Cellular Respiration 1. Write the equation for cellular respiration. For each re

Question

Cellular Respiration 1. Write the equation for cellular respiration. For each reactant and product identify the stage of the process the molecule is either used or produced. Identify the cellular location where each process occurs Chart Area 2. Indicate whether high concentrations of the molecules listed below activate (), inhibit (V) or have no effect (-) on the activity of the indicated enzymes Liver glycogen phosphorylase Muscle glycogen phosphorylase epinephrine AMP glucagon glucagon glucose-6-phosphate NADH 3. Malonate is a competitive inhibitor of succinate dehydrogenase. If 0.01M sodium malonate is added to actively respiring mitochondria that are using pyruvate as a fuel source, respiration soon stops and a metabolic intermediate accumulates. Using the figure below a) identify the intermediate and explain why it accumulates; b) explain why oxygen consumption stops and c) aside from the removal of malonate, how can this inhibition of respiration be overcome? Acetyl-CoA Series "Exclosure Plots" Point" Value: 18.89 Citrate Oxaloacetate Isocitrate ADH Citric co acid cycle o-Ketoglutarate NAD Malate Fumarate NAD Succinyl-CoA FADH Succinate GTP ATP

Explanation / Answer

Q1) Living organisms, like plants, animals, and microorganisms, generate their own energy by a process called Cellular Respiration. cellular respiration is of two types 1) Aerobic ( In presence of oxygen), 2) Anaerobic (In absence of oxygen).During cellular respiration animals generate energy in the form of ATP for their basic functions.

In general cellular respiration is not a single process rather it is a set of metabolic reactions.

The equation of cellular respiration is C6H12O6 +6 O2-------> 6 H2O+ 6 CO2 + ATP Glucose + 6Oxygen-----> 6Water + 6Carbondioxide +ATP

Glucose and oxygen are the reactants of cellular respiration, and water , carbondioxide and ATP are the products of the cellular respiration.

Cellular respiration has four stages they are 1) Glycolysis, 2) Transition reactions 3) Kreb's cycle , 4) Electron transport system

Glycolysis:- This is the first metabolic pathway of cellular respiration, in glycolysis there is breakdown of one molecule of glucose (sugar) into two molecules of pyruvate.
It takes place in the cytosol.

The overall equation of glycolysis is -
C6H12O6+ 2 NAD+ + 2 ADP + 2 P 2 pyruvic acid, (CH3(C=O)COOH + 2 ATP + 2 NADH + 2 H+

In Glycolysis the glucose molecule is used , and ATP is produced.

2) The transition reaction- In this the pyruvate from glycolysis is oxidized to acetyl coA, one molecule of NADH (nicotinamide adenine dinucleotide), and one molecule of carbon dioxide produced

3) Kreb's cycle- In Kreb's cycle or Tricarboxylic Acid (TCA) cycle, or the Citric Acid cycle , it has 8-steps and 18 different enzymes work in this. Krebs cycle, found in the matrix of the mitochondrion, it has a series of oxidation-reduction reactions which leads to the oxidation of the acetyl group produces two carbon dioxide molecules.

During one kreb's cycle it produces 3 NADH, 1 FADH2(flavin adenine dinucleotide), and a GTP (guanosine triphosphate).

so , from one glucose molecule ( 2 pyruvate molecules produced), they produce 6 NADH, 2 FADH2 and 2 ATP molecules .

The goal of the Krebs cycle is to produce high energy electrons from carbon sources. But this process do not generate huge amounts of ATP and does not use oxygen as a precursor molecule. it uses the electrons from acetyl coA to form NADH and FADH2.

Overall reaction of Kreb's cycle is

Acetyl CO-A + 3NAD+ + FAD +GDP+ H2O -----------> 2CO2 + 3NADH + FADH2 +GTP +H2O

The final pathway or stage of cellular respiration is the electron transport chain (ETC) and oxidative phosphorylation they both occur in the inner membrane of the mitochondrion.

ETC is a part of oxidative phosphorylation it makes the chemiosmotic gradient (proton gradient) across the inner membrane of the mitochondrion by oxidizing the NADH from the Krebs cycle . And Oxidative phosphorylation, manages the pathway in which the electrons from the donors are transferred to the acceptors by redox reactions.

In ETC, the electrons are transferred from one complex to the other and the electrons reduce oxygen to produce water. These reactions produces the majority of ATP in cellular respiration. ETC produces water, NAD and FAD ( NAD and FAD are both recycled back to glycolysis and Krebs cycle), and up to 34 ATP per one molecule of glucose is produced. In aerobic cellular respiration from a single glucose molecule up to 38 ATP are produced.

oxygen is found at the end of the ETC (during aerobic respiration) , here they accepts electrons while picking up protons to produce water molecules.Due to this oxygen is called Final electron acceptor.

When there is a decrease in level of oxygen, the cell may undergo a process called fermentation and utilize an alternative pathway at the end of glycolysis. And instead of using oxidative phosphorylation, it uses a substrate level phosphorylation which does not require oxygen for the process.

In animal cells, this process is called the lactic acid fermentation. It is similar to aerobic respiration but here it produces lactic acid in the process.

C6H12O6 2 CH3CH(OH)COOH + 2 CO2+ 2 ATP

In microorganisms like yeast they produce ethanol and carbon dioxide. This process called as the ethanol or alcohol fermentation.

C6H12O6 2 C2H5OH + 2 CO2+ 2 ATP

In both type of fermentation process 2 ATPs procuced from a glucose molecule.

Anaerobic respiration:-
In this process Glycolysis and Kreb's cycle occurs but it is used by Bacteria and Archae where oxygen is not the final electron acceptor rather they use sulfates and nitrates .

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