HONORS BIOLOGY – UNIT 2 (Chapters 4 – 5.9) REVIEW ANSWERS
□ I have finished any/all assignment(s) that is/are currently missing from Gradebook.
□ I can describe the main ideas of the cell theory along with its limitation(s):
CELL THEORY: the cell is the structural and functional unit of all living things, all living
things are made of at least one cell (either prokaryotic or eukaryotic), all cells arise from
previously existing cell.
Cell theory does not answer the fundamental question of from where did the first cell
come
□ I can describe why cells are small and the relationships between cell size and shape to
surface area:volume ratio:
Cells are small due to the effects of surface area to volume ratio. Surface area allows for
the exchange of material into/out of the cell, volume represents space for chemical
reactions to occur…so if a cell has a large volume, but cannot effectively exchange
materials because it has a small SA…that’s not good at keeping chemical reactions
going.
Cells can maximize SA to V ratio by wither (1) being small, or (2) having a flat, elongated
shape…both of these examples are highlighted in the Cell Size Lab exercises.
□ I can describe the similarities and differences between prokaryotic and eukaryotic cells and
give examples of organisms that have these different cells types:
BOTH HAVE: Cell (plasma) membrane, ribosomes, chromosomes containing DNA.
Prokaryotes are much smaller, and always unicellular…include bacteria and
archea…and LACK specialized membrane-enclosed regions and organelles.
Eukaryotes (plant, animal, fungi, protists) are much larger, can be unicellular (like
paramecium) or multicellular. These cells contain a nucleus, as well as other specialized
membrane enclosed structures called organelles. The compartmentalization allows
different regions of the cell to perform specific tasks…much more efficient than having
to do everything in the cytoplasm, like prokaryotes must do.
□ I can describe the major function(s) of the following organelles/cell structures:
□ I can describe the endosymbiosis hypothesis and discuss evidence which supports it:
The hypothesis that some organelles of eukaryotes (Chloroplasts, mitochondria) were
once (billions of years ago) free-living prokaryotes…and these prokaryotes were taken
in by larger cells. The larger cell provided protection, while the smaller cell (now an
organelle) performed a certain metabolic function…like photosynthesis. BOTH cells
benefit from this arrangement. Mitochondria and chloroplasts actually have their own
DNA pieces…which they would have needed as free living cells…that’s pretty strong
evidence that they may once have been free living.
□ I can describe the structure of a phospholipid molecule and how its properties are suited to
its role as a component of cell membranes:
A phospholipid molecule has polar (phosphate “head”) and nonpolar (fatty acid tails)
regions. These different regions create a molecule that has both hydrophilic and
hydrophobic regions…it is both attracted to and repelled by water. This “dual nature” of
that molecule lends itself well in the structure of a membrane…the polar regions are on
the outer and inner surfaces of the membrane, while the hydrophobic regions are in the
middle of the membrane:
This phospholipid bilayer creates a structure that is “selectively permeable”…it only
allows certain substances to pass through. Small, nonpolar substances move trhough
easily, while large, polar substances are essentially blocked and would require a
transport or channel protein to pass through.
□ I can describe why the membrane is referred to as a “fluid mosaic” structure”:
Membranes contain many individual molecules (phospholipids, cholesterol, proteins,
carbohydrates)…all of these pieces contribute to the “mosaic” idea. All of those
molecules can move about within that membrane…much like if you had a bunch of
inflatable balls floating on the surface of a swimming pool…the layer of balls would
present a barrier to the water below, but the objects would be able to move about.
□ I can identify and describe the various macromolecules (in addition to phospholipids) that
are found in a membrane and discuss their functions:
Cholesterol: structural support in the hydrophobic region of the membrane
Glycoprotein: Identification/communication
Proteins: can be enzymes, transport pathways through the membrane, and can form
junctions (attachment) between cells
□ I can describe the similarities and differences between “active” and “passive” transport
processes, and give example(s) of each:
Active transport: REQUIRES ENERGY, moves substances AGAINST concentration
gradients (from low to high), or physically moves substances into/out of the cell by
movement of the membrane (endo- and exocytosis)
Examples: pumping Na+ ions against their concentration gradient, pino- and
phagocytosis
Passive Transport: does NOT REQUIRE ENERGY, substances move with their
concentration gradient (from high to low)
Examples: diffusion (small, nonpolar substances like CO2, O2) and facilitated
diffusion (larger, polar substances like glucose)
□ I can describe what is meant by osmotic conditions, and can compare/contrast the effects
of those conditions on plant vs animal cells:
Osmotic conditions: conditions that can cause the movement of water based upon
varying solute concentration inside vs outside of a cell. Described using three terms:
Isotonic: same solute concentration inside vs outside
Hypotonic: less solute outside than inside (causes water to move into cell)
Hypertonic: more solute outside vs inside (causes water to move out of cell)
Effects of osmotic conditions are much greater for animal cells, as they lack the support
of a cell wall that plants cells have. Animal cells are much more likely to lyse (split apart
or rupture) in hypotonic solution than are plant cells.
□ I can describe the differences between endo- and exocytosis, phago- and pinocytosis:
All involve the movement of substances into (endo-) or out of (exo-) the cell.
Phago- means to “eat” pino- to “drink”, both of these are special cases of endocytosis
involving solid materials and liquid materials, respectively.
□ I have completed the “Key Concepts” and ‘Post Test” online quizzes* for Chapters 4 and 5
(sections 5.1-5.9 only) located at http://www.pearsonhighered.com/campbell/
*Keep in mind that some of these questions are “trivial” in their detail. Be familiar with big ideas
(structure vs function, etc.).
□ I have completed the Questions in the back of each chapter (and checked my answers in
the back of the textbook) for the sections covered in class.