GLYCOLYSIS (“Sugar-breaking”)
**During Glycolysis, 1 molecule of Glucose (which has 6
carbons), is transformed into 2 molecules of Pyruvic Acid
(which has 3 carbons).
GLUCOSE
PYRUVIC ACID
PYRUVIC ACID
**As the bonds in glucose are broken and rearrange, energy
is release.
ATP PRODUCTION:
1. Glycolysis takes a little energy
to get started. 2 ATP molecules
are used up.
2. Glycolysis produces 4 ATP.
3. This gives the cell a net gain
of
2 ATP for each molecule of
glucose.
NADH PRODUCTION:
1. Glycolysis removes 4 electrons
from the molecule.
2. The electrons are passed to
NAD+ (electron carrier)
3. NAD+ can carry a pair of
electrons. 2 NAD+ are
required to carrier the 4
electrons to the electron
transport chain (3rd stage)
where the electrons are used
Summary of Glycolysis
-4 ATP molecules are made from 4 ADP molecules.
-There is a net gain of 2 ATP since 2 ATP are used to start
glycolysis.
-2 ATP is not a lot BUT glycolysis happens very fast so a cell can
produce thousands of ATP in a few milliseconds.
-It does not require oxygen (anaerobic).
-Pyruvic acid moves to the Krebs Cycle (2nd Stage).
-NADH moves to the Electron Transport Chain (3rd Stage).
THE KREBS CYCLE (Citric Acid Cycle)
The Krebs Cycle is the second stage of cellular respiration which
operates only when oxygen is available. The Krebs cycle is a series of
energy-extracting reactions.
Summary of The Krebs Cycle:
1. Pyruvic acid produced by glycolysis enters mitochondria. In the
innermost compartment of a mitochondrion, or the matrix, pyruvic acid
molecules are broken down into carbon dioxide and acetyl-CoA
molecules.
2. Acetyl-CoA combines with a 4-carbon compound, producing a 6carbon molecule—citric acid. Energy released by the breaking and
rearranging of carbon bonds is captured in ATP, NADH, and FADH2.
3. The Krebs cycle produces four types of products:
-high-energy electron carriers (NADH and FADH2)
-carbon dioxide
-2 ATP molecules (per glucose molecule)
-the 4-carbon molecule needed to start the cycle again