cells

• Cell

  Basic unit of living things
• Common cell organelles

  • Cell membrane
  • Cell wall
  • Cytoplasm
  • Ribosome
• Cell membrane

  Supports/protects cell; controls movement of substances into/out of cell; separates cell from its environment
• Cell wall


  Stiff, rigid structure that surrounds the cell membrane to support/protect the cell
• Cytoplasm

  Clear, thick, jelly-like substance inside the cell membrane that contains the other organelles
• Ribosome

  Small bodies floating in cytoplasm (or attached to the endoplasmic reticulum) that make proteins
• Cell movement structures

  • Flagella
  • Cilia
  • Pseudopodia
• Flagella


  Whip/tail-like structure that helps propel the cell forward
• Cilia


  Short, hair-like structure that surround the cell and help it move
• Pseudopodia


  Extension of cytoplasm into the cell membrane that allows the cell to "crawl"
• All cells contain genetic information
• All living things must have genetic information that provides instructions for cellular activities
• Some cells keep this genetic information in a nucleus, while others store it differently
• The cell wall and cell membrane are not the same thing
• All cells have a cell membrane, but not all cells have a cell wall
• Cell walls are very rigid, which makes the cell harder to move
• Cell walls can be made up of a variety of substances, so cell walls in plant cells are different than those found in bacterial cells
• Fluid mosaic model


  The currently accepted model for the structure of the plasma membrane, first proposed in 1972
• Plasma membrane


  • A mosaic of components - primarily phospholipids, cholesterol, and proteins - that move freely and fluidly in the plane of the membrane
• Principal components of the plasma membrane

  • Lipids (phospholipids and cholesterol)
  • Proteins
  • Carbohydrate groups
• Phospholipid


  A lipid made of glycerol, two fatty acid tails, and a phosphate-linked head group
• Phospholipid bilayer


  An arrangement where two layers of phospholipids have their tails pointing inward
• Cholesterol


  A lipid composed of four fused carbon rings, found alongside phospholipids in the core of the membrane
• Membrane proteins

  • Integral (embedded in the membrane)
  • Peripheral (attached to the inside or outside)
• Transmembrane proteins

  Integral membrane proteins that extend across the entire membrane
• Glycoproteins


  Carbohydrates attached to proteins on the outer surface of the plasma membrane
• Glycolipids


  Carbohydrates attached to lipids on the outer surface of the plasma membrane
• Typical composition of a human cell plasma membrane
• Amphipathic


  Having both hydrophilic and hydrophobic regions
• Phospholipid arrangement in water/aqueous solution

  Hydrophobic tails facing each other, hydrophilic heads facing out
• Micelle


  A small, single-layered sphere formed by phospholipids with small tails
• Liposome


  A hollow droplet of bilayer membrane formed by phospholipids with bulkier tails
• Saturated fatty acids


  Fatty acids with no double bonds, relatively straight
• Unsaturated fatty acids


  Fatty acids with one or more double bonds, often resulting in a bent or kinked structure
• Effect of temperature on saturated vs unsaturated fatty acids

  At cooler temperatures, saturated fatty acids pack tightly together making a dense, rigid membrane, while unsaturated fatty acids cannot pack as tightly due to the bent structure, resulting in a more fluid membrane
• Role of cholesterol


  Helps maintain membrane fluidity by minimizing the effects of temperature changes
• Components of the plasma membrane

  • Phospholipids
  • Cholesterol
  • Integral proteins
  • Peripheral proteins
  • Carbohydrates
• Polar heads


  The space between the polar heads would contain saturated and unsaturated fatty acids which forms these tails
• Fatty acid tails


  Can be bent or straight
• Components found in the space between the polar heads

  • Saturated fatty acids
  • Unsaturated fatty acids
  • Integral proteins
  • Cholesterol
  • Water molecules