In-Depth Process

GLYCOLYSIS Glycolysis occurs in the cytoplasm of cells. During this process, glucose (a 6-carbon sugar) undergoes a series of chemical transformations, splitting it into two 3-carbon molecules called pyruvates. This process is anaerobic (does not involve the use of oxygen).

Energy-requiring phase

Glucose is rearranged, and 2 phosphates (which come from ATP) are attached. Catalyzed by phosphofructokinase

Fructose-1,6-biphosphate (unstable)

DHAP (phosphate-bearing 3-carbon sugar)

Energy-releasing phase

DHAP converted into glyceraldehyde-3-phosphate

Energy-releasing phase

series of chemical reactions

series of chemical reactions

pyruvate (3-carbon molecule)

pyruvate (3-carbon molecule)

pyruvate moves into the mitochondrial matrix in eukaryotes and remains in the cytoplasm in prokaryotes

pyruvate moves into the mitochondrial matrix in eukaryotes and remains in the cytoplasm in prokaryotes

PYRUVATE OXIDATION pyruvate dehydrogenase complex carries out this process (aerobic)

A carboxyl group is removed from pyruvate

PYRUVATE OXIDATION pyruvate dehydrogenase complex carries out this process (aerobic)

A carboxyl group is removed from pyruvate

oxidized

attached to Coenzyme A

attached to Coenzyme A

acetyl CoA joins with a four-carbon molecule, oxaloacetate

KREBS/CITRIC ACID CYCLE This cycle takes place in matrix of the mitochondria in eukaryotes and in the cytoplasm in prokaryotes. It is a closed loop (the last part of the pathway reforms the molecule used in the 1st step) (aerobic)

CoA group released

citrate formed (6-carbon molecule)

CoA group released

citrate formed (6-carbon molecule)

OXIDATIVE PHOSPHORYLATION The electron transport chain forms a proton gradient across the inner mitochondrial membrane in eukaryotes and in the plasma membrane in prokaryotes, which drives the synthesis of ATP via chemiosmosis.

Reduced electron carriers (NADH and FADH2) from other cellular respiration steps transfer their electrons to molecules near the beginning of the transport chain.

NADH transfers its electrons directly to complex I, turning back into NAD+

Electrons are passed down the chain, moving from higher energy to lower energy level, releasing energy. Released energy is used to pump protons from the mitochondrial matrix to the intermembrane space. Forms a proton gradient

H+ ions are pumps across the membrane, and electrons are delivered to cytochrome C

Cytochrome C carries the electrons to complex IV

H+ ions are pumped across the membrane with the help of channel proteins that form hydrophilic tunnels across the membrane

H+ ions go through a channel of ATP synthase

As ATP synthase turns, it catalyzes the addition of a phosphate to ADP, capturing energy from the proton gradient as ATP, a process called CHEMIOSIS

NADH transfers its electrons directly to complex I, turning back into NAD+

Electrons are passed down the chain, moving from higher energy to lower energy level, releasing energy. Released energy is used to pump protons from the mitochondrial matrix to the intermembrane space. Forms a proton gradient

H+ ions are pumps across the membrane, and electrons are delivered to cytochrome C

Cytochrome C carries the electrons to complex IV

H+ ions are pumped across the membrane with the help of channel proteins that form hydrophilic tunnels across the membrane

H+ ions go through a channel of ATP synthase

As ATP synthase turns, it catalyzes the addition of a phosphate to ADP, capturing energy from the proton gradient as ATP, a process called CHEMIOSIS

NADH transfers its electrons to pyruvate

NADH donates its electrons to a derivative of pyruvate

bacteria

NADH transfers its electrons to pyruvate

NADH donates its electrons to a derivative of pyruvate

converts pyruvate into acetaldehyde to ethanol