Lecture # 9
Movement into and out of cells:
1. Bulk flow
2. Diffusion and osmosis
3. Transport
Two types of transport
A. facilitated diffusion
B. active transport
Structure of the Cell Membrane
The Danielli Model
The Danielli Model does NOT account for selective
permeability very well.
The Fluid Mosaic Model
The Fluid Mosaic Model gives a better explanation
of the selective permeability of the cell membrane.
Intrinsic proteins
Extrinsic proteins
Organelles of a cell:
1. cell membrane
2. nucleus
The nucleus is the control center of the cell.
Nucleoplasm
Protoplasm = nucleoplasm + cytoplasm
Chromatin
Chromosomes
Chromosomes contain the genes, which are
the units
of hereditary information.
Each species of organism has a characteristic
number of chromosomes.
If a cell has two complete sets of chromosomes
(both
members of each pair), the cell is diploid.
If a cell (like sperm and egg cells) has only one
complete set chromosomes
(one member of each pair),
it is haploid.
The process by which the diploid number
of
chromosomes is maintained in cells
as they divide is
called mitosis.
Centromere
Chromonema
Chromomeres
Each member of a pair of chromosomes
has a similar
pattern of chromomeres.
Half of a replicated chromosome is a chromatid.
A chromatid is an incipient or potential chromosome.
Mitosis is a continuous process but
is divided
into five stages.
1. Interphase is NOT a resting stage.
The
chromosomes replicate during
interphase to
form the duplicated
chromosomes.
2. Prophase:
A. the chromatin threads condense;
B. the centrioles duplicate and separate;
C. spindle fibers begin to form
3. Metaphase:
A. the nuclear membrane disappears;
B. the chromosomes line up on the equatorial plane;
C. the spindle fibers are completed;
D. the centromere on each chromosome divides
4. Anaphase: The new chromosomes move
to
the ends (or poles) of the cell.
Force is applied at the centromere of each
chromosome.
5.Telophase:
A. chromosomes reach the poles of the cell;
B. new nuclear membranes form;
C. the chromosomes elongate and become chromatin;
D. the cytoplasm divides
Cytokinesis
Karyokinesis
Interphase is the critical stage of mitosis.
G1 phase
The Cell Cycle