Yield of ATP in Glycolysis and Aerobic Respiration:

ATP Yield in Eucaryotes from Glycolysis, TCA cycle, and

electron transport:

Glycolytic Pathway:

SLP (ATP) 2 ATPs

OPL with 2 NADH 6 ATPs

2 pyruvates to 2 Acetyl CO-A

OP with 2 NADH 6 ATPs

TCA Cycle

SLP (GTP) 2 ATPs

OP with 6 NADH 18 ATPs

OP with 2 FADH2 4 ATPs

Total Aerobic Yield 38 ATPs

Aerobic Oxidation of glucose to 6 CO2 à 38 ATPS

Anaerobic Respiration:

§ Energy yielding process where the final electron acceptor is different than oxygen:

§ The major acceptors are nitrate, sulfate, and CO2 (NO3-, SO4-, CO2)

§ Bacteria can nitrate to nitrite to produce ATP, but it is not the most effective way to produce ATP.

§ Because Nitrite is toxic, Nitrate is usually reduced to Nitrogen gas, denitrification.

§ Anaerobic respiration does not yield as much ATp as aerobic respiration because less energy is available.

§ Yet Anaerobic Respiration is useful bc it is more efficient than fermentation and allows ATP synthesis by ET and OP in the absence of oxygen.

§ Find Anaerobic Respiration in oxygen depleted soils and sediments.

Anaerobic Respiration

§ respiration in which a terminal electron acceptor other than O2 is used,

§ less energy than aerobic respiration, but allows organisms to live in environments lacking O2.

Photosynthesis

§ Light energy is trapped and converted to chemical energy.

§ Photosynthetic pathways use light, rather than chemical compounds as a source of energy, move it through Photosystems I and II to synthesize ATP and NADH or NADPH.

§ One of the most significant metabolic pathways on earth bc all our energy is ultimately derived from solar energy.

§ Provides photosynthetic organisms with ATP and NADPH to synthesize organic cmpd needed for growth.

§ Replenishing O2 supply

§ Carried out by both Pro and Euc

TWO parts to Photosynthesis:

1. Light Reactions: light is trapped and converted to

chemical energy.

2. Dark Reactions: Energy made during the light reaction is

used here to reduce or fix CO2 and synthesize cell constituents.

Chlorophyll

§ Photosynthetic organisms use chlorophyll to trap sunlight and extract the energy to drive ATP synthesis.

§ Chlorophyll has a chemical structure that is similar to heme, but it contains a magnesium ion instead of iron

§ Light energy is channeled to a chlorophyll molecule contained within a pigment complex called a reaction center.

§ Light hits the reaction center, and excites electrons

§ The excited electron is then passed to a series of electron carriers, each one removing some of the energy, until the electron returns to its ground state where it is passed back to the reaction center complex.

§ The energy derived from the excited electrons by the electron carrier molecules is used to synthesize ATP.

§ This process of light driven ATP synthesis is called cyclic phosphorylation because electrons in a cyclic pathway and ATP is formed.

§ Involving the activity of Photosystem I alone

Non cyclic phosphorylation:

§ In order to reduce CO2 into more complex compounds, the cells require H atoms (or protons) and the reaction center complex does not have the strength required to strip H away from HOH

§ Therefore the Photoautotroph increases the energy by coupling a second reaction center to the first one.

§ Electrons are stripped from HOH and passed to RCII

which is in turn stimulated to an excited state, and passed to RCI

§ Which is stimulated, as the electron is passed through the carrier systems, they are passed to NADP+ to generate NADPH + H+ which in turn is used to reduce CO2

§ This light driven reduction of NADP+ to NADPH + H+ is called non cyclic phosphorylation

§ Involves both photosystem I & II

§

Photosystems

§ In higher plants and algae, reaction centers I and II are found in the chloroplast membranes,

§ If the cyanobacteria, they are found in the cell membrane

§ The purple and green photosynthetic bacteria do not have reaction center II complexes, only RCI

§ Therefore they are incapable of using water as an electron donor and must use other compounds, such as H2S