which step in cellular respiration happens first?

Question

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Answer 1

If the question wanted to get any more specific than that, the absolute first step in cellular respiration is glucose being phosphorylated to Glucose-6-phosphate (the first step of glycolysis, catalyzed by hexokinase enzyme). It does this through the consumption of one ATP molecule, which donates that phosphate group to the glucose (and subsequently knocks out a hydrogen).

 

Overall Reaction

Glucose + ATP => Glucose-6-phosphate + ADP + H

 

Answer 2

Glycolysis - breakdown of glucose molecule to 2 pyruvates which will go into next step/cycle (citric acid cycle aka Krebs cycle).

Answer 3

I believe it is glycolysis that is the first step in cellular respiration.

 

• Complete oxidation of glucose via respiration = four step process used to convert chem energy in glucose to ATP.

• 1. Glycolysis: This is where one 6-carbon molecule of glucose is broken down into two molecules of the three-carbon pyruvate. During this, ATP is made from ADP, and NAD+ is reduced to NADH.
• 2. Pyruvate Processing: Processed to release one molecule of Co2, and the remaining tow carbons are sued to form the compound acetyl CoA. Oxidation of pyruvate = more reduction of NAD+
• 3. Citric Acid Cycle: Acetyl CoA is oxidized to two molecules of Co2, more ATP and NADH is produced, and here, FAD is reduced to FADH2.
• 4. Electron Transport and Oxidative Phosphorylation: Electrons from NADH and FADH2 move through a series of proteins called an electron transport chain (ETC). Energy released is used to create a proton gradient across a membrane; the ensuing flow of protons back across the membrane is used to make ATP. This mode of ATP production is called oxidative phosphorylation.