Cells

• Specialized exchange surfaces


  Parts of an organism over which they exchange substances with their environment
• Specialized exchange surfaces in humans

  • Alveoli
  • Villi
• Alveoli


  • Small sac-like things found in the lungs at the very ends of the bronchioles
  • Exchange oxygen and carbon dioxide between the air and the blood
• Villi


  • Finger-like projections found on the inside lining of the small intestines
  • Help absorb nutrients like glucose and amino acids
• Specialized exchange surfaces in plants

  • Root hair cells
  • Leaves
• Root hair cells


  • Help absorb water and mineral ions from the soil
• Leaves


  • Help absorb the carbon dioxide they need from the air
• Common features of specialized exchange surfaces

  • Large surface area
  • Thin surfaces
  • Permeable to substances being exchanged
  • Good blood supply (internal medium)
  • Good supply of external medium
• Large surface area


  Allows more molecules to diffuse across at the same time, increasing the rate of diffusion
• Thin surfaces


  Short diffusion distance, allowing faster diffusion
• Permeable


  Allows substances to diffuse across rather than blocking them
• Cells


  The basic building blocks of life that can replicate independently
• Good blood supply (internal medium)


  Helps maintain a concentration gradient for substances being absorbed
• Multicellular organisms like animals and plants contain many cells that divide to grow or replace dead cells, not to create new organisms</b>
• Good supply of external medium


  Helps maintain a concentration gradient for substances being absorbed, e.g. air for alveoli, food for villi
• Bacteria are single-celled prokaryotic organisms
• Subcellular structures common to animal and plant cells

  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Ribosomes
• Plant cells


  • Have a rigid cell wall made of cellulose
  • Contain a permanent vacuole with cell sap
  • Contain chloroplasts for photosynthesis
• Bacterial cells


  • Lack mitochondria and chloroplasts
  • Have a single circular strand of DNA instead of a nucleus
  • May have additional plasmids
  • May have flagella for movement
• Bacteria are unicellular organisms, each individual cell is a whole organism
• Photosynthesis occurs in the chloroplasts of plant cells, using chlorophyll to absorb light energy
• Specialized cells


  Different types of cells that make up complex organisms like animals and plants
• Examples of specialized cells in animals


  • Sperm cells
  • Muscle cells
  • Nerve cells
• Examples of specialized cells in plants


  • Root hair cells
  • Phloem cells
  • Xylem cells
• Sperm cell


  • Has half the genetic material of a normal adult cell
  • Has a flagellum to swim
  • Is streamlined to swim
  • Has many mitochondria for energy
  • Has digestive enzymes to break into egg
• Specialized cells


  Have a specific role, shape, structure and organelle composition to fulfill that role
• Differentiation


  The process by which a cell changes to become specialized
• Zygote


  The single fertilized egg cell that life starts from
• Cell division and differentiation

  1. Zygote divides by mitosis into 2 cells

  2. 2 cells divide into 4 cells

  3. Cells undergo differentiation to become specialized
• Stem cells


  Cells that can repeatedly divide by mitosis and differentiate into different specialized cell types
• Prokaryotic cells


  One type of cell distinguished in cell biology
• Eukaryotic cells


  One type of cell distinguished in cell biology
• Animal cell


  One type of eukaryotic cell
• The main function of the plasma membrane is to regulate nutrient and mineral transport
• Cytoplasm


  The fluid inside the plasma membrane that contains nutrients and organelles
• Mitochondria


  Organelles that provide the cell's energy in the form of ATP
• Cell wall


  • Functions as a support skeleton and determines the shape of the cell
  • Acts as a natural barrier against infections of fungi
  • Composed of cellulose embedded in a net with other complex proteins
• Plasma membrane


  Selectively permeable structure out of lipids that regulates nutrient and mineral transport
• Nucleus


  • Stores the majority of the genetic information packed in DNA
• Ribosomes


  Free in the cytoplasm, involved in protein synthesis