Enzymes in the Human Body

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Questions and Answers

What is the primary role of enzymes in the human body?

To provide structural support to cells

To transport nutrients across cell membranes

To release energy from food

To accelerate biological processes (correct)

Which of the following statements is true about ribozymes?

They do not catalyze chemical reactions

They can catalyze reactions among RNAs (correct)

They are found only in the liver

They are solely composed of protein

What happens to an enzyme's activity when its structure is denatured due to heat?

It loses its enzymatic activity (correct)

It remains functional but slows down

It changes its substrates

Its activity increases significantly

What determines the catalytic activity of an enzyme?

The sequence of amino acids in its structure Signup and view all the answers

What type of molecules typically act as substrates for enzymes?

Molecules that the enzymes interact with Signup and view all the answers

In which part of the body do intracellular enzymes primarily function?

In all tissues and fluids Signup and view all the answers

Which of the following enzyme sizes is true based on provided information?

Enzymes can vary from 62 to 2500 amino acid residues Signup and view all the answers

What role do enzymes in the circulatory system play?

Regulating blood clotting Signup and view all the answers

What happens to enzyme activity once all enzyme molecules are occupied by substrate?

The enzyme activity ceases. Signup and view all the answers

Which statement correctly describes a competitive inhibitor?

It structurally resembles the specific substrate and competes for the active site. Signup and view all the answers

How does an increase in substrate concentration initially affect enzyme activity?

Enzyme activity increases until a saturation point is reached. Signup and view all the answers

Which of the following factors does NOT affect enzyme activity?

Pressure levels. Signup and view all the answers

What role do enzymes play in the human body?

Enzymes facilitate various chemical reactions. Signup and view all the answers

What constitutes the active site of an enzyme?

The catalytic site and binding site Signup and view all the answers

Which classification of enzymes catalyzes oxidation and reduction reactions?

Oxidoreductases Signup and view all the answers

What type of enzyme is pepsin?

Hydrolase Signup and view all the answers

Which enzyme catalyzes the joining of two fragments of DNA?

Ligase Signup and view all the answers

In the induced-fit model, what does the binding of the substrate induce?

Weak interactions and conformational changes in the enzyme Signup and view all the answers

What is a cofactor?

A non-protein, essential substance for enzyme activity Signup and view all the answers

What mechanism of catalysis involves the formation of a covalent bond between substrate and enzyme?

Covalent catalysis Signup and view all the answers

What role does activation energy play in enzyme-catalyzed reactions?

It must be reduced by an enzyme to facilitate the reaction Signup and view all the answers

What is the primary function of transferases?

To transfer chemical groups between compounds Signup and view all the answers

Which of the following is NOT a type of enzyme classification?

Fermenters Signup and view all the answers

Which process demonstrates the effect of enzyme action in fermentation?

Formation of carbon dioxide in bread rising Signup and view all the answers

What type of enzymes catalyzes the rearrangement of molecular structures?

Isomerases Signup and view all the answers

The process in which alcohol is produced from fermentation largely depends on which factor?

Plant species and applied enzymes Signup and view all the answers

What happens to substrate and enzyme during the transition state?

They undergo weak interactions leading to strain Signup and view all the answers

What component of the enzymatic action is referred to as the transition state?

The intermediate complex formed after substrate binding Signup and view all the answers

Which amino acids are primarily involved in enzyme active site catalysis?

Aspartate and Histidine Signup and view all the answers

How do enzymes affect the activation energy of reactions?

They lower the activation energy required. Signup and view all the answers

What happens to enzyme activity at temperatures higher than the optimum level?

Enzyme activity decreases due to denaturation. Signup and view all the answers

Which factor does not influence enzyme activity?

Color of the substrate Signup and view all the answers

What is a key characteristic of biological catalysts?

They remain unchanged after the reaction. Signup and view all the answers

What defines the specificity of an enzyme?

The shape and structure of its active site. Signup and view all the answers

How does substrate concentration affect the rate of enzymatic reactions?

At low concentrations, reaction rate increases with concentration. Signup and view all the answers

In which pH range do most enzymes exhibit optimal activity?

Near neutrality, typically around 5 to 7 Signup and view all the answers

Which statement best describes the role of allosteric regulation in enzyme activity?

It allows enzymes to respond to cellular conditions. Signup and view all the answers

What is the first step in the catalytic action of enzymes?

Combining of enzyme and substrate. Signup and view all the answers

What is denaturation in the context of enzymes?

The alteration of an enzyme's structure, leading to loss of function. Signup and view all the answers

Which process describes how enzymes lower activation energy?

By stabilizing the transition state. Signup and view all the answers

What occurs during the disintegration of the enzyme-substrate complex?

The product is released and the enzyme is regenerated. Signup and view all the answers

Study Notes

Enzymes: Biological Catalysts

Enzymes are protein molecules with catalytic activity, crucial for metabolic processes and chemical reactions in cells.
Enzymes react with a molecule (substrate) and convert it into a different molecule (product).
Enzyme regulation is vital for clinical diagnosis.
Ribozymes are RNA catalysts.
Enzymes are present in all tissues and fluids. Intracellular enzymes catalyze metabolic pathways; membrane-bound enzymes respond to cellular signals; circulatory enzymes regulate blood clotting, etc.

Enzyme Structure

Enzymes are linear chains of amino acids forming a 3D structure.
Amino acid sequence determines the enzyme's structure and catalytic activity.
Enzyme structure denatures, and activity is lost with heat.
Enzymes are large molecules, much larger than their substrates, ranging from 62 to 2,500+ amino acid residues.
Only a small part (active site) of the enzyme is involved in catalysis, consisting of the catalytic and binding sites.
Some ribozymes are RNA biological catalysts combined with proteins.

Enzyme Classification

Enzymes are classified into six functional classes according to the type of reaction they catalyze (International Union of Biochemists - IUB).
- Oxidoreductases: Catalyze oxidation-reduction reactions (e.g., pyruvate dehydrogenase).
- Transferases: Transfer chemical groups between molecules (e.g., transaminase).
- Hydrolases: Catalyze hydrolysis reactions (e.g., pepsin hydrolyzes peptide bonds in proteins).
- Lyases: Break bonds without the addition of water (e.g., aldolase).
- Isomerases: Catalyze the formation of isomers (e.g., phosphoglucomutase).
- Ligases: Join two molecules together (e.g., DNA ligase).

Cofactors

Cofactors are non-protein components essential for enzyme function.
The protein part of an enzyme is the apoenzyme.
Enzyme + cofactor = holoenzyme.
Cofactors can be metal ions or organic molecules (coenzymes).

Examples of Enzyme Action

Beverages: Fermentation varies depending on the plant product and enzyme used (e.g., grapes, honey, hops, etc. for wine, beer).
Food: Bread fermentation uses yeast and sugar to produce carbon dioxide gas, giving the bread its texture.
Drug action: Drugs can inhibit or promote enzyme activity by affecting the active site.

Mechanism of Enzyme Action

Collision theory: Molecules must collide with the correct orientation and sufficient energy (activation energy).
Active site: Enzymes have a specific shape and functional groups for substrate binding.
Enzyme-substrate complex: The enzyme and substrate bind weakly, but this interaction induces conformational changes.
Induced fit model: The binding between enzyme and substrate strengthens with changes, with the active site adapting to fit.
Catalysis Mechanisms: Enzymes use various mechanisms:
- Bond strain: The enzyme strains substrate bonds.
- Covalent catalysis: Covalent intermediates form between enzyme and substrate.
- Acid/base catalysis: Enzymes use amino acid side chains as acid or base catalysts.
- Orientation and proximity: Brings substrate groups together
Two-step process: -Enzyme + substrate → enzyme-substrate complex -enzyme-substrate complex → product + enzyme

Factors Affecting Enzyme Activity

Temperature: Optimal temperature increases activity, but extreme temperatures denature the enzyme.
pH: Most enzymes have an optimal pH near neutrality, but some function in more extreme conditions. pH changes can affect amino acid charges (and thus enzyme activity).
Substrate concentration: Low substrate concentration affects reaction rate, but high concentration leads to saturation, where reaction rate plateau.
Inhibitors: Inhibitors can bind to the active site blocking substrate binding (competitive inhibitors) affecting enzyme activity.
Salt concentration: Changes in salinity can affect protein folding and interactions, thus enzyme function.

Active Site

The active site's amino acid residues are crucial for catalysis and substrate binding.
Active site amino acids are not necessarily contiguous, but are properly positioned by 3D folding.
Common active site residues include polar amino acids, aspartate, cysteine, glutamate, histidine, serine, and lysine.

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Description

This quiz explores the essential roles enzymes play within the human body, including their catalytic activities and the effects of various factors on their performance. Test your knowledge on enzyme functionality, substrates, and inhibitors while learning about the significance of enzymes in biological processes.