Anatomy lecture 3

• Cells

  The smallest living units of an organism
• Things all cells have in common

  • Cell membrane
  • Cytoplasm
  • DNA
• Eukaryotic cells


  • Have organelles, including nucleus
  • More advanced complex cells, such as those found in plants and animals
• Prokaryotic cells


  • Don't have a nucleus or membrane-enclosed organelles
  • Have genetic material not contained within a nucleus
  • Always one-celled or unicellular organisms, such as bacteria
• Organelles


  Specialized parts of a cell that have unique jobs to perform
• Nucleus


  • Control center of the cell
  • Contains DNA or genetic material
  • DNA dictates what the cell is going to do and how it's going to do it
  • Contains a nucleolus where ribosomes are made
• Chromatin


  • Tangled, spread-out form of DNA found inside the nuclear membrane
• Chromosomes


  • DNA condenses into these structures when a cell is ready to divide
• Ribosomes


  • Synthesize or make proteins
  • May wander freely within the cytoplasm or attach to the endoplasmic reticulum
• Endoplasmic reticulum (ER)


  • Membrane-enclosed passageway for transporting materials, such as the proteins synthesized by ribosomes
  • Two types: rough ER has ribosomes attached, smooth ER doesn't
• Golgi apparatus


  • Receives proteins and other materials from the endoplasmic reticulum
  • Customizes proteins into usable forms by folding them or adding other materials like lipids or carbohydrates
• Vacuoles


  • Sac-like structures that store different materials, like water in plant cells
• Lysosomes


  • Garbage collectors that take in and break down damaged or worn-out cell parts
• Mitochondria


  • Powerhouse for both animal and plant cells
  • During cellular respiration, make ATP molecules that provide energy for the cell's activities
  • Cells that need more energy have more mitochondria
• Cytoskeleton


  • Maintains the cell's shape
  • Includes microfilaments and microtubules
• Chloroplasts


  • Where photosynthesis happens in photoautotrophic organisms like plants
  • Contains chlorophyll, the green pigment
• Cell wall


  • Found outside the cell membrane in plant cells, shapes, supports, and protects the plant cell
  • Animal cells never have a cell wall
• Other unique cell structures

  • Cilia in human respiratory tract cells
  • Flagella in some bacteria and human sperm cells
• Eukaryotic cells are plant and animal cells with a nucleus and membrane-enclosed organelles
• Prokaryotic cells are unicellular organisms without a nucleus or membrane-enclosed organelles
• Cell


  The basic building block in the body, the smallest unit of life
• Cell components


  • Plasma membrane (cell membrane)
  • Cytoplasm
  • Nucleus
  • Organelles (ribosomes, mitochondria, lysosomes etc.)
• Plasma membrane


  Encloses the cell content, separates the intracellular fluid from the extracellular fluid
• Structure of the plasma membrane

  • Phospholipid bilayer
  • Membrane proteins
  • Membrane carbohydrates
  • Microvilli
• Phospholipid bilayer


  • A continuous layer that forms the bulk of the membrane structure
  • Consists of polar phosphate + head group facing the inside and outside of the cell, and non-polar tails pointing toward the interior
  • Protected from water because they are non-polar
  • Cholesterol is also present to stabilize the membrane
• Transmembrane proteins


  Embedded in the plasma membrane and pass all the way through
• Peripheral membrane proteins


  Attached to either the cytoplasmic (inside) or extracellular (outside) surface of the membrane

  
• Membrane proteins


  Function as channels, receptors and enzymes
• Membrane carbohydrates


  Located only on the outer surface, function in cell to cell recognition, attached to either protein (glycoprotein) or lipid (glycolipid)

  
• Microvilli


  Folds of the plasma membrane that serve to increase surface area, especially important in cells where nutrient absorption occurs
• Cytoplasm


  Viscous fluid that fills the space between the plasma membrane and the nucleus
• Components of cytoplasm


  • Cytosol
  • Organelles

  
• Cytosol


  Semi-transparent, viscous fluid that bathes the organelles, containing water, dissolved ions, suspended carbohydrates and lipids, and melanin granules in certain cells
• Non-membranous organelles


  • Ribosomes
  • Centrosomes
  • Centrioles
  • Cytoskeleton (microfilaments, intermediate filaments, microtubules)

  
• Ribosomes


  Composed of rRNA and protein, responsible for protein synthesis, can be free in the cell or attached to the endoplasmic reticulum

  
• Centrosomes


  A region located near the nucleus, containing a granular matrix and 2 centrioles
• Centrioles


  Small, cylindrically shaped organelles composed of microtubules, located perpendicular to one another, function to direct the movement of chromosomes during cell division
• Cytoskeleton


  • Determines/holds cell shape, used to anchor organelles in place and move materials throughout the cell, composed of microfilaments, intermediate filaments, and microtubules

  
• Microfilaments


  Composed of actin protein, the thinnest component of the cytoskeleton, important for muscle contraction, cell movement, and maintenance of cell shape

  
• Intermediate filaments


  Composition differs based on tissue type, work to support the cytoplasm