Cell Bio Lecture 18 (Chap 15)

(these are from .pptx)

Cytosol

Contains many metabolic pathways and is the site of protein synthesis.

Nucleus

Contains the main genome and is the site of DNA and RNA synthesis.

Endoplasmic Reticulum (ER)

Synthesizes most lipids and proteins for distribution to organelles and the plasma membrane and is the initial site of protein glycosylation.

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids for secretion or delivery to organelles.

Lysosomes

Responsible for intracellular degradation.

Endosomes

Sorts endocytosed material.

Mitochondria

Synthesizes ATP by oxidative phosphorylation.

Peroxisomes

Oxidizes toxic molecules.

Nuclear Transport

The transport of proteins through nuclear pores.

Nuclear Localization Signal (NLS)

A protein domain that directs a protein to the nucleus.

ER Transport

The process by which secretory proteins are directed to the ER during translation, involving signal sequences.

Signal Recognition Particle (SRP)

A complex that binds to the ER signal sequence and targets the ribosome to the ER membrane.

KDEL Signal

A C-terminal sequence (KDEL) that retrieves ER resident proteins from the Golgi.

Constitutive Secretion

Unregulated, continuous secretion of proteins and lipids.

Regulated Secretion

Regulated secretion of proteins in response to a specific signal.

Signal sequences

Necessary and sufficient to direct proteins to the correct cellular location(s)

Nuclear transport receptors

Karyopherins, importins, exportins

Ran

GTP binding protein

ER signal sequences

Consist of a long stretch of hydrophobic amino acids at the N-terminus