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McKinley/O’Loughlin
Human Anatomy, 2nd Edition
CHAPTER 2
Answers to “What Did You Learn?”
1.
TEM provides greater magnification and resolution than LM, allowing details of
structures inside cells and attachments to the cell surface to be studied.
2.
The basic functions of cells are covering, lining, storage, movement, connection,
defense, communication, and reproduction.
3.
The three main regions of a cell are (1) the plasma membrane, a vital boundary
around the cell; (2) cytoplasm, composed of all cellular contents between the
plasma membrane and the nucleus; and (3) the nucleus, the cell’s control center.
4.
Phospholipids, cholesterol, and glycolipids are found in the plasma membrane.
5.
Ions, nutrients, wastes, and secretory products may cross a selectively permeable
membrane.
6.
Diffusion is the tendency of molecules to move down their concentration
gradients (from regions of higher concentration to regions of lower
concentration).
7.
Osmosis is a special type of passive transport by which water diffuses from one
side of the selectively permeable membrane to the other side of the membrane.
8.
Both facilitated diffusion and receptor-mediated endocytosis require a transport
protein within the plasma membrane.
9.
Cytosol is the viscous, syruplike fluid of the cytoplasm that contains many solutes
(ions, nutrients, proteins, carbohydrates, lipids, and other small molecules).
10.
Lysosomes are membrane-bound sacs that contain catalysts (digestive enzymes)
used by the cell to digest waste products and other macromolecules.
Mitochondria are double-membrane-bound organelles that produce large amounts
of ATP. Centrioles are responsible for organizing microtubules that attach to
chromosomes during cell division (mitosis).
11.
Proteins synthesized by free ribosomes remain within the cell and function for
cellular activities. Proteins synthesized on fixed ribosomes (1) are exported
outside of the cell, (2) are incorporated into the plasma membrane, or (3) form
enzymes within a new lysosome.
McKinley/O’Loughlin
12.
Human Anatomy, 2nd Edition
Cilia are cytoplasmic projections whose beating-like movement moves materials
along the exposed cell surface.
13.
The nuclear envelope is the boundary around the nucleus that controls the entry
and exit of materials between the nucleus and the cytoplasm.
14.
Chromatin is a strand of unwound DNA and its associated proteins.
Chromosomes are the highest level of organization of genetic material. Within
them, the molecule of DNA and associated proteins are tightly wound.
15.
The parts of interphase are: the G1 phase, characterized by cell growth, protein
production, and metabolic activities; the S phase, during which DNA is replicated
prior to cell division and growth activities continue; and the G2 phase,
characterized by completion of centriole replication, organelle production, and
synthesis of proteins needed for cellular division.
16.
Mitosis stages: In Prophase, chromosomes appear after chromatin coils; the
nucleolus breaks down; elongated microtubules grow from centrioles; and the
nuclear envelope disappears. In Metaphase, chromosomes align in the equatorial
middle of the cell. In Anaphase, microtubule strands pull sister chromatids apart
at the equatorial middle of the cell. In Telophase, new chromosomes arrive at
each pole of the new cells.
17.
Programmed cell death is called apoptosis.
18.
Cancer’s main characteristic is uncontrolled cell growth.
Answers to “Content Review”
1.
The cell has three main regions: (1) the plasma membrane is a boundary bilayer of
lipids and proteins that encloses the cell; (2) the cytoplasm includes all of the
contents of the cell (cytosol, organelles, and inclusions) between the plasma
membrane and the nucleus; and (3) the nucleus is the cell’s control center, and it
contains all of the genetic material of the cell.
2.
The plasma membrane forms the cell border. It is composed of both lipids and
proteins. It regulates the passage of gases, nutrients, and wastes between the
internal and external environments.
McKinley/O’Loughlin
3.
Human Anatomy, 2nd Edition
Passive transport is a mechanism to move substances across a plasma membrane
without the expenditure of energy by the cell. Passive transport process includes
simple diffusion, osmosis, facilitated diffusion, and bulk filtration.
4.
Active transport differs from passive transport in that substances are moved
against a concentration gradient and energy in the form of ATP must be
expended. The types of endocytosis are phagocytosis, pinocytosis, and receptormediated endocytosis.
5.
Organelles are complex, organized cellular structures that are either (1)
membrane-bound or (2) non-membrane-bound. The most obvious difference is
that membrane-bound organelles are enclosed within a membrane similar to a
plasma membrane to separate organelle components from the rest of the cell, and
no-membrane-bound organelles are always in direct contact with the cytosol of
the cell.
6.
The smooth ER is an interconnected network of membrane tubules and vesicles
with no attached ribosomes. It is involved in the synthesis of lipids (steroids, fatty
acids, and phospholipids); metabolizes carbohydrates; and detoxifies drugs and
alcohol. The rough ER is a flattened intracellular network of membrane sacs
called cisternae. It has ribosomes attached on its cytoplasmic surface. It is
involved in the synthesis of proteins for secretion, new proteins for the cell
membrane, and lysosomal enzymes. Additionally, it transports and stores some
molecules.
7.
The cytoskeleton is composed of microfilaments, intermediate filaments, and
microtubules. Microfilaments are composed of thin protein filaments (actin
proteins) organized into two intertwined strands. The maintain cell shape, support
cell shape changes, help muscles contract, separate the two cells formed during
cell division, and facilitate cytoplasmic streaming. Intermediate filaments are
slightly larger and more rigid than microfilaments. They support cells structurally
and stabilize junctions between cells. Microtubules are hollow tubules composed
of long chains of proteins called tubulin. They help hold organelles in place,
maintain cell shape and rigidity, direct organelle movement between different
regions of the cell, provide a means of cell motility, and move chromosomes
during the process of cell division.
McKinley/O’Loughlin
8.
Human Anatomy, 2nd Edition
The nucleus contains three basic components: a nuclear envelope, nucleoli, and
chromatin. The nuclear envelope is a double is a double membrane structure that
encloses the nucleus. Nucleoli are dark-staining bodies responsible for making
both small and large subunits of ribosomes. Chromatin is the name of the tightly
coiled strands of DNA and protein in the nucleus.
9.
Interphase is a time in the cell cycle when the cell appears to be resting because
no overt activity is observed. However, if the cell is preparing for division, it is
also a time of growth and making new cellular parts. It is composed of three
distinct phases G1, S, and G2.
10.
There are four consecutive phases (or stages) during mitosis: prophase,
metaphase, anaphase, and telophase. During Prophase, the replicated DNA in
chromatin supercoils into chromosomes; a duplicated chromosome is composed
of two sister chromatids, the nucleolus breaks down and disappears; microtubules
form from centrioles that move to opposite sides of the cell; and the nuclear
envelope disappears. During Metaphase, the chromosomes line up in the
equatorial plate; the mitotic spindle is completely formed. During Anaphase,
sister chromatids are pulled apart and begin to move toward opposite sides of the
cell. During Telophase, single-stranded chromosomes arrive at each pole of the
cell; the mitotic spindle breaks up; and new nucleoli appear.