Chapter 4
Which of the following are common traits of chloroplasts and mitochondria?
Both have their own DNA.
Which of the following statements concerning cells of bacteria and archaea is correct?
DNA is present in both archaea and bacteria.
Which molecules do not normally cross the nuclear membrane?
DNA; All processes involving DNA take place in the nucleus.
A cell has formed a food vacuole as it ingested a food particle. Which of the following events is associated with the breakdown of that food particle?
Digestion of the food particle occurs in a vesicle enclosed by a membrane that separates the digestion from the cytoplasm.
True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy.
False; Cytoplasmic proteins called importins bind to large proteins containing an NLS and mediate their transport across the nuclear membrane through an active transport (energy-requiring) process.
_____ are surface appendages that allow a bacterium to stick to a surface.
Fimbriae
Which of the following produces and modifies polysaccharides that will be secreted?
Golgi apparatus
Why isn't the mitochondrion classified as part of the endomembrane system?
It is not derived from the endoplasmic reticulum or Golgi.
Which of the following will be found in nearly all eukaryotic cells?
Mitochondria
Which plant cell organelle contains its own DNA and ribosomes?
Mitochondria
All proteins are synthesized by ribosomes in the cell. Some ribosomes float freely in the cytosol, while others are bound to the surface of the endoplasmic reticulum. Most proteins made by free ribosomes function in the cytosol. Proteins made by bound ribosomes either function within the endomembrane system or pass through it and are secreted from the cell. Which of the following proteins are synthesized by bound ribosomes?
Most proteins that function in the cytosol (such as actin) or in the nucleus (such as DNA polymerase) are synthesized by free ribosomes. Proteins that function within the endomembrane system (such as lysosomal enzymes) or those that are destined for secretion from the cell (such as insulin) are synthesized by bound ribosomes. As a protein destined for the endomembrane system is being synthesized by a ribosome, the first amino acids in the growing polypeptide chain act as a signal sequence. That signal sequence ensures that the ribosome binds to the outer membrane of the ER and that the protein enters the ER lumen.
Which one of the following statements about the endomembrane system is correct?
Proteins that will be secreted from the cell are likely to be found in closed spaces bounded by membranes of the endomembrane system.
Which of the following statements about the nuclear envelope is false?
The nuclear envelope is continuous with the Golgi apparatus.
A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from
any eukaryotic organism.
lysosomes
autophagy macromolecule digestion
smooth ER
calcium ion storage poison detoxification lipid synthesis
What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?
cell wall
Thylakoids, DNA, and ribosomes are all components found in
chloroplasts
A biologist ground up some plant leaf cells and then centrifuged the mixture to fractionate the organelles. Organelles in one of the heavier fractions could produce ATP in the light, whereas organelles in the lighter fraction could produce ATP in the dark. The heavier and lighter fractions are most likely to contain, respectively,
chloroplasts and mitochondria.
In a liver cell detoxifying alcohol and some other poisons, the enzymes of the peroxisome remove hydrogen from these molecules and
combine the hydrogen with oxygen molecules to generate hydrogen peroxide.
Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. In animal cells, which of the following organelles contains these hydrolytic enzymes?
lysosomes
The cilia and flagella of eukaryotic cells are composed of _____.
mictrotubules
Which animal cell organelle contains enzymes that transfer hydrogen from various substrates to oxygen?
peroxisome
Mitochondria are found in __________.
plant and animal cells All eukaryotic cells, including plant and animal cells, contain mitochondria.
The volume enclosed by the plasma membrane of plant cells is often much larger than the corresponding volume in animal cells. The most reasonable explanation for this observation is that
plant cells contain a large vacuole that reduces the volume of the cytoplasm.
A cell with an abundance of free ribosomes is most likely
producing primarily cytoplasmic proteins.
Which structure is the site of the synthesis of proteins destined for export from the cell?
rough ER
Which organelle often takes up much of the volume of a plant cell?
vacuole
Which of the following clues would tell you if a cell is prokaryotic or eukaryotic?
whether or not the cell is partitioned by internal membranes
Prokaryotes are classified as belonging to two different domains. What are the domains?
Bacteria and Archaea
A small protein (molecular weight = 25,000 daltons) is injected into a cell and observed in the nucleus a short time later. What type of transport has taken place?
Passive transport; A 25,000-dalton protein is small enough to diffuse through nuclear pores without any expenditure of energy.
Which of the following statements correctly describes some aspect of protein secretion from prokaryotic cells?
Proteins that are secreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane.
Which statement correctly describes the nuclear envelope of a eukaryotic cell?
The nuclear envelope is continuous with the endoplasmic reticulum.
The DNA-containing region of this bacterial cell is indicated by the letter _____.
The nucleoid region contains DNA.
The structure that regulates the passage of material into and out of this bacterial cell is indicated by the letter _____.
The plasma membrane is selectively permeable.
The nuclear lamina is a netlike array of filaments on the inner side of the nuclear membrane. If a method were found that could cause the lamina to fall into disarray, what would you expect to be the most likely immediate consequence?
a change in the shape of the nucleus
The evolution of eukaryotic cells most likely involved
endosymbiosis of an oxygen-using bacterium in a larger host cell; the endosymbiont evolved into mitochondria.
If plant cells are grown on media containing radioactively labeled thymine for one generation, where will radioactively labeled macromolecules be detected?
in the nucleus, mitochondria, and chloroplasts
What types of proteins are synthesized by the rough ER?
lysosomal proteins
Which organelle plays a role in intracellular digestion?
lysosome
What types of proteins are synthesized somewhere other than the rough ER?
mitochondrial proteins
One of the key innovations in the evolution of eukaryotes from a prokaryotic ancestor is the endomembrane system. Which eukaryotic organelles or features might have evolved as a part of, or as an elaboration of, the endomembrane system?
nuclear envelope
Where is a bacterial cell's DNA found?
nucleoid region
The chemical reactions involved in respiration in prokaryotic and eukaryotic cells are virtually identical. In eukaryotic cells, ATP is synthesized primarily on the inner membrane of the mitochondria. In light of the endosymbiont theory for the evolutionary origin of mitochondria, where is most ATP synthesis likely to occur in prokaryotic cells?
on the plasma membrane
In an animal cell, DNA may be found
only in the nucleus and mitochondria.
The _____ is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell.
plasma membrane
Which of the following organelles is found exclusively in plant cells?
plastids
What is a function of a bacterium's capsule?
protection
Which of the following statements correctly describes a function of the Golgi apparatus?
protein modification and sorting
Golgi apparatus
protein modification and sorting cisternal maturation
Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
proteins
In a bacterium, where are proteins synthesized?
ribosomes
Some key innovations in the evolution of eukaryotes from a prokaryotic ancestor are membrane-bound organelles. Which of the following organelles or features is likely to be a common component shared by both eukaryotic cells and their prokaryotic ancestors?
ribosomes
Which of the following correctly describes the pathway taken by a protein destined for secretion from an animal cell?
rough ER → transport vesicle → Golgi → transport vesicle → plasma membrane
The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and therefore abundant in liver cells?
smooth ER
Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?
smooth endoplasmic reticulum
The membranes of various organelles in the endomembrane display differences in their lipid and protein compositions. These differences are largely established by
the function of the Golgi apparatus in modifying, sorting, and directing membrane components to their final destinations.
Comparison of samples from the liver of an alcoholic with samples from the liver of a non-drinker when examined by transmission electron microscopy would likely reveal that
the liver of the alcoholic has expansive smooth ER compared to the non-drinker's liver.
Tay-Sachs disease is a human genetic abnormality that results in cells accumulating very large, complex, undigested lipids. Which cellular organelle must be defective in this condition?
the lysosome
Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is _____.
transferring of information from DNA to messenger RNA