1. Cell Biology
I. Overview
II. Membranes: How Matter Get in and Out of Cells
III. Cellular Respiration
IV. Photosynthesis
V. Protein Synthesis
VI. Cellular Reproduction

2. VII. CELL REPRODUCTION
Overview: Why Reproduce?

3. Overview: Why Reproduce?
VII. CELL REPRODUCTION
Overview: Why Reproduce?
Reproduction is selected for, by definition. X X X X

4. - WHY??
Bigger is better….
So selection favors growth…
But as cells increase in size, they decrease in efficiency.

5. - WHY??
Bigger is better….
So selection favors growth…
But as cells increase in size, they decrease in efficiency.
So, to get bigger, most organisms increase cell number, not cell size….

6. - WHY??
And with many cells, cell specialization can increase efficiency at the organismal level.

7. Overview: Why Reproduce? A. The Cell Cycle
VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle G1 G2 S
(DNA synthesis)
INTERPHASE
Cytokinesis
MITOTIC
(M) PHASE
Mitosis

8. Overview: Why Reproduce? A. The Cell Cycle
VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle
    1.  Interphase:       a.  G1: high metabolic activity (protein synthesis) chromosomes diffuse; one DNA double helix per chromosome
               

9. LE 12-15 G0
G1 checkpoint G1 G1
If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.
If a cell does not receive a go-ahead signal at the G1 checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state.

12. Overview: Why Reproduce? A. The Cell Cycle 1. Interphase a. G1 b. S
VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle
    1.  Interphase
a. G1
b. S
Chromosome
duplication
(including DNA
synthesis)
Centromere
Sister chromatids A C G T G C A C G T G C A C G T G C
Two identical double-helices, each composed of an ‘old’ and ‘new’ strand. Creating two chromatids in each chromosome

13. VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle
    1.  Interphase
a. G1
b. S
c. G2

14. VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle
    1.  Interphase
2. Mitosis

15. INTERPHASE PROPHASE PROMETAPHASE LE 12-6aa Centrosomes
(with centriole pairs
Chromatin
(duplicated)
Early mitotic
spindle
Aster
Fragments
of nuclear
envelope
Kinetochore
Nonkinetochore
microtubules
Centromere
Nucleus
Nuclear
envelope
Plasma
membrane
Chromosome, consisting
of two sister chromatids
Kinetochore
microtubule

16. METAPHASE ANAPHASE TELOPHASE LE 12-6ba Metaphase plate Cleavage furrow
Nucleolus
forming
Nuclear
envelope
forming
Centrosome at
one spindle pole
Daughter
chromosomes
Spindle

17. Overview: Why Reproduce? A. The Cell Cycle B. DNA Replication
VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle
B. DNA Replication
C. Mitosis
G2 OF INTERPHASE
PROPHASE
PROMETAPHASE

18. Overview: Why Reproduce? A. The Cell Cycle B. DNA Replication
LE 12-6da
VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle
B. DNA Replication
C. Mitosis  
TELOPHASE AND CYTOKINESIS
METAPHASE
ANAPHASE

19. Overview: Why Reproduce? A. The Cell Cycle B. DNA Replication
VII. CELL REPRODUCTION
Overview: Why Reproduce?
A. The Cell Cycle
B. DNA Replication
C. Mitosis  
10 µm
Nucleus
Chromatin
condensing
Chromosomes
Nucleolus
Cell plate
Prometaphase. We
now see discrete chromosomes; each
consists of two identical sister chromatids. Later
in prometaphase, the
nuclear envelope will fragment.
Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at
the metaphase plate.
Anaphase. The
chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro-
tubules shorten.
Prophase. The
chromatin is condensing.
The nucleolus is beginning to disappear.
Although not yet visible in the micrograph, the mitotic spindle is starting to form.
Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.