Metabolic Pathways
What is the primary purpose of glycolysis in cellular respiration?
Glycolysis breaks down glucose to form pyruvate, yielding ATP and NADH, which enter further stages of cellular respiration.
What is the purpose of ATP in the cell?
ATP acts as the main energy currency, fueling endergonic reactions by releasing energy when converted to ADP and phosphate.
Where does the Krebs cycle occur in a eukaryotic cell?
The Krebs cycle takes place in the mitochondrial matrix of eukaryotic cells.
What effect does an enzyme have on activation energy?
Enzymes lower the activation energy required for a reaction, making it proceed faster without being consumed.
What are biofilms, and how are they formed?
Biofilms are organized colonies of bacteria held together by sticky substances; these colonies often form on surfaces like teeth.
Name one major difference between catabolic and anabolic reactions
Catabolic reactions break down larger molecules and release energy, while anabolic reactions build larger molecules and consume energy.
What is the total energy released when ATP breaks down?
When ATP hydrolyzes to ADP and inorganic phosphate, it releases approximately 7.3 kcal/mol of energy.
What molecule is the terminal electron acceptor in aerobic respiration?
Oxygen acts as the terminal electron acceptor, combining with electrons and protons to form water.
What is the role of an inhibitor in enzyme function?
Inhibitors reduce or prevent enzyme activity, typically by binding to the enzyme and altering its active site or overall shape.
Describe quorum sensing.
Quorum sensing is a mechanism where bacteria regulate gene expression based on cell density, facilitating coordinated activities like biofilm formation.
What is the difference between a spontaneous and non-spontaneous process in thermodynamics?
A spontaneous process occurs without added energy and increases entropy, such as diffusion, while non-spontaneous processes require energy input, like active transport.
Explain how NAD+ is reduced to NADH in a redox reaction.
NAD+ is reduced to NADH by gaining two electrons and one proton during glycolysis and the Krebs cycle, helping carry electrons to the electron transport chain.
How many ATP molecules are produced by glycolysis?
Glycolysis produces 2 ATP molecules (net) per molecule of glucose through substrate-level phosphorylation
What is allosteric regulation?
Allosteric regulation involves molecules binding to an enzyme at a site other than the active site, changing the enzyme's shape and activity.
Name two types of local chemical signaling in the body.
Paracrine signaling (affects nearby cells) and synaptic signaling (between neurons) are examples of local signaling.
In what way is the second law of thermodynamics relevant to metabolic processes?
The second law of thermodynamics states that systems tend toward disorder, or entropy, requiring living organisms to constantly expend energy to maintain order.
Describe the electron transport chain’s role in oxidative phosphorylation.
The electron transport chain transfers electrons through a series of proteins, creating an H+ gradient that drives ATP production during chemiosmosis.
What is oxidative phosphorylation, and where does it occur?
Oxidative phosphorylation is ATP synthesis powered by redox reactions; it occurs across the inner mitochondrial membrane.
What is feedback inhibition in enzyme regulation?
Feedback inhibition is a regulatory mechanism where the end product of a pathway inhibits an earlier step to prevent overproduction.
How do G-protein receptors transduce signals in the cell?
G-protein receptors transmit signals by binding a ligand, activating a G-protein, which then activates downstream signaling molecules or enzymes.
Describe how feedback inhibition regulates metabolic pathways and provide an example from cellular respiration.
Feedback inhibition occurs when the end product of a metabolic pathway inhibits an enzyme involved earlier in the pathway, preventing overproduction of the product. For example, in cellular respiration, excess ATP can inhibit the enzyme phosphofructokinase in glycolysis.
Explain how FAD and FADH2 function in cellular respiration.
FADH2 is a reduced electron carrier formed in the Krebs cycle; it donates electrons to the electron transport chain to help produce ATP.
Describe the process of chemiosmosis in ATP synthesis.
Chemiosmosis is the movement of H+ ions down their gradient through ATP synthase, generating ATP from ADP and inorganic phosphate.
What is cooperativity in enzyme activity, and give an example.
Cooperativity occurs when binding of a substrate to one active site on an enzyme enhances binding at other sites. Example: Hemoglobin binding oxygen.
What is signal amplification, and why is it beneficial in cell signaling?
Signal amplification occurs when a small number of ligands generate a large cellular response, allowing cells to react strongly with minimal resources.