Biochemistry: Enzyme Structure and Function

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Questions and Answers

What is the primary function of thrombin in the blood clotting process?

To promote the formation of red blood cells

To break down clots

To convert fibrinogen to fibrin (correct)

To initiate the fibrinolytic system

Which of the following describes the physical characteristics of plasma?

Opaque and saturated

Light-yellow color of whole blood (correct)

Completely transparent fluid

Dark red colored fluid

Where are plasma-specific enzymes primarily secreted?

Bone marrow

Liver (correct)

Kidneys

Pancreas

In which system does thrombin primarily exert its action?

Blood clotting mechanism Signup and view all the answers

What role do plasma-specific enzymes play in the bloodstream?

They facilitate various functions including coagulation Signup and view all the answers

What defines the active site of an enzyme?

The specific region that interacts with substrate molecules Signup and view all the answers

What is the role of a coenzyme in the context of an apoenzyme?

It enhances enzyme activity and stability Signup and view all the answers

Which component forms a holoenzyme?

Apoenzyme combined with a coenzyme Signup and view all the answers

What is a substrate?

The molecule that an enzyme acts upon Signup and view all the answers

What characterizes allosteric sites in enzymes?

They can bind regulatory molecules affecting the enzyme function Signup and view all the answers

What happens during the transition state of an enzyme-catalyzed reaction?

Molecules must attain a high energy state to react Signup and view all the answers

What is a common feature of metalloenzymes?

They contain inorganic metal activators as part of their structure Signup and view all the answers

Which option best describes primary structure in the context of enzymes?

The sequence of amino acids in a polypeptide Signup and view all the answers

What is the primary significance of CK-MB in medical diagnostics?

It indicates acute myocardial infarction within the first 12 hours. Signup and view all the answers

Which classification of enzyme names is characterized by being not specific and based on organic observation?

Empirical names Signup and view all the answers

What role does electrophoresis play in the study of isoenzymes?

It classifies different sub-units based on their electrical charge. Signup and view all the answers

Which enzyme is not considered as an arbitrary name classification?

CK-MB Signup and view all the answers

Which of the following statements about isoenzymes is true?

Isoenzymes can vary in their molecular weight and charge. Signup and view all the answers

Which enzyme listed is primarily involved in protein digestion?

Pepsin Signup and view all the answers

What does the term 'bilocular' refer to in the context provided?

An organelle producing energy. Signup and view all the answers

Which characteristic distinguishes CK-MB from CK-MM?

CK-MB is more specific for cardiac conditions. Signup and view all the answers

What suffix is typically added to the name of enzymes based on the substrate or group they act upon?

-ase Signup and view all the answers

Which enzyme class is primarily responsible for transferring intact groups of atoms like amine or phosphate from one substrate to another?

Transferase Signup and view all the answers

Which enzyme is classified as a hydrolase that catalyzes the hydrolysis of various bonds with the presence of water?

Phosphatase Signup and view all the answers

Which of the following enzymes catalyzes the removal of groups from substrates without hydrolysis?

Lyase Signup and view all the answers

What is the function of aldolase in the context of enzyme classification?

To catalyze a splitting reaction leading to double bonds Signup and view all the answers

Which enzyme is specifically mentioned as an inhibitor for ACP in plasma?

Oxidase Signup and view all the answers

Which of the following enzymes is NOT categorized under hydrolases?

Aminotransferase Signup and view all the answers

Which enzyme catalyzes the conversion of starch into glucose?

Amylase Signup and view all the answers

Which classification of enzyme is primarily responsible for catalyzing oxidation and reduction reactions?

Oxidoreductases Signup and view all the answers

According to the lock and key theory, what is essential for the enzyme and substrate interaction?

The active site of the enzyme must match the substrate. Signup and view all the answers

What does the induced fit theory suggest about enzyme-substrate interaction?

The enzyme adapts its shape to fit the substrate upon binding. Signup and view all the answers

Which factor does NOT influence the binding of enzymes to substrates?

Temperature of the environment Signup and view all the answers

Which enzyme classification is best associated with the assessment of liver problems?

Dehydrogenases Signup and view all the answers

Study Notes

Active Site

The specific region on an enzyme where the substrate binds, forming an enzyme-substrate complex.
Both binding and catalytic reactions occur at the active site.

Substrate

The substance acted on by an enzyme.

Product

The substance derived from a transformed substrate (enzyme + substrate).

Allosteric Site

A cavity on the enzyme, separate from the active site, that can bind regulatory molecules.
This site influences the enzyme's structure and function.

Apoenzyme

The enzyme portion that cannot function alone, requiring a coenzyme.

Holoenzyme

The complete enzyme complex composed of an apoenzyme and a coenzyme.

Metalloenzyme

An enzyme that contains an inorganic activator as part of its molecular structure.

Primary Structure

The specific amino acid sequence of an enzyme.

Enzyme Variants

Heteroenzyme: Enzymes with the same enzymatic activity but specific to different biological species (e.g., Lactate dehydrogenase (LDH) of rabbits and humans).
Plasma-Specific Enzymes: Enzymes secreted by the liver and released into the plasma. They contribute to plasma function (e.g., blood clotting, fibrinolytic system).
Bilocular: Enzymes released by mitochondria and cell sap.

Isoenzymes

Multiple forms of an enzyme that catalyze the same reaction but have slightly different structures and properties.
CK-MB: A sub-unit of creatine kinase (CK) important for heart and skeletal muscle function. More specific and sensitive than CK-MM. Used in diagnosing acute myocardial infarction, particularly within the first 12 hours.

Characteristics of Isoenzymes

Electrophoresis: Used to classify isoenzyme sub-units based on their charge and mobility.
Response to Activation and Inactivation: Isoenzymes respond differently to activation and inactivation processes (e.g., formaldehyde activation of ACP-RBC and inactivation of ACP-Prostate).
Response to Inhibitors: Plasma enzymes are susceptible to inhibitors. Various substances like fluoride, heparin, or oxalic acid can inhibit ACP activity.

Nomenclature and Classifications of Enzymes

Empirical Names

Not specific, based on organ, observation, experiences, or the type of chemical reaction.
- Arbitrary: Not specific (e.g., Ptyalin, Trypsin, Pepsin, Rennin).
- Suffix -ase: Added to the name of the substrate or group acted upon by the enzyme to describe the catalyzed reaction (e.g., Maltase).

Classifications of Enzymes

Oxidoreductase: Catalyze oxidation (addition of H ion) and reduction reactions (removal of H ion) between two substances (e.g., Oxidases, Dehydrogenases).
Transferase: Catalyze the transfer of an intact group of atoms (amine or phosphate group) from one substrate to another (e.g., Aminotransferase, Kinase, Phosphorylase, Methyltransferase).
Hydrolases: Catalyze hydrolysis of various bonds, requiring water for the reaction to proceed (e.g., Phosphatase, Phosphodiesterase, Protease).
Lyases: Catalyze the removal of groups from substrates without hydrolysis. This leads to double bonds (e.g., Decarboxylase).

Factors Affecting Enzyme Binding

Energy: Activation energy required for a reaction.
Molecular Compatibility: The similarity between the enzyme and substrate.
Space Availability: The number of enzymes and substrates available for reaction.
Specificity: The enzyme's ability to catalyze a specific substrate.

Specificity of Enzyme Action

Lock and Key Theory: Proposed by Emil Fischer. The active site of the enzyme is always complementary to the substrate, ensuring recognition between the two.
Induced Fit Theory: Proposed by Daniel Koshland. The enzyme modifies its shape upon substrate binding, ensuring complementarity between the two only after binding.

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Description

Explore the fundamental concepts related to enzyme structure, including active sites, substrates, and types of enzymes. Understand how different sites and structures, such as allosteric and holoenzymes, influence enzymatic activity. This quiz will deepen your knowledge of biochemistry and enzyme functionality.