IB Biology Topic C2.1.14 Regulation of Cell Signalling Pathways by Positive and Negative Feedback Revision Notes (HL)

IB Biology Topic C2.1.14 Regulation of Cell Signalling Pathways by Positive and Negative Feedback Revision Notes (HL) | RevisionDojo

Written by official IB examiners

Feedback Keeps Cell Signalling Under Control

Definition

Feedback Inhibition

Feedback inhibition is a process where the end product of a metabolic pathway inhibits an enzyme involved in its own synthesis.

A signalling pathway that could not switch off would keep driving a response long after it was needed, which is harmful to the cell.
Feedback solves this by feeding the size of the response back onto the pathway that produced it.
Negative feedback
1. Switches the pathway off once a response is achieved, returning the system toward its baseline.
2. This is stabilising and is by far the most common form of feedback.
Positive feedback
1. Amplifies or reinforces the signal, driving the response further from baseline.
2. It is less common and pushes the system to a distinct end point rather than holding it steady.

Negative Feedback Returns the System to Baseline

A receptor pathway is switched on by a signal, and the response it produces is detected and used to shut the pathway down again.
This self-correcting loop keeps a value close to a set point, so it underpins homeostasis.
Because the response opposes the original change, the signal cannot run away and overshoot.

Analogy

A thermostat detects room temperature.
If the temperature falls below the set point, the heater turns on.
If the temperature rises above the set point, the cooling turns on.
The system always works to return to the set point.

Testosterone Regulation: A Hormone Held Steady

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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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Feedback Keeps Cell Signalling Under Control

Definition

Feedback Inhibition

Feedback inhibition is a process where the end product of a metabolic pathway inhibits an enzyme involved in its own synthesis.

A signalling pathway that could not switch off would keep driving a response long after it was needed, which is harmful to the cell.
Feedback solves this by feeding the size of the response back onto the pathway that produced it.
Negative feedback
1. Switches the pathway off once a response is achieved, returning the system toward its baseline.
2. This is stabilising and is by far the most common form of feedback.
Positive feedback
1. Amplifies or reinforces the signal, driving the response further from baseline.
2. It is less common and pushes the system to a distinct end point rather than holding it steady.

Negative Feedback Returns the System to Baseline

A receptor pathway is switched on by a signal, and the response it produces is detected and used to shut the pathway down again.
This self-correcting loop keeps a value close to a set point, so it underpins homeostasis.
Because the response opposes the original change, the signal cannot run away and overshoot.

Analogy

A thermostat detects room temperature.
If the temperature falls below the set point, the heater turns on.
If the temperature rises above the set point, the cooling turns on.
The system always works to return to the set point.

Testosterone Regulation: A Hormone Held Steady

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 C2.1.14: Regulation of Cell Signalling Pathways by Positive and Negative Feedback Notes

Feedback Keeps Cell Signalling Under Control

Negative Feedback Returns the System to Baseline

Testosterone Regulation: A Hormone Held Steady

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

Feedback Keeps Cell Signalling Under Control

Negative Feedback Returns the System to Baseline

Testosterone Regulation: A Hormone Held Steady

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

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics