Why cellular respiration occurs

Acetyl CoA enters into the matrix of mitochondria, where it is fully oxidized into Carbon Dioxide via the Krebs cycle. Finally, During the process of oxidative phosphorylation, the electrons extracted from food move down the electron transport chain in the inner membrane of the mitochondrion.

As the electrons move down the ETC and finally to oxygen, they lose energy. Glycolysis The first stage of cellular respiration is glycolysis. Results of Glycolysis Energy is needed at the start of glycolysis to split the glucose molecule into two pyruvate molecules. Transformation of Pyruvate into Acetyl-CoA In eukaryotic cells, the pyruvate molecules produced at the end of glycolysis are transported into mitochondria, which are sites of cellular respiration. Citric Acid Cycle Before you read about the last two stages of cellular respiration, you need to review the structure of the mitochondrion, where these two stages take place.

The space inside the inner membrane is full of fluid, enzymes, ribosomes, and mitochondrial DNA. This space is called a matrix. The inner membrane has a larger surface area as compared to the outer membrane. Therefore, it creases. The extensions of the creases are called cristae. The space between the outer and inner membrane is called intermembrane space. Through a series of steps, citrate is oxidized, releasing two carbon dioxide molecules for each acetyl group fed into the cycle.

Because the final product of the citric acid cycle is also the first reactant, the cycle runs continuously in the presence of sufficient reactants. Results of the Citric Acid Cycle After the second turn through the Citric Acid Cycle, the original glucose molecule has been broken down completely.

Oxidative phosphorylation Oxidative phosphorylation is the final stage of aerobic cellular respiration. Chemiosmosis The pumping of hydrogen ions across the inner membrane creates a greater concentration of these ions in the intermembrane space than in the matrix — producing an electrochemical gradient. How Much ATP? Review What is the purpose of cellular respiration?

Provide a concise summary of the process. State what happens during glycolysis. Describe the structure of a mitochondrion. Outline the steps of the Krebs cycle.

What happens during the electron transport stage of cellular respiration? How many molecules of ATP can be produced from one molecule of glucose during all three stages of cellular respiration combined? Do plants undergo cellular respiration? Why or why not? Explain why the process of cellular respiration described in this section is considered aerobic.

Name three energy-carrying molecules involved in cellular respiration. True or False. ATP synthase acts as both an enzyme and a channel protein. The carbons from glucose end up in ATP molecules at the end of cellular respiration. The Amoeba Sisters. Cellular Respiration and the Mighty Mitochondria. Glucose also called dextrose is a simple sugar with the molecular formula C6H12O6.

Glucose is the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight.

A set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate ATP. A complex organic chemical that provides energy to drive many processes in living cells, e. Found in all forms of life, ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer.

An organism that produces complex organic compounds such as carbohydrates, fats, and proteins from simple substances present in its surroundings, generally using energy from light photosynthesis or inorganic chemical reactions chemosynthesis. An organism that cannot produce its own food, relying instead on the intake of nutrition from other sources of organic carbon, mainly plant or animal matter.

In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers. Glycolysis is a sequence of ten enzyme-catalyzed reactions. The aqueous component of the cytoplasm of a cell, within which various organelles and particles are suspended. The jellylike material that makes up much of a cell inside the cell membrane, and, in eukaryotic cells, surrounds the nucleus. The organelles of eukaryotic cells, such as mitochondria, the endoplasmic reticulum, and in green plants chloroplasts, are contained in the cytoplasm.

A double-membrane-bound organelle found in most eukaryotic organisms. Mitochondria convert oxygen and nutrients into adenosine triphosphate ATP. ATP is the chemical energy "currency" of the cell that powers the cell's metabolic activities. The space occurring between two or more membranes. In cell biology, it's most commonly described as the region between the inner membrane and the outer membrane of a mitochondrion or a chloroplast.

In the mitochondrion, the matrix is the space within the inner membrane. The word "matrix" stems from the fact that this space is viscous, compared to the relatively aqueous cytoplasm. A series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

A specific type of exothermic reaction which not only releases energy, but also occurs spontaneously. In the process, protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water. A gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and the electrical gradient, or difference in charge across a membrane.

The process of producing cellular energy involving oxygen. Cells break down food in the mitochondria in a long, multi-step process that produces roughly 36 ATP. The first step in is glycolysis, the second is the Krebs cycle and the third is the electron transport system. Cellular respiration is the aerobic process by which living cells break down glucose molecules, release energy, and form molecules of ATP.

Generally speaking, this three-stage process involves glucose and oxygen reacting to form carbon dioxide and water. Anaerobic respiration occurs in the absence of oxygen. It releases a much smaller amount of energy than aerobic respiration. Anaerobic respiration does not release enough energy to power human cells for long — think about how long a person can live if they are not able to breathe. Anaerobic respiration occurs in muscle cells during hard exercise after the oxygen has been used up.

It also occurs in yeast when brewing beer. Many prokaryotes perform anaerobic respiration. There are several different types of anaerobic respiration, which will be discussed in more detail later. What are the 4 stages of cellular respiration? There are 4 stages of the cellular respiration process. These are Glycolysis, the transition reaction, the Krebs cycle also known as the citric acid cycle , and the electron transport chain with chemiosmosis.

Glycolysis is a series of reactions that extract energy from glucose by splitting it into 2 molecules of pyruvate. Glycolysis is a biochemical pathway that evolved long ago and is found in the majority of organisms.

In organisms that perform cellular respiration, glycolysis is the first stage of the process. Before glycolysis begins, glucose must be transported into the cell and phosphorylated. In most organisms, this occurs in the cytosol. Glycolysis does refer to other pathways, one such pathway described is the Entner—Doudoroff pathway. This article concentrates on the EMP pathway. Glycolysis takes place in 10 steps. See figure 7. The enzyme hexokinase phosphorylates glucose using ATP to transfer a phosphate to the glucose molecule to form glucosephosphate.

This reaction traps the glucose within the cell. Glucosephosphate is isomerized into fructosephosphate. This involves the change of an aldose into a ketose. The enzyme phosphoglucose isomerase catalyzes this reaction. A molecule of ATP provides the phosphate group. Phosphofructokinase PFK with magnesium as a cofactor phosphorylates glucosekinase to fructose 1,6-bisphosphate.

This enzyme catalyzes the transfer of a phosphoryl group from ATP to fructosephosphate. This reaction yields ADP and fructose 1, 6-bisphosphate. PFK is a significant enzyme in the regulation of glycolysis. Citric acid is also known to inhibit the action of PFK. These first 3 stages of glycolysis have used up a total of 2 ATP molecules; hence it is known as the investment phase. The enzyme aldolase is utilized to split fructose 1, 6-bisphosphate into glyceraldehydephosphate GAP and dihydroxyacetone phosphate DHAP.

GAP is the only molecule that continues in the glycolytic pathway. At this point there are two molecules of GAP, the next steps are to fully convert to pyruvate. The phosphate group then attacks the GAP molecule and releases it from the enzyme to yield 1,3 bisphosphoglycerate, NADH, and a hydrogen atom.

Phosphoglycerate kinase PGK with the help of magnesium converts 1,3 bisphosphoglycerate to 3-phosphoglycerate by removing a phosphate group. Phosphoglycerate mutase rearranges the position of the phosphate group on 3-phosphoglycerate allowing it to become 2-phosphoglycerate. Enolase dehydrates 2 phosphoglycerate molecules by removing water. In aerobic respiration, the transition reaction occurs in the mitochondria. Pyruvate moves out of the cytoplasm and into the mitochondrial matrix.

In anaerobic conditions, pyruvate will stay in the cytoplasm and be used in lactic acid fermentation instead. The Krebs cycle, or also known as the citric acid cycle was discovered by Hans Adolf Krebs in It can be described as a metabolic pathway that generates energy.

This process happens in the mitochondrial matrix, where pyruvate has been imported following glycolysis. These products are generated per single molecule of pyruvate.

The products of the Krebs cycle power the electron transport chain and oxidative phosphorylation. Acetyl CoA enters the Krebs cycle after the transition reaction has taken place conversion of pyruvate to acetyl CoA. See figure 9. There are 8 steps in the Krebs cycle. Below reviews some of the principal parts of these steps and the products of Krebs cycle:.

Acetyl CoA joins with oxaloacetate releasing the CoA group and producing citrate, a six-carbon molecule. The enzyme involved in this process is citrate synthase. Citrate is converted to isocitrate by the enzyme aconitase. This involves the removal then the addition of water. The ketone is then decarboxylated i. CO 2 removed by isocitrate dehydrogenase leaving behind alpha-ketoglutarate which is a 5-carbon molecule.

Isocitrate dehydrogenase, is central in regulating the speed of the Krebs cycle citric acid cycle. Oxidative decarboxylation takes place by alpha-ketoglutarate dehydrogenase. Succinyl-CoA is converted to succinyl phosphate, and then succinate. Succinate thiokinase other names include succinate synthase and Succinyl coenzyme A synthetase , converts succinyl-CoA to succinate, and free coenzyme A. Firstly, the coenzyme A at the succinyl group is substituted by a hydrogen phosphate ion.

Succinyl phosphate then transfers its phosphoric acid residue to guanosine diphosphate GDP so that GTP and succinate are produced. Succinate is oxidized to fumarate by succinate dehydrogenase. Flavin adenine dinucleotide FAD is the coenzyme bound to succinate dehydrogenase.

FADH 2 is formed by the removal of 2 hydrogen atoms from succinate. This releases energy that is sufficient to reduce FAD. FADH remains bound to succinate dehydrogenase and transfers electrons directly to the electron transport chain. Succinate dehydrogenase performs this process inside the mitochondrial inner membrane which allows this direct transfer of the electrons. L-malate is formed by the hydration of fumarate.