Enzymes

catalyst is a substance that speeds up a chemical reaction without being consumed in the reaction itself. Catalysts provide an alternative reaction pathway with a lower activation energy, thereby accelerating the reaction rate.

Catalysts in Metabolic Reactions

Metabolic reactions are all the chemical reactions that occur within cells. These reactions are crucial for life processes, including energy production, growth, and repair.

• Metabolic reactions are catalysed by enzymes.

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Types of Chemical Reactions

There are two main types of chemical reactions involved in metabolism:

1. Anabolic reactions: These reactions build complex compounds from simpler ones.

   • Example: Photosynthesis, where plants convert carbon dioxide and water into glucose.

2. Catabolic reactions: These reactions break down complex compounds into simpler ones.

   • Example: Digestion, where the body breaks down food into smaller molecules for absorption.

Summary: Catalysts speed up reactions without being consumed. Metabolic reactions are chemical reactions in cells, including anabolic (building up) and catabolic (breaking down) reactions.

Enzymes: Biological Catalysts

Enzymes are proteins that function as biological catalysts, accelerating the rate of chemical reactions within living organisms.

Properties of Enzymes

Enzymes have several key properties that make them effective catalysts:

• Enzymes are proteins.

• Enzymes are biological catalysts.

• Enzymes can be reused multiple times.

• Enzyme activity is affected by temperature and pH.

• Enzymes are specific to the reactions they catalyze.

Enzyme-Substrate Interaction

Enzymes interact with specific molecules called substrates.

• Only molecules with the correct shape fit into the enzyme's active site.

• The lock and key model explains this specificity, where only one type of enzyme speeds up a specific reaction.

  The lock and key model is a simplified analogy. The induced fit model provides a more accurate description of enzyme-substrate interaction.

Active Site and Enzyme-Substrate Complex

• A substrate is a molecule upon which an enzyme acts.

• The active site is the specific region on the enzyme where the substrate binds. It is often described as a dent or pocket on the enzyme's surface.

• When a substrate binds to the enzyme's active site, it forms an enzyme-substrate complex.

  The enzyme-substrate complex is a crucial intermediate step in the catalytic process.

Enzyme Action

After the enzyme acts on the substrate:

• New molecules leave the active site, and the enzyme is ready to catalyze another reaction.

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Summary: Enzymes are proteins that act as biological catalysts. They have specific properties such as reusability, sensitivity to temperature and pH, and high specificity to their substrates. The interaction between an enzyme and its substrate occurs at the active site, forming an enzyme-substrate complex.

Factors Affecting Enzyme Activity

Enzyme activity can be significantly affected by temperature and pH levels.

Effect of Temperature

• Each enzyme has an optimum temperature, at which it functions most efficiently.

• Low temperatures slow enzyme activity because molecules have less kinetic energy.

• High temperatures can cause enzymes to denature.

  • Denaturation is a permanent change in the enzyme's structure, which alters the shape of the active site and stops enzyme activity.

  An analogy: Think of an egg white. When you cook it (increase the temperature), it changes permanently and cannot revert to its original state.

Effect of pH

• Each enzyme has an optimum pH, at which it functions most efficiently.

• Extreme pH levels can also cause enzymes to denature irreversibly.

• Some enzymes work best in neutral conditions, while others work best in acidic or alkaline conditions.

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Summary: Temperature and pH significantly impact enzyme activity. Each enzyme has an optimum temperature and pH at which it functions best. Extreme temperatures and pH levels can lead to denaturation, permanently impairing enzyme function.

Applications of Enzymes

Enzymes have diverse applications across various industries, including their roles in seed germination, biological washing powders, and the food industry.

Enzymes in Seed Germination

Seeds contain inactive enzymes and nutrients. When seeds absorb water:

• Enzymes activate.

• Amylase digests starch into maltose.

• Proteins are digested into amino acids.

• Lipase digests lipids into fatty acids.

  These enzymatic reactions provide the energy and building blocks needed for the seed to germinate and grow.

Enzymes in Biological Washing Powders

Enzymes are used in biological washing powders to:

• Break down insoluble stains.

• Protease digests protein stains into amino acids.

• Lipase digests fat stains into fatty acids.

• Amylase digests starch stains into sugars.

Enzymes in the Food Industry

Enzymes are widely used in the food industry for various purposes:

• Renin clots milk to make cheese.

• Pectinase extracts juice from fruits.

• Amylase breaks down starch in bread dough.

• Trypsin pre-digests proteins in baby food.

• Papain tenderizes meat.

Think About It:

Summary: Enzymes play crucial roles in seed germination by breaking down stored nutrients. In biological washing powders, enzymes break down stains, and in the food industry, they are used for a variety of processes such as cheese making, juice extraction, and tenderizing meat.

Comprehensive Review

• A catalyst is a substance that speeds up a reaction.

• Metabolic reactions are all chemical reactions that occur in cells, including anabolic reactions (building up) and catabolic reactions (breaking down).

• Enzymes are proteins that act as biological catalysts.

• Enzymes have specific properties such as reusability, sensitivity to temperature and pH, and high specificity to their substrates.

• The active site is the region on the enzyme where the substrate binds, forming an enzyme-substrate complex.

• Enzyme activity is affected by temperature and pH, with each enzyme having an optimum temperature and pH.

• Extreme temperatures and pH levels can cause enzymes to denature, leading to a permanent loss of function.

• Enzymes are used in seed germination, biological washing powders, and the food industry for various purposes