IB Biology Topic C1.1.13 Cyclical and Linear Pathways in Metabolism Revision Notes (HL)

IB Biology Topic C1.1.13 Cyclical and Linear Pathways in Metabolism Revision Notes (HL) | RevisionDojo

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Metabolic Pathways Run in Two Shapes: Straight Lines and Loops

Metabolic pathways are sequences of enzyme-catalysed reactions that transform molecules in cells.
Thousands of these reactions run constantly to support respiration, biosynthesis, and other vital processes.
A pathway takes one of two shapes: linear (start to end) or cyclical (a loop that regenerates its own starting molecule).

Linear Pathways: A One-Way Sequence

Definition

Linear pathway

A straight sequence of reactions where each product becomes the substrate for the next step, moving in one direction without looping back.

A linear pathway begins with a clear starting substrate and finishes with an end product.
Each step depends on the one before it, like dominoes falling in order.
The product moves on and does not re-enter the pathway.

Glycolysis: A Linear Pathway in Action

Glycolysis takes place in the cytoplasm and breaks glucose (6C) into two pyruvate molecules (3C), producing ATP and NADH.
It is linear because glucose enters at one end and pyruvate leaves at the other.
Pyruvate never re-enters; it passes to the link reaction in aerobic conditions or to fermentation in anaerobic conditions.

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Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Metabolic Pathways Run in Two Shapes: Straight Lines and Loops

Metabolic pathways are sequences of enzyme-catalysed reactions that transform molecules in cells.
Thousands of these reactions run constantly to support respiration, biosynthesis, and other vital processes.
A pathway takes one of two shapes: linear (start to end) or cyclical (a loop that regenerates its own starting molecule).

Linear Pathways: A One-Way Sequence

Definition

Linear pathway

A straight sequence of reactions where each product becomes the substrate for the next step, moving in one direction without looping back.

A linear pathway begins with a clear starting substrate and finishes with an end product.
Each step depends on the one before it, like dominoes falling in order.
The product moves on and does not re-enter the pathway.

Glycolysis: A Linear Pathway in Action

Glycolysis takes place in the cytoplasm and breaks glucose (6C) into two pyruvate molecules (3C), producing ATP and NADH.
It is linear because glucose enters at one end and pyruvate leaves at the other.
Pyruvate never re-enters; it passes to the link reaction in aerobic conditions or to fermentation in anaerobic conditions.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic C1.1.13: Cyclical and Linear Pathways in Metabolism Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Metabolic Pathways Run in Two Shapes: Straight Lines and Loops

Linear Pathways: A One-Way Sequence

Glycolysis: A Linear Pathway in Action

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Metabolic Pathways Run in Two Shapes: Straight Lines and Loops

Linear Pathways: A One-Way Sequence

Glycolysis: A Linear Pathway in Action

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account