Chapter 7 Reading quiz
1. What does “cell fractionation” do?
2. What is the boundary called that
ALL cells have?
3. What is the simplest cell type?
4. Which tiny organelles make protein?
5. Which organelle acts as the cell’s
“post office”?
1. Distinguish between magnification and
resolving power.
Magnification
Resolving Power
• How much larger an • Minimum distance
object is made to
between two points
appear compared to
that can still be
its real size
distinguished as 2
separate points
• Limited by the
wavelength of
visible light 
2. Describe the advantages and limitations of
the light microscope, transmission electron
microscope, and the scanning electron
microscope.
1.
2.
3.
•
•
Light – 1000X magnification, wavelength problem
TEM – absorbs electrons – transmitted through
by using electromagnetic lenses; can study
internal cellular ultrastructure
SEM – studies surface of a specimen – beam
scans surface usually coated in gold & excites
secondary electrons on surface
produces a 3D image
Disadvantages of electrons  only dead cells
(elaborate preparation needed) 
3. Describe the major steps of cell
fractionation and explain why it is a useful
technique (top of p. 105)
•
1.
2.
3.
4.
5.
Involves centrifuging disrupted cells at various
speeds & durations to isolate components of
different sizes, densities, and shapes
Homogenize tissue
Centrifuge slowly – form pellet
Supernatant decanted & centrifuged again to
get small stuff (faster)
3rd step repeated each time faster and faster to
get smaller
Once components are separated & identified,
functions may be determined 
4. Distinguish between prokaryotic and
eukaryotic cells.
•
•
•
•
Prokaryotes
Bacteria/
archaebacteria
No true nucleus or
envelope
Genetic stuff in
nucleoid region
No membrane-bound
organelles
Eukaryotes
• Protista, Fungi, Plants,
Animals
• True nucleus with
nuclear envelope
• Cytoplasm with
membrane-bound
organelles 
5. Explain why there are both upper and
lower limits to cell size.
Lower limits – probably determined by the
DNA to program metabolism (metabolic
requirements)
• Ribosomes, enzymes & cellular components
Upper limits – by surface area to volume
ratio (volume does not grow
proportionately to surface area)
• Plasma membrane – exchange oxygen,
nutrients, wastes 
6. Explain why compartmentalization is
important in eukaryotic cells.
• Compensate for small surface area to
volume ratio by having internal membranes
• Partitions cell into compartments
• Unique compositions depending on functions
• Enzymes may be incorporated
• Provide localized environmental conditions
necessary for specific metabolic processes

7. Describe the structure and function of
the nucleus, and briefly explain how the
nucleus controls protein synthesis in the
cytoplasm.
Nucleus – membrane-bound cellular organelle
in eukaryotes
• Contains most of the genes that control
the entire cell
mRNA transcribed in nucleus from DNA 
passes through nuclear pores to cytoplasm
 attaches to ribosomes where the
genetic message is translated into primary
protein structure 
8. Describe the structure and function of a
eukaryotic ribosome.
• Cytoplasmic organelle that is the site for
protein synthesis
• Complexes of RNA and protein
• Constructed in the nucleolus (no membrane)
• Cells with high rate of protein synthesis
have lots of ribosomes bound and free
(ER vs. cytoplasmic)

9. Describe the structure and function of
the ER, the Golgi apparatus, lysosomes, and
vacuoles and summarize the relationships
among them.
1.
2.
3.
4.
5.
Nuclear envelope – double membrane with pores
ER – manufactures membranes (smooth vs.
rough/ lipid vs. protein synthesis)
Golgi apparatus – finishes, sorts, and ships cell
products
Lysosomes – bag of hydrolytic enzymes; digest
all macromolecules
Vacuoles – sac; come in food, contractile, and
central forms 
10. Distinguish among the types of vacuoles
and explain how their functions differ.
1.
Food vacuole – formed by phagocytosis 
site of intracellular digestion by some
protists and macrophages
2. Contractile vacuole – vacuole that pumps
excess water from cell in some
freshwater protozoa
3. Central vacuole – large vacuole found in
most mature plant cells 
11. Describe the structure of the
mitochondrion and explain the importance of
compartmentalization in mitochondrial
function.
• Organelle which is the site of cellular
respiration, a catabolic oxygen-requiring
process that uses energy from food to
produce ATP
• Number of mitochondria correlates with
cell activity
• Can move, change shape, and divide
• 2 membranes – outer and inner
• Mitochondrial matrix 
12. Distinguish among amyloplast,
chromoplast, and chloroplast.
• All are plastids
1. Amyloplast – colorless, store starch,
found in roots and tubers
2. Chromoplast – pigments other than
chlorophyll – responsible for fruit,
flower, and autumn leaf colors
3. Chloroplast – chlorophyll containing – site
for photosynthesis 
13. Describe the structure of a chloroplast,
and explain the importance of
compartmentalization in chloroplast function.
1. Intermembrane space – separates
chloroplast from cytosol
2. Thylakoid space – another membrane
system – segregates the chloroplast into
2 compartments (thylakoid and stroma)
Chlorophyll is here stacked into grana
(light rxns)
3. Stroma – (dark reactions) energy  sugar
• Viscous fluid outside thylakoids 
14. Identify why peroxisomes are important
in eukaryotic cells.
• Membrane- bound organelles that
contain specialized teams of enzymes
for specific metabolic pathways
• All contain peroxide-producing
oxidases
• Breakdown fatty acids into smaller
molecules for food
• Detoxification of alcohol, etc. 
15. Describe probable functions of the
cytoskeleton.
1.
2.
3.
4.
5.
Gives mechanical support to the cell and
helps maintain shape
Enables cell to change shape in an
adaptive manner
Associated with motility
Signal transmission from surface to
interior
Constructed from 3 types of fibers 
16. Describe the structure, components and
functions of microtubules, microfilaments
and intermediate filaments.
• Microtubules – straight hollow fibers
- globular proteins called tubulin
- used in cell support, organelle movement,
separation of chromosomes during cell division
• Microfilaments – solid rods, globular protein
monomers (actin)
- cell support, muscle contraction, localized cell
contraction
• Intermediate – diverse class of cytoskeletal
elements (keratin)
- bear tension, reinforce shape, fix organelle
position 
17. Describe the development of plant cell
walls.
1.
2.
3.
Young plant cell
secretes a thin
flexible primary cell
wall
Between the primary
walls of adjacent
cells a middle lamella
made of pectins
cements cells
together
Cell stops growing
and strengthens wall

18. Describe the structure and list some of
the functions of the extracellular matrix in
animal cells.
• Meshwork of macromolecules outside the
plasma membrane of animal cells (ECM)
• Provides support and anchorage for cells
• Helps control gene activity in nucleus
(mechanical stimuli)
• Functions in cell’s dynamic behavior
(orient filaments) 
19. Describe the structure of intercellular
junctions found in plant and animal cells, and
relate their structure to function.
Plants
• Plasmodesmata = channels
that perforate plant cell
walls – cytoplasmic strands
communicate
• Lined by plasma membrane
of adjacent cells are
continuous
• Allows free passage of
water, etc. (cytoplasmic
streaming)
Animals
• Tight junctions 
intercellular junctions that
hold cells together tightly
enough to block transport
of substances
• Desmosomes  junctions
that rivet cells together
into strong sheets, but still
permit substances to pass
freely
• Gap junctions 
intercellular junctions
specialized for material
transport between the
cytoplasm of adjacent cells
