BioChem- Enzyme Regulation

What are the three main types of enzyme regulation?

Negative feedback, positive feedback, and feed-forward regulation.

What does negative feedback do in enzyme regulation?

It inhibits earlier steps in a metabolic pathway to maintain balance.

What is an example of negative feedback in glycolysis?

ATP inhibits phosphofructokinase 1 (PFK-1) to control energy production.

How does positive feedback work in cellular systems?

It enhances the effect of downstream products causing a rapid cycle until a specific event occurs.

What is an example of positive feedback during childbirth?

Oxytocin increases uterine contractions, leading to more oxytocin release.

What is feed-forward regulation?

It prepares metabolic pathways for future activity by responding to early intermediates.

Give an example of feed-forward regulation in glycolysis.

Fructose 1,6-bisphosphate activates pyruvate kinase.

What does cooperativity in enzymes refer to?

The easier binding of substrates after the initial ligand has bound.

What is hemoglobin's primary function?

Transporting oxygen.

What characteristic does hemoglobin exhibit in oxygen binding?

Cooperativity.

What happens to the binding curve of hemoglobin when cooperativity is involved?

It becomes S-shaped (sigmoidal).

What does the Hill coefficient quantify?

Cooperativity of enzyme binding.

What does a Hill coefficient greater than 1 indicate?

Positive cooperativity.

What does a Hill coefficient of 1 indicate?

Non-cooperativity.

What role do non-covalent interactions play in enzyme regulation?

Substrates and allosteric regulators bind enzymes through weak interactions.

What are the main types of non-covalent interactions involved in enzyme regulation?

Hydrogen bonding, ionic interactions, and hydrophobic effects.

What is a zymogen?

An inactive precursor enzyme that prevents premature enzymatic activity.

How is trypsinogen activated?

By cleavage into trypsin in the small intestine.

What is phosphorylation in terms of enzyme regulation?

The addition of a phosphate group to specific amino acid residues.

What enzymes catalyze phosphorylation?

Kinases.

What do phosphatases do in enzyme regulation?

They catalyze dephosphorylation.

What are prosthetic groups?

Tightly bound cofactors that are essential for enzyme activity.

What are holoenzymes?

Complete, catalytically active enzymes with their bound cofactors.

What distinguishes a cofactor from a coenzyme?

Cofactors can be inorganic or organic, while coenzymes are organic molecules often derived from vitamins.

What is the role of coenzyme A (CoA)?

Transfer acyl groups within a reaction.

Why are vitamins relevant to enzyme function?

They are the source of many coenzymes required for enzymatic activity.

What is the significance of the shape of a sigmoidal binding curve?

Indicates cooperative binding of ligands, enhancing functionality.

What does the term 'apoenzyme' refer to?

An inactive enzyme without its cofactor, requiring addition to function.

How does the concept of cooperativity help hemoglobin?

It enhances hemoglobin's efficiency in oxygen transport.

What happens to enzyme activity during post-translational modifications?

It can alter activity, stability, and cellular location.

What is the role of allosteric regulation in enzyme function?

It involves conformational changes that affect enzyme activity.

Why is zymogen activation crucial for digestive enzymes?

To ensure digestive enzymes act only in the right location and at the right time.

What does increased temperature affect in terms of enzyme activity?

It generally increases activity up to a certain point before denaturation.

How can enzyme activity be regulated?

Through allosteric regulation and covalent modifications.

What does a S-shaped binding curve indicate about an enzyme?

It indicates the presence of cooperativity in ligand binding.

What is the function of cofactors in enzymatic reactions?

Stabilize enzyme structure or participate directly in enzymatic reactions.

What is an example of a metal ion cofactor?

Magnesium ion (Mg²+) or zinc ion (Zn²+).

What type of modification do zymogens undergo to become active enzymes?

Cleave of peptide bonds.

How do non-covalent interactions impact enzyme conformation?

They influence the shape and function of the enzyme during regulation.

What does the term 'post-translational modification' refer to?

Chemical modifications occurring to proteins after translation, including phosphorylation.

In what ways can enzyme activity be enhanced or inhibited?

Through allosteric regulation, phosphorylation, or covalent modifications.

What kind of interaction occurs during substrate binding to an enzyme?

A combination of multiple weak interactions.

Why is it important that enzymes can be regulated?

To maintain homeostasis and proper metabolic control in cells.

What is the primary role of coenzymes in enzymatic reactions?

To carry chemical groups that are transferred during reactions.

What would a Hill coefficient of less than 1 indicate about ligand binding?

Negative cooperativity, where the binding of one ligand decreases the binding affinity of subsequent ligands.

What change occurs in blood pH during active muscle metabolism?

It decreases, causing a shift in the oxygen dissociation curve of hemoglobin.

What is typical of the behavior of enzymes at optimal temperatures?

They exhibit maximal activity.

What is the significance of high enzyme specificity?

It allows enzymes to catalyze specific reactions without interference.

How do changes in substrate concentration affect enzyme activity?

Enzyme activity usually increases with an increase in substrate concentration to a point.

What factors can lead to enzyme denaturation?

Extreme temperature, pH changes, and high substrate concentrations.

What is the effect of temperature on enzyme activity in general?

Increases up to a certain optimum and then decreases.

How do competitive inhibitors affect enzyme activity?

They compete with substrates for binding to the active site, reducing reaction rates.

What effect do non-competitive inhibitors have on enzymes?

They bind to an enzyme at an allosteric site and reduce activity regardless of substrate concentration.

What is the significance of enzyme kinetics in biochemistry?

It helps understand how enzymes function and can be regulated.

What type of bond is typically formed between enzymes and substrates?

Weak interactions such as hydrogen bonds and ionic bonds.

How can enzyme inhibitors be applied in medicine?

They can be used to block enzyme activity that leads to disease processes.

What role do allosteric sites play in enzyme function?

They allow regulatory molecules to enhance or inhibit enzyme activity.

What is an enzyme's active site?

The specific region where substrates bind to the enzyme.

How do allosteric activators influence enzyme behavior?

They induce a conformational change that increases activity.

What aspect of hemoglobin's structure contributes to its cooperative binding?

The presence of multiple subunits that alter each other's binding affinity.

What is the main regulatory mechanism for glycolytic enzymes?

Feedback inhibition and feed-forward regulation.

How does enzyme regulation by phosphorylation generally affect enzyme activity?

It can either activate or inhibit enzymes, depending on the context.

What measurement indicates how tightly a ligand binds to its enzyme?

The dissociation constant (Kd).

In the context of metabolism, what does the term 'flux' refer to?

The rate of flow of metabolites through a pathway.

Why do metabolic pathways often have multiple regulatory points?

To allow fine-tuning of metabolic flux and maintain balance within the cell.

How does oxygen concentration affect hemoglobin's oxygen binding?

Higher oxygen concentration increases binding affinity due to cooperativity.

Which aspect of enzymology is critical for developing drugs targeting specific pathways?

Understanding enzyme mechanisms and regulation.

What is the significance of enzyme specificity in biological reactions?

It ensures that enzymes catalyze only the desired reactions without unwanted side reactions.

In enzyme kinetics, what does the Michaelis-Menten equation describe?

The rate of enzyme-catalyzed reactions as a function of substrate concentration.

What is the function of the enzyme chymotrypsin?

To cleave peptide bonds in proteins during digestion.

How does pH affect enzyme activity?

Each enzyme has an optimal pH at which its activity is maximized.

What term describes the maximum rate of enzyme activity?

Vmax.

What does the term 'turnover number' (kcat) represent?

The number of substrate molecules converted to product per enzyme molecule per second.

What is the role of RNA in enzymatic functions?

Certain RNA molecules can function as enzymes, known as ribozymes.

What are the common characteristics of most enzyme-catalyzed reactions?

They are highly specific, efficient, and reversible.

Why is it important that enzymes do not change during reactions?

It allows them to be reused in multiple cycles of catalysis.

What does the term 'substrate specificity' refer to?

An enzyme's preference for a particular substrate over others.

What are enzyme cofactors necessary for?

Providing functionality that enzymes cannot achieve alone.

What happens to enzyme activity if the concentration of the enzyme increases?

It generally increases the activity until limited by substrate availability.