Descriptive notes made after chapter readings as instructed by the professor. Then edited again during lectures. Includes everything that is on the exams. Try to memorize definitions and remember dates and names.
Chapter 15 - Without sorting signals, they remain in the cytosol
permanently
- Cells use different strategies to isolate and organize their
- A water-soluble protein must be transported with the help
chemical reactions
of other organelles due to the hydrophilic membrane of the
- One strategy is to aggregate enzymes into multicomponent
membrane enclosed organelle it was produced in
complexes
- Proteins move into the nucleus through nucleus
- This strategy is used for synthesizing DNA, RNA, and
pores that penetrate both the inner and outer side
proteins
of the membrane. These pores are selective gates
- Another strategy is to confine different metabolic processes
and actively transport selective proteins but smaller
within membrane-enclosed compartments
molecules can diffuse easily
- This strategy is most highly developed in eukaryotic cells.
- Protein translocators in the membrane transport
MEMBRANE-ENCLOSED ORGANELLES proteins to the ER, mitochondria, and chloroplasts.
They must unfold to make it through the
- Prokaryotic cells have a single compartment enclosed by the membranes
plasma membrane - Proteins being transported by the ER are
- Eukaryotic cells are subdivided by internal membranes transferred into secretory vesicles which pinch off
- Cross section through a eukaryotic cell shows numerous from the membrane of the ER and then fuse with
membrane-enclosed organelles the organelle membrane they are transporting to
- Organelles are distinct structures that carry out specialized
functions Signal Sequences Direct Proteins to the Correct
- Each organelle contains a unique set of large and small
Compartment
molecules.
PROTEIN SORTING - A sorting signal sequence is 15-60 amino acid long
- It is removed from the protein once it is sorted
Proteins Are Transported into Organelles by Three Mechanisms - Importance of signalling sequence has been shown through
experiments where the sequence has been deleted or
- Synthesis of all proteins begins in the cytosol on the
transferred from one protein to another by genetic
ribosomes
engineering techniques
- Some mitochondrial and chloroplast proteins are made on
- Signal sequences with the same destination can look very
ribosomes inside those organelles; but most of it is made
different
outside
- The fate of any protein depends on its sorting signal
- It directs the protein to its destined organelle
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