Question

This week we covered the details of Cellular Respiration. Your assignment this week is in two parts. Using Excel (or some other Table creating program) create a table that describes the four sub-steps of cellular respiration. Insert the table into a Word document and provide a discussion of how each sub part contributes to overall process of cellular respiration.

Answer 1

The four stages of cellular respiration
Stages	Name	Location	Substrate	End product
Stage-1	Glycolysis	Cytosol	Glucose	Pyruvate
Stage-2	Pyruvate oxidation (Transition reaction)	Cytosol	Pyruvate	Acetyl COA
Stage-3	Kreb's Cycle	Mitochondria	Acetyl COA	NADH, FADH2
Stage-4	Electron Transport Chain	Inner mitochondrial membrane	NADH, FADH2	ATP

Every organism requires energy for the sustaining of their life. The energy generated in the organism through the process of respiration (conversion of stored energy in food into chemical energy). In normal circumstances, the cells utilise glucose as an energy source. The glucose molecule breaks through cellular respiration and releases energy for cellular functions. The cellular respiration divided into four parts/stages.

Stage-1: Glycolysis: This is the cell cytoplasmic process in the absence of oxygen. In this process, overall combinations of ten reactions of reversible and irreversible are involved to convert one glucose (a 6 carbon) molecule into two molecules of pyruvate (3 carbons). In this process, 2molecules of ATPs are utilised and 4 molecules of ATPs are generated. So the net gain of 2ATPs from each cycle of glycolysis

Stage-2: Pyruvate oxidation (Transition reaction): The fate of generated pyruvate in glycolysis depends on the availability/unavailability of oxygen to the cells. In the presence of oxygen, the generated pyruvate goes through Kreb’s cycle to generate reducing equivalent needed for the generation of energy. For that pyruvate (3 carbon compound) is converted into Acetyl CoA (2 Carbon compound) in presence of oxygen and an intermediate of two molecules each of CO2 and NADH released from one molecule of glucose. The reaction takes place in the cytosol of the cells.

Stage-3: Kreb's Cycle: Series of enzyme catalysed reaction takes place in the mitochondrial matrix and generate 1ATP, 3NADH and 1 FADH2 from each turn (from one acetyl COA). From 1 molecule of glucose 2 molecules of pyruvate then 2 molecules of acetyl CoA are generated, so two cycles of Kreb's cycle run for one molecule of glucose and generate 2ATP, 6NADH and 2 FADH2.

Stage-4: Electron Transport Chain: Takes place in the inner mitochondrial membrane. The generated reducing equivalents (NADH and FADH2) from Kreb's cycle used to generate energy in the form of ATP, which is utilised by cells for their physiological functions.

From one molecule of glucose 36 molecules of ATPs are generated.