Enzyme Overview and Functions

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Questions and Answers

What is the term for the catalytically active form of an enzyme?

Cofactor

Apoenzyme

Substrate

Holoenzyme (correct)

Which factor does not affect enzyme activity?

Enzyme concentration

Substrate shape (correct)

Temperature

What is the unit of activity for an enzyme?

1 mmol substrate converted in 1 minute

1 µmol substrate converted in 1 hour

1 µmol substrate converted in 1 minute (correct)

1 nmol substrate converted in 1 minute

What does the Km value indicate in enzyme kinetics?

Affinity of the enzyme for the substrate Signup and view all the answers

What defines the optimum temperature for an enzyme?

The temperature where it exhibits maximum activity Signup and view all the answers

What type of inhibitor permanently alters enzyme activity?

Irreversible inhibitor Signup and view all the answers

Enzymes in humans typically show maximum activity at what temperature range?

35-40 °C Signup and view all the answers

Which statement is true regarding enzyme concentration?

Higher enzyme concentration increases the potential reaction rate. Signup and view all the answers

What is the primary role of enzymes in biochemical reactions?

To decrease the activation energy Signup and view all the answers

Which type of enzyme is responsible for catalyzing oxidation-reduction reactions?

Oxidoreductases Signup and view all the answers

Which statement accurately describes the efficiency of enzyme-catalyzed reactions?

They are highly efficient, proceeding from 10³ to 10⁸ times faster. Signup and view all the answers

What distinguishes enzymes in terms of specificity?

They exhibit reaction specificity and substrate specificity. Signup and view all the answers

What is the relationship between enzyme activity and the Michaelis constant (Km)?

Lower Km values suggest higher enzyme affinity for the substrate. Signup and view all the answers

Which of the following is NOT a classification of enzymes?

Condensases Signup and view all the answers

Which of the following characteristics is true for all enzymes?

Most enzymes are proteins, albeit some are ribozymes. Signup and view all the answers

What defines a catalyst in the context of enzymatic reactions?

A catalyst decreases the activation energy and is not consumed. Signup and view all the answers

Study Notes

Enzyme Overview

Enzymes are biological catalysts
They increase the rate of biochemical reactions
They are highly specific for their substrate and reaction type
Enzymes are not consumed in the reaction
Most are proteins, some are ribozymes (RNA)
Lower activation energy by stabilizing the transition state

Learning Objectives for Enzymes

Describe enzymes and their properties
List enzyme classifications
Describe factors affecting enzyme activity
Explain the relationship between Km and enzyme activity
Explain enzyme inhibition and different types of inhibition

Metabolic Reactions and Enzymes

Enzymes facilitate metabolic reactions, including both anabolic (building up) and catabolic (breaking down) pathways
Enzymes increase the rate of these reactions, which are fundamental to life processes
Enzymes catalyze reactions by lowering activation energy
This speeds up reaction rates
Enzymes can modify molecules by binding temporarily for transport, degradation, or modifications within cells.
With some special molecules

Glycolysis Overview

Glycolysis is a metabolic process that breaks down glucose into pyruvate
Enzymes are crucial to facilitate these reactions (e.g., hexokinase, phosphofructokinase, etc.)
Each reaction step is catalyzed by specific enzymes

Enzyme Activity

Enzyme activity is the rate at which an enzyme catalyzes a reaction
Measured by the amount of substrate converted to product in a given time
One unit of enzyme activity converts 1 μmol of substrate to product in one minute under optimal conditions
Enzyme activity is influenced by several factors, including enzyme concentration, substrate concentration, temperature, pH, and inhibitors.
Enzyme activity can be measured and optimized according to these factors

Factors Affecting Enzyme Activity

Enzyme concentration: Higher concentration, faster reaction
Substrate concentration: More substrate, speeds reaction up until saturation
Temperature: Optimal temperature for max efficiency; high temp, denatures/slows reactions
pH: Affects enzyme structure and function (optimal pH for every enzyme)
Inhibitors: Substrates that reduce enzyme rate.

Enzyme Nomenclature

Enzymes are classified in an organized way
This is done according to their function (i.e. oxidoreductases, transferases, hydrolases, etc.)
Each enzyme is given a unique EC number for precise identification

Enzyme Kinetics and Km

Km reflects the enzyme's affinity for its substrate
Low Km means higher affinity (higher substrate concentration required to reach half V-max)
High Km means lower affinity (requires high substrate concentration to get half Vmax)
Vmax is the maximum reaction rate of an enzyme

Enzyme Regulation

Factors influencing enzyme activity
Enzymes can be regulated by changing the amount (synthesis/degradation), enzyme modification (e.g., phosphorylation / dephosphorylation), or the compartments in a cell.
These factors influence enzyme activity at different stages/steps

Isoenzymes

Enzymes that share the same catalytic function but have different structures(sequences) and different regulatory properties
Examples include lactate dehydrogenase and creatine kinase
Can be used to distinguish between different tissues or cellular conditions

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Description

Explore the fundamental concepts of enzymes, including their roles as biological catalysts and their properties that influence biochemical reactions. This quiz will cover enzyme classifications, factors affecting enzyme activity, and the dynamics of metabolic reactions facilitated by enzymes.