LESSON 1

• Our inherited traits, quirks, and illnesses arise from the activities of cells
• Understanding cell function reveals how a healthy body works and develops from one cell to trillions
• Understanding what goes wrong in certain cells to cause symptoms can suggest ways to treat the condition
• Our bodies include more than 290 specialized cell types that form the four basic tissue types: Epithelial, Connective, Muscle, and Nervous tissue
• Somatic cells (body cells) are diploid, having two copies of the genome
• Germ cells (sex cells), such as sperm and egg cells, are haploid, having one copy of the genome
• The genome is the set of DNA or genetic information in an organism
• All cells share features enabling them to perform basic life functions like reproduction, growth, response to stimuli, and energy use
• Specialized characteristics emerge as cells express different subsets of protein-encoding genes
• Prokaryotic cells do not have a nucleus, while eukaryotic cells have nuclei and all multicellular organisms
• Cells are composed of molecules, including macromolecules like carbohydrates, lipids, proteins, and nucleic acids
• Carbohydrates provide energy and contribute to cell structure, with monosaccharides as building blocks
• Lipids form hormones, membranes, provide insulation, and store energy, with glycerol and fatty acids as building blocks
• Proteins enable various functions in the body, with amino acids as building blocks
• Enzymes are proteins that facilitate biochemical reactions
• Nucleic acids translate information from past generations into specific collections of proteins
• Lactase deficiency affects the breakdown of lactose, causing digestive issues
• Familial hypercholesterolemia results from a mutation reducing protein receptors for cholesterol, leading to heart issues
• Maple syrup urine disease causes urine to smell like maple syrup due to amino acid accumulation in the bloodstream
• Lesch-Nyhan syndrome is caused by a deficiency of the enzyme HGPRT, leading to various symptoms and intellectual disabilities
• Biotinidase deficiency slows the body's use of biotin, affecting various functions
• Wilson disease results in copper buildup in the body, affecting liver function and causing distinct physical signs
• Cells contain organelles like the nucleus, endoplasmic reticulum, Golgi apparatus, vesicles, and exosomes
• The nucleus is a prominent organelle containing DNA and is the nerve center of the cell
• The endoplasmic reticulum is where most protein synthesis occurs, with rough ER containing ribosomes and smooth ER for lipid synthesis
• The Golgi apparatus processes and packages proteins and lipids for secretion
• Exosomes are vesicles that transport molecules between cells, aiding in communication and waste removal
• Secretion is the release of substances from a cell, involving various organelles and processes
• Caseins are nutritive proteins that protect against infection and enzymes
• Lactocytes are epithelial cells involved in milk production
• Organelles like the nucleus, endoplasmic reticulum, Golgi apparatus, and vesicles play crucial roles in cellular functions
• Exosomes are small vesicles that aid in intercellular communication and waste removal
• Exosomes:

  • Size: 30 to 100 nanometers in diameter
  • Functions: remove debris, transport immune system molecules, provide communication network among cells
• Process of secretion:

  1. Body sends biochemical message to cell to produce substance
  2. Genes copied into messenger RNA (mRNA) which exits nucleus
  3. In cytoplasm, mRNAs with ribosomes and transfer RNA (tRNA) direct manufacture of milk proteins, including caseins
• Protein synthesis:

  • Begins on rough ER when attached to ribosomes
  • Amino acids linked in cytoplasm following mRNA's sequence to form proteins
  • Rough ER leads to smooth ER where lipids are made and added to proteins
  • Proteins exit ER in vesicles, which pinch off from membrane
• Lysosomes:

  • Sac containing digestive enzymes
  • Degrades debris, recycles cell contents
  • Functions: dismantle bacterial remnants, worn-out organelles, excess cholesterol
  • Engages in autophagy (cells disposing its own trash)
• Mitochondria:

  • Provide energy by breaking chemical bonds in nutrient molecules
  • Structure: two membranes, inner membrane enzyme-studded
  • Releases energy in form of ATP
  • Cristae: folds of inner membrane hold enzymes for energy release
• Biological membranes:

  • Structure: double layer of phospholipids
  • Phospholipids: fat molecule with attached phosphate groups
  • Phosphate end is hydrophilic, attracted to water
  • Two tails are hydrophobic, move away from water
  • Proteins act as gates, carry carbohydrates inside cell
  • Specificity: particular transport molecules fit specific gates
• Plasma membrane enables cell-to-cell communication:

  • Receptors: extend from plasma membrane
  • Ligands: molecules that bind to receptors, trigger chemical reactions
  • Processes: signal transduction, cellular adhesion
• Cytoskeleton:

  • Meshwork of protein rods and tubules
  • Functions: cell's architecture, positioning organelles, providing 3D shape
  • Includes three major types of proteins: microtubules, microfilaments, intermediate filaments