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Feedback Loops

Feedback Loops

In most cases, excessive hormone production is prevented by negative feedback—a loop that starts with a stimulus inducing the release of a particular substance, like a hormone, to maintain a certain level before triggering a signal that results in a decrease in further release of the hormone.

Allergic Reactions

Allergic Reactions

Feedback Inhibition

Feedback Inhibition

Biochemical reactions are occurring constantly in cells, converting starting substances to different products, usually with the help of enzymes that speed the reactions. Without enzymes, it would take far too long for most reactions to occur to be useful to the cell!

Proofreading

Proofreading

Proofreading

Proofreading

Synthesis of new DNA molecules is carried out by the enzyme DNA polymerase, which adds nucleotides on the daughter strand complementary to the template DNA strand. DNA polymerase has a higher affinity to add the correct base and ensures fidelity during DNA replication. Furthermore, it exhibits proofreading activity during replication, using an exonuclease domain that cuts off incorrect nucleotides from the nascent DNA strand.
Errors During Replication are Corrected by the DNA Polymerase Enzyme

Internal Receptors

Internal Receptors

Many cellular signals are hydrophilic and therefore cannot pass through the plasma membrane. However, small or hydrophobic signaling molecules can cross the hydrophobic core of the plasma membrane and bind to internal, or intracellular, receptors that reside within the cell. Many mammalian steroid hormones use this mechanism of cell signaling, as does nitric oxide (NO) gas.

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Related Experiment Video

Updated: May 11, 2026

An In Vitro Approach to Photodynamic Therapy

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Published on: August 17, 2018

Author's reply

David P Cork¹, Amit K Mehrotra, Mardi Gomberg-Maitland

¹Department of Cardiology, The University of Chicago, Chicago, Illinois, USA davidpcork@gmail.com.

Pulmonary Circulation

|May 11, 2013

Summary

No abstract available in PubMed .

Related Experiment Videos

Last Updated: May 11, 2026

An In Vitro Approach to Photodynamic Therapy

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