Biochemical Oscillators and Circadian Clocks Study Guide

These flashcards cover key vocabulary and concepts related to circadian clocks, cholesterol metabolism, and mitochondrial regulation.

Circadian clock

A biochemical oscillator that regulates physiological processes based on a 24-hour cycle.

PERs and CRYs protein levels

Highest during the night; they dimerize and translocate to the nucleus.

REV-ERBa/b protein levels

Increase in the morning and inhibit Bmal1 transcription.

SREBP-Scap complex

Transported from the endoplasmic reticulum to the Golgi apparatus.

bHLH-zip domain

Found in the amino end of SREBP; responsible for binding DNA.

Regulatory domain (Reg)

Found in the carboxy terminal of SREBP; upon cleavage, it enters the nucleus.

S1P

Site protease that cleaves SREBP in the luminal loop.

SCAP

An integral membrane protein involved in cholesterol homeostasis.

Insig proteins

Bind to SCAP under conditions of high sterol levels and prevent cholesterol synthesis.

COPII

A type of vesicle coat protein that transports proteins from the rough ER to the Golgi apparatus.

HMG-CoA reductase

Target of cholesterol-lowering statins; inhibited by Insig binding to SCAP.

2-Cys Prx

Homodimers consisting of two catalytic cysteine residues involved in reducing peroxides.

H2O2

Hydrogen peroxide, which, when levels are high, causes hyperoxidation of peroxidatic Cys.

Sulfiredoxin (Srx)

Reactivates sulfinylated Prx by reducing sulfinic acid.

Prohibitin

Located in the mitochondrial inner membrane, associated with mitochondrial nucleoid and Lon protease.

COX4-1 and COX4-2

Subunits of cytochrome c oxidase (complex IV); COX4-2 is expressed under hypoxic conditions.

Orexin A and B

Neuropeptides that regulate arousal and appetite; derived from prepro-orexin.

Glymphatic pathway

A system that facilitates drainage of cerebrospinal fluid and waste clearance from the brain.

AQP4

Aquaporin-4, a water channel protein expressed in astrocytes, important for maintaining CSF dynamics.

SIRT1

A protein that deacetylates various substrates, including BMAL1, affecting circadian regulation.

TFAM

Mitochondrial transcription factor that regulates mtDNA transcription and replication.

Mitophagy

The process by which damaged mitochondria are targeted for degradation.

PGC-1α

A coactivator that regulates nuclear genes involved in mitochondrial biogenesis.