Cellular Transport and the Cell Cycle
Chapter 8
Chapter 8 Voc. Word List: Osmosis, Isotonic, Hypotonic, Hypertonic, Passive Transport, simple
diffusion, facilitated diffusion, channel proteins, carrier proteins, uniporter carrier proteins, active
transport, Symport, Antiport, Endocytosis, Exocytosis, DNA, RNA, histones, cyclins, genes, Cell Cycle,
Mitosis, kinetochores (centromeres), Interphase (Growth phase), Cytokinesis, and daughter cells
Chapter 8.1-Cellular Transport
Osmosis is the diffusion of water across the plasma membrane of cells
 Regulation of water through the plasma membrane is an important factor in
maintaining the homeostasis within the cell.
o The water and the materials combine to form solutions.
 The right amount of water and materials within the osmosis
process must be balanced or the cell will suffer damage.
Three types of cellular solutions
1. Isotonic-The concentration of dissolved substances in the solution
outside the cell is the same as the concentration of dissolved substances
inside the cell
2. Hypotonic-The concentration of dissolved substances in the solution is
lower in the outside the cell than the concentration of dissolved
substances inside the cell
 In animal cells the cells will swell until they burst (See Figure 8.3
on p. 197)
 In plant cells the cell swells beyond normal size and the central
vacuole also increases in size
3. Hypertonic- The concentration of dissolved substances in the solution
outside the cell is the higher as the concentration of dissolved substances
inside the cell
 In animal cells the cells shrink has they lose water (See Figure 8.4
on p. 197)
 In plant cells the cell loses pressure as the plasma membrane
shrinks away from the cell wall and the organelles get tiny and go
to the middle of the central vacuole (the central vacuole itself
swells as in hypotonic solutions)
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Molecules are transported through the cell in four different ways.
1. Passive Transport-by simple or facilitated diffusion and move with the
concentration gradient (particles moving from a higher concentration
level to a lower concentration level)
 The cell uses no energy to move particles across the plasma
membrane-simple diffusion
 When using transport proteins- facilitated diffusion
 Again no energy is used to move particles across the
plasma membrane
o Some transport proteins are known as channel
proteins because they form channels or gates to
allow specific molecules through the plasma
membrane (Na and K pumps are examples of ion
gates)
o Other transport proteins are called carrier
proteins. These proteins change their shape
according to the specific molecule or ion to allow
the material through
 Carrier proteins change their shape to
match the molecule or ion needed (after
the molecule or ion binds to it). The carrier
protein then changes back to its original
shape after the task is completed.
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
The carrier proteins in passive transport are
called uniporter carrier proteins-they carry
one solute (Ex. Glucose carriers)
2. Active Transport-Energy is required from the cell for this type of
transport because the material moved moves against the concentration
gradient (particles move from a lower concentration level to a higher
concentration level)
 The process allows molecules and ions into and out of a cell
 Coupled transporter carrier proteins are used in active transport
(two types)
A.) Symport carry solutes and ions through the cell in the
same direction
B.) Antiport carry solutes and ions in opposite directions
3. Endocytosis-This process is for large particles
 In this case, a large molecule, group of molecules, or even whole cells
can be moved.
 Endocytosis is the process where the cell surrounds and engulfs the
material from its environment and is enclosed by part of the plasma
membrane. Than that portion of the plasma membrane breaks away
and the resulting vacuole with its contents moves to the inside of the
cell.
4. Exocytosis- is the reverse process of Endocytosis
 In this case, waste or secretions (like hormones)are taken from
the cell
8.2/8.3-Cell Growth and Reproduction/Control of the Cell Cycle
Review:
DNA (Deoxyribonucleic acid) and RNA (ribonucleic acid) are nucleic acids.
 The DNA is the master blueprint for each cell’s genetic information code.
o The RNA forms the copy of DNA for use in making proteins.
o The cell can’t survive without enough DNA to support the protein needs of the cell.
Chromosomes exist as chromatin, long strands of DNA wrapped around proteins called
histones.
 Under an electron microscope, chromatin look like beads (the histones) on a string
(chromatin).
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
The chromosome structure undergoes changes in shape and structure so new cells can
form during the Cell Cycle
Proteins and enzymes control the cell cycle
 Cyclins are proteins that control cell cycle. A set of enzymes attach to the cyclins to
activate the cell cycle.
o If control is lost the cell can die or possibly form cancerous growth
 Enzyme production is directed by genes.
o A gene is a segment of DNA that controls the production of a protein.
Cell Cycle
I.
Growth (Also called Interphase: 3 phases-G1, S, G2)
a. G1-Normal cell functions and cell growth exist
b. S-DNA replicates producing 2 copies of each chromosome
c. G2-The cell continues to prepare for Mitosis and Cell division
II.
Mitosis: (nuclear division) 4 phases-Prophase, Metaphase, Anaphase, and Telophase
a. Prophase
 The nuclear membrane and nucleolus begin to breakdown
 As it continues the DNA condenses to form chromosome spindles, made
of proteins called microtubules.
o The chromosomes become visible and condense, becoming
shorter and thicker
 Each identical copy of a single chromosome is called a
sister chromatid.
 While the mitotic microtubules begin to form they attach to the
kinetochores (also called centromeres-are the circle-like structure in the
center of a chromosome, which holds sister chromatids together) on
each chromosome.
 The nuclear envelope breaks down and spindle fibers form as the
microtubules grow out of the centrioles (a pair of small cylinder shaped
structures composed of microtubules) that move to opposite poles of the
cell
b. Metaphase
 The double-stranded chromosomes are moved to the central plate (equator
of the cell) of the cell by the spindle microtubules
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
The spindles is now fully formed and the microtubules attach to each of the
sister chromatids
c. Anaphase
 The microtubules attached to the centromeres of each chromosome
 They shorten, drawing the chromatids to each chromosome to opposite ends
of the cell while the attached microtubules elongate stretching the cell
 The centromeres divides and move away from each other along its spindle
fiber
d. Telophase
 The two groups of chromosomes reach the opposite ends of the cell and the
nuclear envelope starts to form around each group and the nucleoli forms
 Then the chromosomes uncoil and the spindle disappears
o The chromatins are now officially called chromosomes
o The chromosomes relax and release and unwind the long
strand of DNA
 Now the process of Cytokinesis can occur
III.
Cytokinesis - cytoplasmic division (also called C phase)
 The division of the cytoplasm and the organelles occur
o In animal cells a cleavage furrow forms at the center on either side of the
cell “pinching through” until the original cell divides into 2 parts called
daughter cells-these are genetically identical cells
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Cleavage Furrowing in an Animal Cell
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