UNSW Cell Biology

This lecture introduces how information is transferred from stable stored information (DNA) converted to an intermediate (mRNA, rRNA, tRNA) of variable stability, exported from the nucleus to the cytoplasm where mRNA is then translated into Protein. This is gene expression, the products of this process are used either within the cell, exported (exocytosis) or used to replace worn out components.

We will study this topic at the level of the cellular components and organelles involved in the process: ribosomes, endoplasmic reticulum, Golgi apparatus, vesicles (transport and secretory).

Lecture Text: Lecture Word Document 248 Kb

Lab 03 Group Project

Cartoon of Exocytosis and Endocytosis

Page Links: Introduction | Objectives | Lecture Audio | Textbooks | Looking in the Cytoplasm | Cytosol | Compartments are Dynamic | Protein Synthesis | Ribonucleic Acid (RNA) | Ribosomal RNA (rRNA) | Ribosome Structure | Ribosome Function | Polyribosomes | Endoplasmic_Reticulum | Rough Endoplasmic Reticulum - Function | Glycoproteins | Rough Endoplasmic Reticulum | Smooth Endoplasmic Reticulum - Structure | Smooth Endoplasmic Reticulum - Function | Transport Vesicles | GolgiApparatus - History | Golgi Apparatus - Structure | Golgi Apparatus - Function | Exocytosis | Abnormalities | References | Online Textbooks | Web Links | 2007 Lecture Slides | Comments Acronyms

• Membrane bound compartment
• About 1/2 total cell volume
• Intermediary metabolism takes place in the cytosol
  • Chemical biological reactions
  • Degradation
  • Synthesis
• Protein molecules
  • cell has about 10 billion (1x1010)
  • 10,000–20,000 different kinds

• Membrane bound compartments change shape and size
• Related to cell cycle, differentiation, signaling

• provide framework for dozens of proteins involved in assembly of AA sequence into protein
• most abundant RNA in cells
• Usually characterized by sedimentation coefficient
  • 40S & 60S
• rRNA genes are located in nucleolus

• All RNA components mRNA, rRNA and tRNA come together in this structure
• two ribosome types with identical structure
• different locations
• free and membrane bound
  • Free in cytoplasm
  • Bound to endoplasmic reticulum

• polyribosomes or polysomes are the EM visible granules
• many ribosomes bound to a single mRNA
• single ribosome covers a 54bp mRNA region
• the synthesised single amino acid chain can then be "modified"
  • in the cytoplasm or in specialised organelles
• Protein Modification/Function

• endoplasmic “within the cell”
• reticulum “a little net”
• an organelle, membrane bound compartment. within the cytoplasmic space
• One structural compartment
• Two functional compartments
  • Rough Endoplasmic Reticulum (RER)
  • Smooth Endoplasmic Reticulum (SER)

(Endoplasmic Reticulum Images: em, flourescent)

• about 50% of cell membrane
• continuous with outer nuclear membrane
• single highly convoluted membrane enclosing a single space
• ER lumen = ER cisternae
• “rough” because of many ribosomes attached to the membrane
• ribosomes bound only to cytoplasmic side of ER membrane

• RER synthesized material is transferred by budding off of membrane
• Forms transport vesicle
• Transports substances to different cellular locations
• Most transport to Golgi apparatus
• Active transport mainly along microtubules (cytoskeleton)

Movies

JCB - movie - transport vesicles and lipid (large 9.7 Mb)

• Discovered over 100 years ago
• Camillo Golgi (1898)
  • seen in neurons as anastomosing threads
  • “internal reticular apparatus"
• Soon detected in many cells
• Nobel Prize1906 Camillo Golgi, Santiago Ramón y Cajal
  • http://nobelprize.org/medicine/articles/golgi/

• organelle, membrane enclosed structural compartment
• cell may contain one or more Golgi apparatus
• located near the nucleus
• disc shaped membrane stack
• Golgi stack
• from 6-30/stack
• 3-100’s stacks/cell
• many sets of membrane bound smooth surfaced cisternae

• Sorting of cytosolic/secreted proteins
• Glycosylation of secreted proteins
• Modification of carbohydrates
• Side chains are also trimmed
• Trans vesicles fuse with the plasma membrane

Transport ER to Golgi

Golgi Apparatus Pathways

Movie: Golgi to Cell surface

• protein export (secretion)
  • constitutive and regulated
• related also to membrane turnover
  • new lipid
  • new cholesterol
  • new membrane proteins

Movies

JCB - movie - transport vesicles and lipid (large 9.7 Mb)

JCB - movie - View of many Carriers

"There are three types of behaviors of the post-Golgi carriers: (1) carriers that are stationary; (2) carriers that are moving, but not fusing; and (3) carriers that fuse to the plasma membrane. As can be seen on the extreme left and right, fusion occurs with a bright local burst of fluorescence followed by a spread of the fluorescence. The carrier on the extreme left was observed doing transport, docking, and fusion during the acquisition time. The two carriers on the extreme right did not move significantly before they fused."

• accumulation of abnormal proteins
  • misdirected (wrong “postcode”)
  • truncated or altered modification (missing enzymes)
• Genes and Diseases
  • http://www.ncbi.nlm.nih.gov/books/bookres.fcgi/gnd/tocstatic.html
• OMIM - Online Mendelian Inheritance in Man
  • http://www.ncbi.nlm.nih.gov/sites/entrez?db=omim

In 2008 a new way of presenting course content online is being trialled. Please let me know of any difficulties/suggestions or things that work well.

Notice also that in some slides I have added annotations in brackets with my initials (MH - )

Links: Current Course Outline 2008