Enzymes and Metabolic Pathways

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Questions and Answers

What is the term for the protein part of an enzyme?

Apoenzyme (correct)

Cofactor

Holoenzyme

Substrate

Which statement correctly defines the optimum temperature for an enzyme?

Temperature where no enzyme activity occurs

Temperature that activates substrate

Temperature that maximizes enzyme activity (correct)

Temperature at which enzyme denatures

What does Km signify in enzyme kinetics?

Rate of product formation

Maximum reaction speed

Temperature sensitivity of the enzyme

Enzyme's affinity for the substrate (correct)

Which of the following factors does NOT affect enzyme activity?

Color of the solution Signup and view all the answers

What is the characteristic of reversible inhibitors?

They can dissociate from the enzyme Signup and view all the answers

What defines the unit of enzyme activity?

Amount of substrate converted in optimal conditions Signup and view all the answers

Which type of inhibitor permanently decreases enzyme activity?

Irreversible inhibitor Signup and view all the answers

What is the effect of pH on enzyme activity?

Every enzyme has an optimum pH for maximum activity Signup and view all the answers

What is the primary function of enzymes?

To decrease activation energy and increase reaction rate Signup and view all the answers

Which type of enzymes are specifically known as ribozymes?

Ribonucleic acid biocatalysts Signup and view all the answers

Which enzyme classification is NOT correctly placed in the order?

Catalysts Signup and view all the answers

What does the term 'substrate specificity' refer to in the context of enzymes?

Each enzyme typically uses a specific molecule or chemically related molecules Signup and view all the answers

What is the efficiency range of enzyme-catalyzed reactions compared to uncatalyzed reactions?

10^3 to 10^8 times faster Signup and view all the answers

Which of the following is a true statement about the action of enzymes?

Enzymes speed up reactions without being consumed Signup and view all the answers

What aspect is affected by the catalytic activity of an enzyme?

Activation energy Signup and view all the answers

Which of the following enzymes is considered one of the fastest known?

Carbonic anhydrase Signup and view all the answers

Study Notes

Learning Objectives

Describe enzymes and their common properties
List enzyme classifications in correct order
Describe factors that change enzyme activity
Explain the relationship between Km and activity
Explain enzyme inhibition and inhibition types

Metabolic Reactions

Enzymes facilitate metabolic reactions
Enzymes speed up reactions by lowering activation energy
Enzymes alter the rate and change the classic biochemical reaction
Enzymes facilitate transport of molecules

Glycolysis

Glycolysis is a metabolic pathway for glucose breakdown
Enzymes like hexokinase and phosphofructokinase are key in glycolysis
Chemical reactions in glycolysis are shown in diagrams.

Activation Energy

Activation energy is the energy needed for a reaction
Catalysts, like enzymes, lower the activation energy, increasing reaction rates.
Enzymes do not cause a chemical or nuclear reaction, but rather speed up an existing one.

Activation Energy and Catalysts

Catalysts increase reaction rate without being consumed
Catalysts decrease activation energy, making reactions easier
Enzymes are biological catalysts

Enzymes

Enzymes are biological catalysts
Enzymes increase reaction rate by lowering activation energy
Enzymes bind to substrates—reactants—to make products.

Properties of Enzymes

Most enzymes are proteins
Ribozymes are RNA enzymes
Enzymes change reaction rate
They are specific for substrates and reactions.

Efficiency

Enzyme-catalyzed reactions are much faster than uncatalyzed reactions
Carbonic anhydrase is a very fast enzyme, hydrating CO2
Enzymes are highly efficient

Specificity

Reaction specificity means enzymes catalyze specific reactions
Substrate specificity means enzymes work on specific substrates or related molecules

Enzyme Nomenclature: Classification

Enzymes are classified using an EC number
Classification groups enzymes by function
This classification system provides a hierarchical structure for enzymes.

Enzyme Kinetics and Km

Km is a measure of enzyme affinity for substrate
High Km means low affinity
Enzymes work quickly and efficiently at high substrate concentration.
Affinity and binding power are affected by substrate concentration.

Km, A Clinical Example

Km is used to assess the efficiency of enzymes in clinical situations.
Enzymes efficiency is relevant to the toxicity of substances.

Regulation of Enzyme Activity

Enzyme activity can be regulated through multiple mechanisms.
Enzyme amount (synthesis and degradation)
Enzyme modification (covalent and non-covalent)
Isozymes and compartments
Feed-forward activation and feedback inhibition are important regulatory processes.
These regulatory mechanisms allow the body to adjust enzyme activity based on cellular needs.

Enzyme Structure

Apoenzyme: protein part of an enzyme
Cofactor: non-protein part of an enzyme
Holoenzyme: complete catalytically active enzyme
Active site: where substrates bind and reactions occur.

Enzyme Structure: Active Site

Active sites are highly specific for substrates
Amino acid residues in the active site interact with substrates

Enzyme Activity

Enzyme activity is measured by the rate of product formation
One unit of enzyme activity converts one µmole of substrate to product
Reaction speed depends on the number of substrates that change into products.

Factors Effecting Enzyme Activity

Enzyme concentration affects the speed of a reaction
Substrate concentration affects how quickly substrates move into reactants
Temperature changes enzyme structure, and affects activity
pH changes can affect enzyme activity
Inhibitors can decrease reaction speed and are important to understanding enzyme functions.

Enzyme Concentration

Enzyme concentration directly impacts reaction speed
Increasing enzyme concentration increases the rate at which substrates can be converted to products

Substrate Concentration

Increasing substrate concentration increases reaction speed until maximum rate is reached
Km, the substrate concentration at half maximum reaction rate, reflects enzyme affinity for a substrate

Temperature

Temperature affects enzyme shape and activity
Enzymes have optimal temperatures for maximum activity
Extreme temperatures can denature enzymes, stopping reactions.

pH

pH affects enzyme shape and activity
Enzymes have optimal pH ranges
Extreme pH values can denature enzymes

Inhibitors

Inhibitors decrease enzyme activity
Reversible inhibitors bind temporarily
Irreversible inhibitors bind permanently

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Description

This quiz covers the essential concepts of enzymes, their properties, classifications, and roles in metabolic pathways like glycolysis. It also explores the concepts of activation energy and enzyme inhibition. Test your understanding of how enzymes facilitate biochemical reactions and influence metabolic processes.