1. Cellular transport and the Cell Cycle
Diffusion is the net movement of particles from
an area of higher concentration to an area of
lower concentration. Diffusion results because of
the random movement of particles.
Ex. Food coloring (solute) and water (solvent)
Three key factors---- Concentration, temperature,
and pressure-----affect the rate of diffusion.
2.
3. Osmosis: Diffusion of water
Remember the plasma membrane is a
semipermeable so it regulates what goes in and
out of the cell. So how does water move in and
out of the cell? The diffusion of water across a
selectively permeable membrane is called
osmosis.
Regulating the water flow through the plasma
membrane is an important factor in maintaining
homeostasis within the cell.
4. Osmosis
• Water diffuses across the membrane it is in equal
concentration on both sides of the membrane.
• It is important to understand how osmosis affects
cells.
• In isotonic solution, the concentration of
dissolved substance in the solution is the same
the cell. This means that osmosis is occurring but
because water diffuses into and out of the cells at
the same rate, the cells retain their normal shape.
5. In an a hypotonic solution, the concentration of
dissolved substances is lower in the solution
outside the cell than the concentration inside the
cell. Meaning there is more water outside the cell
than inside.
Water moves through the plasma membrane into
the cell. The cell swells and its internal pressure
increases.
The effect on this on an animal cell is that if to
much water enters the cell the pressure increases
greatly and the cell will burst. Due to the cell wall in
plant cells, the cells expand but do not burst.
6. • In a hypertonic solution, the concentration of
dissolved substances outside the cell is higher
than the concentration inside the cell.
• Cells in a hypertonic solution experience osmosis
that causes water to flow out.
• The effect of hypertonic solution on an animal
cell is that water flows out of the cell and causes
the cell to shrivel because of the decreased
pressure in the cell. Plant cells mainly lose water
from the vacuole and the plasma membrane and
cytoplasm shrink away from the cell wall.
Pressure drops.
7.
8. Passive Transport
• When no energy is required to move particles
across the membrane is classified as passive
transport.
• Passive transport that uses transport proteins
is called facilitated diffusion.
• Channel proteins and carrier proteins allow
the movement of substances across the
membrane with the concentration gradient
(high to low)and requires no energy input
from the cell.
9.
10. Active Transport
• Movement of materials through a membrane
against a concentration gradient is called active
Transport and requires energy from the cell.
• What happens is a carrier protein binds with a
molecule or ion to be transported. When the
proper molecule or ion binds with the
protein, chemical energy allows the cell to
change the shape of the carrier protein so that
the particle to be moved is released on the
other sided of the membrane.
11. • Once the particle is released, the protein’s
original shape is restored.
• Active transport allows movement into or out
of a cell against a concentration gradient. (Low
to high)
• The transport of substances across the cell
membrane is required for cells to maintain
homeostasis.
12.
13.
14. Transport of Large particles
• Some cells can take in large molecules, groups
of molecules, or even whole cells.
• Endocytosis is a process by which a cell
surrounds and takes in material from its
environment.
• How it works. The material does not pass the
membrane directly, instead it is engulfed and
enclosed by a portion of the plasma
membrane.
15.
16. • Exocytosis is the expulsion or secretion of
materials from a cell. Cells use exocytosis to
expel wastes or hormones produced by cell.
• Because endocytosis and exocytosis both
move masses of material, they both require
energy.
17. Cell growth and reproduction
All cells grow and carry out a their function. The
function of a cell depends on what kind of cell it
is. Ex. Liver cells, skin cells, muscle cells.
Once a cell reaches a maximum size it must
divide. Remember all cells come from
preexisting cells.
Cells grow, divide then die. So it is important to
replace the dying cells.
18. Cell Growth and Reproduction
• Prokaryotic organisms grow until reaching a
critical size and then divide. This process is
repeated over and over. The rate of growth of
bacteria cells depend greatly on
environmental factors such are nutrient
availability and temperature.
• Prokaryotic cells divide in the process of
fission.
20. Eukaryotic cell
• The cell cycle (life of a cell) is more complex
than a prokaryotic cell.
• The cell cycle is the sequence of growth and
division of cells.
• The cell cycle is divide into phase.
Interphase, prophase, metaphase, anaphase, t
elophase.
21.
22. Interphase
Cells spend most of their time in interphase.
3 phases in Interphase.
G1 is the first phase. Cell grows rapidly and carries
out metabolic activity (doing its job)
S is the second phase and in this phase DNA is
synthesized and replicated. (A copy of DNA is made)
G2 is the last phase of interphase and in these
phase the cell assemble cell parts needed for cell
division. (Cell is preparing itself to divide)
23. The Phases of Mitosis
• Mitosis is the process by which two daughter
cells are formed, each containing a complete
set of chromosomes.
• Mitosis is cell division.
• Prophase, Metaphase, Anaphase and
Telophase all occur during mitosis.
• End result of mitosis is 2 new cells.
24. Prophase
• Prophase is the first phase of mitosis.
1. Chromatin coils and makes a chromosome.
2. Centrioles move to opposites ends of cell.
3. As prophase continues, the nucleus begins
to disappear as the nuclear envelope and the
nucleolus disintegrate.
The chromosomes is made up by sister
chromatids. Sister chromatids are held together
by a structure called a centromere.
25.
26. Metaphase
Chromosomes become attached to spindle
fibers by their centromere.
The chromosomes are pulled by the spindle
fibers and begin to line up on the midline, or
equator, of the spindle.
27. Anaphase
• The separation of sister chromatids marks the
beginning of anaphase.
• The centromeres split apart and chromatid
pairs from each chromosome separate from
each other. Chromatids make their way to
opposite ends of the cell.
28. Telophase
• Chromatids are at opposite poles.
• Spindle fibers break down, the nucleolus
reappears, and a new nuclear envelope forms
around each set of chromosomes.
• A membrane starts form between the 2
nuclei.
29. Cytokinesis
• The cell’s cytoplasm divides in a process called
cytokinesis.
• Animal cells the plasma membrane pinches in
along the equator and the two new cells are
separated.
30. Control of the cell cycle
• Proteins and enzymes control the cell cycle
• The interaction of these molecules, based in the
cell’s environment and inside the cell, controls
the cell cycle.
• Occasionally, cells lose control of the cell cycle.
So what can happen is uncontrolled dividing of cells
can result from the failure to produce certain
enzymes, overproduction of enzymes, or the
production of other enzymes at the wrong time.
31. j
• Enzymes production is directed by genes
located on the chromosomes.
• A Gene is a segment of DNA that controls the
production of a protein.
Cancer: A mistake in the cell cycle.
Cancer results of changes in one or more of the
genes that produce substances that are involved
in controlling the cell cycle.
Cancerous cells form masses of tissue call
tumors that deprive normal cells of nutrients.
32. • Cancer is the second leading cause of death in
the United States.
• The causes of cancer are difficult to pinpoint
because both genetic and environmental factors
are involved.
• Environmental factors such as cigarette smoke,
air and water pollution, and exposure to
ultraviolet radiation from the sun, are all known
to damage the genes that control the cell cycle.
• Cancer may also be caused by viral infection that
damage the genes.
