Question

Imagine that you have a large and sudden craving for Krispy Kreme doughnuts, so you purchase a box filled with 10 colorful doughnuts and while you are binge watching your favorite show, you managed to eat all 10 of the doughnuts. Now that have you ingested large amounts of sucrose, the glucose and fructose that exceed caloric requirements are transformed to fatty acids for triacylglycerol synthesis. This fatty acid synthesis consumes acetyl-CoA, ATP, and NADPH. How are these substances produced from glucose?

Answer 1

Acetyl CoA, ATP and NADH are produced from glucose during aerobic cellular respiration.

Cellular respiration is the breakdown of glucose into carbon dioxide and water for the generation of ATP and takes place in the presence of oxygen. It occurs in the mitochondria of eukaryotes.

Cellular respiration is divided into the following steps -

In the first step, glycolysis, one molecule of glucose is broken down into two molecules of pyruvic acid along with the formation of ATP and NADH. It occurs in the cytoplasm. It is a common step for aerobic and anaerobic respiration.

In the second step, pyruvic acid is oxidized into acetyl coenzyme a along with the release of carbon dioxide with the help of enzyme pyruvate dehydrogenase. This is called as pyruvate oxidation or pyruvate decarboxylase action and occurs in mitochondrial matrix along with the release of NADH.

In the third step, acetyl coenzyme a enters citric acid cycle where it is completely oxidized into carbon dioxide along with the formation of GTP, NADH and FADH₂. This process occurs in mitochondrial matrix.

In the fourth step, electron transport chain, all the high energy electron carriers, NADH and FADH₂, produced in above steps are oxidized and the electron enters electron transport chain. In this process of electron is transported from one electron carrier to the other all of which are arranged in increasing order of their electrode potential. Ultimately the electron is accepted by oxygen which gets reduced to form water. This step occurs in inner mitochondrial membrane.

When electrons are transferred from one electron carrier to the other, protons and also pumped from mitochondrial Matrix to intermembrane space. This results in the generation of proton gradient across inner mitochondrial membrane. The electrochemical energy stored in Proton gradient is utilised by ATP synthase enzyme for the formation of ATP and this is the last process of cellular respiration and is called as oxidative phosphorylation.

glycolysis 1 glucose step 772 pjuric acid + 2 NADH + 2ATP NADH transporter outer mitochondrial membrane cytosol pyruvate transporter step 4 to 1 intermembrane space step 5 electron oxidative transport phosphorylation/ system/chain chemiosmosis H+ H+ H+ 'H+ J. ATP synthase & pyunic acid ADP H*H* ATP inner mitochondrial membrane It pyruvate dexarboxylation/ step 2 preparatory step (2 rounds) to 1 d acetyl.com +, + &'NADH to 1 step 3 Kreb's cycle (2 rounds) + 3 NADH X2-6 →2 CO₂ X 2 =4 I FASH, X2-24 toll IGTP X2=2 mitochondrial matrix OVERVIEW OF AEROBIC CELLULAR RESPIRATION

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