Download Ch. 3 Cells

Chapter 3
Cells
Introduction
•
Cells are the smallest
living unit in our body
that varies in shape &
size
•
Differences in cell shape
makes different functions
possible!
Cells have 3 main parts:
1. Plasma membrane
2. Cytoplasm
3. Nucleus
1. Plasma Membrane Function
-Regulates movement of substances in &
out of cell = selectively permeable
-Participates in signal transduction
-Helps cells adhere to other cells
-Is adapted to increase surface area
-seals tiny breaks or cell dies
3-4
Plasma Membrane Structure
-Double layer that is soluble and allows
lipids (steroids, hormones) to pass thru!
-Embedded cholesterol (fat) molecules
strengthen membrane and make it less
permeable to water-soluble substances
3-5
2. Cytoplasm
Contains:
- Cytosol a clear liquid
- Cytoskeleton for
support
3-6
3. Nucleus
Has a double layered
membrane containing
large pores that allow
substances to pass thru
a. Nucleolus is
composed of RNA and
protein; site of ribosome
production; and directs
activities of cell
b. Chromatin consists of
loosely coiled fibers of
protein & DNA
Super Eve –Mitochondrial DNA

Each human has
mutations that have
replaced or added gene
sequences
 Mitogenomes are
passed from mother to
offspring, with very
few exceptions
Cell Membrane Movement
1-Passive Mechanisms:
Diffusion
-Movement of
molecules from area
of greater to lesser
concentration
–(like diffusion from
alveoli in lungs into
capillaries)
Cell Membrane Movement
2-Facilitated Diffusion
-Membrane
proteins actively
move molecules
through
-insulin promotes
glucose diffusion
in this way
Cell Membrane Movement
3- Osmosis
-Water moves from
area of greater
concentration
(less pressure)
to area of lower
concentration
(greater
pressure)
FYI: Preserving Fruits & Meats
 Dehydration
of fruit & salt-curing of meat
A solution with:
-Same osmotic pressure as
body fluids is isotonic
-Higher osmotic pressure
than body fluids is
hypertonic = cell shrinks
-Lower osmotic pressure is
hypotonic = cell expands
3 - 13
Plasma used by hospitals to store
RBC’s is isotonic to prevent RBC from
either bursting or desiccating
3 - 14
Filtration
Due to osmotic
pressure, molecules
are forced through
membranes by
filtration
-Blood pressure is a
type of osmotic
pressure
FYI: Dialysis

Dialyzing membrane allows water, salts and other
wastes in blood to pass into tank of distilled water
 RBC are too large to enter and return to patient's body
Cell Membrane Movement
Active Mechanisms
4-Active Transport
Uses energy to move molecules from
areas of low to high concentration
through carrier molecules
40% of our energy fuels this process!
3 - 17
Actively Transported
Particles:
-sugars
-amino acids
-sodium
-potassium
-calcium
-hydrogen ions
-nutrient molecules
Cell Cycle
Series of changes
a cell undergoes
from time it is
formed until it
reproduces and
dies.
Cell Cycle Phases
► Interphase- is a period of cell growth
and new molecules are synthesized
► S phase- DNA of cell is replicated to
prepare for cell division
► G1 & G2 phases- cell grows and other
structures are duplicated
3 - 20
Cell cycle is very regulated & most cells don’t divide
continually, they have a maximum # of times they can
divide because of built-in “clocks” (telomeres) on tips
of chromosomes
Dolly
When Dolly, a cloned sheep, died at the premature age of 6, scientists
discovered unusually short telomeres in her cells
3 - 21
Cells develop into different types of cells with
specialized functions via cell differentiation;
shows genetic control of nucleus as some genes
are turned on while others are turned off
Cell Division Problems

Progenitor cells are
daughter stem cells that
give rise to cells that
become tissues and
organs
– These are activated when
tissues are injured to
rebuild damage
The End of Males?
Mouse made without sperm
National Geographic April 21, 2004
•
•


-Kaguya, a fatherless mouse
-She was only one to survive to
adulthood out of 450 embryos
created, of which 371 were
implanted
-10 were born alive
-Scientists who created her say it
would be "completely unethical" to
try to create a human this way
Cell Death
Apoptosis
refers to a
cells death;
like peeling
sunburnt skin