week 5 and week 6 ppt 1 Flashcards
where does glycolysis take place and what is glycolysis?
Glycolysis takes place in the cytosol:
* Converts glucose into pyruvate
* Produces a small amount of energy* Generates no CO2
What is phosphorylation?
Phosphorylation is the addition of a phosphate group to a molecule.
What is substrate-level phosphorylation?
Phosphorylation is the addition of a phosphate group to a molecule. Substrate-level phosphorylation is an enzyme-catalyzed transfer of a phosphate group from a donor molecule to ADP, forming ATP.
What happens during pyruvate oxidation and where does it occur?
Pyruvate oxidation is the process that links glycolysis to the citric acid cycle and occurs in the mitochondrial matrix. During this process, pyruvate is oxidized to acetate, releasing CO2, and NAD+ is reduced to NADH, capturing energy. Some of the energy is stored by combining acetate with Coenzyme A (CoA) to form acetyl CoA.
What is the role of acetyl CoA in cellular respiration and what are the inputs and outputs of the citric acid cycle?
Acetyl CoA is the starting point for the eight-reaction citric acid cycle. The inputs of the cycle include acetyl CoA, water, and electron carriers NAD+, FAD, and GDP. Energy released during the cycle is captured by ADP and the electron carriers, producing the outputs CO2, reduced electron carriers (NADH and FADH2), and GTP, which can be used to convert ADP to ATP.
what is the equation for the metabolism of glucose?
C6H12O6 + 6O2 -> 6CO2 + 6H2O + free energy
what is he equation for the glucose metabolism pathway that traps the free energy in ATP?
ADP + P(i) + free energy -> ATP
What is oxidative phosphorylation and what are its two stages?
Oxidative phosphorylation is the process where ATP is synthesized by the reoxidation of electron carriers in the presence of oxygen (O2). It consists of two stages: electron transport and chemiosmosis.
What happens during the electron transport stage of oxidative phosphorylation?
During electron transport, electrons from NADH and FADH2 pass through the respiratory chain of membrane-associated carriers in the mitochondria. This flow of electrons results in a proton concentration gradient across the mitochondrial membrane, which is then used to produce ATP.
Why is the electron transport chain (ETC) a series of reactions rather than just one step?
The ETC is a series of reactions rather than just one step because a single reaction releasing the entire free energy at once would be too much for the cell to harness efficiently. By releasing energy in a series of smaller steps, each step can be coupled to an endergonic reaction, such as the synthesis of ATP, allowing the cell to capture and utilize the energy more effectively.
Where is the respiratory chain located and how does it contribute to ATP formation during oxidative phosphorylation?
The respiratory chain is located in the inner mitochondrial membrane. As electrons are passed between carriers within this chain, energy is released. This energy is used to pump protons across the membrane, creating a proton gradient. The flow of protons back into the mitochondrial matrix through ATP synthase drives the synthesis of ATP. Examples of electron carriers in the respiratory chain include protein complexes I, II, III, IV, Cytochrome c, and ubiquinone (Q).
What happens to protons during the electron transport phase of oxidative phosphorylation?
During the electron transport phase of oxidative phosphorylation, protons are actively transported across the inner mitochondrial membrane into the intermembrane space. This creates a high concentration of protons (a proton gradient) and a charge difference across the membrane, which stores potential energy known as the proton-motive force.
How does the proton-motive force contribute to the formation of ATP?
The proton-motive force, created by the proton gradient and charge difference, drives protons back across the inner mitochondrial membrane through the enzyme ATP synthase. As protons flow through ATP synthase, the potential energy is converted into mechanical energy which is then used to synthesize ATP from ADP and inorganic phosphate (Pi).
What is chemiosmosis and how does it facilitate ATP synthesis?
Chemiosmosis is the process where protons diffuse back into the mitochondrial matrix through ATP synthase, a specialized channel protein. This diffusion of protons is energetically coupled to ATP synthesis, utilizing the potential energy stored in the proton gradient to drive the production of ATP from ADP and inorganic phosphate.
Why is ATP synthesis favored over ATP hydrolysis within mitochondria?
ATP is transported out of the mitochondria once it is synthesized, which keeps its concentration within the mitochondria relatively low. This low concentration of ATP inside the mitochondria encourages the formation of more ATP.
The proton gradient necessary for ATP synthesis is continuously maintained by ongoing electron transport and active proton pumping across the inner mitochondrial membrane. This persistent proton gradient ensures a constant potential energy source for driving ATP synthesis.
How can ATP synthesis be uncoupled, and what role does thermogenin play?
ATP synthesis can be uncoupled by inserting a different H+ diffusion channel into the mitochondrial membrane, causing the energy to be lost as heat instead of being used for ATP synthesis. The uncoupling protein thermogenin, found in human infants and hibernating animals, facilitates this process. Instead of protons driving ATP synthesis via ATP synthase, thermogenin allows protons to flow back into the mitochondrial matrix without generating ATP, releasing energy as heat to maintain body temperature
What are the components of ATP synthase and their roles?
ATP synthase consists of two main components:
F0 subunit: A transmembrane channel that allows protons to flow through it.
F1 subunit: Projects into the mitochondrial matrix and houses the active sites for ATP synthesis, where ADP and inorganic phosphate are combined to form ATP
How is energy harvested from glucose in the absence of oxygen?
In the absence of oxygen, energy from glucose can still be harvested through glycolysis followed by fermentation. This process occurs in the cytosol and allows for the regeneration of NAD+ from NADH + H+, which is crucial for the continuation of glycolysis under anaerobic conditions.
What is lactic acid fermentation, and where does it occur?
Lactic acid fermentation is a process that occurs in microorganisms and some muscle cells under anaerobic conditions. Pyruvate, the end product of glycolysis, acts as the electron acceptor and is reduced by NADH + H+ to form lactate. This process regenerates NAD+, allowing glycolysis to continue. Lactate can accumulate, leading to muscle fatigue.
What is alcoholic fermentation, and which organisms use this process?
Alcoholic fermentation is a process used by yeasts and some plant cells to harvest energy from glucose in the absence of oxygen. This process requires two enzymes to convert pyruvate into ethanol. First, pyruvate is decarboxylated to acetaldehyde, which is then reduced by NADH + H+, producing ethanol, NAD+, and allowing glycolysis to continue.
How does the energy yield of cellular respiration compare to that of fermentation?
Cellular respiration yields significantly more energy per glucose molecule than fermentation. Glycolysis followed by fermentation produces a net gain of 2 ATP per glucose molecule, whereas glycolysis followed by cellular respiration can produce up to 32 ATP per glucose molecule. However, in some cells, the shuttling of NADH may use ATP, resulting in a net yield of approximately 30 ATP.
How are metabolic pathways interrelated and regulated?
Metabolic pathways are interrelated through the interchange of molecules, with many pathways sharing substances. They are regulated by enzyme activity, which can be influenced by various factors including enzyme inhibitors. This regulation ensures efficient control over the flow of substrates and the rate of product formation, maintaining metabolic balance and cellular homeostasis.
What are catabolic interconversions and how do they contribute to metabolic pathways?
Catabolic interconversions are processes where complex molecules are broken down into simpler ones, releasing energy and providing intermediates for metabolic pathways. Examples include:
Polysaccharides being hydrolyzed to glucose, which then enters glycolysis and cellular respiration.
Lipids being broken down into glycerol (which enters the pathway as dihydroxyacetone phosphate, DAP) and fatty acids (which are converted to acetyl CoA).
Proteins being hydrolyzed to amino acids, which can feed into glycolysis or the citric acid cycle.
What are anabolic interconversions, and how do they relate to metabolic regulation?
Anabolic interconversions involve the synthesis of complex molecules from simpler ones, often using energy in the process. These reactions can be the reverse of catabolic reactions, such as gluconeogenesis, where glucose is formed from citric acid cycle and glycolysis intermediates. Anabolic and catabolic pathways are integrated, allowing the cell to balance energy release with the synthesis of new molecule
How are catabolism and anabolism integrated and regulated within the cell?
Catabolism and anabolism are integrated and regulated through mechanisms like negative and positive feedback controls, which help maintain constant concentrations of biochemical molecules such as glucose in the blood. This integration ensures that energy release and the synthesis of cell components are balanced according to the cell’s needs.
How are key metabolic pathways like glycolysis, the citric acid cycle, and the respiratory chain regulated?
Key metabolic pathways such as glycolysis, the citric acid cycle, and the respiratory chain are subject to allosteric regulation of key enzymes. This means the activity of these enzymes can be modulated by the binding of molecules at sites other than the active site, which can enhance or inhibit their function. This type of regulation allows the cell to finely tune metabolic pathways in response to the cell’s energy demands and the availability of substrates.
What is the main control point in glycolysis and how is it regulated?
The main control point in glycolysis is phosphofructokinase, which is allosterically inhibited by ATP. When ATP levels are high, this inhibition slows down glycolysis, preventing the wasteful production of more ATP.
What regulates the citric acid cycle’s main control point.
The main control point in the citric acid cycle is isocitrate dehydrogenase, which is inhibited by NADH + H+ and ATP. High levels of NADH + H+ and ATP indicate abundant energy, leading to the slowing down of the cycle to prevent excessive production of energy carriers
How does the accumulation of citrate affect metabolic pathways when ATP levels are high?
When ATP levels are high, the accumulation of citrate can divert acetyl CoA away from the citric acid cycle to fatty acid synthesis for storage. Later, these fatty acids may be metabolized to produce more acetyl CoA, providing a way to store energy for future needs.
What are some examples of protein secretion across different organisms?
In microbes, an example is fungal sex pheromones.
In plants, gibberellins are secreted (though not proteins).
In mammals, an example of a secreted protein is growth hormone.
Why do organisms secrete proteins?
Organisms secrete proteins for various reasons, including:
Construction of cell walls in microbes and plants.
Extracellular degradation of nutrient sources through enzymes like lignases, cellulases, phosphatases, and lipases.
Cell communication, such as the secretion of sex pheromones in microbes and hormones in animals and plants.
How do hormones function in cell communication?
Hormones secreted by cells diffuse into the extracellular fluid and are often distributed by the circulatory system to coordinate anatomical, physiological, and behavioral changes in an animal. They play a crucial role in intercellular communication, affecting various aspects of organismal function.
What is the relationship between endocrine cells and endocrine glands?
Some endocrine cells aggregate into secretory organs known as endocrine glands. These glands are responsible for the production and release of hormones into the bloodstream, facilitating long-distance signaling and regulation within an organism.
