Exam 2

• Lipid Bilayer

  • semipermeable barrier
  • flexible, fluid, self healing, and can grow by adding
  • amphipathic
  • made of lipids with embedded proteins
• 2 classes of fatty acids

  • saturated - maximum number of Hs (stearic acid)
  • unsaturated - fewer Hs, double bonds (oleic acid)
• Phospholipid

  may contain different heads, vary chain lengths, saturated/unsaturated fatty acids
• membrane fluidity

  how easy the lipids on the bilayer are moving
• why is membrane fluidity important?

  • proteins need to move around to interact with each other
  • molecules need to move from where they were before
  • membranes need to fuse together
  • membrane need to grow and pinch off
• membrane fluidity movement


  flexion, rotation, lateral diffusion, and flip-flop of phospholipids
• what affects fluidity?


  lipid composition
• lipid composition examples

  • more structure = less fluid
  • cholesterol = less fluid
  • shorter chain lengths = more fluid
  • unsaturated = more fluid
  • heat = more fluid-like consistency
• passive diffusion

  • uses concentration gradient
  • no energy
  • high to low concentration
• facilitated diffusion

  • type of passive diffusion
  • move across concentration gradient with help of transporter protein and channels
• active diffusion

  • against concentration gradient
  • requires energy
  • low to high concentration
  • carried out by pumps
• transporter protein

  • active or passive diffusion
  • contains binding site for specific molecule/ions
• channel protein

  • passive diffusion
  • "gated"
  • specific for change and shape
• rate of molecules goes across membrane depends on...

  • membrane fluidity
  • chemical properties (charge, polarity, size)
  • presence/amount of carrier proteins
  • concentration gradient
  • charge difference across membrane
• membrane potential


  charges inside and outside membrane produce voltage difference across membrane
• what is concentrated inside cell?

  K+ and anions
• what is concentrated outside cell?

  Na+, Cl- and Ca2+
• electrochemical gradient


  both membrane potential and concentration gradient
• passive transporter


  along electrochemical gradient (ex. glucose transporter)
• active transporter types

  1. gradient driven - potential energy from concentration gradient
  2. ATP driven - chemical energy from ATP hydrolysis
  3. light driven - light energy
• channel mechanisms

  1. voltage gated
  2. ligand gated (intracellular/extracellular)
• nerve cell signaling


  ions are unequally distributed across cell membrane creating a difference in charge and concentration (set up membrane potential)
• resting membrane potential

  • no stimulus/signal
  • sits at about -60mV
• stimulus

  • signal is received
• threshold potential

  mV that must be reached for depolarization (about -40mV)
• depolarization

  • voltage gated Na+ channels open allowing Na+ to rush INTO the neuron
  • Na+/K+ pump is also working
• equilibrium point

  • Na+ and K+ are balanced
  • around +40mV, which inactivates voltage gated Na+ channels and allowing the opening of K+ channels
• repolarization

  voltage gated K+ channels and K+ leak channels are opened allowing K+ to go OUT of neuron to restore resting membrane potential

  Na+/K+ pump is also working
• Na+/K+ pump

  sets up gradient
• K+ leak channels

  sets up -60mV resting potential
• because of Na+ channel inactivation, action potential spreads in one direction down membrane
• function of mitochondria

  • ATP production
  • regulation of NAD+
  • biosynthesis of precursors
• mitochondria has

  • dynamic nature
  • maternally inherited
• cellular respiration


  glucose + O2 ---> CO2 + H2O + ATP
• cellular respiration steps

  1. glycolysis
  2. pyruvate transport
  3. kreb cycle
  4. oxidative phosphorylation (electron transport chain and ATP synthesis)
• glycolysis (cytoplasm)

  • input - glucose, ADP, NAD+
  • output - 2 pyruvate, 2 ATP, 2 NADH
• pyruvate transport (into mitochondria matrix via active transport)

  • 2 pyruvate make 2 acetyl COA
  • CO2 is released and NADH is produced
• kreb cycle (mitochondria matrix)

  • input - 2 acetyl COA, NAD+, ADP, FADH
  • output - CO2, NADH, ATP, FADH2
• Electron transport chain (matrix)

  1. NADH gives up electron to Complex I and becomes NAD+

  2. Electrons that enter Complex I give the energy to pump H+ from the matrix to the intermembrane space

  3. Complex I pass electrons to electron carrier

  4. Electron carrier will pass electrons to Complex II, which gives it energy to pump H+ from matrix to intermembrane space

  5. Complex II passes electrons to 2nd electron carrier

  6. 2nd electron carrier will pass electrons to Complex III, which gives it energy to pump H+ from matrix to intermembrane space

  7. Electrons are passed to O2 (final electron acceptor) which split oxygen atoms than protons are added creating H2O
• what happens when O2 gets few electrons?

  • Oxygen becomes a free radical, which can be very reactive
  • fixed by antioxidant