Biol 1441 Exam 2
1. 6.1 1. How do stains used for light microscopy compare with those used for electron microscopy?:
Stains used for light microscopy are colored molecules that bind to cell com- ponents, affecting
the light passing through, while stains used for electron mi- croscopy involve heavy metals
that affect the beams of electrons.
2. 2. Which type of microscope would you use to study
(a) the changes in shape of a living white blood cell
(b) the details of surface texture of a hair?: (a) Light microscope
(b) scanning electron microscope
3. 6.3 1. What role do ribosomes play in carrying out genetic instructions?: - Ribosomes in the
cytoplasm translate the genetic message, carried from the DNA in the nucleus by mRNA,
into a polypeptide chain.
4. 2. Describe the molecular composition of nucleoli and explain their func- tion.: Nucleoli consist of
DNA and the ribosomal RNA (rRNA) made according to its instructions, as well as proteins
imported from the cytoplasm. Together, the rRNA and proteins are assembled into large and
small ribosomal subunits. (These are exported through nuclear pores to the cytoplasm, where
they will participate in polypeptide syn- thesis.)
5. 3. As a cell begins the process of dividing, its chromosomes become shorter, thicker, and
individually visible in an LM. Explain what is happening at the molecular level.: Each chromosome
consists of one long DNA molecule attached to numerous protein molecules, a combination
called chromatin. As a cell begins division, each chromosome becomes "condensed" as its
,Biol 1441 Exam 2
diffuse mass of chromatin coils up.
6. 6.4 1. Describe the structural and functional distinctions between rough and smooth ER.: The
primary distinction between rough and smooth ER is the presence of bound ribosomes on the
rough ER. Both types of ER make phospholipids, but membrane proteins and secretory
proteins are all produced by the ribosomes on the rough ER. The smooth ER also functions in
detoxification, carbohydrate me- tabolism, and storage of calcium ions.
7. 2. Describe how transport vesicles integrate the endo-membrane system.-
: Transport vesicles move membranes and substances they enclose between other
components of the endomembrane system.
8. 3. Imagine a protein that functions in the ER but requires modification in the Golgi apparatus
before it can achieve that function. Describe the protein's path through the cell, starting with the
mRNA molecule that specifies the protein.: The mRNA is synthesized in the nucleus and then
passes out through
a nuclear pore to be translated on a bound ribosome, attached to the rough ER. The protein is
synthesized into the lumen of the ER and perhaps modified there. A transport vesicle carries
the protein to the Golgi apparatus. After further modifica-
,Biol 1441 Exam 2
tion in the Golgi, another transport vesicle carries it back to the ER, where it will perform its
cellular function.
9. 6.5 1. Describe two common characteristics of chloroplasts and mitochon- dria. Consider both
function and membrane structure.: Both organelles are involved in energy transformation,
mitochondria in cel- lular respiration and chloro- plasts in photosynthesis. They both have
multiple membranes that separate their interiors into compartments. In both organelles, the
innermost membranes—cristae, or infoldings of the inner membrane, in mito- chondria, and
the thylakoid membranes in chloroplasts—have large surface areas with embedded enzymes
that carry out their main functions.
10. 2. Do plant cells have mitochondria? Explain.: Yes. Plant cells are able to make their own
sugar by photosynthesis, but mitochondria in these eukaryotic cells are the organelles that are
able to generate energy from sugars, a function required in all cells.
11. 3. A classmate proposes that mitochondria and chloroplasts should be classified in the endo-
membrane system. Argue against the proposal.: Mito- chondria and chloroplasts are not derived
from the ER, nor are they connected physically or via transport vesicles to organ- elles of the
endomembrane system. Mitochondria and chloroplasts are structurally quite different from
vesicles derived from the ER, which are bounded by a single membrane.
12. 6.6 1. Describe shared features of microtubule-based motion of flagella and microfilament based
muscle contraction.: Both systems of movement involve long filaments that are moved in
relation
,Biol 1441 Exam 2
to each other by motor proteins that grip, release, and grip again adjacent poly- mers.
13. 2. Males afflicted with Kartagener's syndrome are sterile because of im- motile sperm, and they
tend to suffer from lung infections.This disorder has a genetic basis. Suggest what the underlying
defect might be.: Such individuals have defects in the microtubule-based movement of cilia and
flagella. Thus, the sperm can't move because of malfunctioning or nonex- istent flagella, and
the airways are compromised because cilia that line the trachea malfunction or don't exist,
and so mucus cannot be cleared from the lungs.
14. 6.7 In what way are the cells of plants and animals structur- ally different from single-celled
eukaryotes?: The most obvious difference is the presence
of direct cytoplasmic connections between cells of plants (plasmodesmata) and animals (gap
junctions). These connections result in the cytoplasm being continuous between adjacent cells.
15. If the plant cell wall or the animal extracellu- lar matrix were impermeable, what effect would this
have on cell function?: The cell would not be able to
1. 6.1 1. How do stains used for light microscopy compare with those used for electron microscopy?:
Stains used for light microscopy are colored molecules that bind to cell com- ponents, affecting
the light passing through, while stains used for electron mi- croscopy involve heavy metals
that affect the beams of electrons.
2. 2. Which type of microscope would you use to study
(a) the changes in shape of a living white blood cell
(b) the details of surface texture of a hair?: (a) Light microscope
(b) scanning electron microscope
3. 6.3 1. What role do ribosomes play in carrying out genetic instructions?: - Ribosomes in the
cytoplasm translate the genetic message, carried from the DNA in the nucleus by mRNA,
into a polypeptide chain.
4. 2. Describe the molecular composition of nucleoli and explain their func- tion.: Nucleoli consist of
DNA and the ribosomal RNA (rRNA) made according to its instructions, as well as proteins
imported from the cytoplasm. Together, the rRNA and proteins are assembled into large and
small ribosomal subunits. (These are exported through nuclear pores to the cytoplasm, where
they will participate in polypeptide syn- thesis.)
5. 3. As a cell begins the process of dividing, its chromosomes become shorter, thicker, and
individually visible in an LM. Explain what is happening at the molecular level.: Each chromosome
consists of one long DNA molecule attached to numerous protein molecules, a combination
called chromatin. As a cell begins division, each chromosome becomes "condensed" as its
,Biol 1441 Exam 2
diffuse mass of chromatin coils up.
6. 6.4 1. Describe the structural and functional distinctions between rough and smooth ER.: The
primary distinction between rough and smooth ER is the presence of bound ribosomes on the
rough ER. Both types of ER make phospholipids, but membrane proteins and secretory
proteins are all produced by the ribosomes on the rough ER. The smooth ER also functions in
detoxification, carbohydrate me- tabolism, and storage of calcium ions.
7. 2. Describe how transport vesicles integrate the endo-membrane system.-
: Transport vesicles move membranes and substances they enclose between other
components of the endomembrane system.
8. 3. Imagine a protein that functions in the ER but requires modification in the Golgi apparatus
before it can achieve that function. Describe the protein's path through the cell, starting with the
mRNA molecule that specifies the protein.: The mRNA is synthesized in the nucleus and then
passes out through
a nuclear pore to be translated on a bound ribosome, attached to the rough ER. The protein is
synthesized into the lumen of the ER and perhaps modified there. A transport vesicle carries
the protein to the Golgi apparatus. After further modifica-
,Biol 1441 Exam 2
tion in the Golgi, another transport vesicle carries it back to the ER, where it will perform its
cellular function.
9. 6.5 1. Describe two common characteristics of chloroplasts and mitochon- dria. Consider both
function and membrane structure.: Both organelles are involved in energy transformation,
mitochondria in cel- lular respiration and chloro- plasts in photosynthesis. They both have
multiple membranes that separate their interiors into compartments. In both organelles, the
innermost membranes—cristae, or infoldings of the inner membrane, in mito- chondria, and
the thylakoid membranes in chloroplasts—have large surface areas with embedded enzymes
that carry out their main functions.
10. 2. Do plant cells have mitochondria? Explain.: Yes. Plant cells are able to make their own
sugar by photosynthesis, but mitochondria in these eukaryotic cells are the organelles that are
able to generate energy from sugars, a function required in all cells.
11. 3. A classmate proposes that mitochondria and chloroplasts should be classified in the endo-
membrane system. Argue against the proposal.: Mito- chondria and chloroplasts are not derived
from the ER, nor are they connected physically or via transport vesicles to organ- elles of the
endomembrane system. Mitochondria and chloroplasts are structurally quite different from
vesicles derived from the ER, which are bounded by a single membrane.
12. 6.6 1. Describe shared features of microtubule-based motion of flagella and microfilament based
muscle contraction.: Both systems of movement involve long filaments that are moved in
relation
,Biol 1441 Exam 2
to each other by motor proteins that grip, release, and grip again adjacent poly- mers.
13. 2. Males afflicted with Kartagener's syndrome are sterile because of im- motile sperm, and they
tend to suffer from lung infections.This disorder has a genetic basis. Suggest what the underlying
defect might be.: Such individuals have defects in the microtubule-based movement of cilia and
flagella. Thus, the sperm can't move because of malfunctioning or nonex- istent flagella, and
the airways are compromised because cilia that line the trachea malfunction or don't exist,
and so mucus cannot be cleared from the lungs.
14. 6.7 In what way are the cells of plants and animals structur- ally different from single-celled
eukaryotes?: The most obvious difference is the presence
of direct cytoplasmic connections between cells of plants (plasmodesmata) and animals (gap
junctions). These connections result in the cytoplasm being continuous between adjacent cells.
15. If the plant cell wall or the animal extracellu- lar matrix were impermeable, what effect would this
have on cell function?: The cell would not be able to
