Metabolic Pathways

Question 1

What is the collective term for the thousands of biochemical reactions that occur within a cell?

Answer 1

Cell metabolism

Metabolism encompasses the integrated and controlled pathways of enzyme-catalysed reactions.

Question 2

Define a metabolic pathway.

Answer 2

A series of chemical reactions occurring within a cell

These reactions are enzyme-catalysed.

Question 3

What are the two main types of metabolic pathways?

Answer 3

• Anabolic pathways
• Catabolic pathways

These pathways involve different processes of energy usage and molecule transformation.

Question 4

What do anabolic pathways require and involve?

Answer 4

• Require energy
• Involve biosynthetic processes

Anabolic pathways build larger molecules from smaller ones.

Question 5

What do catabolic pathways release and involve?

Answer 5

• Release energy
• Involve the breakdown of molecules

Catabolic pathways break down larger molecules into smaller ones.

Question 6

True or false: Metabolic pathways can have reversible and irreversible stages.

Answer 6

TRUE

Some pathways may also have alternative routes.

Question 7

What is an example of a linked pathway in metabolism?

Answer 7

Bypass pathway when glucose is in plentiful supply

This shows how metabolic pathways can adapt based on substrate availability.

Question 8

What is the definition of metabolic pathways?

Answer 8

Metabolic pathways are sequences of chemical reactions occurring within a cell.

They involve various enzymes and substrates that facilitate biochemical processes.

Question 9

How can metabolic pathways be controlled?

Answer 9

• Presence or absence of particular enzymes
• Regulation of the rate of reaction of key enzymes

Control mechanisms ensure that metabolic pathways function efficiently and respond to cellular needs.

Question 10

What does induced fit describe?

Answer 10

The change when a molecule of substrate enters the active site, causing the active site to change shape to fit closely around the substrate.

This concept illustrates the dynamic nature of enzyme-substrate interactions.

Question 11

What is the role of the active site in an enzyme?

Answer 11

The active site is flexible and dynamic, specific to its substrate, and binds only to one particular substrate.

The shape of the active site must match the shape of the substrate for effective binding.

Question 12

What is the affinity relationship between the substrate and the active site?

Answer 12

The substrate has a high affinity for the active site, while the resulting products have a low affinity and leave the active site.

This affinity difference facilitates the release of products after the reaction.

Question 13

What is activation energy?

Answer 13

Activation energy is the energy needed to break chemical bonds in the reactant chemicals.

It is a crucial factor in determining the rate of chemical reactions.

Question 14

How does induced fit affect activation energy?

Answer 14

Induced fit lowers the activation energy needed by reactants and increases the reaction rate.

This mechanism enhances the efficiency of enzymatic reactions.

Question 15

True or false: The majority of metabolic reactions are irreversible.

Answer 15

FALSE

Most metabolic reactions are reversible, and the presence of a substrate or removal of a product can drive reactions in a particular direction.

Question 16

What are the three methods of controlling metabolic pathways?

Answer 16

• Competitive inhibition
• Non-competitive inhibition
• Feedback inhibition

These methods involve the regulation of enzyme activity.

Question 17

In competitive inhibition, what do the inhibitor molecules compete with?

Answer 17

Molecules of the substrate

The inhibitor’s structure is similar to that of the substrate, allowing it to attach to the enzyme’s active site.

Question 18

True or false: Competitive inhibition can be reversed by increasing substrate concentration.

Answer 18

TRUE

Increasing substrate concentration allows more substrate to bind to the active sites.

Question 19

What happens to the active site during non-competitive inhibition?

Answer 19

The shape of the active site changes

This change prevents the substrate from binding to the enzyme.

Question 20

Fill in the blank: Non-competitive inhibition cannot be reversed by increasing _______.

Answer 20

substrate concentration

This distinguishes it from competitive inhibition.

Question 21

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

Answer 21

A place other than the active site

This binding alters the shape of the active site.

Question 22

What is feedback inhibition in metabolic pathways?

Answer 22

A process where the end-product binds to an earlier enzyme, altering its active site and stopping the pathway

This prevents excessive production of the end-product.

Question 23

How does the concentration of the end-product affect metabolic pathways?

Answer 23

As the concentration drops, inhibition ceases and the pathway resumes

This allows for regulation of metabolic reactions.

Question 24

What can control metabolic reactions besides feedback inhibition?

Answer 24

• Presence of a substrate
• Removal of a product

These factors can drive reactions in a particular direction.

Question 25

In feedback inhibition, what happens to the **active site** of the enzyme?

Answer 25

It changes shape and can no longer bind to the substrate ## Footnote This alteration prevents the conversion of the initial substrate.

Question 26

Fill in the blank: The **end-product** binds to an earlier enzyme in the metabolic pathway, causing _______.

Answer 26

feedback inhibition ## Footnote This process is crucial for regulating metabolic pathways.