Cellular Respiration - Definition, Steps, Types Objectives

Cells break down carbohydrates into a form that may be used by the cell as energy through a process known as cellular respiration. All forms of life experience this. Food is converted into ATP through cellular respiration, a molecule that the cell uses as fuel. Aerobic respiration is the term for this process, which typically involves oxygen. The three main stages of mitochondrial respiration are glycolysis, the citric acid cycle, and oxidative phosphorylation.

Cells Size Shape Count

centrioles

Cellular Respiration

Cell Division

Cellular Respiration Types

Aerobic respiration

• Cellular respiration occurs in eukaryotic species' mitochondria, which are organelles built to break down carbohydrates and create ATP effectively. Because they can generate so much ATP, mitochondria are sometimes called "the powerhouse of the cell."
• Because oxygen is the most potent electron acceptor found in nature, aerobic respiration is extremely effective. Oxygen "loves" electrons, and this love "pulls" the electrons through the mitochondria's electron transport chain.
• The mitochondria's unique architecture, which assembles all the components required for cellular respiration in a condensed, membrane-bound region within the cell, also plays a role in the high efficiency of aerobic respiration.
• Most eukaryotic cells may also engage in several forms of anaerobic respiration, including lactic acid fermentation, without oxygen. However, the amount of ATP produced by these activities is insufficient to support the cell's vital operations, and without oxygen, cells would eventually perish or stop working.

Cell Organization

Fermentation

• In the absence of oxygen, several distinct kinds of anaerobic respiration—including those carried out by certain eukaryotic cells, bacteria, and archaebacteria—are called fermentation.
• These processes can employ different electron acceptors and generate different byproducts. Several fermentation processes include:
• Alcoholic fermentation: Sugar is broken down by yeast cells and a few other types of cells, yielding alcohol and carbon dioxide as byproducts. Beers are carbonated because the yeasts emit ethyl alcohol and carbon dioxide gas during fermentation, which causes bubbles to develop.
• Human muscle cells and some bacteria carry out lactic acid fermentation, a type of fermentation carried out without oxygen. Humans employ lactic acid fermentation to produce yoghurt. Unharmful bacteria are cultured in milk to create yoghurt. These bacteria generate lactic acid, which interacts with milk proteins to give yoghurt its peculiar sharp-sour flavour and thick, creamy texture.
• Swiss cheese is produced by the fermentation of propionic acid, carried out by certain microorganisms. Swiss cheese is known for its particularly strong, nutty flavour caused by propionic acid.
• The holes in the cheese result from these microorganisms producing gas bubbles.
• Acetogenesis is fermentation by bacteria that produce acetic acid as a byproduct. Acetic acid is the distinguishing component in vinegar that gives it its characteristic flavour and odour. It's interesting to note that the bacteria responsible for acetic acid production run on ethyl alcohol. This implies that to make vinegar, a sugar-containing solution must first undergo yeast fermentation to generate alcohol, followed by bacterial fermentation to convert the alcohol to acetic acid.

Aerobic and Anaerobic Respiration

Methanogenesis

• Archaebacteria are the only organisms capable of methanogenesis, a special form of anaerobic respiration. Carbon dioxide and methane are produced during methanogenesis, which uses carbohydrates as a fuel source.
• The digestive systems of several animals, including cows and even humans, contain symbiotic bacteria that produce methane. Some of these bacteria can break down cellulose, a sugar that exists in plants but cannot be broken down by cellular respiration. Thanks to symbiotic bacteria, these indigestible carbohydrates may now be used as fuel by cows and other animals.

Cell Wall and Cell Membrane

Cellular Respiration Steps

• The First Step of Cellular Respiration
• The sole phase that is common to all forms of respiration is glycolysis. Two molecules of ATP are produced when a sugar molecule, such as glucose, is divided in half during glycolysis.
• The glycolysis equation is as follows C 6 H 12 O 6 (glucose) + 2 NAD+ 2ADP + 2 Pi → 2 C H 3 COCO O - + 2 NADH + 2 ATP + 2 H 2 O + 2 H +
• The word "glycolysis" is a combination of the Greek words "glyco" (sugar) and "lysis" (to divide). This may aid in retaining the memory that glycolysis involves breaking sugar.
• Glycolysis typically begins with glucose, which is subsequently divided into two molecules of pyruvic acid. Following additional processing, these two pyruvic acid molecules are transformed into other byproducts, such as lactic acid or ethyl alcohol.
• The second step of the procedure is reduction. To "reduce" a molecule in chemical terms is to add electrons.
• Lactic acid and NAD+ are the byproducts of lactic acid fermentation, which occurs when NADH contributes an electron to pyruvic acid. Because glycolysis requires NA D + , this is advantageous to the cell.
• Pyruvic acid passes through an extra process during alcoholic fermentation, losing one carbon atom in the form of C O 2 . Acetaldehyde, the resultant intermediate molecule, is oxidised to provide NA D + and ethyl alcohol.
• These procedures are elevated to a new level by aerobic respiration. Aerobic respiration uses oxygen as the last electron receptor rather than directly reducing Krebs cycle intermediates.
• However, the electron transport chain must first handle the electrons and protons bound to electron carriers (such as NADH). The mitochondrial membrane contains a chain of proteins that utilise the energy from these electrons to pump protons to one side of the membrane.
• As a result, an electromotive force is generated, which is then used by the protein complex ATP synthase to phosphorylate many ATD molecules and produce ATP.

Cellular Respiration Products

ATP

• Adenosine triphosphate is the primary byproduct of all cellular respiration. (ATP). This molecule serves as a reservoir for the energy created during respiration, enabling the cell to distribute this energy throughout the cell. Numerous cellular components use ATP as a source of energy. For instance, an enzyme could require ATP energy to mix two molecules. ATP is frequently employed on proteins called transporters, which transfer chemicals across cell membranes.

Carbon Dioxide

Additional products

Objectives of Cellular Respiration

• Energy must be able to enter and exit all cells to fuel life-sustaining processes. Cells must be able to run vital machinery, such as pumps in their cell membranes that regulate the cell's internal environment in a condition conducive to life, to continue to exist.
• Cells most frequently use ATP, a molecule with much energy stored in its phosphate bonds, as their "energy currency." These bonds can be broken to release that energy and affect other molecules, such as those required for cell membrane pumps, in a way that modifies them.
• ATP is not employed for long-term energy storage since it is unstable over extended periods. Instead, cells must continuously metabolise carbohydrates and fats to create fresh ATP since they are long-term storage forms. This is how respiration works.
• Each sugar molecule yields a significant quantity of ATP during aerobic respiration. A plant or animal cell that digests a sugar molecule produces 36 molecules of ATP. Comparatively, just 2-4 ATP molecules are typically produced during fermentation.
• Smaller quantities of ATP are produced by the anaerobic respiration methods utilised by bacteria and archaebacteria, but they may still occur without oxygen. We'll go through several cellular respiration processes in more detail below.

Rate Determination in Cellular Respiration

• These enzymes catalyses the rate-limiting phases, the slowest reactions in the series.
• Phosphofructokinase-1, or PFK-1, is the enzyme that controls the pace of glycolysis by converting fructose-6-phosphate to fructose-1,6-bisphosphate. Fructose-2,6-bisphosphate, AMP, and citrate are used to promote and inhibit it.
• Pyruvate dehydrogenase, activated by elevated NA D + , ADP, or C a 2+ , is the sole enzyme involved in pyruvate oxidation.
• Isocitrate dehydrogenase, an enzyme that turns isocitrate into -ketoglutarate, controls the rate of the TCA cycle. ADP stimulates a particular process, which ATP and NADH hinder.

Causes of Water Scarcity

Conditions impacting Cellular Respiration?

• Several disorders can impact cellular respiration. Many of these disorders seriously impact people because cellular respiration is so important to biological processes.
• Pyruvate kinase insufficiency, erythrocyte hexokinase deficiency, and glucose phosphate isomerase deficiency are the conditions that have the greatest impact on glycolysis. These illnesses are often passed down through the autosomal recessive gene, and those who are homozygous (i.e., have two afflicted genes) for them experience hemolytic anaemia, jaundice, and splenomegaly.
• Deficiencies can hamper pyruvate oxidation in the enzyme pyruvate dehydrogenase. These can lead to lactic acidosis, characterised by a buildup of lactate and an increase in serum alanine because of an accumulation of pyruvate that ferments into lactic acid.
• The TCA cycle contains several enzymes, including succinyl-CoA synthase and fumarase, that can be harmed and cause illness. Many people who suffer from these illnesses are deaf and have dystonia, or uncontrollable muscular contractions, in their posture.
• Genetic conditions known as mitochondrial myopathies can interfere with oxidative phosphorylation or the generation of electron transport chain-related enzymes. These illnesses may involve muscular paralysis and are typically characterised by muscle weakness and exhaustion.
• Oxidative phosphorylation or the electron transport chain can be impacted by exposure to harmful substances or certain medications in excessive doses. Carbon monoxide and cyanide can block complexes in the electron transport chain directly. Other chemicals, such as oligomycin, may block ATP synthase or sever the link between the electron transport chain and ATP synthase.