hr part 2 Flashcards
Why do cells divide?
growth and development
How do cells know when to divide?
Using chemical signals from special proteins called cyclins
tell cells when to start
dividing and later when to stop dividing
Cyclins
- when a cell cannot stop dividing
Cancer
How much dead skin cells we lose everyday?
30,000 to 40,000
A cycle of alternating stages of division and rest
from division of a cell
Cell Cycle
Two stages of Cell cycle
Interphase and Cell Division
non-dividing stage of the cell
Interphase
Longest stage of the cell cycle
Interphase
Dividing Stage
Cell Division
Cell is metabolically active
Nutrition
Biosynthesis
Respiration
for growth and normal metabolic roles
G₁ -
or DNA replication
S -
for growth and preparation for mitosis
G₂
Quiescent stage
* Cells are not able to move to the S phase
* Cells are unable to replicate their DNA
GAP 0 Phase (Go Phase)
Division of cytoplasm
* Production of daughter cells
CYTOKINESIS
containing the
haploid number (n)
of chromosomes -
divide by meiosis
Sex Cells
all body cells except the
sex cells, and
containing diploid
(2n) number of
chromosomes -
divide by mitosis
Somatic Cells
Somatic cell division
* Production of two daughter cells with the
same quantity and quality of
chromosomes as the parent cell Involves karyokinesis followed by cytokinesis
Mitosis
How often do cells divide?
1 cycle within 24hours
Apical meristem of onion root (how many hours)
20 hours
Epithelial cells of intestine
every 10 hrs
threadlike structures in the nucleus that are
made up of molecules of proteins and DNA.
Chromosomes
Cells that contain two sets of chromosomes
* Symbol: 2n
Diploid Cells
