Cell Biology Basics

Cell Biology Study Notes

• Cell Definition: The smallest living units in the body, typically 0.1 mm in diameter. Named by Robert Hooke, observed via microscopy.

• Cell Function: Building blocks of all plants and animals, derived from pre-existing cells. Responsible for vital physiological functions and maintaining cellular homeostasis.

• Organization of Living Things (Hierarchy):

  • Atoms work together to form Molecules
  • Molecules work together to form Organelles
  • Organelles work together to form Cells
  • Similar cells form Tissues
  • Tissues form Organs
  • Organs form Organ Systems
  • Organ Systems form an Organism

• Fundamental Tissues: Consist of cells and extracellular matrix. Characteristic associations allow for recognition of subtypes. Most organs are composed of a precise combination of multiple tissue types. Histology is dependent on microscopes due to the small size of cells and matrix components.

• Cell Membrane Structure: A thin membrane composed primarily of phospholipid and protein layers; less than a millionth of an inch thick with 65-100 Angstroms (Å) thickness. Composed of a double layer of phospholipids with larger proteins embedded.

• Cell Membrane Components: Phospholipid bilayer,Peripheral membrane proteins,Integral membrane proteins,Cholesterol,Protein channels,Glycoprotein,Glycolipid,and Cytoskeletal filaments.

• Cell Membrane Function:

  • Separates the interior of a cell from its extracellular environment.
  • Controls passage of substances into and out of the cell.
  • Regulates passage of substances into and out of the cell (a highly selective exchange process).

• Cell Membrane Permeability Factors:

  • Size of molecules (e.g., larger molecules are less permeable, smaller ones like water and amino acids are more permeable).
  • Ionic charge (like charges repel).
  • Lipid solubility (substances readily dissolved in lipids pass easily).
  • Carrier molecules (specialized membrane proteins facilitate transport).
  • Pressure differences.

• Transport Across Cell Membranes:

  • Diffusion: Movement of substances from high to low concentration.
  • Simple Diffusion: Substances cross the membrane on their own (e.g., gases, like CO2 and O2).
  • Facilitated Diffusion: Movement with help of carrier proteins. Faster than simple diffusion and specific.
  • Osmosis: Water movement from high to low water concentration across a membrane.
  • Filtration: Movement of substances from high to low pressure.
  • Active Transport: Molecules move from low to high concentration; requires energy (ATP).

• Endocytosis: A process where cells engulf material with specific receptors for certain substances.

  • Phagocytosis: Cells engulfing solid particles.
  • Pinocytosis: Cells engulfing liquids.
  • Receptor-mediated endocytosis: Cells ingesting molecule that attach to specific receptors.

• Exocytosis: A process of removing unwanted materials from inside the cell by packaging it into vesicles and fusing them to the plasma membrane to release the material outside the cell

• Cytoplasm: The material within the cell membrane, but outside the nucleus.

• Organelles: Specialized structures within the cytoplasm with distinct functions.

• Nucleus Structure: A spheroid/oval body near the cell's center, containing DNA (the genetic material). It controls cellular activities.

• Ribosomes: Composed of two subunits. Involved in protein synthesis occur at these subunits.

• Lysosomes: Membrane-bound organelles contain digestive enzymes; break down cellular waste and foreign materials, including worn-out organelles.

• Peroxisomes: Similar in size to lysosomes but have different enzymes. Involved in detoxification, lipid breakdown, and synthesis of certain lipids like cholesterol

• Intercellular Junctions: Structures where cells connect; important for adhesion, communication. Includes tight junctions, adherens junctions, desmosomes, gap junctions, and interdigitations between cell membranes.

• Cell Surface Specializations:

  • Microvilli: Finger-like extensions that increase the surface area for absorption in cells like those in the small intestine.
  • Stereocilia: Long, nonmotile extensions that increase surface area for absorption and secretion in cells in the male reproductive tract (epididymis and ductus deferens).
  • Cilia and Flagella: Cylindrical motile extensions that facilitate movement of materials along cells surfaces. Flagella move the entire cell (e.g., sperm).

This quiz covers fundamental concepts in cell biology, including the structure and function of cell membranes, processes such as endocytosis, and specialized organelles involved in digestion. Test your knowledge on the components and functions of cells with these key questions.