Biology Unit 4 Notes

• Negative feedback loops


  Homeostasis: achieved by regulating internal, chemical, and physical conditions within living organisms
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Osmotic Pressure


  Minimum pressure needed to prevent the flow of solvent across the membrane
• Osmoregulation


  Regulation of fluid balance
• Osmolarity


  Number of moles per liter of solution
• Hypoosmotic


  The net flow of water into the cell
• Hyperosmotic


  The net flow of water out of the cell
• Isotosmotic


  No net water movement
• Reasons for osmoregulation


  • Control solute concentration (Electrolytes)
  • Balance of water loss and gain
• Chemical reactions depend on specific internal conditions
• Plants: water is necessary for the acquisition of nutrients
• Animal: kidneys allow for the excretion of nitrogenous wastes and proper water balance
• Osmoregulatory organisms


  • Snakes
  • Bears
• Osmoconformers


  • Crabs
  • Sharks
  • Whales
• Strategies for removing nitrogenous wastes

  • Ammonia
  • Urea
  • Uric acid
• Ammonia


  Most aquatic animals secrete it directly into water
• Urea


  Formed in the liver: NH3 + CO2, transported to kidneys for excretion, needs water (trade-off)
• Uric acid

  Least toxic, needs less water than urea, high energy needed
• Ammonia itself is very toxic, which is why we use water to dilute its derivative
• Functions of the kidneys

  • Regulate pH
  • Influence red blood cell production
  • Influence blood pressure
• Parts of the excretory system

  • Ureter
  • Renal arteries
  • Kidney
  • Renal vein
  • Renal pelvis
  • Bladder
  • Urethra
• Nephron types


  • Bowman's capsule
  • Proximal tubule
  • Descending/ascending limb
  • Distal tubule
  • Collecting duct
• Water is required for chemical reactions in plant cells, including photosynthesis
• Leaves need moisture for uptake of CO2 for photosynthesis
• Rigidity is needed for herbaceous plants to remain upright
• Plant cells require turgidity, where plant cells push against the wall, allowing it to become upright
• Xylem is a unidirectional flow from roots to leaves
• Transpiration


  Water evaporating from stomata
• Transpiration creates a force that pulls water up from the roots
• Cohesion


  Water molecules stick together because water is a polar molecule
• Adhesion


  Water molecules sticking to other things, like xylem in a plant
• Water potential


  The tendency of water to move from one place to another, refers to potential energy or how much energy is stored in water molecules
• In plants, water goes from soil (-0.3 MPa) to outside air (-100.0 MPa)
• The entropy of the universe is always increasing
• Life needs ordered structures and cannot be at equilibrium
• Life runs on a lot of chemical reactions
• Biological Macromolecules


  • Proteins
  • Lipids
  • Nucleic acids
  • Carbohydrates
• Proteins


  Enzymes, build and repair tissue, hormones
• Lipids


  Make cellular membranes (phospholipids), store energy, form a gradient for chemical reactions
• Nucleic acids


  Store information, like DNA