CELLS AND CELL DIVISION
I. BASIC CELL COMPOSITION (fig. 2.1)
A. Plasma Membrane (Cell Membrane) - surrounds cell and gives it form
B. Cytoplasm - consists of:
1) cytosol:
2) organelles:
C. Nucleus - contains DNA (deoxyribonucleic acid)
II. PLASMA MEMBRANE (fig. 2.4)
-- Structure: double layer of phospolipids
* proteins
* glycoproteins
* glycolipids
-- selectively permeable
What do you think? what are some benefits and some disadvantages of having a selectively permeable membrane?
-- Some plasma membranes have:
1) microvilli
(fig 2.3):
*
2) cilia
(figs 2.3, 2.16):
*
III. CYTOPLASMIC ORGANELLES (fig. 2.3 and others)
A. Mitochondria
* make ATP (adenosine triphosphate)
* contains its own DNA
B. Ribosomes - involved
in protein synthesis (synthesis = production)
* two kinds: Free ribosomes or ribosomes
attached to Rough ER
C. Endoplasmic Reticulum (ER) - a network of
tubules used to transport & synthesize
(produce) materials
1) Rough ER - has ribosomes on walls
*
synthesizes & distributes proteins
2) Smooth ER - has no ribosomes
*
synthesizes lipids, mainly steroids
* detoxify
drugs and alcohol
D. Lysosomes - contain
digestive enzymes
E. Centrioles (fig
2.15) - involved in cell division
IV. NUCLEUS (fig 2.3, 2.17)
-- contains DNA
(deoxyribonucleic acid)
-- when cell is NOT
dividing, DNA in the form of chromatin
-- some nuclei have a nucleolus
* makes the "parts" that
form ribosomes
REVIEW AND LEARN THE FUNCTIONS OF THE CELLULAR
STRUCTURES WITH A STUDY PARTNER. WORK TOGETHER
ON THE Cellular
structures memory matrix
V. CELL CYCLE (fig. 2.19)
-- cells divided into:
1) Sex cells (sperm and oocytes)
2) Somatic cells (all other cells)
-- cell cycle subdivided into 2 phases:
1) Interphase
- cell not dividing
* DNA is
duplicated during this time
2) Mitosis (cell division
for somatic cells)
or Meiosis
(cell division for sex cells)
VI. MITOSIS (fig. 2.20)
1) Prophase ("Puffy")
* DNA in form of double-stranded chromosomes
* double-stranded
(duplicated) chromosomes consist of 2 chromatids
joined at a centromere
** (chromatid = each half of the duplicated chromosome)
* spindle
fibers go from centrioles to chromatids
* breakdown
of nuclear membrane
2) Metaphase ("Middle")
* chromosomes along center of cell
3) Anaphase ( "Apart")
* chromatids
split apart at centromere
* each
set of chromatids (now called single-stranded
chromosomes) pulled to
opposite ends of cell
4) Telophase
("Two")
* nuclear envelope reforms
* nucleolus reappears
* cleavage
furrow develops
* cytokinesis
occurs
-- Cell now re-enters interphase
VII. MEIOSIS (figs. 3.1, 3.2)
Def: cell division where gametes (sperm cells
or oocytes) are formed
-- Differences between mitosis and meiosis:
1) Mitosis produces 2 cells
containing 46 chromosomes (23 pairs)
* daughter
cells identical to original (parent) cell
* cells are diploid: they have 2 of each chromosome
2) Meiosis produces 4 cells
containing only 23 chromosomes
* daughter
cells genetically different from parent cell
* these cells have a haploid number of chromosomes
(only 1 of each
chromosome)
-- Start off with one cell that has 23 pairs of
chromosomes
* one set of chromosomes came from
MOTHER, the other from FATHER
-- Interphase: DNA is
duplicated
* DNA will form double-stranded
chromosomes
* cell
now contains 23 pairs of double-stranded (duplicate) chromosomes
-- 1st meiotic prophase, homologous chromosomes
pair up
--Crossing Over: process by which genetic material
is exchanged between
homologous chromosomes
* occurs
during 1st prophase
What do you think? How does crossing over relate to genetic diversity among individual sex cells?
-- cell finishes 1st meiotic division, producing 2 daughter cells
* daughter
cells each have 23 double-stranded chromosomes (each chromosome
consists of
2 chromatids)
* parent
cell had 23 PAIRS of chromosomes, but daughter cells have
only 23
chromosomes!
-- cells go through 2nd meiotic
division:
* 4 cells produced, each with 23
single-stranded chromosomes (each chromosome
has only 1 chromatid now)
* these
4 cells are gametes
-- Nondisjunction (page 59): a process by which the chromatids fail to properly separate during meiosis
COMPARE AND CONTRAST MITOSIS VERSUS MEIOSIS. WORK WITH
A STUDY PARTNER ON THE
mitosis/meiosis
learning exercise .
Which statement is TRUE about the plasma membrane?
a. it is composed of a triple layer of carbohydrates
b. all materials may easily pass through (diffuse through) the cell membrane
c. all plasma membranes contain microvilli
d. proteins are scattered within and "float" within the membrane
e. none of the above are true