Enzimi Biochimica - Tipologie e classi

Med90 appunti per Studenti

22 Jan 202109:13

Summary

TLDRThis video script delves into the world of enzymes, highlighting their role as biological catalysts that speed up chemical reactions without being consumed. It categorizes enzymes into six classes based on the reactions they catalyze, such as oxidoreductases and transferases. The script further explains how enzymes function through energy changes and active site interactions, and how factors like substrate concentration, pH, and temperature influence their activity. It also touches on enzyme inhibitors, allosteric regulation, and covalent regulation, emphasizing the importance of enzymes in adjusting metabolic processes to cellular energy demands.

Takeaways

🧬 Enzymes are biological catalysts, which are proteins that speed up chemical reactions without being consumed in the process.
🔍 Enzymes selectively channel substrates in biochemical reactions, maintaining their structure and energy balance throughout the process.
📚 There are six classes of enzymes defined by the reactions they catalyze: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
🍏 Oxidoreductases catalyze oxidation-reduction reactions, such as the conversion of lactate to pyruvate.
🔄 Transferases facilitate the transfer of functional groups like carbon, nitrogen, or potassium, exemplified by the conversion of serine to glycine.
💧 Hydrolases catalyze the breaking of bonds through the addition of water, playing a crucial role in digestion and other processes.
🔗 Lyases catalyze the breaking of various chemical bonds, including carbon-carbon, carbon-sulfur, and some carbon-nitrogen bonds.
🔄 Isomerases catalyze the transfer of atoms within a molecule to form isomeric forms, such as the conversion of malate to fumarate.
🔗 Ligase enzymes catalyze the formation of bonds between carbon, oxygen, nitrogen, and sulfur, often coupled with the hydrolysis of high-energy phosphates.
🔑 The function of enzymes can be influenced by energy changes and the stabilization of the transition state through various catalytic mechanisms.
⚗️ Factors affecting enzyme speed include substrate concentration, pH, and temperature, with enzymes having an optimal pH and temperature for activity.
🛑 Enzyme inhibitors can be reversible or irreversible, with competitive inhibition being a common type where the inhibitor binds reversibly to the active site.
🔄 Regulatory enzymes, or allosteric enzymes, adjust their catalytic activity in response to physiological signals and regulators, ensuring metabolic pathways adapt to cellular energy demands.

Q & A

What are enzymes and what is their primary function?
-Enzymes are biological catalysts, which are proteins that increase the rate of chemical reactions without being consumed in the process. They remain unchanged after the reaction, allowing them to catalyze the reaction multiple times.
How do enzymes selectively channel substrates during their function?
-Enzymes selectively channel substrates by binding to them in a way that is complementary in shape and charge, stabilizing the transition state of the reaction and thus facilitating the process without altering the substrate or enzyme itself.
What are the six classes of enzymes and what do they catalyze?
-The six classes of enzymes are: Oxidoreductases (catalyze oxidation-reduction reactions), Transferases (catalyze the transfer of groups), Hydrolases (catalyze the breaking of bonds with the addition of water), Lyases (catalyze the cleavage of carbon-carbon, carbon-sulfur, and some carbon-nitrogen bonds), Isomerases (catalyze the transfer of atoms within a molecule to form isomers), and Ligases (catalyze the formation of carbon-oxygen, carbon-nitrogen, and carbon-sulfur bonds).
How do energy changes and the active site of an enzyme contribute to catalysis?
-Energy changes involve the activation energy and the reaction speed, which are alternatives for the reaction. The active site of an enzyme is structured to bind only to a specific substrate, stabilizing it in its transition state and increasing molecular interactions, allowing the reaction to proceed correctly.
What are the three factors that influence the speed of an enzyme-catalyzed reaction?
-The three factors influencing the speed of an enzyme-catalyzed reaction are substrate concentration, pH, and temperature. The reaction speed increases with substrate concentration until a maximum is reached, is optimal at a specific pH that reflects the environment where the enzyme functions, and increases with temperature until an inactivation point is reached.
What are enzyme inhibitors and how do they affect enzyme activity?
-Enzyme inhibitors are molecules that interfere with catalysis by slowing down or blocking the reactions catalyzed by enzymes. They can be reversible, binding non-covalently and allowing the enzyme to resume activity once dissociated, or irreversible, rendering the enzyme permanently inactive.
What are the two common types of enzyme inhibition and how do they differ?
-The two common types of enzyme inhibition are competitive inhibition, where the inhibitor binds reversibly to the site that the substrate should occupy, and non-competitive inhibition, where the inhibitor can bind to the enzyme or the enzyme-substrate complex, blocking the reaction without competing for the substrate binding site.
What are allosteric enzymes and how do they function?
-Allosteric enzymes are enzymes that vary their catalytic activity in response to physiological signals through the action of regulators or modulators. They bind to these regulators in a site different from the active site, affecting the enzyme's activity and adjusting the speed of metabolic sequences to match cellular energy demands.
What are homotropic and heterotropic effectors, and how do they influence enzyme activity?
-Homotropic effectors are substrate molecules that, when bound to an enzyme at a site different from the active site, increase the catalytic activity of other sites, cooperating with each other. Heterotropic effectors are different from the substrate and can influence enzyme activity in various ways, such as feedback inhibition, where the end product of a metabolic pathway inhibits an enzyme earlier in the pathway.
What are covalent regulators and how do they regulate enzymes?
-Covalent regulators are enzymes that are regulated through the addition or removal of groups such as phosphate to specific residues like serine, threonine, and tyrosine. Phosphorylation and dephosphorylation, catalyzed by kinases and phosphatases respectively, are major cellular processes that regulate enzyme activity.
How do the levels of enzyme expression and activity regulation interplay?
-Enzyme expression and activity regulation work on three levels: rapid and reversible activation/inactivation mechanisms, slower covalent modulation affecting enzyme activity, and gene expression that adjusts enzyme concentration in response to long-term exposure or specific conditions.

Outlines

00:00

🧬 Enzymes: Biological Catalysts and Their Classification

This paragraph introduces the concept of enzymes as biological catalysts, which are proteins that speed up chemical reactions without being consumed. It explains that enzymes remain unchanged after the reaction and can be reused multiple times. The paragraph then delves into the classification of enzymes into six main classes based on the type of reactions they catalyze: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Each class is briefly described with examples, such as lactate dehydrogenase for oxidoreductases and serine protease for transferases. The paragraph also touches on how enzymes function, focusing on the energy changes involved in the activation of reactions and the stabilization of transition states through the active site's interaction with substrates.

05:00

🔬 Factors Influencing Enzyme Activity and Regulation

The second paragraph discusses the factors that affect the rate of enzyme-catalyzed reactions, including substrate concentration, pH, and temperature. It explains that the reaction velocity increases with substrate concentration until a maximum velocity is reached, and that each enzyme has an optimal pH reflecting its natural environment. The paragraph also covers the influence of temperature, noting that enzyme activity increases with temperature up to a peak before becoming inactive at higher temperatures. Furthermore, it explores enzyme inhibitors, which can be reversible or irreversible, and their mechanisms of action, such as competitive inhibition where the inhibitor binds reversibly to the active site, and non-competitive inhibition where the inhibitor can bind elsewhere on the enzyme. The paragraph concludes with an overview of allosteric regulation, where effectors or modulators bind to a site other than the active site, influencing enzyme activity in response to physiological signals. It also mentions homotropic and heterotropic effects, covalent regulation, and the levels at which enzymes can be regulated, including activation/inactivation mechanisms, cellular activity coordination, covalent modulation, and gene expression.

Mindmap

Keywords

💡Enzymes

Enzymes are biological catalysts, which are proteins that speed up chemical reactions without being consumed in the process. They play a central role in the video's theme by being the main subject of discussion. The script explains that enzymes remain unchanged after catalyzing a reaction, allowing them to be reused multiple times, which is crucial for understanding their function in biological systems.

💡Catalysts

In the context of the video, catalysts refer to substances that increase the rate of a chemical reaction without being altered themselves. Enzymes are a type of catalyst, and this concept is fundamental to understanding how enzymes function within biological processes, as they facilitate reactions without being used up.

💡Substrates

Substrates are the reactants or molecules upon which enzymes act. The video script discusses how enzymes selectively channel substrates in biochemical reactions, emphasizing the specificity of enzyme-substrate interactions, which is essential for the regulation of metabolic pathways.

💡Oxidoreductases

Oxidoreductases are a class of enzymes that catalyze oxidation-reduction reactions. The script mentions lactate dehydrogenase as an example, highlighting the importance of this enzyme class in biological processes such as cellular respiration.

💡Transferases

Transferases are enzymes that catalyze the transfer of a specific group, such as carbon, nitrogen, or phosphorus, from one molecule to another. The script provides the example of serine being converted to pyruvate, illustrating the role of transferases in metabolic reactions.

💡Hydrolases

Hydrolases catalyze the cleavage of various bonds by the addition of water. The video script explains that this class of enzymes is involved in breaking down compounds, which is vital for digestion and other metabolic processes.

💡Lyases

Lyases are enzymes that catalyze the cleavage of carbon-carbon, carbon-sulfur, and some carbon-nitrogen bonds. The script uses the example of aldolase converting fructose-1,6-bisphosphate to glyceraldehyde-3-phosphate, showing the importance of lyases in carbohydrate metabolism.

💡Isomerases

Isomerases catalyze the rearrangement of atoms within a molecule to form isomeric compounds. The video script discusses the conversion of maleate to fumarate as an example, demonstrating the role of isomerases in metabolic pathways.

💡Ligases

Ligases are enzymes that catalyze the joining of atoms to form bonds, often coupled with the hydrolysis of high-energy compounds like ATP. The script mentions pyruvate as an example, indicating the importance of ligases in energy transfer within cells.

💡Active Site

The active site is the region of an enzyme where the substrate binds and the chemical reaction occurs. The video script describes the active site as complementary in shape and charge to the substrate, which is crucial for the enzyme's specificity and catalytic activity.

💡Allosteric Regulation

Allosteric regulation refers to the modulation of an enzyme's activity by the binding of effectors or regulators at a site distinct from the active site. The script explains that allosteric regulators can be activators or inhibitors, and their binding can either increase or decrease the enzyme's activity, which is essential for the control of metabolic pathways.

💡Covalent Modification

Covalent modification is a regulatory mechanism where enzymes are regulated through the addition or removal of chemical groups, such as phosphate groups. The script mentions phosphorylation and dephosphorylation as examples, which are major regulatory processes in cellular functions, controlling enzyme activity and other cellular processes.

💡Enzyme Kinetics

Enzyme kinetics is the study of the rates of enzymatic reactions and the factors that affect them. The video script discusses how factors like substrate concentration, pH, and temperature influence enzyme activity, which is fundamental to understanding how enzymes function under different conditions.

💡Inhibitors

Inhibitors are molecules that interfere with enzyme catalysis, slowing down or blocking the reactions. The script describes two main types of inhibitors: reversible and irreversible, with examples of competitive and non-competitive inhibition, which are crucial for understanding enzyme regulation.

Highlights

Enzymes are biological catalysts that speed up chemical reactions without being consumed.

Enzymes selectively channel substrates in biochemical reactions without altering their structure.

There are six classes of enzymes defined by the reactions they catalyze.

Oxidoreductases catalyze oxidation-reduction reactions, such as lactate dehydrogenase.

Transferases catalyze the transfer of functional groups like carbon, nitrogen, or potassium.

Hydrolases catalyze the cleavage of bonds through the addition of water.

Lyases catalyze the cleavage of carbon-carbon, carbon-sulfur, and some carbon-nitrogen bonds.

Isomerases catalyze the transfer of atoms within a molecule to form optical or geometric isomers.

Ligases catalyze the formation of carbon-oxygen, nitrogen, and sulfur bonds, coupled with the hydrolysis of high-energy phosphates.

Enzyme function can be analyzed by energy changes and how the active site facilitates catalysis.

The active site of an enzyme is structured to bind only a specific substrate, stabilizing it in its transition state.

Factors influencing enzyme speed include substrate concentration, pH, and temperature.

Enzyme inhibitors can be reversible or irreversible, interfering with catalysis by binding to the enzyme.

Common types of inhibition include competitive, non-competitive, and mixed inhibition.

Regulatory enzymes, or allosteric enzymes, adjust their catalytic activity in response to physiological signals.

Allosteric enzymes are regulated by effectors or modulators that bind to a site different from the active site.

Homotropic and heterotropic effects describe how the presence of substrate or effectors can influence enzyme activity.

Covalent regulation involves enzymes being regulated through the addition or removal of phosphate groups.

Phosphorylation and dephosphorylation are key regulatory mechanisms in cellular processes, catalyzed by kinases and phosphatases.

Enzyme expression levels determine the efficiency of metabolic pathways, regulated at multiple levels including activation, covalent modulation, and gene expression.