Cellular Respiration

• fermentation


  a catabolic process that makes a limited amount of ATP from glucose without an electron transport chain & that produces a characteristic end product, such as ethyl alcohol or lactic acid; partially breaks down sugars without using oxygen
• aerobic respiration


  a catabolic pathway that consumes oxygen & organic molecules, producing ATP
• cellular respiration


  the catabolic pathways of aerobic & anaerobic respiration, which break down organic molecules for the production of ATP
• The breakdown of glucose is exergonic
• redox reaction


  a chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another
• oxidation


  loss of electrons from a substance involved in a redox reaction
• reduction


  addition of electrons to a substance involved in a redox reaction
• reducing agent


  electron donor in a redox reaction
• oxidizing agent


  electron acceptor in a redox reaction
• Label the arrows as either oxidization or reduction.

  A) oxidation

  B) reduction

  
• Glucose is oxidized & oxygen is reduced
• NAD+


  nicotinamide adenine dinucleotide, a coenzyme that can accept an electron & acts as an electron carrier in the electron transport chain
• Hydrogen atoms are passed to an electron carrier called NAD+
• During cell respiration, electrons follow this route:

  Glucose -> NADH -> ETC -> Oxygen
• • NAD+ traps electrons when an enzyme called dehydrogenase removes 2 hydrogen atoms from a substrate.
  • Enzyme delivers 2 electrons & 1 proton to NAD+
  • By getting 2 negatively charged electrons & only 1 positive proton, NAD+ has its charge neutralized & is reduced to NADH
• electron transport chain


  a sequence of electron carrier molecules that shuttle electrons during the redox reactions that release energy used to make ATP

  • made of molecules built into the inner membrane of the mitochondria
  • electrons are shuttled down in an exergonic reaction, losing a small amount of energy in each step
• 3 Stages of Cellular Respiration

  1. Glycolysis
  2. Citric Acid Cycle
  3. Oxidative Phosphorylation: electron transport & chemiosmosis
• glycolysis


  splitting of glucose into pyruvate
• Glycolysis occurs in the cytosol
• Glycolysis is anaerobic
• Glycolysis: Reactants & Products

  Reactants:

  • glucose
  • 2 ATP

  Products:

  • 2 pyruvate + 2H20
  • 2 ATP
  • 2NADH + 2H+
• Citric Acid Cycle


  a chemical cycle involving 8 steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing pyruvate to carbon dioxide
• The citric acid cycle occurs in the mitochondria in eukaryotes and the cytosol of prokaryotes
• The citric acid cycle is aerobic
• oxidative phosphorylation


  production of ATP using energy derived from the redox reactions of an electron transport chain
• Oxidative phosphorylation occurs in the inner membrane of the mitochondria of eukaryotes and the plasma membrane of prokaryotes
• substrate level phosphorylation


  formation of ATP by an enzyme directly transferring a phosphate group to ADP from an intermediate substrate of catabolism
• What is the difference between oxidative phosphorylation & substrate-level phosphorylation?

  In substrate-level phosphorylation, an enzyme transfers a phosphate group from a substrate to ADP, rather than adding an inorganic phosphate to ADP like oxidative phosphorylation.
• Oxidative phosphorylation produces about 32 to 34 ATP
• Substrate-level phosphorylation produces about 4 ATP
• For each molecule of glucose broken down, the cell can make up to 38 ATP
• Glycolysis can be divided into 2 phases:

  1. Energy investment (spends ATP)
  2. Energy payoff (produces ATP)
• What is the net energy yield of glycolysis?

  2 ATP & 2 NADH
• What intermediate step must occur between glycolysis & the citric acid cycle?

  Pyruvate must be coverted to acetyl CoA
• acetyl CoA

  acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme
• Citric Acid Cycle Steps:

  1. Pyruvate's carboxyl group is removed & given off as CO2
  2. 2 carbon fragment form acetate & extracted electrons are transferred to NAD+ which become NADH
  3. Coenzyme A is attached to the acetate by an unstable bond
• Most of the ATP made in respiration comes from oxidative phosphorylation when NADH & FADH2 transfer electrons to the ETC
• In the ETC, electrons are passed "downhill" & the amount of free energy decreases
• Products of the Citric Acid Cycle (after 2 cycles)

  • 6 NADH
  • 4 CO2
  • 2 FADH2
  • 2 ATP
• ATP synthase


  a complex of several membrane proteins that provide a port through which protons diffuse

  • functions w/ adjacent ETCs, using the enrgy of a hydrogen ion concentration gradient to make ATP
  • found in the mithochondrial membrane of eukaryotic cells & in the plasma membrane of prokaryotes