Fundamentals of Anatomy and Physiology

Cellular Metabolism and Reproduction: Mitosis and Meiosis 63

Glycolysis

Step one in respiration

Glucose (C 6 H 12 O 6 )

ATP

ADP + PO^4

Glucose phosphate: Quickly changes to fructose phosphate (C 6 )

ATP

ADP + PO 4

Fructose diphosphate

Cleaves

2 Phosphoglyceraldehyde (C 3 ): PGAL

2 NAD^

2 NADH 2 *

Oxidizes (each loses two H atoms to NAD)

* 6 ATP made via

electron transport

High energy

releasing reactions

2 Phosphoglyceric acid (C 3 ): PGA

2 Pyruvic acid (C 3 )

Final product

4ADP

4PO^4

4 ATP^

(must pay back the

above two, net

gain of only two)

(^) ®
Learning
Cengage ©
Figure 4- 1 The basic steps in glycolysis, the first step in biochemical
respiration.
In the next step of glycolysis, the fructose diphos-phate
splits or cleaves into two C 3 molecules of phos-
phoglyceraldehyde (fos-foh-GLISS-er-AL-deh-hyde),
abbreviated as PGAL. The PGAL is now oxidized (loses
electrons) by the removal of two electrons and two H^1 ions
to form two phosphoglyceric (fos-foh-GLISS-er-ik)
acids, abbreviated as PGA. The two hydrogen atoms that
come off each of the two PGALs go to the electron trans-
port system and are taken up by the electron carrier
molecule nicotinamide adenine dinucleotide (nik-oh-
TIN-ah-mide ADD-eh-neen dye-noo-klee-oh-tide),
-abbreviated as NAD. This step is actually part of the
electron transport system and will result in the produc-tion
of six ATP molecules. However, this step occurs only if
oxygen is present. In this process, NAD gets re-duced
(gains electrons) to NADH 2. Because there were two
PGALs, it happens twice. Each time an NAD gets reduced
to NADH 2 and the electron transport system