Key Concepts for Week 5: Lectures 16-18
Monday, Nov. 2, Lecture 16: Photosynthesis
Organisms use organic compounds for energy production
o Autotrophs
 Self-feeders (make their own energy)
 Phototrophs – use light to make their energy
o Heterotrophs
 Live off of compounds made by other organisms
 Dependent upon phototrophs for food
Photosynthesis takes place in chloroplasts
6CO2 + 6H2O  C6H12O6 + 6O2
o Creates high energy (sugar) for plants – reaction fueled by solar energy (absorbed by chlorophyll)
Photosynthesis has two processes:
o Light reactions (in thylakoids)
 H2O  O2
 Photosystem I and II (II works first)
 Light is absorbed and drives ATP and NADPH synthesis
 Via linear electron flow
 Or circular electron flow (only goes through PS I)
o Dark reactions / Calvin cycle (in stroma)
 CO2  sugar
 Done by using ATP and NADPH
 Byproduct G3P is used to make sugars, fats, and proteins for plant
*** Both mitochondria and chloroplasts make ATP by chemiosmosis
Wednesday, Nov. 4, Lecture 17: Cell Cycle, Mitosis
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Collection of a cell’s genetic information = genome
o DNA packaged into chromosomes
Cell division important for reproduction and growth
o Same genetic material needs to be passed from parent to offspring cell
 Occurs through mitosis
Cell cycle phases
o Interphase (90% of the cell cycle)
 G1 – synthesis of macromolecules and cytoplasmic organelles
 S – Chromosome duplication
 G2 – Additional growth; preparation into mitosis
o Mitotic phase
 Mitosis – 5 subphases (prophase, prometaphase, metaphase, anaphase, telophase)
 Equal division of genetic material to 2 daughter cells
 Cytokinesis – splitting of the cytoplasm
 Different between animal and plant cells
Binary fission – happens in bacteria
o Duplication of DNA happens at origin of replication  bacterial cell splits in half to form 2
daughter cells
Friday, Nov. 6, Lecture 18: Cell Cycle Regulation, Cancer
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Checkpoints at different stages of cell cycle help to regulate cycle (stop and go signals)
Regulatory molecules:
o Protein kinases and cyclins – give the OK during interphase (G1 and G2 checkpoints)
 If cell receives OK from regulatory molecules at G1, it continues on with cell cycle
 If cell does not get the OK, cell exits to G0 phase, a non-dividing state
 Some cells can go from G0 back into cell cycle by growth factors
Internal / external cues to regulate cell cycle
o Growth factors
o Density dependent inhibition
o Anchorage dependence
Cells that have defects in their cell cycle regulation = tumor cells
o Don’t exhibit anchorage dependence or density dependent inhibition
o Progression of a cancer cell
 Transformation of normal cell to a cancerous cell
 Benign tumor
 Malignant tumor (able to spread to new areas and impair function of different organs)