Properties of Enzymes Quiz

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Questions and Answers

What effect does competitive inhibition have on the Km value?

Varies depending on Vmax

Decreases Km

Increases Km (correct)

No change in Km

In non-competitive inhibition, where does the inhibitor bind to the enzyme?

Transition state

Substrate binding site

Active site

Allosteric site (correct)

What happens to the Vmax value in non-competitive inhibition?

Increases

Fluctuates

No change

Decreases (correct)

In uncompetitive inhibition, when does the inhibitor bind to the enzyme?

After the substrate binds Signup and view all the answers

What is the primary effect of uncompetitive inhibition on Vmax and Km?

Decreases Vmax, Increases Km Signup and view all the answers

Which type of inhibition involves binding at a site other than the active site?

Non-competitive inhibition Signup and view all the answers

What is the term used to refer to intact enzymes with their bound cofactors?

Holoenzymes Signup and view all the answers

Which complex is also known as NADH dehydrogenase or NADH oxireductase?

Complex I Signup and view all the answers

In enzyme kinetics, what term is used to describe the rate or velocity of a reaction?

Kinetics Signup and view all the answers

What is the initial velocity (v0) in enzyme kinetics?

Velocity at the beginning of a reaction Signup and view all the answers

Which type of enzymes follow a second-order reaction in enzyme kinetics?

Allosteric enzymes Signup and view all the answers

What does ATP hydrolysis result in?

Increase in concentration of ADP Signup and view all the answers

What is the main role of a catalyst in a chemical reaction?

Increasing the rate of the reaction Signup and view all the answers

How do catalysts affect the activation energy of a reaction?

Decrease it Signup and view all the answers

Why do living systems, like biological organisms, rely on catalysts like enzymes to increase reaction rates?

To avoid damaging structures with high temperatures Signup and view all the answers

What type of bond is formed during the creation of peptide bonds?

Covalent bond Signup and view all the answers

In the formation of peptides, what is the function of peptidyl transferase?

Facilitates the formation of peptide bonds Signup and view all the answers

What was discovered by Linus Pauling related to C-N bonds in amino acids?

C-N bonds between two amino acids are shorter than other C-N bonds Signup and view all the answers

What effect does a decrease in pH have on oxygen binding to hemoglobin?

Weakens oxygen binding and enhances oxygen release Signup and view all the answers

Which molecule besides oxygen can lower the oxygen binding affinity of hemoglobin?

Carbon dioxide (CO2) Signup and view all the answers

Which type of hemoglobin is predominant in adult humans?

HbA (α2β2) Signup and view all the answers

What is the function of 2,3-bisphosphoglycerate (BPG) in relation to hemoglobin?

Decreases oxygen binding affinity Signup and view all the answers

How does an increase in CO2 affect the pH and oxygen binding to hemoglobin?

Decreases pH and weakens oxygen binding Signup and view all the answers

What is the role of 2,3-bisphosphoglycerate (BPG) when energy demand is high?

Stabilizes oxyHb for increased oxygen transport Signup and view all the answers

What type of conditions can lead to protein denaturation?

All of the above Signup and view all the answers

Which structure of a protein is disrupted during denaturation?

Tertiary structure Signup and view all the answers

What is the primary function of myoglobin?

Reversible oxygen binding in muscles Signup and view all the answers

In which state is deoxygenated hemoglobin considered?

Taut state Signup and view all the answers

What is the composition of an HbA molecule in red blood cells?

2 α-chains and 2 β-chains (α2β2) Signup and view all the answers

What stabilizes the oxygen binding site in hemoglobin?

Non-polar amino acids Signup and view all the answers

What causes hemoglobin to alternate between the T and R states?

Oxygenation/Deoxygenation Signup and view all the answers

Study Notes

Enzyme Inhibition

Competitive inhibition increases Km value, meaning more substrate is needed to reach half-maximal velocity.
In non-competitive inhibition, the inhibitor binds to an allosteric site, not the active site of the enzyme.
Vmax remains unchanged in non-competitive inhibition as the maximum reaction rate can still be achieved but at different substrate concentrations.
Uncompetitive inhibition occurs when the inhibitor binds to the enzyme-substrate complex, preventing the reaction from proceeding.
Uncompetitive inhibition decreases both Vmax and Km, as it stabilizes the enzyme-substrate complex but reduces the overall capacity for product formation.
Non-competitive inhibition involves binding at a site other than the active site, affecting enzyme activity without competing with the substrate for binding.

Enzyme Composition and Complexes

Intact enzymes bound to their cofactors are referred to as holoenzymes.
The complex known as NADH dehydrogenase or NADH oxireductase is involved in electron transport and energy production.

Enzyme Kinetics

The term "velocity" describes the rate at which a reaction occurs in enzyme kinetics.
The initial velocity (v0) in enzyme kinetics refers to the rate of reaction at the very start, often measured when substrate concentration is at its maximum.
Second-order reaction kinetics typically applies to enzymes that catalyze reactions involving two substrates.

Catalysis and Reaction Rates

ATP hydrolysis results in the release of energy, which is fundamental for cellular processes.
A catalyst lowers the activation energy required for a reaction to proceed, thereby accelerating the reaction rate.
Living organisms rely on catalysts like enzymes to increase reaction rates to sustain life, as most biochemical reactions are too slow without them.

Protein Structure and Function

Peptide bonds form during protein synthesis, creating covalent links between amino acids.
Peptidyl transferase catalyzes the formation of peptide bonds during translation.
Linus Pauling discovered that C-N bonds in amino acids are not rigid, allowing for conformational flexibility in proteins.

Hemoglobin and Oxygen Binding

A decrease in pH reduces hemoglobin's oxygen binding affinity, promoting oxygen release to tissues.
2,3-bisphosphoglycerate (BPG) is another molecule, in addition to CO2, that can lower hemoglobin's oxygen affinity.
Hemoglobin type predominant in adult humans is HbA, composed of two alpha and two beta chains.
2,3-bisphosphoglycerate (BPG) functions to facilitate oxygen release, especially during high energy demand situations.
Increased CO2 lowers pH and further decreases oxygen binding affinity of hemoglobin, promoting oxygen delivery to metabolically active tissues.

Protein Denaturation

Conditions such as extreme pH, high temperature, or harsh solvents can lead to protein denaturation.
During denaturation, primarily the secondary and tertiary structures of proteins are disrupted, resulting in loss of function.

Myoglobin and Hemoglobin States

The primary function of myoglobin is to store and transport oxygen in muscle tissues.
Deoxygenated hemoglobin is referred to as being in the T (tense) state, which has a lower affinity for oxygen.
The oxygen binding site in hemoglobin is stabilized by interactions with surrounding amino acids.
Hemoglobin alternates between T and R (relaxed) states in response to changes in oxygen concentration and binding events.

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Test your knowledge on the properties of enzymes, catalysts that enhance the rate of biochemical reactions without being permanently altered. Explore how enzymes modify reaction pathways to lower activation energy and increase reaction rates through temperature, reactants, and catalysts.