Factors Affecting Enzyme Activity & Hemoglobinopathies

Practice exam flashcards covering enzyme activity, chicken liver catalase experiments, factors affecting reaction rates, sickle cell disease, and thalassemias.

What gas is released when hydrogen peroxide ($H_2O_2$) is added to chicken liver catalase?

Oxygen ($O_2$) gas is released.

What is the primary function of catalase in chicken liver tissue?

It converts hydrogen peroxide ($H_2O_2$) into water ($H_2O$) and oxygen ($O_2$) via the reaction $2H_2O_2 \rightarrow 2H_2O + O_2$.

Why does boiling liver tissue prior to adding hydrogen peroxide ($H_2O_2$) prevent bubbling?

Catalase is denatured by excessive heat, losing its functional three-dimensional shape.

Which two primary factors influence the rate of bubbling when hydrogen peroxide ($H_2O_2$) is added to fresh chicken liver?

Catalase activity in the liver tissue and the temperature of the liver sample.

Why is catalase important in cells?

It prevents toxic accumulation of hydrogen peroxide ($H_2O_2$), which is a metabolic byproduct that can cause oxidative cellular damage.

Why is bubbling minimal when the catalase reaction is conducted at $\text{pH } 2$?

Catalase is denatured outside its optimal pH range because changes in pH alter ionization and the structure of the enzyme's active site.

What type of chemical reaction is catalyzed by catalase?

A catabolic reaction (breaking down molecules).

Why is catalase activity more vigorous at $37\,^\circ\text{C}$ than at $0\,^\circ\text{C}$?

Higher temperature increases molecular kinetic energy, enhancing effective collisions between the enzyme and substrate.

Under what condition will doubling the amount of fresh chicken liver double the rate of oxygen production?

When the amount of hydrogen peroxide ($H_2O_2$) is in excess.

Why is catalase found in large amounts in the liver?

The liver produces hydrogen peroxide ($H_2O_2$) during detoxification reactions.

What is the genetic defect responsible for sickle cell disease?

A missense point mutation causing substitution of valine for glutamic acid in the $\beta$-globin chain ($\text{Glu} \rightarrow \text{Val}$).

What clinical features are characteristic of hemoglobinopathies?

Jaundice, anemia, fatigue, and splenomegaly.

What is the underlying cause of thalassemias?

Abnormal production (reduced or absent synthesis) of globin chains.

Which form of hemoglobin normally decision-predominates in healthy adults and what is its subunit composition?

Hemoglobin A ($\text{HbA}$), composed of two $\alpha$ and two $\beta$ chains ($\alpha_2\beta_2$).

Under what condition does Hemoglobin S ($\text{HbS}$) cause red blood cells to become sickle-shaped?

Low oxygen tension (deoxygenation).

Which diagnostic test is commonly used to confirm sickle cell anemia?

Hemoglobin electrophoresis.

What is the primary cause of $\alpha$-thalassemia?

Reduced or absent production of $\alpha$-globin chains.

What treatment do patients with $\beta$-thalassemia major frequently require?

Regular blood transfusions.

Which form of hemoglobin is increased in newborns and helps protect against sickle cell disease symptoms early in life?

Fetal hemoglobin ($\text{HbF}$, $\alpha_2\gamma_2$), which interferes with $\text{HbS}$ polymerization.

What is the hallmark feature of all hemoglobinopathies?

Abnormal structure or production of hemoglobin.

What occurs when liver kept on ice is warmed to $37\,^\circ\text{C}$ in the presence of $H_2O_2$?

Vigorous bubbling returns because cooling slows enzyme activity without permanently destroying catalase.

Why does increasing substrate concentration eventually result in little further increase in reaction rate?

All enzyme active sites become fully occupied (saturated) with substrate.

What is the best experimental measure of catalase activity in liver-$H_2O_2$ experiments?

The amount or rate of oxygen ($O_2$) produced.

Which organelle within cells is specifically associated with catalase and the degradation of $H_2O_2$?

The peroxisome.

How does sickle cell disease fundamentally differ from thalassemia?

Sickle cell disease primarily involves an abnormal globin chain structure, whereas thalassemia primarily involves decreased globin-chain production.

What causes painful vaso-occlusive episodes in sickle cell disease?

Obstruction of small blood vessels by rigid sickled red blood cells.

What clinical condition results from chronic red blood cell destruction in sickle cell disease?

Hemolytic anemia and jaundice.

What globin chain composition corresponds to Hemoglobin $\text{A}_2$ ($\text{HbA}_2$)?

Two $\alpha$ chains and two $\delta$ chains ($\alpha_2\delta_2$).

What is the primary cause of $\beta$-thalassemia?

Reduced or absent production of $\beta$-globin chains.

What major long-term complication can arise from repeated blood transfusions in patients with $\beta$-thalassemia major?

Iron overload.