Cellular Respiration
Overview of Cellular Respiration
Cellular respiration: An ATP-generating process within cells.
Energy is extracted from energy-rich glucose to form ATP from ADP and inorganic phosphate (Pi).
Chemical equation:
Glucose can also be represented with general formulas:
or (for carbohydrates).
Aerobic vs Anaerobic Respiration
Aerobic respiration: Occurs in the presence of oxygen.
Components of aerobic respiration:
Glycolysis
Krebs cycle
Oxidative phosphorylation
These three processes make up cellular respiration
Glycolysis
Glycolysis: The breakdown (lysis) of glucose (glyco) into pyruvate (or pyruvic acid).
Produces nine intermediate products, each catalyzed by an enzyme.
Six steps utilize magnesium ions (Mg²⁺) as cofactors for enzyme activity.
Conversion process:
Glucose (6 carbs) splits into 2 pyruvate (3 carbs each).
Steps of Glycolysis
Energy investment phase:
2 ATP are added to change glucose for ensuing steps.
Formation of NADH:
2 NADH produced:
NADH forms when NAD⁺ combines with 2 energy-rich electrons and H⁺ from an intermediate in glucose breakdown.
ATP production:
4 ATP produced.
End products of glycolysis:
2 pyruvate formed.
Summary of glycolysis:
1 glucose → 2 pyruvate + 2 NADH + 2 net ATP
(4 produced but 2 used)
Occurs in the cytosol (cytoplasm).
Detailed Enzymatic Pathways in Glycolysis
Key enzymes and intermediates:
Hexokinase, Phosphoglucose isomerase, Phosphofructokinase, Aldolase, etc. mentioned with transition between intermediate molecules from glucose to pyruvate.
Overall structure and energy changes in the pathway detailed in schematic representation.
The Krebs Cycle
The Krebs cycle also called citric acid cycle or tricarboxylic acid (TCA) cycle.
Pyruvate to Acetyl CoA:
Pyruvate combines with coenzyme A (CoA) to produce acetyl CoA; producing 1 NADH and 1 CO₂ as well.
Cycle runs twice per glucose (producing 2 pyruvate).
Steps of the Krebs Cycle
Acetyl CoA combines with oxaloacetate (OAA) to form citrate.
Produces 3 NADH, 1 FADH₂, 1 ATP, and releases CO₂.
The CO₂ produced is exhaled by animals.
Oxidative Phosphorylation
Definition: The process where ATP is extracted from NADH and FADH₂.
Mechanism:
Electrons from NADH and FADH₂ move through an electron transport chain (ETC) of proteins.
Energy released from electron transfer phosphorylates ADP to form ATP.
NADH generates approximately 3 ATP, while FADH₂ generates around 2 ATP.
Final electron acceptor:
Oxygen (O₂) forms water with electrons and H⁺ ions.
Utility:
Cytochrome c serves as a common comparison point among species for genetic relatedness.
Theoretical ATP Yield from Glucose
Calculation of ATP from glycolysis and Krebs cycle:
Glycolysis provides:
2 NADH, 2 ATP, and 2 pyruvate
Pyruvate conversion to Acetyl CoA yields:
2 NADH.
Krebs cycle yields:
6 NADH, 2 FADH₂, and 2 ATP.
In total, initial calculations suggest 38 ATP possible from 1 glucose, adjusted to 36 due to the reduction in cytoplasmic NADH yield and mitochondrial transport costs.
Practical yields hover around 30 ATP due to mitochondrial efficiency and competition.
Mitochondrial Structure
Major processes of aerobic respiration occur within the mitochondria.
Structures of mitochondria:
Outer membrane: Phospholipid bilayer.
Intermembrane space: Area between membranes where H⁺ ions accumulate.
Inner membrane: Convoluted with cristae where oxidative phosphorylation occurs; contains the electron transport chain.
Matrix: Contains enzymes, DNA, and ribosomes, where the Krebs cycle takes place.
Chemiosmosis Mechanism
Chemiosmosis: ATP generation occurs by establishing a proton concentration gradient across the mitochondrial membrane.
Process description:
NADH and FADH₂ produced by the Krebs cycle enter the ETC.
Electrons from these molecules are used to transport H⁺ ions to create gradients.
Gradient leads to potential energy akin to water stored behind a dam.
ATP synthase allows H⁺ ions to flow back into the matrix, utilizing energy for ATP generation, analogous to dam turbines.
Types of Phosphorylation
Substrate-level phosphorylation: Direct transfer of a phosphate to ADP from a substrate yielding ATP.
Occurs during glycolysis.
Oxidative phosphorylation: Indirect transfer where the energy of electron flow powers ATP production.
Anaerobic Respiration
Definition: Occurs without oxygen, leading to no electron acceptor at the end of the ETC, resulting in NADH accumulation.
Glycolysis and Krebs cycle cease due to lack of NAD⁺ leading to ATP depletion and cell death.
Pathways of Anaerobic Respiration (To avoid cell death)
Two common processes:
Alcohol fermentation:
Converts pyruvate to acetaldehyde then to ethanol, with NADH converting back to NAD⁺.
Source of carbonation in drinks: The carbon dioxide produced during this process is what gives alcoholic beverages their fizz.
Lactic acid fermentation:
Converts pyruvate to lactate, regenerating NAD⁺ for glycolysis. In mammals, lactate can be transported to the liver for glucose conversion when ATP is scarce.
Detailed Process of Alcohol Fermentation
Steps:
Pyruvate is decarboxylated to acetaldehyde and CO₂.
Acetaldehyde is converted to ethanol, with NADH being oxidized back to NAD⁺.
Purpose:
To regenerate NAD⁺, ensuring glycolysis continues despite lack of oxygen.
Gain of 2 ATP from glycolysis per glucose.
Detailed Process of Lactic Acid Fermentation
Involves:
A single step where pyruvate converts to lactate with NADH converting to NAD⁺.
Lactate can be further processed in the liver, contributing to glucose synthesis when ATP levels allow.
The reactants of photosynthesis are the products of cellular respiration, and the products of photosynthesis are the reactants of cellular respiration.
Of ADP, AMP, and ATP, ATP has the most stored energy.
The organelle that makes ATP is the mitochondria.
Lowering the temperature would lower the rate of respiration.
ATP is called an "energy currency" because it is used by cells as a direct source of energy for biochemical reactions.
Energy is released from ATP when a phosphate group is hydrolyzed, converting ATP to ADP and Pi.
ATP stands for Adenosine Triphosphate.
ATP is made from ADP by adding a phosphate group.
In respiration, energy is transformed, not created.
If an organism stopped producing ATP, it would eventually die due to lack of energy for essential processes.
Organisms need to store energy to maintain metabolic functions and support growth and development.
Plants exchange gases through stomata, while animals exchange gases through lungs or skin.
Respiration is different from photosynthesis as respiration releases energy by breaking down glucose, whereas photosynthesis stores energy by building glucose.
The equation for respiration is: .
Photosynthesis and respiration are related as they are opposite processes; photosynthesis captures energy, while respiration releases it.
Energy is stored in the phosphate bonds of ATP.
Cellular respiration is the process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water.
Products of anaerobic respiration include lactic acid or ethanol and carbon dioxide, depending on the organism.
The purpose of anaerobic respiration is to generate energy when oxygen is unavailable.
Glycolysis takes place in the cytosol (cytoplasm).
The step in respiration that produces the most ATP is oxidative phosphorylation.
Two substances carried by our bloodstream to cells to begin the process of respiration are oxygen and glucose.
Muscle fatigue is caused by the accumulation of lactic acid and depletion of energy stores in muscle cells.
Aerobic and anaerobic respiration are related as both processes produce ATP; however, aerobic respiration requires oxygen, while anaerobic respiration does not.
The value of the alcohol fermentation pathway is that it allows for energy production in the absence of oxygen, enabling certain organisms to survive and generate ATP.
The purpose of oxygen in aerobic respiration is to act as the final electron acceptor in the electron transport chain, allowing for the efficient production of ATP.
The processes that produce ATP are glycolysis, the Krebs cycle, and oxidative phosphorylation.
After strenuous exercise, a muscle cell would contain increased amounts of lactic acid due to anaerobic respiration.
Processes that release CO₂ include the Krebs cycle and alcohol fermentation.
The summary statement describes the results of the reaction: Glucose (C6H12O6) is broken down with oxygen (O2) to produce carbon dioxide (CO2), water (H2O), and energy (ATP).
A covalent bond between two atoms represents potential energy.
The chief energy currency of all cells is a molecule called ATP (Adenosine Triphosphate).
Life's ultimate source of energy is derived from the sun, through the process of photosynthesis in plants.
The chemistry of living systems representing all chemical reactions is called metabolism.
Before entering the Krebs cycle, pyruvate is converted to acetyl CoA.
The electrons carried by NADH and FADH2 are transferred to the electron transport chain, where they help generate ATP.
When an atom or molecule gains one or more electrons, it is said to be reduced.
Under anaerobic conditions in animals, the end product of glycolysis is converted to lactic acid.
Enzymes catalyize chemical reactions by loweing the activation energy required, thus facilitating the conversion of substrates into products more efficiently.
most enzymes are highly specific, meaning they only catalyze particular reactions involving specific substrates, which is crucial for maintaining metabolic pathways and cellular processes.
a hydrogen ion consists of a single proton and no neutrons, which contributes to its positive charge and plays a significant role in various biochemical processes, including enzymatic reactions and the generation of ATP during cellular respiration.
blood sugar refers to what molecule circulating in blood glucose, which serves as a primary energy source for cells and is crucial in regulating metabolic processes.
the kerbs cycle occurs where within the cell , specifically in the mitochondrial matrix, where it plays a key role in further breaking down acetyl-CoA to produce energy-rich compounds.
the proccessis is required for the complete oxidiation of glucose is the combination of glycolysis, the Krebs cycle, and oxidative phosphorylation, collectively ensuring that glucose is fully converted to carbon dioxide and water, releasing energy in the form of ATP.
in glycolysis, glucose is coverted into pyruvate through a series of enzyme-catalyzed reactions, generating a small amount of ATP and NADH in the process.
in eucaryotes, the glycolytic reactions (glycolysis) takes place in the cytoplasm, allowing for the initial breakdown of glucose before the products enter the mitochondria for further processing in the Krebs cycle.
as energy is being reconverted throughmany firms it is continusly lost as heat, thereby diminishing the overall efficiency of the energy transfer process in cellular respiration.
A molecule that stores energy by linking charged phosphate groups near the other is called ATP
the majority of the ATP produced durring aerobic resperation is made by oxidative phosphorylation, which occurs in the inner mitochondrial membrane and utilizes the electron transport chain to drive the synthesis of ATP from ADP and inorganic phosphate.
not a useful product of glycolysis is ethanol, which is produced during alcoholic fermentation in anaerobic conditions. This contrasts with the valuable production of ATP and NADH during glycolysis that supports cellular energetic needs.
first stage of cellular respiration and the oldest term of evolution is glycolysis, which occurs in the cytoplasm of the cell and does not require oxygen. During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate, resulting in the production of a net gain of 2 ATP molecules and 2 NADH molecules.
A single glucose molecule can drive the krebs cycle , entering the cycle as acetyl-CoA after being converted from pyruvate, leading to the production of additional ATP, NADH, and FADH2, which are crucial for the subsequent oxidative phosphorylation process.
Oxidation and reduction reactions are chmeical processes that result in a gain or loss in electrons, which are essential for energy transfer within the cell. In cellular respiration, these redox reactions occur during glycolysis, the Krebs cycle, and the electron transport chain, enabling the conversion of energy stored in glucose into usable ATP.
during one complete turn of the cycle, three CO2 molecules are released, as each acetyl-CoA that enters the Krebs cycle contributes to the release of two carbon atoms in the form of carbon dioxide.
a chemical reaction in which the products contain less energy than the reactants will tend to proceed spontaneously
during a redox reaction the molecles that gain selectrons has been oxidized, while the molecules that lose electrons are reduced, illustrating the fundamental principle that electron transfer drives the energy transformations central to metabolic processes.
The reaction C6H12O6 + 6O2 —> 6CO2 + 6 H2O when it occures in living cells is know as cellular respiration, which is the process that organisms use to convert glucose into energy in the form of ATP, releasing carbon dioxide and water as byproducts.
Which of the following is the best explanation for energy: Energy is the capacity to do work or produce change
durring aerobic respeiration the last carrier protein transfers a pair of electrons to molecular oxygen, resulting in the formation of water and allowing for the continuation of the electron transport chain.
The formation of ATp from ADP and phospate is analogous to a rechargeable battery being restored to a fully charged state, where energy from the electron transport chain is used to facilitate this reaction, ultimately providing the energy necessary for cellular activities.
Yeast cells under anarobic conditions can carry out fermentation, which generates ATP through the partial oxidation of glucose, producing byproducts such as ethanol and carbon dioxide.
The NET result of a single glycolysis run is the formation of 2 ATP molecules (net gain), 2 NADH molecules, 2 pyruvate molecules, which can then enter the citric acid cycle during aerobic respiration or be converted into fermentation products under anaerobic conditions.
The energy associated with a molecle of gkycose is stored in its chemical bonds, which is released during the process of glycolysis and the citric acid cycle, ultimately contributing to ATP synthesis.
Can celular respeication occur in the abstance of oxygen ? Yes, cellular respiration can occur in the absence of oxygen through anaerobic respiration and fermentation, allowing organisms like yeast to survive and generate energy without relying on aerobic pathways.
WHat is the role of NAD+ in the process of cellular respeiration ? NAD+ acts as an electron carrier in cellular respiration, specifically during glycolysis and the citric acid cycle, where it accepts electrons during oxidation reactions to form NADH. This conversion is critical as NADH subsequently donates electrons to the electron transport chain, facilitating the production of ATP through oxidative phosphorylation.
A single turn of the Krebs cycle wil yield, 3 NADH, 1 FADH2, 1 ATP (or GTP), 2 CO2 molecules,
Reactions that occurs spontaneously and release free energy are called exergonic reactions, which play a vital role in metabolic pathways, including those within cellular respiration, as they help drive the overall process by providing energy for the endergonic reactions that require it.
The electron that are transformed throigh the electron transpor system initialy belonged to glucose molecules that were broken down during glycolysis and the Krebs cycle, ultimately resulting in the high-energy products NADH and FADH2, which transfer electrons to the chain.
WHere is the highets energy stored in a moleclue of ATP? The highest energy in a molecule of ATP is stored in the phosphate bonds, particularly in the bonds connecting the second and third phosphate groups, which, when broken, release energy that can be utilized for cellular work.
ATP gives up energy when it is convered to ADP (adenosine diphosphate) and an inorganic phosphate, a process known as hydrolysis, enabling various cellular processes such as muscle contraction, active transport, and biochemical synthesis.
WHich is the best definition of cellular respeiration ? Cellular respiration is the metabolic process by which cells convert glucose and oxygen into energy in the form of ATP, while releasing carbon dioxide and water as byproducts.
How is ATP produced in glycolysis ? ATP is produced in glycolysis through substrate-level phosphorylation, where a phosphate group is directly transferred to ADP to form ATP from intermediate metabolites such as 1,3-bisphosphoglycerate and phosphoenolpyruvate during the breakdown of glucose.
which are essential for the subsequent steps in the electron transport chain, amplifying ATP production.
ATP gives up energy when it is converted to ADP or AMP.
First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.
Second Law of Thermodynamics: In any energy transfer, the total entropy of a closed system will always increase.
The three processes required for the complete oxidation of glucose are glycolysis, the Krebs cycle, and oxidative phosphorylation.
The energy associated with a molecule of glucose is stored in its chemical bonds.
ATP is produced by glycolysis through substrate-level phosphorylation, where a phosphate group is directly transferred to ADP from an intermediate metabolite during glucose breakdown.
The majority of the ATP produced during aerobic respiration is made by oxidative phosphorylation.
The role of NAD⁺ in cellular respiration is to act as an electron carrier, accepting electrons during glycolysis and the Krebs cycle to form NADH.
Useful products of glycolysis include ATP and NADH, while non-useful products include ethanol (under anaerobic conditions) in some organisms.
Fermentation is important as it allows cells to generate ATP when oxygen is not available, helping them survive.
The Krebs cycle occurs in the mitochondrial matrix.
Electrons carried by NADH and FADH₂ are transferred to the electron transport chain, ultimately contributing to ATP production.
Yes, cellular respiration can occur in the absence of O₂ through anaerobic respiration and fermentation processes.
The catabolism of fatty acids results in the production of Acetyl CoA and NADH.
Evidence that glycolysis evolved early includes its universality among organisms and the lack of oxygen requirement.
Cellular respiration is the metabolic process by which cells convert glucose and oxygen into energy (ATP),-carbon dioxide, and water.
Amino acids must undergo deamination to allow for their catabolism for energy.
Primitive prokaryotes probably used HS instead of water, releasing sulfur compounds into the environment during their photosynthesis.
NAD serves as an important electron carrier due to its ability to undergo reduction and oxidation cycles, enabling efficient energy transfer.
For each glucose molecule consumed, 6 CO₂ molecules are released from the Krebs cycle.
The mechanism by which pyruvate dehydrogenase is inhibited by the end product is known as feedback inhibition.
In glycolysis, glucose is converted to pyruvate.
The NET result of a single glycolysis run is the formation of 2 NADH and 2 ATP.
Under anaerobic conditions in animals, the end product of glycolysis is converted to lactic acid.
Cells obtain energy by oxidizing food molecules such as glucose, which involves taking electrons away.
A hydrogen atom consists of one proton and one electron.
Before entering the Krebs cycle, pyruvate is converted to acetyl CoA.
A single "turn" of the Krebs cycle will yield 1 ATP, 3 NADH, and 1 FADH₂.
The initial reaction of the Krebs cycle involves adding a 2-carbon acetyl CoA to a 4-carbon oxaloacetate.
The electron transport chain in bacteria is located in the plasma membrane.
During aerobic respiration, the last carrier protein transfers a pair of electrons to molecular O₂, forming water.
The electrons transferred through the electron transport system initially belonged to NADH and FADH₂.
A molecule that stores energy by linking charged phosphate groups is called ATP.
In eukaryotes, the glycolytic reactions take place in the cytoplasm of the cell.
The first stage of cellular respiration, and the oldest in terms of evolution, is glycolysis.
In the absence of oxygen, hydrogen atoms generated by glycolysis are donated to organic molecules in a process called fermentation.
The reaction when it occurs in living cells is known as cellular respiration.
The total amount of free energy potentially available from the complete oxidation of glucose can yield around 30-36 ATP, representing an energy efficiency of about 30-38%.
A single glucose molecule can drive the Krebs cycle for 2 turns as it produces 2 pyruvate molecules.
The oxygen utilized in cellular respiration ultimately shows up as water (H₂O).
Yeast cells under anaerobic conditions produce ethanol and CO₂.
A gram of fatty acid can yield approximately 2-3 times more energy than one gram of glucose.