Question

Metabolism Overview Worksheet Protein Carbohydrates Lipids Using the diagram on the next page as a guide, explain in your own words the three major processes. You do not need to explain each step in detail but provide a summary of the starting substrate (be specific for each macronutrient in glycolysis), the purpose, the mechanisms, and the end products. Use your book as a reference. 1) Glycolysis: 2) TCA Cycle: 3) Electron Transport Chain: Electron Transport Chain # 3 osplay Setting: -

Answer 1

1.Glycolysis

The cellular degradation of simple sugar glucose to yield pyruvic acid, and ATP as energy source is called Glycolysis.

The starting substrate: glucose ( 6 cabon sugar)

The end product: Pyruvate ( 3 carbon sugar)

Purpose: Purpose of Glycolysis is ' Splitting sugars " to release energy.

Mechanism: Glycolysis  is the first stage of cellular respiration and is the process of breaking down of glucose, consist of 10 steps.

I. Glucose become Glucose 6 phosphate ( G6P) through the addition of a phosphate group and consumption of one ATP.

II. G6P converts into Fructose phosphate through isomerisation wit the help of enzyme phosphoglucomutase.

III. F6P converts into Fructose 1,6 biphosphate with the help of phospho fructokinase and one ATP molecule.

IV. Fructose 1,6 biphosphate split into ketone znd Aldehyde molecule by the help of enzyme aldolase.

V. Ketone molecule ( dihydroxy acetone phosphate), DHAP converts into GAP, glyceradehyde 3 phosphate with the help of enzyme triose phosphate isomerase.

Vi. GAP converts into 1,3 bisphospho glycerate ( BPG) through oxydation. In this step NAD + ( Nicotinamide adenine dinucleotide) become NADH+H , through the addition of hydrogen molecule from GAP .

VII. 1, 3 bi phospoglycerate becomes 3 phospho glycerate ( 3 PGA) . This reaction releases 2 ATP molecule.( enzyme: phospho glycerokinase).

VIII. 3 phospho glycerate forms into 2 PGA ( enzyme: phosphoglyceromutase)

IX. Phosphoenol Pyruvate ( PEP) from 3 PGA with the help of enzyme enolase

X. PEP converts into Pyruvate and 2 ATP molecules, with the help of enzyme pyruvate kinase.

Total energy yield : 2 ATP.( 4 ATP generate from Glycolysis, but 2 ATP are used).

2. TCA cycle

TCA cycle ( Trcarboxylic acid cycle)is also called as Citric acid cycle or Kerb's cycle. It is the second stage in cellular respiration . It happens in mitochondria, an intracellular organell. In TCA cycle acetyl coenyme A ( acetyl CoA) , the substrate, is converted into energy and Carbon dioxide dioxide( end products). The Purpose of TCA cycle is to produce energy from Acetyl CoA( that derived from Carbohydrates, fats and protien) , in the presence of Oxygen, through series of chemical reactions .

Mechanism: TCA cycle consist of 8 steps. Each step is catalyzed by the presence of enzymes.

I. Acetyi CoA reacts with Oxaloacetate produce Citrate and releases CoA - SH ( Co enzymeA).

II. Citrate converts into Isocitrate ( rearrangement)

III. Through oxidation isocitrate becomes Alpha- ketoglutarate , releases Carbon dioxide.

IV. Alpha ketoglutarate becomes oxidized into Succinyl CoA by lossing a molecule of Carbon dioxide.

V. Succinyl CoA converts into Succinate and one molecule of ATP is produced.

( Usually in TCA cycle ATP produce from NAD , Nicotinamide adenine dinucletide).

VI. Succinate becomes fumarate through oxidation.

VII. Through Hydration fumarate converts into malate

VIII. Through oxidation Malate converts into oxaloacetic acid.  

In TCA cycle, there generates 2FADH2 , 6NADH and 2ATP. Totally 24 ATP produced from this cycle.

3. Electron Transport Chain

It is the third stage of cellular respiration. In Electron Transport Chain, through oxidative phosphorylation ATP molecules are released.

Energy from FADH2 and NADH is transferred to ATP molecules in Electron Transport chain. It consists of a chain or series of electron carriers. Electron carriers carries or transfer electrons from FADH2 and NADH to Oxygen. This process happens in mitochondrial membrane. Then protons are pumped from the matrix to mitochondrial intermembrane space, formation of water by the reduction of oxygen molecule also happens.

End products: ATP and water.