Lecture 1 Flashcards
What are cells
Highly dynamic; constituent elements all in continuous state of flux; dynamic self organising system.
Self-organising
Cell scale phenomena - spatial and temporal organisation. Cell has to manage interactions between actin monomers and other constituent elements.
Self organising systems require continuous energy input. => Entropy; not favourable to greater organisation.
1 human lifetime
10^9 seconds
Cells are made out of
Atoms, mostly C, H2O.
Macromolecules - proteins, nucleic acids, lipids, sugars.
size of protein
Median size = approx 400 AAs, 40kDa, 5nm.
But, large range.
Median lifetime of protein
in human cells, 2 days; varies based on type of protein.
Size of bacterial cell
1um.
Generally, cells tend to be in micron range; but there’s a huge amount of morphological diversity - relative sizes are important. Proteins are at least 3 orders of magnitude smaller than cells.
Size of nucleus
Tends to scale with cell size.
Diameter approx 10 um in human cells.
Size of human genome
1 m, which is much bigger than 10um nucleus diameter.
The human genome contains approximately
one billion base pairs.
Each base pair is approximately 1 nm long.
Typical lifetime of a cell
Cells can live up to 4
orders of magnitude
longer than the
typical protein
Neurons - most mitotic. Red blood cells - live 4 months, but no nucleus. Haemoglobin is very stable - approx 120 day lifetime.
How do cells regulate interactions among macromolecules
and thus large-scale cellular phenomena?
Cells control:
- Localization patterns
- Expression levels (changes probability of interactions)
- Binding affinities (strength of binding between molecule A and B).
TOR
master regulator of cell growth. Regulates binding affinities; determined by non covalent bonds between macromolecules. TOR modifies likelihood of these bonds forming.
TOR = kinase; Kinase - adds P group to protein. Post-translational modifications can change morphology of protein, changing the binding ability.
How do cells control binding affinities?
By regulating post-translational modifications, protein conformation, and formation of non-covalent bonds.
Impact of TOR-mediate phosphorylation on localisation patterns and expression levels?
Regulates the localisation of TFs ==> expression levels.
How do cells control expression levels
Cells control expression levels by regulating transcription,
translation, and degradation
6 points of control of protein expression from transcription to degradation
- transcriptional control
- RNA processing control
- RNA transport and localisation control
- translational control OR 5. mRNA degradation control.
- If translated, protein degradation control.
