Transcript Chapter 8 Cellular Transport & Cell Cycle

Chapter 8
Cellular Transport & Cell Cycle
8.1 Cellular Transport
• Osmosis- diffusion of H2O
– H2O moves freely through plasma membrane
– H2O tries to maintain equal concentration on
both sides of plasma membrane
– Control of Osmosis
• Concentration gradient- unequal distribution of
particles
Isotonic solution
• concentration of dissolved substances in
solution = concentration inside cell
• Cells in isotonic solution do not experience
osmosis + retain normal shape ~ Fig. 8.2 p.
202
• Cells are not damaged
hypotonic solution
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concentrate of solution < concentrate inside
H2O moves into cell
Cell swells
Internal pressure increases
Animal cells can burst
Plants cells cannot burst because of cell
wall  becomes firm
hypertonic solution
• concentrate of solution > concentrate inside
• H2O moves out of cell by osmosis
• Animal cells shrivel- inter pressure
decreases
• Plant cells- internal pressure decreases plant
wilts
Passive Transport
• Movement of particles such as lipids, lipidsoluble subs., & H2O across membranes
using no E
Passive transport by proteins
• Facilitated diffusion- passive transport of
mat’ls across p.m.
• W/ aid of transport proteins (fig. 8.5 p.204)
transport proteins provide convenient
opening for particles to pass through
• Common method of moving sugars & a.a.
across membranes
• Factor- conc. grad.
Active Transport
• Moving mat’ls against conc. grad.- from lower to
higher concentrate
• Requires E
• How it happens- Fig. 8.6 p.205
• Carrier protein ( form of a transport protein) binds
w/ particle of subs.• Chemical E allows cell to shape of carrier protein
so that particle to be moved is released on
opposite side of membrane
Lg. Particle transport
• Endocytosis- process by which a cell surrounds &
takes in mat’l from environment
• mat’l does not pass directly through membrane
• engulfed by portion of p.m.
• that portion of p.m. breaks away & resulting
vacuole + contents moves into cell
• active transport  + E
Lg. Particle transport
• Exocytosis
• opposite of endocytosis
• used to expel wastes & secrete substances
like hormones
• active transport  + E
8.2 Cell growth & Reproduction
Factors Limiting Cell Size
• Diffusion is slow & inefficient over long
distances & lg. Sizes
• DNA
• Limit to rate off genetic mat’l replication
• In large cells, more than one nucleus has
evolved
• Surface Area (SA) to volume (V) Ratio
• Volume increases faster then SA
Cell Reproduction
• New cells made through cell division
• Results in 2 identical cells
Chromosomes
• Short, stingy, dark- staining structures in
nucleus that contain DNA
• Structure of eukaryotic chromosomes
• Most of time, chromosomes exist as
chromatin
Chromatin- long strands of DNA
wrapped around proteins
• As nucleus starts to divide, chromatin
becomes, reorganized tightly packed
chromosomes
Cell Cycle- Inside Story p.211
• Sequence of cell growth & division
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Interphase- growth period in
which a cell spends most of its
life
Cell grows in size
Carries on metabolism
Chromosomes are duplicated
stages of interphase
Gl
• beginning
• chromosomes are not visible under light
microscope because they are uncoiled
• protein synthesis occurring rapidly
S stage
• chromosomes replicated in nucleus
G2
• chromosomes begin to shorten & coil
• high rate of protein synthesis
• in animals, centriole pair replicates & prepares to
form mitotic spindle
• mitosis
• follows interphase
• nuclear division
• process by which 2 daughter cells are formed,
each containing a complete set of chromosomes
Cytokenisis
• division of cytoplasm
• after mitosis
• chromosomes divide to form identical sister
chromatids connected by a centromere
Phases of Mitosis
Prophase
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1st & longest phase
chromatin coils up into visible chromosomes
chromosomes look hairy
made up of 2 halves
sister chromatids held together by centromere
nucleus disappears
nuclear envelope & nucleolus disintegrate
in animal cells, centioles begin to migrate to
opposite ends
Prophase
Centrioles
• sm. Dark, cylindrical structures made of
microtubules & are located just outside nucleus
• as centrioles migrate, spindle, forms between them
• Spindle
– football shaped cage-like structure consisting of thin
fibers of microtubules
– in plant cells, spindle forms without centrioles
Metaphase
• Short 2nd stage
• Doubled chromosomes attach to spindle
fibers by their centromeres
• Chromosomes pulled by spindle fibers &
line up at equator of spindle
Metaphase
Anaphase
• 3rd Phase
• beginning marked by separation of sister
chromosomes
• centromeres split apart
• chromatid pair from each other
• chromatids pulled apart by shortening of
spindle fibers
Anaphase
Telephase
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Fourth and final phase
Begins when chromatids reach the opposite poles
Many changes of prophase are reversed
Chromosomes unwind
Spindle begins to break down
Nucleolus reappears
Nuclear environment forms around each set of
chromosomes
• New double membrane begins to form between 2
new nuclei
Telephase
Cytokenisis
• cytoplasm divides