Cells regulate their size through diffusion and osmosis. Diffusion is the movement of substances from high to low concentration areas, while osmosis is the diffusion of water across membranes. During cell division, the cell cycle consists of interphase, where the cell grows and duplicates its DNA, and mitosis, where the cell divides into two identical daughter cells through the stages of prophase, metaphase, anaphase, and telophase. Cytokinesis then separates the cytoplasmic components of the parent cell.

1. DIFFUSION & OSMOSIS

2. A cell can’t just keep growing and growing.
- As cell gets larger, surface area to volume ratio decreases
- Less surface area for passage of nutrients and waste across the
membrane
- Substances would take too long to diffuse to where they are
needed in the cell
DIFFUSION

3. Diffusion: Substances move from areas of high concentration
to areas of low concentration.
DIFFUSION

4. Osmosis: Diffusion of water
Water can diffuse into and out of cells based on
concentration of solute inside and outside a cell.
OSMOSIS

5. Water can move in or out of a cell, causing it to expand or shrink,
based on the type of solution it is placed in:
Hypotonic – lower solute concentration outside the cell
Isotonic – same solute concentration outside the cell
Hypertonic – higher solute concentration outside the cell
OSMOSIS

6. A hypotonic solution can swell an animal cell to the point of
lysis, but plant cells have cell walls to prevent this.
OSMOSIS

7. Passive transport: Movement of substance across a
membrane without using energy
Passive transport relies on diffusion and concentration
gradients.
PASSIVE TRANSPORT

8. Active transport: Movement of substances across a
membrane using energy against concentration gradient.
PASSIVE TRANSPORT

9. CELL DIVISION

10. Why do cells need to divide?
-To allow an organism to
grow
-To pass on genetic material
-To assist an organism’
survival
CELL DIVISION

11. 3 stages of cell cycle:
Interphase
Mitosis (division of nuclear
material)
Cytokinesis (division of
cytoplasm)
CELL DIVISION

12. Interphase
- Cell is not dividing but
also not dormant
- Cell is active and
growing and also
preparing for division
- Sometimes called
resting phase but this
is inaccurate (real
resting phase is G0)
- DNA/chromosomes
not visible (unwound)
INTERPHASE

13. Interphase: 4 stages
Gap 0 (G0):
- Cell rest cycle
- may be temporary
or permanent (where
cells are functional
but no new cells are
produced (i.e.
neuron)
G0
INTERPHASE

14. Interphase: 4 stages
Gap 1 (G1):
- Rapid growth (4hr)
- cell takes in
nutrients for energy,
growth, repair
- Cells either go into S
or G0 after G1
G0
INTERPHASE

15. Interphase: 4 stages
S phase (S):
- 10 hrs
- DNA synthesis/
replication
- the cell duplicates
its genetic material to
make an identical
copy of its DNA
G0
INTERPHASE

16. Interphase: 4 stages
Gap 2 phase (G2):
- 3-4hr
- second period of
growth in preparation
for cell division
-cell grows larger in
size
G0
INTERPHASE

17. S phase (S): Let’s take a closer look
DNA replication
Normally
DNA
duplication
After duplication
INTERPHASE

18. Mitosis:
- A process by which somatic cells grow and divide
- Cells come from pre-existing cells
- Parent cell divides to produce two new identical daughter cells
- asexual reproduction (offspring from one parent)
- 4 phases:
MITOSIS

19. Prophase
- nuclear membrane breaks down
- chromosomes shorten and
thicken
- Other structures important for
mitosis are also forming (i.e. the
centrioles)
MITOSIS: PROPHASE

20. Prophase
- A centromere holds two copies of the same chromosome together
- Each copy of a chromosome is called a chromatid
MITOSIS: PROPHASE

21. Mother’s
side
Prophase
- A centromere holds two copies of the same chromosome
together
- Remember, every chromosome has been duplicated during the S
phase of interphase.
- Recall this:
Mitosis
Mother’s
side Mother’s
side
Colors are not accurate
MITOSIS: PROPHASE
 centromere

22. Prophase
MITOSIS: PROPHASE

23. Metaphase
- Microtubules (spindle fibres)
attach at the centromeres
and the chromosomes move
to the centre (the metaphase
plate)
MITOSIS: METAPHASE
metaphase plate

24. Metaphase
MITOSIS: METAPHASE

25. Anaphase
- Paired chromosomes separate
at the kinetochores and move
to opposite sides of the cell
MITOSIS: ANAPHASE

26. Telophase
- Chromatids arrive at opposite
poles of cell
- New membranes form around
the daughter nuclei
- Chromosomes disperse and
are no longer visible under the
light microscope
- spindle fibres disperse
MITOSIS: TELOPHASE

27. Cytokinesis
- Animal cells: the
cell membrane
pinches (forming
a cleavage furrow)
into two daughter
cells, each with
one nucleus
CYTOKINESIS: ANIMAL CELLS

28. Cytokinesis
- In plant cells, a
cell plate (made
of rigid cellulose)
is synthesized
between the two
daughter cells.
CYTOKINESIS: PLANT CELLS

29. Mitosis and cytokinesis: Review
MITOSIS & CYTOKINESIS