Allosterism and allosteric proteins Flashcards
What is the activation energy of a reaction?
Activation energy is the energy required to initiate a chemical reaction by enabling reactants to reach the transition state.
What is an endergonic reaction?
An endergonic reaction requires an input of energy to proceed, as the products have a higher energy level than the reactants. Example: Protein synthesis.
What is an exergonic reaction?
An exergonic reaction releases energy as it proceeds, with reactants starting at a higher energy level than the products. Example: ATP hydrolysis.
How do enzymes affect activation energy?
Enzymes lower the activation energy required for a reaction to occur, making the reaction faster and more efficient without changing the overall energy released or absorbed.
How do enzymes lower activation energy?
Enzymes stabilize the transition state, align reactants in the correct orientation, or provide an alternative reaction pathway.
Do enzymes alter the overall energy released or absorbed in a reaction?
No, enzymes only lower the activation energy; they do not change the overall energy released or absorbed in the reaction.
What happens to reaction speed in the presence of an enzyme?
The reaction proceeds much faster due to the lower activation energy barrier provided by the enzyme.
Why are enzymes important for biological systems?
Enzymes enable biochemical reactions to occur rapidly and efficiently under physiological conditions, such as normal body temperature and pH.
What diseases are linked to enzyme dysfunction?
Metabolic disorders like phenylketonuria (enzyme mutation in phenylalanine metabolism) and liver dysfunction (elevated ALT/AST levels) can result from enzyme abnormalities.
How are enzymes used in medicine?
Enzymes are targeted in therapies (e.g., protease inhibitors for HIV, ACE inhibitors for hypertension) and used as diagnostic markers for diseases.
What is the Bohr Effect?
The Bohr Effect describes how lowered pH (increased H⁺) and increased CO₂ reduce hemoglobin’s affinity for oxygen, promoting oxygen release to tissues.
Who discovered the Bohr Effect, and when?
The Bohr Effect was discovered by Christian Bohr in 1904.
How does CO₂ affect hemoglobin?
CO₂ is hydrated in tissues to form carbonic acid, which dissociates into H⁺ and bicarbonate. The increased H⁺ lowers pH, stabilizing the T-state of hemoglobin and reducing oxygen affinity.
What is the T-state of hemoglobin, and how is it relevant?
The T-state (Tense state) of hemoglobin has a low affinity for oxygen. Increased H⁺ and CO₂ stabilize this state, promoting oxygen release to tissues.
How does CO₂ directly bind to hemoglobin?
CO₂ binds to the amino-terminal ends of hemoglobin’s globin chains, forming carbaminohemoglobin. This stabilizes the T-state and facilitates oxygen unloading.
What happens to hemoglobin in the lungs?
In the lungs, high oxygen levels promote oxygen binding to hemoglobin, shifting it to the R-state (Relaxed state) and releasing H⁺ and CO₂.
What factors cause a rightward shift in the oxygen dissociation curve?
A rightward shift is caused by:
Increased H⁺ (low pH).
Increased CO₂ concentration.
Increased temperature.
Increased 2,3-Bisphosphoglycerate (BPG).
What does a rightward shift in the oxygen dissociation curve indicate?
A rightward shift indicates reduced hemoglobin affinity for oxygen, facilitating oxygen release to tissues.
Why is the Bohr Effect important in oxygen delivery?
The Bohr Effect ensures efficient oxygen release in metabolically active tissues where CO₂ and H⁺ are elevated, and oxygen is needed most.
How does the Bohr Effect contribute to adaptation at high altitudes?
At high altitudes, increased 2,3-BPG production shifts the oxygen dissociation curve to the right, aiding oxygen release in low-oxygen conditions.
What clinical conditions are related to the Bohr Effect?
Acidosis (low pH) or hypercapnia (high CO₂) can enhance oxygen unloading.
Alkalosis or hypocapnia can impair oxygen delivery to tissues.
What happens to CO₂ at active tissues?
CO₂, a byproduct of cellular respiration, diffuses from tissues into systemic capillaries and enters red blood cells.
How is CO₂ converted in red blood cells at tissues?
CO₂ combines with water to form carbonic acid (H₂CO₃) via carbonic anhydrase, which dissociates into H⁺ and bicarbonate (HCO₃⁻).
What is the role of hemoglobin in pH regulation at tissues?
Hemoglobin binds H⁺ ions, stabilizing its T-state, reducing oxygen affinity, and facilitating oxygen release to tissues (Bohr Effect).
What is the chloride shift?
At tissues, HCO₃⁻ is transported out of red blood cells in exchange for Cl⁻ ions to maintain electrochemical balance.
What happens to CO₂ in the lungs?
CO₂ is released as H⁺ recombines with HCO₃⁻ to form carbonic acid, which is converted back into CO₂ and water by carbonic anhydrase. CO₂ is then exhaled.
What happens to hemoglobin in the lungs?
Oxygen binds to hemoglobin, displacing H⁺ ions and stabilizing the R-state (high oxygen affinity), allowing oxygen loading.
What enzyme is essential for CO₂ transport and pH regulation?
Carbonic anhydrase catalyzes the reversible conversion of CO₂ and water into carbonic acid (H₂CO₃).
What is the primary goal of systemic circulation (tissues)?
To offload oxygen and pick up CO₂ produced by metabolically active cells.
What is the primary goal of pulmonary circulation (lungs)?
To offload CO₂ and pick up oxygen from the alveoli for transport to tissues.
