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CHAPTER 7 OBJECTIVES
1. Distinguish between prokaryotic and eukaryotic cells.
Prokaryotic cells lack nuclei and membrane-enclosed organelles; bacteria are
prokaryotes. All other organisms are made up of eukaryotic cells with membraneenclosed nuclei surrounded b cytoplasm, in which are suspended specialized organelles
not found in prokaryotic cells.
4. Describe the structure and function of the nucleus, and briefly explain how the nucleus
controls protein synthesis in the cytoplasm.
The nucleus contains the genetic material, DNA, organized with proteins in a
characteristic number of chromosomes in each eukaryotic species. The nucleus is the
most conspicuous organelle in a eukaryotic cell controlling the cell. The nucleolus is the
nuclear site where the parts of ribosomes are produced. Ribosomes are responsible to
carry out protein synthesis in the cytosol.
5. Describe the structure and function of a eukaryotic ribosome.
Eukaryotic ribosomes are composed of rRNA (ribosomal RNA) and composition.
6. List the components of the endomembrane system, describe their structures and
functions and summarize the relationships among them.
The endomembrane system is composed of:
*Golgi
*cell membrane
*nucleus envelope
*rough ER
*smooth ER
*transport vesicle
*lysosome
*secretary vesicle
*vacuole
*ribosomes
1. Nuclear envelope
2. Endoplasmic reticulum
a) Smooth ER
(1) Lacks ribosomes
(2) Produces lipids, phospholipids, and steroids
(3) Participates in carbohydrate metabolism
(4) Detoxifies drugs and poisons
(a) Adds –OH
(b) Makes substance water soluble
(c) Substance can be excreted
(5) Stores Ca2+ in muscle cells
b) Rough ER
(1) Has attached ribosomes
(2) Continuous with nuclear envelope
(3) Bound ribosomes produce proteins
(4) ER system of channels
(5) Makes new membrane components
(a) Proteins produced by bound ribosomes
(b) Phospholipids produced by enzymes within ER
(6) Transport vesicles
(a) Pinch off ER
(b) Transport materials from ER to Golgi
3. Golgi
a) Stacked, flattened, membranous sacs
b) Has polarity
(1) Incoming face (cis)
(2) Outgoing face (trans)
c) Functions
(1) Modifies, stores, routes ER products
(2) Alters some phospholipids
(3) Modifies oligosaccharides
(4) Makes certain macromolecules
d) Produces
(1) Lysosomes
(2) Secretory vesicles
4. Lysosomes
a) Membrane bound
b) Contain hydrolytic enzymes
(1) Lipases
(2) Carbohydrases
(3) Proteases
(4) Nucleases
(5) Optimal pH = 5
c) Membrane
(1) Sequesters enzymes
(2) Enzymes pump H+ into lumen
d) Functions
(1) Intracellular digestion
(2) Recycle cell contents
(3) Programmed cell destruction
(4) Tay-Sach’s disease
(a) Missing lipase
(b) Result = accumulation of lipids in brain
5. Vacuoles
1. Membrane bound
2. Storage
a) Food
b) Contractile – collect and remove excess water
3. Central vacuole
a) Found in plants
b) Membrane = tonoplast
c) Storage of
(1) Water
(2) Organic materials
(3) Ions
d) Contains hydrolytic enzymes
e) Sequesters dangerous by-products
f) Contains soluble pigments
g) Contains poisons and unpalatable chemicals
h) Involved in cell growth
6. Peroxisomes
1. Microbodies
2. Membrane bound
3. May have granular or crystalline core of enzymes
4. Contain oxidases
a) Break down fats into smaller molecules
b) Detoxifies alcohol and other poisons
7. Describe the vacuole & list types of vacuoles
. Vacuoles 1. Membrane bound 2. Storage a) Food b) Contractile – collect and remove
excess water 3. Central vacuole a) Found in plants b) Membrane = tonoplast c) Storage of
(1) Water (2) Organic materials (3) Ions d) Contains hydrolytic enzymes e) Sequesters
dangerous by-products f) Contains soluble pigments g) Contains poisons and unpalatable
chemicals h) Involved in cell growth
-food vacuoles
-contractive vacuoles
-central vacuole
8. Explain the role of peroxisomes in eukaryotic cells.
Peroxisomes function in a variety of metabolic processes that produce hydrogen peroxide
as a waste product, then voncerts the peroxide to water.
9. Describe the structure & function of a mitochondrion
Mitochondrion is the site of cellular respiration at the catabolic process that generates
ATP by extracting energy from sugars, fats and other fuels with the help of oxygen.
An outer membrane compartmentalizes mitochondria and an inner membrane folded into
convolutions called critae.
11. Identify the three functional compartments of a chloroplast
Chloropasts, a specialized members of a family of plant organelles called plastids,
contain chlorophyll and other pigments, which function in photosynthesis. Two
membranes surrounding the fluid called stroma, in which are embedded the membranous
thylakoids, enclose Choloroplasts. These flattened sacs are stacked in soome regions,
forming grana.
12. Describe probable functions of the cytoskeleton.
The cytoskeleton provides support and functions in cell motility. The cytoskeleton is
constructed from microtubules, mocrofilaments, and intermediate filaments.
Microtubules radiate out from the entrosome and shape and support the cell, guide the
movement of organelles, and participate in chromosome separation in cell division.
Microfilaments interact with the protein myosin to cause contraction and also function in
ameboid movement, cytoplasmic streaming, and support from cellular projections, such
as microvilli. Intermediate filaments are important in supporting cell shape and fixing
various organelles in place.
13. Describe the structure, monomers and functions of microtubules, microfilaments and
intermediate filaments.
Microtubules: the thickest fiber constructing the cytoskeleton. Microtubules are found in
the cytoplasm of all eukaryotic cells. They are straight, hollow rods, constructed from
globular proteins.
Microtubules shape and support the cell and also serve as tracks along which organelles
equipped with motor vehicles can move.
Microfilaments: the thinnest fiber constructing the cytoskeleton. Microfilaments are
solid rods about 7 nm in diameter and are built from molecules of actin. Microfilaments
are part of the contractile apparatus in muscle cells. They function in support.
Intermediate filaments: are constructed each from a different molecular subunit.
Intermediate filaments are also permanent fixtures of cells than are microfilaments and
microtubules. Intermediate filaments may function as the framework of the entire
cytoskeleton.
14. Explain how the ultra structure of cilia and flagella relates to their function.
A cilium or flagellum has a core of microtubules unsheathed in an extension of the
plasma membrane. Cilia and flagella are motile cellular appendages consisting of a
"9+2" arrangement of microtubules. Movement of cilia and flagella occurs when arms
consisting of the protein dyne in move the microtubule doublets past each other. In the
beating mechanism of cilia and flagella, we see once again that structure fits function.
17. Describe the structure of intercellular junctions found in plant and animal cells, and
relate their structure to function.
Intercellular junctions integrate cells into higher levels of structure and function.
Plants have plasmodesmata, cytoplasmic channels that pass through adjoining cell walls.
Tight junctions, desmosomes, and gap junctions provide cell-to-cell contact in animals.
CHAPTER OBJECTIVES
1. Describe the function of the plasma membrane.
The plasma membrane is a membrane at the boundary of every cell that acts as
a selective barrier, thereby regulating the cell's chemical composition.
5. Describe the fluid properties of the cell membrane and explain how membrane
fluidities influenced by membrane composition.
A membrane is a fluid mosaic of lipids, proteins, and carbohydrates. Proteins with
diverse functions are either embedded in the lipid bilater or attached to the surface.
Membranes have specific inside and outside faces arising from diferencesin the lipid
composition of the two bilayers and directional orientation of proteins and any attached
carbohydrates. Carbohydrates linked to the proteins and lipids are important for cell-cell
recognition.
6. Explain how hydrophobic interactions determine membrane structure and function.
The hydrophobic core of the membrane impedes the transport of ions and polar
molecules that are hydrophilic. Hydrophobic molecules can dissolve in the membrane
and cross it with ease. Hydrophobic substances pass through membranes rapidly because
of their solubility in the lipid bilayer. Larger polar molecules and ions require specific
transport proteins, which provide channels.
7. Describe how proteins are spatially arranged in the cell membrane and how they
contribute to membrane function.
Proteins with diverse functions are either embedded in the lipid bilayer or attached to
the surface. Specific proteins facilitate the passive transport of selected solutes.
Transport proteins may hasten the movement of certain substances across a membrane
down their concentration gradients. Specialized membrane proteins transmit extracellular
signals to the inside of the cell.
8. Describe factors that affect selective permeability of membranes.
Factors that affect selective permeability of membranes include:
* the hydrophobic core of the membrane
* transport proteins
* the discriminating barrier of the lipid bilayer
9. Define diffusion; explain what causes it and why it is a spontaneous process.
Diffusion is the spontaneous movement of a substance down its concentration
gradient; movement of any material from an area of high concentration to low
concentration. Molecules have intrinsic kinetic energy called thermal motion, or heat,
resulting in diffusion. It is a spontaneous process because it decreases free energy.
10. Explain what regulates the rate of passive transport.
Membranes selective permeability affects the rates of diffusion of various
molecules.
12. Define osmosis and predict the direction of water movement based upon differences
in solute concentration.
Osmosis is the passive transport of water. Water flows across a membrane from side
to side where solute is less concentrated to where solute is more concentrated. If the
concentrations are equal, no net osmosis occurs.
14. Describe how living cells with and without walls regulate water balance.
Cell survival depends on balancing water uptake and loss. Cells lacking cell walls (
as in animals) are isotonic with their environments or have adaptations for
osmoregulation. Plant cells are firm and generally healthiest in a hypotonic environment,
where the tendency for continued uptake of water is balanced by the elastic wall pushing
back on the cell.
16. Describe one model for facilitated diffusion.
The transport protein alternates between two conformations, moving a solute across
the membrane as the shape of the protein changes. The protein can transport the solute in
either direction, with the net movement being down the concentration gradient of the
solute.
17. Explain how active transport differs from diffusion.
Active transport is the pumping of solutes against their gradients. Specific
membrane proteins that perform the active transport harness energy usually in the form of
ATP. In facilitated diffusion, transport proteins hasten the movement of certain
substances across a membrane down their concentration gradients.
20. Explain how large molecules are transported across the cell membrane.
Large molecules are transported across the cell membrane through exocytosis and
endocytosis. Exocytosis: transport vesicles migrate to the plasma membrane, fuse with it,
and release their contents. Endocytosis: Large molecules enter cells within vesicles
pinched inward from the plasma membrane.
21. Give an example of receptor-mediated endocytosis.
In receptor-mediated endocytosis, coated pits form vesicles when specific molecules
bind to receptors on the cell surface. Notice that there is a greater relative proportion of
bound molecules inside the vesicle, though other molecules are also present. After the
ingested material is liberated from the vesicle for metabolism, the receptors are recycled
to the plasma membrane.
Figure 8.17 (P. 154) exemplifies receptor-mediated endocytosis in an animal cell.
CHAPTER 12 OBJECTIVES
2. Overview the major events of cell division that enable the genome of one cell to be
passed on to two daughter cells.
Mitosis: division of the nucleus
Cytokinesis: the division of the cytoplasm
3. Describe how chromosome number changes throughout the human life cycle.
DNA is partitioned among chromosomes, making it easier for the eukaryotic cell to
replicate and distribute its huge amounts of DNA. As the cell prepares to divide, it
duplicates each of its multiple chromosomes. A duplicated chromosome consists of two
sister chromatids joined at their centromeres.
4. List the phases of the cell cycle and describe the sequence of events that occurs during
each phase.
The mitotic (M) phase: when mitosis and cytokinesis actually divide
the nucleus and cytoplasm, mitotic phase is the shortest part of the cell cycle.
Interphase: accounts for about 90% of the time that elapses during the cell
cyle. Interphases consists of three periods of growth: G1 phase, the S phase,
and the G2 phase. A cell grows (G1), continues to grow as it copies
chromosomes (S), grows more as it completes preparations for cell division (G2)
and divides (M).
5. List the phases of mitosis and describe the events characteristic of each phase.
prophase: changes occur in both the nucleus and the cytoplasm. In the nucleus, the
nucleoli disappear. During prophase, the centrosomes move away from each other.
metaphase: the centromeres of all the chromosomes are aligned with one another ,
and sister chromatids of each other straddle the metaphase plate.\
anaphase: the two poles of the cell have equivalent and complete collections of
chromosomes.
telophase: the nonkinetochore microtubules elongate the cell still more and the
daughter nuclei begin to form at the two poles of the cell where the chromosomes have
gathered. Nuclear envelopes are formed from he fragments of the parent cell's nuclear
envelopes and other portions of the endomembrane system.
6. Recognize the phases of mitosis from diagrams or micrographs.
I can recognize all the phases of mitosis from diagrams.
8. Describe what characteristic changes occur in the spindle apparatus during each phase
of mitosis.
The mitotic spindle begins to form in the cytoplasm during prophase. At metaphase,
the chromosomes are arranged on the metaphase plate, attached to kinetochore
microtubules radiating from the centrosomes at the poles of the cell. At anaphase, sister
chromatids seperate and move toward opposite poles and at telophase, daughter nuclei
from at opposite ends of the cell.
10. Compare cytokinesis in animals and plants.
Cytokinesis divides the cytopplasm. In a dividing animal cell a cleavage furrow
appears on the cell surface. Microfilaments form a ring just inside the plasma membrane
at the location of furrowing. These microfilaments consist of actin and myosin, which
causes the cleavage furrow to deepen until the cell is pinched in two. In a plant cell,
membrane-bounded vesicules fuse to form a double membrane, which encloses the cell
plate at the equator of the cell. Materials are secreted into the space between the
membranes to form the new cell wall.
14. Explain how abnormal cell division of cancerous cells differs from normal cell
division.
Cancer cells elude normal regulation and divide out of control, forming tumors.
Malignant tumors invade surrounding tissues and can metastasize, exporting cancer ells
to other parts of the body