types
  • Induced pluripotent stem cells: Adult cells reprogrammed to have embryonic stem cell-like properties