• A prion disease • Prions are misfolded proteins • Prions are infec8ous: can be transferred from organism to organism, and ‘convert’ normal proteins • Results in ‘plaques’ of proteins and holes in brain 8ssue 3
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Figure 5.16-1
Lower solute concentra<on Solute
ATP Higher solute concentra<on Ac<ve transport
4
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Figure 5.19
Outside
of cell Recep<on Receptor protein
Cytoplasm Transduc<on
Proteins of signal transduc<on
pathway Epinephrine (adrenaline) from adrenal glands
Response Hydrolysis of glycogen releases glucose for energy
Plasma membrane
5
Chapter 8
Cellular Reproduction: Cells from Cells
6
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7
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Chromosome (one long piece of DNA)
Centromere
Centromere
Sister
chromatids
Duplicated chromosome
8
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S phase
(DNA synthesis; chromosome duplication)
Figure 8.6
Interphase: metabolism and growth (90% of time)
G1
G2
Mitotic
(M) phase: cell division
(10% of time)
Cytokinesis
(division of cytoplasm) Mitosis
(division
of nucleus)
9
THE CELL CYCLE AND MITOSIS
Objec8ves:
• Outline the stages of the cell cycle, describing the events that occur (figure 8.6) • Describe the checkpoints of the cell cycle, what is ‘checked’, and what happens if a cell ‘fails’ a checkpoint • Outline the stages of mitosis, describing the events that occur during each stage (Figure 8.7)
10
The Cell Cycle
• Highly controlled – Ensures there are no errors mostly
– Ensures condi8ons are right for cell division
• Cell cycle control is via proteins – Cyclins Bind to
– Cylin-‐dependent kinases – Integrate informa8on from the environment and other cells and send ‘stop’ and ‘go’ signals at checkpoint using signal transduc8on pathways 11
The Cell Cycle Control System
Figure 5.19
Outside
of cell
Cytoplasm
Receptor protein
cdk Response
Proteins of signal transduc<on
pathway
Binds to a cyclin protein
Plasma membrane
Signal transduction pathway: Chain reaction of passing a signal along via one or more molecules
12
S phase
The Cell Cycle
Control (DNA synthesis; chromosome duplication)
System
G1 checkpoint
G1
Are conditions right for cell division? Is the DNA undamaged? Interphase: metabolism and growth (90% of time)
Mitotic
(M) phase: cell division
(10% of time)
G2
13
S phase
The Cell Cycle
Control (DNA synthesis; chromosome duplication)
System
Interphase: metabolism and growth (90% of time)
G1
Is the DNA undamaged? Are there enough of the proteins needed for M phase?
Mitotic
(M) phase: cell division
(10% of time)
G2
G2 checkpoint
14
S phase
The Cell Cycle
Control (DNA synthesis; chromosome duplication)
System
Interphase: metabolism and growth (90% of time)
G1
Checks that spindle apparatus (moves and sorts chromosomes) is intact Mitotic
(M) phase: cell division
(10% of time)
G2
Metaphase checkpoint
15
The Cell Cycle Control System
• Checkpoint proteins
– delay the cell cycle un8l problems are fixed – prevent cell division if the problem cannot be fixed
• This prevents division of cells with DNA damage or the wrong number of chromosomes
