biology

• The postulates of the cell theory are: a. Cell is the basic unit of life b. All organisms are made up of cell c. Cell comes from pre-existing cell
• Cells contain genetic material, cytoplasm, and ribosomes, which are found in both prokaryotes and eukaryotes
• Eukaryote cells have membrane-bound organelles with different functions
• Cells interact with their environment and must have control over what goes in and out to maintain homeostasis
• Cell membrane


  A very important structure that all cells contain to control what goes in and out, helping regulate homeostasis
• Cell membrane

  • Made of a phospholipid bilayer
  • Part of the lipids are polar, part are nonpolar
• Simple diffusion

  1. Small non-polar molecules like gases can directly pass through the phospholipid bilayer

  2. Moves with the concentration gradient from high to low concentration

  3. Requires no energy (passive transport)
• Facilitated diffusion


  1. Transport proteins in the membrane help larger or polar molecules cross the membrane

  2. Still moves with the concentration gradient from high to low concentration

  3. Requires no energy (passive transport)
• Transport proteins

  Some act as channels, some change shape, some open and close based on stimuli, to help molecules cross the membrane
• Charged ions and glucose require transport proteins to cross the cell membrane
• Water crosses the membrane rapidly through protein channels called aquaporins
• Active transport


  Movement of molecules from low to high concentration, requiring energy (typically ATP)
• The sodium-potassium pump is an example of active transport
• Endocytosis


  1. Cell membrane fuses with large molecules to bring them into the cell, often forming vesicles

  2. Different types include phagocytosis, pinocytosis, and receptor-mediated endocytosis
• Exocytosis


  Molecules exit the cell, used to get rid of waste or release important materials the cell has produced
• Plant cells use exocytosis to release carbohydrates to build the cell wall
• Nucleus - controls all activities within the cell
• Cytoplasm - contains enzymes that catalyze chemical reactions
• Cell wall - provides support, maintains shape, protects against pathogens
• Ribosomes - site of protein synthesis
• Chloroplasts - site of photosynthesis
• Vacuoles - store water, nutrients, pigments, and wastes
• Chloroplasts - contain chlorophyll which absorbs light energy during photosynthesis
• Cell membrane - regulates what enters/exits the cell
• Vacuole - stores water, waste products, pigments
• Endoplasmic reticulum (ER) - involved in protein production and transport
• Mitochondria - site of aerobic respiration
• Plasma membrane - regulates movement of substances into and out of the cell
• Mitochondria - produce ATP through aerobic respiration
• Plasma membrane - regulates what enters or leaves the cell
• Nucleus - controls the activities of the cell by containing genetic material (DNA)
• Rudolf Virchow proposed that all cells come from existing cells, completing the cell theory


  1855
• Leeuwenhoek discovered bacteria


  1683
• Matthias Schleiden concluded that all plants are made up of cells


  1838
• Theodor Schwann concluded that all animals are made up of cells


  1839
• Robert Hooke published his book Micrographia, which contains his drawings of a section of cork, as seen through one of the first microscopes

  1665
• Anton Van Leeuwenhoek observed tiny living organisms in drops of pond water through his simple microscopes

  1674
• What is the cell membrane also known as?

  Plasma membrane
• What is the primary function of the cell membrane?

  To provide structural support and regulate the movement of substances in and out of the cell
• What are the key properties of the cell membrane?

  • Selective permeability
  • Fluid mosaic model