Finish Membranes, Start Organelles

1
Stephen Fish, Ph.D. Marshall University J. C. E.
School of Medicine Fish_at_Marshall.edu
2
Note to instructors I use these PowerPoint
slides in cell biology lectures that I give to
first year medical students. Copy the slides, or
just the illustrations into your own teaching
media. We all know that teaching science often
requires compromises and simplification for
specific student populations, or the requirements
of a specific course. Please feel free to offer
suggestions for improvements, corrections, or
additional illustrations. I would be pleased to
hear from anyone who finds my work useful, and am
always willing to make it better. Also, the
images have been compressed to screen resolution
to keep PowerPoint file size down, and I can
provide them at any resolution. Stephen E.
Fish, Ph.D.
3
Organelles Molecular Traffic Mitochondria,
Peroxisomes
4
How peroxisomes are made

• All genes are in the nucleus
• But a cell cant generate new ones from scratch
• Existing ones grow by delivery of proteins
  membrane
• Then they divide on their own
• Numbers are controlled by the cell by manufacture
  of components
• When cells divide, some are passed on to each
  daughter cell

5
Mitochondria
6
Mitochondria Structure
7
Mitochondrial Function in 1 Minute
8
Gradients across the inner membrane made by
electron chain transport
9
Transport through the inner membrane
10
Most Mitochondrial Proteins are Translated in the
Cytosol, then Chaperoned in an Unfolded State
11
Protein import a TOM TIM duet

• Matrix proteins have a positively charged sorting
  sequence
• Inner membrane electrical gradient special hsp
  70 pulls the protein in
• Signal peptidase cuts off the sequence, hsp 70
  60 help folding

12
Outer Membrane Protein Import

• A stop sequence (membrane a-helix) triggers
  release into the membrane

13
Protein Import into the Intermembrane Space

• Similar to the previous one, but no a-helix stop
  sequence

14
Inner Membrane Proteins (Transporters)

• Internal signal sequence binds accessory TOM
• Tiny accessory TIMs act like chaperones in the
  intermembrane space
• a-helix locks into inner membrane

15
Some Inner Membrane Intermembrane Space
Proteins Have two Sorting Sequences

• Snipping of the first reveals the second
• The second directs the protein back out of the
  matrix through another TOM

16
Sherman says
If you would just throw one of those little
molecular things I would gladly bring it back