Human Body Cells

Cells of the Body

• Cells are the fundamental units of life, providing structure, stability, energy, and means of reproduction for an organism.
• The size and shape of a cell depend on its function, which can include:
  • Transporting gases like O2 and CO2
  • Fighting disease-causing viruses and bacteria
  • Producing movement
  • Storing nutrients
  • Manufacturing protein, chemicals, or liquids
  • Maintaining homeostasis (a state of equilibrium)
  • Creating new life

Basic Structure of a Cell

• Cell membrane: a protective barrier that selectively allows certain substances to move in and out when needed.
• Two types of proteins associated with the cell membrane:
  • Integral proteins: permanently attached to the plasma membrane, with functions such as channeling or transporting molecules across the membrane, or acting as cell receptors.
  • Peripheral proteins: temporarily attached to the plasma membrane, with functions such as:
    • Communication: passing messages to integral proteins
    • Enzymes: breaking down or combining molecules
    • Supported: maintaining intracellular cytoskeleton and components of the extracellular matrix
    • Molecule Transferase: transferring electrons from integral proteins, storing energy from glycolysis breakdown into accessible molecules (ATP)

Nucleus

• The nucleus is the control center of the cell, governing cell function and storing genetic instructions for protein manufacturing.
• Inside the nucleus, DNA contains the blueprint for everything a cell will do and all the products it will make.
• The nucleus sends "commands" to the cell via molecular messengers that translate DNA information.

Cytoplasm

• Cytoplasm is the jelly-like substance inside the cell membrane, comprising mostly water and dissolved nutrients.
• Components of cytoplasm include:
  • Cytosol (a gel-like substance)
  • Organelles (internal sub-structures)
  • Cytoplasmic inclusions

Lysosome

• Lysosomes contain enzymes that break down and digest unneeded cellular components, such as damaged organelles (autophagy).
• Lysosomes also break down foreign material, like bacteria, which are phagocytized by immune defense cells.

Mitochondria

• Mitochondria are the "powerhouse of the cell," producing energy (ATP) through respiration and regulating cellular metabolism.
• Mitochondria have additional functions, such as storing calcium and producing heat.
• Mitochondrial DNA is a small, circular chromosome passed from mother to offspring.

Endoplasmic Reticulum

• Endoplasmic reticulum (ER) exists in two forms: rough ER and smooth ER.
• Rough ER (RER) has ribosomes attached, synthesizing proteins for the cell membrane or export from the cell.
• Smooth ER (SER) lacks ribosomes and is involved in:
  • Lipid synthesis (phospholipids, steroid hormones)
  • Calcium storage and regulation
  • Detoxification of certain toxins
  • Carbohydrate metabolism

Golgi Apparatus

• The Golgi apparatus sorts, modifies, and ships products from the rough ER, similar to a post office.
• Products are packaged into vesicles, which then migrate to the cell surface and release their cargo.

Types of Tissue

• There are four main types of tissue:
  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue

Epithelial Tissue

• Epithelial tissue forms sheets of cells covering the body's exterior surfaces, lining internal cavities and passageways, and forming glands.
• Epithelial tissue is also found in skin, airways, digestive tract, urinary and reproductive systems, and hollow organs.

Connective Tissue

• Connective tissue binds cells and organs together, providing protection, support, and integration.
• Connective tissue cells are dispersed in a matrix, which plays a major role in the tissue's function.

Muscle Tissue

• Muscle tissue is excitable, responding to stimulation and contracting to provide movement.
• There are three main types of muscle tissue: skeletal (voluntary), smooth, and cardiac.

Nervous Tissue

• Nervous tissue is excitable, allowing for electrochemical signal propagation and communication between body regions.
• Nervous tissue consists of two main cell types: neurons and neuroglia.