Download Cellular Respiration: Glycolysis

Cellular Respiration:
Glycolysis
Ria, Robin, Clayton, Candace and Brittany
Glycolysis
● The first step to cellular respiration where
sugar is broken down
● First 10 reactions of cellular respiration
● 6-carbon sugar (glucose) is broken down
into two 3-carbon sugars (pyruvic acid)
● All these reactions occur in the cytoplasm
● Each step is catalysed by a specific enzyme
● Anaerobic respirations occur here which
doesn't require oxygen
● Only converts 2.1% of free energy available
in 1 mol glucose into ATP during glycolysis
alone
● Some energy is released as heat but most is
trapped in 2 pyruvate and 2 NADH
● Earliest form of energy metabolism
● All organisms carry out glycolysis as either
their only source of ATP or as the 1st part of
a more elaborate and productive energy
yielding process
General Equation
glucose + 2 ADP + Pi + 2 NAD -> 2 Pyruvate + 2 ATP + 2(NADH + H)
Energy yield
4 ATP produced
2 ATP used
2 ATP produced net (used immediately)
2 NADH produced (further used to obtain more ATP)
Investment
Energy is invested to be recouped later
-Phase 1 consists of steps 1-5
1)Glucose--->Glucose 6-phosphate: One ATP is transferred
into ADP.
2)Glucose 6-phosphate--->Fructose 6-phosphate
3)Fructose 6-phosphate--->Fructose 1, 6-bisphosphate:
Another ATP is needed to produce one ADP
4/5)Fructose 1, 6-phosphate--->dihydroxyacetone
phosphate (DHAP) + Glyceraldehyde 3-phosphate (G3P).
- DHAP is then converted to another G3p. This results in
the production on 2G3p.
1-5)Two moles of ATP are consumed for each mole of
glucose
Division
6-Carbon Sugar is broken into 2 3-Carbon Sugars
Phase 2 consists of the 6th step.
6)2 Glyceraldehyde 3-phosphate (G3P)--->2
bisphosphoglycerate (BPG)
-Two G3p are converted into two BPG
-During this, hydrogen atoms reduce NAD+ to NADH so
that NADH can continue into the krebs cycle and ETC to
produce more ATP.
-If the ETC stops then NADH is transferred to pyruvate.
This produces lactate acetylalcohol but less carbon dioxide.
-This step breaks the process of glycolysis into two separate
chains. In each chain the same reactions occur.
Return
Energy Generation
Phase 3 consists of steps 7-10
7) 1, 3-bisphosphoglycerate (BPG)--->3-phosphoglycerate (3PG)
-During this step, one ADP is converted to one ATP because of a
high energy phosphate group (Pi).
8)3-phosphoglycerate(3PG)--->2-phosphoglycerate(2PG)
9)2-phosphoglycerate(2PG)--->phosphoenolpyruvate(PEP)
-This occurs by removing the H2O molecule in 2PG
10)phosphoenolpyruvate(PEP)--->Pyruvate
-A high energy phosphate group on PEP phosphorylates ADP to
ATP
-Within the return phase of glycolysis 4 ATP are produced
-Additional ATP may be obtained with further processing of the
pyruvate and NADH during aerobic respiration in later stages
Anaerobic Respiration
● Anaerobics respiration follows the glycolysis
pathway
● Doesn't require Oxygen to produce ATP
● Produces less ATP/glucose molecule than
aerobic
● Inefficient in energy production when
compared to aerobic
● Produces CO2, Lactic Acid, and 2 ATP
Starting with glucose (six carbons) how many ATP are made using anaerobic
glycolysis?
Step
ATP (used-) (produced+)
1
-1
3
-1
5 - NADH to pyruvic acid to lactic acid. E.T.C. not used
0
6 used twice
1 x 2 = +2
9 used twice
1 x 2 = +2
NET
+2
More ATP can be produced by aerobic respiration which is the result of
further processing of the pyruvate and NADH in the later stages of cellular
respiration.
Discussion questions...
1. Where is ATP used/ produced in glycolysis and how
much?
2. Where does glycolysis happen?
3. What are the three main stages of glycolysis? And what
happens in each?
4. How does each type of respiration relate to glycolysis?