week 15 Flashcards
How many ATP molecules can be produced from a single glucose molecule through these processes?
The processes can produce a total of 32 ATP molecules.
Can the number of ATP molecules produced vary? If so, why?
Yes, the number of ATP molecules produced can vary. It may be 30 ATP instead of 32 ATP. The variation is due to shuttle systems that move NADH between different parts of the cell.
What is the role of the shuttle systems in the variation of ATP production?
The shuttle systems help transfer NADH from the cytosol to the mitochondria. The way NADH transfers its energy to a hydrogen ion can affect the total ATP produced.
How does the transfer of energy impact the total ATP produced?
The transfer of energy between NADH and the hydrogen ion can affect the efficiency of ATP production, resulting in either 32 ATP or 30 ATP.
What is the summary of the variation in ATP production from glucose?
The variation in the total ATP amount produced from glucose is due to shuttle systems that move NADH between different parts of the cell, impacting the transfer of energy and resulting in either 32 ATP or 30 ATP.
Where is NADH+H+ recharged or “reoxidized” in cellular respiration?
NADH+H+ is recharged or “reoxidized” in the Electron Transport Chain (ETC).
What molecules can easily pass through the inner membrane of the mitochondria?
Molecules like CO2, water, and oxygen can easily pass through the inner membrane of the mitochondria.
Where is NADH+H+ located in the cytosol or the matrix of the mitochondria?
NADH+H+ produced during glycolysis is located in the cytosol, while NADH+H+ produced in processes like pyruvate oxidation and the citric acid cycle is located in the matrix of the mitochondria.
How are the NADH+H+ molecules produced in the matrix of the mitochondria reoxidized?
The NADH+H+ molecules produced in the matrix of the mitochondria are reoxidized in a specific complex of the Electron Transport Chain called Complex 1.
What is the challenge in reoxidizing the NADH+H+ located in the cytosol?
The challenge is that NADH+H+ in the cytosol cannot directly cross the inner mitochondrial membrane as there is no specific transport system for it.
Can the NADH+H+ generated in the mitochondria easily reach the Electron Transport Chain?
Yes, the NADH+H+ molecules generated in the mitochondria can easily reach the Electron Transport Chain and be reoxidized.
What is the main difference between NADH+H+ in the mitochondria and the cytosol in terms of crossing the inner mitochondrial membrane?
NADH+H+ molecules in the mitochondria can directly cross the inner mitochondrial membrane, while those in the cytosol face a challenge because they cannot directly cross the inner mitochondrial membrane.
What are the two shuttles involved in the transport of electrons from the cytosol into the mitochondria?
The two shuttles involved are the malate-aspartate shuttle and the glycerol-3-phosphate shuttle.
Where does NAD exist in the cell?
NAD exists in both the cytosol and the matrix of the mitochondria.
Do the pools of NAD in the cytosol and the matrix mix together?
No, the pools of NAD in the cytosol and the matrix do not mix together.
What role do the cofactors of NAD play in cellular processes?
The presence and ratio of cofactors in the cytosol and the matrix of NAD play a significant role in determining metabolic processes inside the cells.
Why can’t NADH+H+ from the cytosol directly enter Complex 1 of the electron transport chain?
NADH+H+ from the cytosol cannot directly enter Complex 1 of the electron transport chain because NAD+ (the oxidized form of NAD) cannot cross the inner membrane of the mitochondria directly.
How are electrons from NADH in the cytosol transported into the mitochondria?
The electrons from NADH in the cytosol are transported into the mitochondria through the malate-aspartate shuttle and the glycerol-3-phosphate shuttle.
What is the function of the malate-aspartate shuttle and the glycerol-3-phosphate shuttle?
The malate-aspartate shuttle and the glycerol-3-phosphate shuttle help move electrons across the mitochondrial inner membrane, allowing their participation in the electron transport chain.
What is the mitochondria carrier family?
The mitochondria carrier family is a group of proteins located in the inner membrane of mitochondria, consisting of 53 carriers.
How many carriers in the mitochondria carrier family have unknown functions?
About one-third of the carriers in the mitochondria carrier family have unknown functions.
What is the main purpose of the carriers in the mitochondria carrier family?
The main purpose of these carriers is to transport various substances across the impermeable inner membrane of mitochondria to support important cellular processes like oxidative phosphorylation.
What are some examples of substances transported by the carriers in the mitochondria?
Some examples of transported substances include amino acids, nucleotides (such as ADP and ATP), cofactors like thiamine pyrophosphate, inorganic ions, phosphate, protons, and fatty acids and di- and tri-carboxylates.
What are the different mechanisms used by these carriers?
The carriers can work through different mechanisms. Antiporters transport one molecule in while another molecule is transported out. Symporters transport two molecules in the same direction, often accompanied by a hydrogen ion. Uniporters transport a single molecule from one side of the membrane to the other.
What role do these carriers play in cellular processes?
These carriers in the inner mitochondrial membrane play a crucial role in transporting different substances to support various cellular processes, contributing to energy production and other metabolic functions.
What is the function of the malate-aspartate shuttle?
The malate-aspartate shuttle transports NADH+H+ molecules from glycolysis into the mitochondria’s matrix.
What molecule is converted into malate in the malate-aspartate shuttle?
Oxaloacetate, which is involved in the citric acid cycle, is converted into malate in the shuttle.
How does malate enter the matrix and what is transported out simultaneously?
A transporter called malate-alpha-ketoglutarate transporter helps move malate into the matrix, while alpha-ketoglutarate is transported out into the cytosol.
What reaction converts malate back into oxaloacetate in the matrix?
Malate dehydrogenase converts malate back into oxaloacetate in the matrix.
How is aspartate formed from oxaloacetate?
Oxaloacetate is converted into aspartate through a reaction called transamination, which involves exchanging an amino group from glutamate with the ketone group of oxaloacetate.
What happens to aspartate and glutamate in the shuttle?
Aspartate is transported out of the matrix, while glutamate is transported into the matrix through an antiporter.
How is oxaloacetate restored in the intermembrane space?
Aspartate converts back into oxaloacetate through the same enzyme action in the intermembrane space.
What is the purpose of the malate-aspartate shuttle?
The malate-aspartate shuttle transfers the reducing equivalent carried by NADH+H+ through the conversion of malate, allowing for the transfer of hydrogens and the creation of a reducing cofactor for the electron transport chain.
What role does the malate-aspartate shuttle play in metabolic processes?
The malate-aspartate shuttle ensures the continuation of important metabolic processes by transporting reducing equivalents from glycolysis into the mitochondria’s matrix.
What is the significance of the reactions and metabolites being identical on both sides of the inner mitochondrial membrane?
The identical reactions and metabolites on both sides of the inner mitochondrial membrane allow for the exchange of metabolites between compartments, filling in missing information if a metabolite is lacking on one side.
What is the role of the malate-aspartate shuttle?
The malate-aspartate shuttle is responsible for transporting reducing equivalents gained during glycolysis and helps to reoxidize NAD in the cytosol.
In which tissues does the malate-aspartate shuttle play a particularly important role?
The malate-aspartate shuttle plays a particularly important role in tissues like the liver, kidney, and heart muscle.
What additional purpose does the malate-aspartate shuttle serve in the liver?
In the liver, the malate-aspartate shuttle is dominant and contributes to the production of urea in the urea cycle. It helps eliminate toxic ammonium, a breakdown product of amino acids.
How does the malate-aspartate shuttle assist in the removal of ammonium in the liver?
The aspartate molecule carried into the cytosol through the malate-aspartate shuttle can be used in the production of urea, which helps eliminate toxic ammonium.
What is the primary energy source for the heart muscle, and what role does the malate-aspartate shuttle play?
While we may think that glucose is the primary energy source for the heart muscle, it actually relies primarily on fatty acids. The malate-aspartate shuttle in the heart ensures that the NADH+H+ generated during the conversion of lactate to pyruvate is balanced and reoxidized, allowing both lactate and glucose to be effectively used as fuels for the heart.
How does the malate-aspartate shuttle assist in the utilization of lactate as a fuel for the heart?
The malate-aspartate shuttle helps balance and reoxidize the NADH+H+ generated during the conversion of lactate to pyruvate in the heart muscle, allowing lactate to be effectively used as a fuel.
What is the significance of the malate-aspartate shuttle in energy metabolism?
The malate-aspartate shuttle plays a significant role in energy metabolism by facilitating the transfer of reducing equivalents and ensuring efficient utilization of energy sources.
What is the overall role of the malate-aspartate shuttle in various tissues?
The malate-aspartate shuttle connects different metabolic processes, assists in the elimination of toxic byproducts, and ensures the efficient utilization of energy sources in tissues such as the liver and heart muscle.
What is the role of the glycerol-3-phosphate shuttle?
The glycerol-3-phosphate shuttle helps transfer the reducing equivalents produced during glycolysis to the electron transport chain.
In which tissues is the glycerol-3-phosphate shuttle commonly used?
The glycerol-3-phosphate shuttle is commonly used in tissues such as skeletal muscle and adipose tissue. There is also evidence suggesting its presence and importance in the brain.
How does the glycerol-3-phosphate shuttle transfer reducing equivalents?
The glycerol-3-phosphate shuttle involves two enzymes: cytosolic glycerol-3-phosphate dehydrogenase and mitochondrial glycerol-3-phosphate dehydrogenase. Dihydroxyacetone phosphate captures the reducing equivalents produced in glycolysis and forms glycerol-3-phosphate, which transfers the reducing equivalents to FADH2. FADH2 can then transfer the reducing equivalents to Coenzyme Q, activating complex III of the electron transport chain.
What is the difference between the glycerol-3-phosphate shuttle and the malate-aspartate shuttle?
The glycerol-3-phosphate shuttle activates the electron transport chain faster than the malate-aspartate shuttle. However, it converts NADH+H+ to FADH2, which is less efficient and produces fewer ATP molecules (1.5 ATP) compared to NADH+H+ (2.5 ATP) produced by the malate-aspartate shuttle.
What are the implications of using the glycerol-3-phosphate shuttle in terms of ATP production?
The glycerol-3-phosphate shuttle produces less ATP compared to the malate-aspartate shuttle during glucose oxidation. The conversion of NADH+H+ to FADH2 in the glycerol-3-phosphate shuttle results in a lower ATP yield.
What are some other functions of the glycerol-3-phosphate shuttle?
The glycerol-3-phosphate shuttle and its intermediate molecule, glycerol-3-phosphate, are associated with intellectual disabilities and play a role in learning and memory. Additionally, glycerol-3-phosphate is involved in fat metabolism and serves as a glycerol backbone in adipose tissue.
How does the choice of shuttle affect the overall ATP yield during glucose oxidation?
The choice of shuttle, whether malate-aspartate or glycerol-3-phosphate, affects the overall ATP yield during glucose oxidation. The malate-aspartate shuttle produces more ATP compared to the glycerol-3-phosphate shuttle due to the higher energy yield of NADH+H+.
What is the pentose phosphate pathway?
The pentose phosphate pathway is an alternative pathway to glycolysis that utilizes glucose 6-phosphate and produces ribose phosphate, necessary for DNA and RNA synthesis.
What is the specific role of the pentose phosphate pathway?
The pentose phosphate pathway is responsible for producing ribose phosphate, which is essential for the synthesis of DNA and RNA.
How does the pentose phosphate pathway differ from glycolysis?
The pentose phosphate pathway is an alternative pathway to glycolysis. While glycolysis primarily focuses on the production of ATP and pyruvate, the pentose phosphate pathway focuses on generating ribose phosphate for nucleotide synthesis.
What molecule is utilized as the starting point in the pentose phosphate pathway?
The pentose phosphate pathway utilizes glucose 6-phosphate as the starting molecule.
What is the significance of ribose phosphate in the cell?
Ribose phosphate is crucial for the synthesis of DNA and RNA, which are essential for genetic information storage and protein synthesis in cells.
Can you explain the process of ribose phosphate production in the pentose phosphate pathway?
In the pentose phosphate pathway, glucose 6-phosphate undergoes a series of enzymatic reactions to produce ribose phosphate. The pathway involves oxidative and non-oxidative phases, resulting in the conversion of glucose 6-phosphate to ribose 5-phosphate and other intermediates.
Why is the production of ribose phosphate important for the cell?
Ribose phosphate is necessary for the synthesis of DNA and RNA, which are essential for cell growth, proliferation, and genetic information transfer.
Are there any other products or byproducts generated in the pentose phosphate pathway?
Along with ribose phosphate, the pentose phosphate pathway also produces NADPH (nicotinamide adenine dinucleotide phosphate), which is an important reducing agent involved in various cellular processes, including antioxidant defense and fatty acid synthesis.
What are the different phases of the pentose phosphate pathway?
The pentose phosphate pathway consists of two phases: the oxidative phase, which generates NADPH and converts glucose 6-phosphate to ribose 5-phosphate, and the non-oxidative phase, which involves a series of rearrangement reactions to interconvert various sugar phosphates.
What are the key applications of the pentose phosphate pathway in cellular metabolism?
The pentose phosphate pathway is crucial for providing ribose phosphate for DNA and RNA synthesis and generating NADPH for cellular redox reactions and biosynthetic processes. Additionally, it plays a role in protecting cells from oxidative stress and providing intermediates for other metabolic pathways.
What are the multiple uses of glucose in the body?
Glucose has multiple uses in the body, including energy production, production of pyruvate, glycogen synthesis, and involvement in the pentose phosphate pathway.
Where does the pentose phosphate pathway take place?
The pentose phosphate pathway takes place in the cytosol of every cell in the human body, unlike glycolysis, which occurs in the cytosol of cells that have mitochondria.
In which tissues is the role of the pentose phosphate pathway particularly important?
The role of the pentose phosphate pathway is particularly important in tissues that are rapidly dividing, exposed to free radicals and reactive oxygen species, and actively synthesizing fatty acids and cholesterol.
What is the significance of the pentose phosphate pathway in rapidly dividing tissues?
The pentose phosphate pathway is important in rapidly dividing tissues because it provides the necessary ribose phosphate for DNA and RNA synthesis, which is essential for cell growth and proliferation.
How does the pentose phosphate pathway contribute to cellular defense against free radicals and reactive oxygen species?
The pentose phosphate pathway generates NADPH, which acts as a reducing agent and is involved in various cellular antioxidant defense mechanisms. NADPH helps neutralize free radicals and reactive oxygen species, protecting the cells from oxidative damage.
What is the role of the pentose phosphate pathway in fatty acid and cholesterol synthesis?
The pentose phosphate pathway provides intermediates, such as ribose 5-phosphate and NADPH, which are required for the synthesis of fatty acids and cholesterol.
Can you explain the relationship between glucose and glycogen synthesis?
Glucose can be used for glycogen synthesis, where excess glucose molecules are converted and stored as glycogen in the liver and muscle cells. Glycogen serves as a storage form of glucose and can be broken down when energy demands increase.
Why is the pentose phosphate pathway more active in certain tissues?
The pentose phosphate pathway is more active in tissues that have high demands for nucleotide synthesis, require protection against oxidative stress, and are involved in lipid synthesis. These tissues benefit from the production of ribose phosphate and NADPH provided by the pathway.
Are there any other pathways or processes where glucose is involved?
Yes, glucose is also involved in other pathways and processes, such as gluconeogenesis (the synthesis of glucose from non-carbohydrate sources), glycogenolysis (the breakdown of glycogen to release glucose), and the Krebs cycle (a central metabolic pathway in cellular respiration).
What are the two main products of the pentose phosphate pathway?
The pentose phosphate pathway produces two main products: NADPH+H+ (a reducing cofactor) and ribose 5-phosphate.
Where is NADPH+H+ used as an electron donor?
NADPH+H+ is used as an electron donor for the production of fatty acids in the liver, adipose tissue, and lactating mammary glands.
What are some other functions of NADPH+H+?
NADPH+H+ is also involved in the synthesis of cholesterol and steroid hormones in the liver, adrenal glands, and gonads. Additionally, it plays a role in repairing oxidative damage caused by reactive oxygen species (ROS) in cells such as erythrocytes, lens cells, and cornea cells.
How does NADPH+H+ contribute to fatty acid production?
NADPH+H+ provides the reducing power necessary for the biosynthesis of fatty acids in the liver, adipose tissue, and lactating mammary glands. It supplies the electrons needed for the reduction of fatty acid precursors, allowing for the synthesis of complex lipid molecules.
In which tissues is NADPH+H+ involved in the synthesis of cholesterol and steroid hormones?
NADPH+H+ participates in the synthesis of cholesterol and steroid hormones in tissues such as the liver, adrenal glands, and gonads. These tissues require NADPH+H+ as a reducing agent for the enzymatic reactions involved in the production of these important molecules.
What role does NADPH+H+ play in repairing oxidative damage?
NADPH+H+ is crucial for the regeneration of reduced glutathione (GSH), an antioxidant molecule. It supplies the necessary reducing power to convert oxidized glutathione (GSSG) back to its reduced form (GSH), enabling the cellular defense against oxidative damage caused by reactive oxygen species (ROS).
Which cells benefit from NADPH+H+’s role in repairing oxidative damage?
Cells such as erythrocytes (red blood cells), lens cells (in the eyes), and cornea cells (in the eyes) benefit from NADPH+H+’s role in repairing oxidative damage. These cells are exposed to high levels of reactive oxygen species (ROS) due to their physiological functions or environmental factors, and NADPH+H+ helps maintain their redox balance and protect against oxidative stress.
Can you explain the significance of ribose 5-phosphate produced by the pentose phosphate pathway?
Ribose 5-phosphate is essential for the synthesis of nucleotides, including those required for DNA and RNA synthesis. It serves as a precursor for the production of the five-carbon sugar backbone necessary for nucleotide formation, which is crucial for cellular processes such as cell growth, proliferation, and genetic material synthesis.
Are there any other functions or uses of NADPH+H+ or ribose 5-phosphate?
Yes, NADPH+H+ is also involved in various other cellular processes, such as the detoxification of drugs and chemicals by hepatic enzymes. Ribose 5-phosphate can also be diverted into alternative pathways, such as the synthesis of coenzymes and nucleotide sugars used in glycosylation reactions.
What are the two main products of the pentose phosphate pathway?
The pentose phosphate pathway produces two main products: NADPH+H+ and ribose 5-phosphate.
What is the significance of ribose 5-phosphate in the cell?
Ribose 5-phosphate is important for the synthesis of nucleotides, which are the building blocks of DNA, RNA, and coenzymes such as ATP, NAD, FAD, and coenzyme A. It provides the necessary sugar backbone for the formation of nucleotides, enabling the synthesis of genetic material and essential coenzymes involved in various cellular processes.
Which cells rely on the pentose phosphate pathway for nucleotide synthesis?
Rapidly dividing cells, such as those found in the bone marrow, skin, intestinal mucosa, and tumors, rely on the pentose phosphate pathway for nucleotide synthesis. These cells have high demands for DNA and RNA production, and the pathway provides the ribose 5-phosphate required for nucleotide biosynthesis.
What role does the pentose phosphate pathway play in cell growth and survival?
The pentose phosphate pathway plays a crucial role in cell growth and survival by providing the necessary components for DNA, RNA, and coenzyme synthesis. These components are vital for cellular processes involved in cell division, genetic material replication, energy metabolism, and various enzymatic reactions. The pathway ensures the availability of nucleotides and coenzymes required for these essential processes.
How does the pentose phosphate pathway contribute to individuality?
The pentose phosphate pathway contributes to individuality through its role in DNA and RNA synthesis. DNA carries genetic information, and RNA participates in gene expression and protein synthesis. The pathway provides the necessary components for the unique sequences and structures of DNA and RNA, contributing to the individuality of each person’s genetic makeup.
Apart from nucleotide synthesis, what are some other uses of ribose 5-phosphate?
Ribose 5-phosphate can be utilized for other purposes, such as the synthesis of other important biomolecules. It can be converted into nucleotide sugars for glycosylation reactions, where sugars are attached to proteins or lipids to form glycoproteins or glycolipids. Additionally, ribose 5-phosphate can contribute to the synthesis of certain coenzymes and metabolic intermediates.
How can the pentose phosphate pathway be simplified into two phases?
The pentose phosphate pathway can be simplified into two phases: the oxidative phase and the non-oxidative phase.
What is the main goal of the oxidative phase in the pentose phosphate pathway?
The main goal of the oxidative phase is to convert glucose 6-phosphate into ribose 5-phosphate and produce NADPH+H+. It aims to generate 5-carbon sugars and the reducing cofactor NADPH+H+.
Is the oxidative phase reversible?
No, the oxidative phase of the pentose phosphate pathway is irreversible.
