Cell Theory and Specialized Cells

Cell Theory

• Explains the relationship between cells and living things
• Three components:
  • All living things are made of one or more cells
  • Cells are the smallest unit of structure and function in living things
  • New cells are produced from other cells
• The idea that cells exist was not common knowledge until the late 1500s
• Microscopes invented around 1590 led to the examination of living things, and advancements by the 1800s allowed scientists to formulate the cell theory.

Specialized Cells

• Different cell types in the body have unique structures to perform specific functions
• Examples include muscle cells for contraction, nerve cells (neurons) to transmit signals
• Each cell type is specialized for its particular job

Tissues

• A group of specialized cells working together forms a tissue
• Four major types of tissues:
  • Connective tissue: protects and connects other tissues (e.g., bone, cartilage, blood)
  • Epithelial tissue: covers and protects surfaces of the body and organs (e.g., skin)
  • Muscle tissue
  • Nervous tissue

Levels of Organization

• Organs are composed of tissues working together
• Examples include the heart (composed of cardiac muscle tissue); heart tissue is composed of cardiac muscle cells.
• Organ systems are groups of organs working together like the cardiovascular system (heart, blood vessels, and blood)
• Organ systems function to perform essential body functions or tasks.

Cell Functions and Components

• All cells perform common functions, including metabolism
• Metabolism: the set of chemical reactions that cells use energy from food to build necessary substances , involving two parts. Extracting energy from food molecules and using this extracted energy to fuel processes
• Cells also reproduce via cell division, where parent cells divide to create 2 identical daughter cells.

Cell Components

• Different cell components perform specific functions within a cell
• Includes:
  • Cell membrane, allows substances into and out of the cell
  • Mitochondria; site of cell metabolism, converting energy to a usable cell form
  • Nucleus,stores cell's DNA
  • Ribosomes; site where proteins are built
• Enzymes, proteins helping chemical reactions occur faster in the cell, essential for the cell to produce necessary substances

Cell Division

• Cells reproduce through cell division, which includes the replication of DNA to create identical daughter cells
• Mitosis, the second stage of cell division, is the process where the cell's nucleus divides into two identical nuclei
• Stages of Mitosis: Prophase, Metaphase, Anaphase, Telophase

Meiosis

• Special type of cell division for producing reproductive cells (like eggs and sperm), leading to cells with half the number of chromosomes as body cells
• The process of Meiosis has two stages: Meiosis I , resulting in two cells, each with half the original number of chromosomes and Meiosis II, leading to 4 cells each with half the number of chromosomes as the original cell.
• Meiosis differs from mitosis in that there is no DNA replication in Meiosis II

Types of cells

• Different types of cells, e.g. blood cells, surface skin cells, bone cells, epithelial and goblet cells, nerve cells, cardiac muscle cells, smooth muscle cells, skeletal muscle cells