Photosynthesis , Light energy

Catabolic pathways

Catabolic pathways release stored energy

  • election transfer plays major role in the pathways

  • central to cellular respiration

Catabolic pathways/production of ATP

  • breakdown of organic molecules is exergonic

  • Fermentation - partial degredations of sugars without O2

  • Aerobic respiration - consumes organic moledules and O2 and yields ATP 

  • Anaerobic respiratoin - ^ consumes compounds other than O2


Cellular respiration includes both aeroni and anaerobic respitation but more often used referring to aerobic respiration 



Principle of Redox 

  • chemical reactions taht trasnfer electrons between reactants 

    • called oxidation-reduation reactants of redox-reduction

    • In oxidation, a substance loses electrons or is oxidized

    • in reduction, substance gains electrons, or is reduced (positive charge is reduced)

Oxidiation of organic fuel molecules during cellular respiation 

  • During cellular respiation (such as glucose) is oxodized, and O2 is reduced 

Energy harvest via NAD+, electron transport chain 

  • in celular resp, glucose and other organic molecules are broken down in a series of steps

  • electrons from organic compounds are usually first transferred to NAD+, a coenzyme

  • each NAD+ (reduced form of NAD+) represents energy that is tapped to synthesize ATP

NADH passes through the electrons to the electron transport chain

  • the electron TC passes electtrons in a series of steps instead of one explosive reaction 

  • O2 pulls electrons down the chain in an energy-yielding tuble

    • energy yielded is used to regen APT 


Stages of cellular respiratin 

  • The stages 

    • Glycolosis  (breaks down glucose into two molecules of pyruvate)

    • Citric Acid Cycle (completes the breakdown of glucose)

    • Oxidative Phosporylation (accounts for most of the ATP synthesis)    

      • almost 90% of the ATP generates

Glycolosis harvest chemical energy by oxidixing glucose to pyruvate


Breaks down glucose into two molecules of pyruvate

Glycolosis occurs in the cytoplasm and has two major phases 

  • energy investment phase 

  • energy payoff phase 

  • occurs wether or not O2 is present 

After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules 

In the presence of O2 , pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed

  • Before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle

The citric acid cycle (krebs cycle) 

Completes the break down of pyruvate to CO2

  • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn

Oxidative Phosphorylation/Osmosis

NADH and FADH2 are two electron carriers that donate electrons to the ETC , powers ATP synthesis via oxidative phosphorylation 

  • most cellular respirations requires O2 to produce ATP 

    • without O2, ETC will not work 

      • glycolosis coupled with anaerobis respiration or fermentation to produce ATP 

    • Anaerobic respiration uses ETC with a final electron acceptor other than O2

    • Fermentation uses substrate level phosphorylation instead of ETC to generate ATP 

Types of Fermentation 

Glycolysis plus reactions that regenerate NAD+, which can be reused by glycolosis 

  • 2 common types : alchohol fermentation and lactic acid fermentation 

  • Obligate anaerobes carry out fermenation or anaerobis respiration and cannot survive in the presene of O2

  • Yeah and many bacteris are faculative anaerobes, can survive fermentation or cellular respiration