3 The cell

• Cell theory states that:

  • The cell is the smallest unit of life
  • Cells make up all living things
  • New cells can arise only from pre-existing cells
• There are two basic types of cells:

  • Eukaryotic cells:
  • Structurally complex
  • Typically larger
  • Have membrane-bound organelles
  • Found in plants, animals, fungi, protists
  • Prokaryotic cells:
  • Structurally simple
  • Typically smaller
  • Lack membrane-bound organelles
  • Include bacteria and Archaea
• Cell size and microscopy:

  • Cells vary in size but cannot exceed the volume that can be nourished by materials passing through the surface membrane
  • Most eukaryotic and prokaryotic cells are typically measured in micrometers (μm), which equal 10^-6 meters
  • Cells can be seen through light or electron microscopes
  • Micrographs are photographs taken with a microscope
• Specialized cells differentiate from one cell:

  • Specialized cells have structures reflecting their functions
  • Example: Muscle cells and fibers
• Plasma membrane:

  • Maintains structural integrity of the cell
  • Selectively permeable, regulating movement of substances into and out of the cell
  • Glycoproteins provide recognition between cells
  • Receptors provide communication between cells
  • Cell adhesion molecules stick cells together to form tissues and organs
• Substances movement into and out of the cell:

  • Passive transport: movement across the membrane without energy
  • Simple diffusion: movement from high to low concentration
  • Facilitated diffusion: assisted by a membrane protein
  • Osmosis: movement of water from high to low water concentration
  • Active transport: movement across the membrane requiring energy
• Organelles:

  • An organelle is a subcellular structure with specific functions in the cell
  • Eukaryotic cells contain membrane-bound and non-membranous organelles with different functions
• Nucleus:

  • Contains almost all genetic information of the cell (DNA)
  • Surrounded by the nuclear envelope, a double membrane allowing communication through nuclear pores
• Endoplasmic Reticulum:

  • Rough endoplasmic reticulum (RER) contains ribosomes guiding cell product production
  • Smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in phospholipid production and detoxification
• Golgi Complex:

  • Series of interconnected, flattened membranous sacs
  • Proteins are packaged in vesicles and transferred for processing and packaging
  • Contains about 40 digestive enzymes breaking down macromolecules, old organelles, and invaders
• Mitochondrion:

  • Sites of cellular respiration, providing energy through glucose breakdown to produce ATP
  • Double-membrane organelle with inner foldings called cristae
• Cellular Respiration:

  • Catabolic pathway generating cellular energy
  • Requires oxygen to break down glucose into final products
  • Four phases: Glycolysis, Transition reaction, Citric acid cycle, Electron transport chain
• Fermentation:

  • Breakdown of glucose without oxygen
  • Takes place in the cytoplasm and is inefficient compared to cellular respiration
  • Lactic acid fermentation occurs in muscles during low oxygen supply
• Organelle that is membranous, modifies proteins, and can use vesicles to ship them to other organelles is the Golgi complex
• Most body systems aim to get oxygen to the mitochondria so that ATP can be produced
• where does the electron transport chain located?

  inner mitochondrial membrane
• What is phagocytosis

  intake of SOLID materials
• What is pinocytosis?

  intake of liquid materials
• Which phase of the cellular respiration produces CO2 as a waste product?

  citric acid (kreb) cycle