Unit 1: The Cell
Which of the following groups is primarily involved in synthesizing molecules needed by the cell?
Ribosomes, rough endoplasmic reticulum, and smooth endoplasmic reticulum
A substance moving from outside the cell into the cytoplasm must pass through __________.
the plasma membrane
Observing a fluorescent micrograph cell with intermediate filaments would help you identify the cell as a __________.
human skin cell
Dye injected into a plant cell might be able to enter an adjacent cell through __________.
plasmodesmata Dye injected into a plant cell might be able to enter an adjacent cell through plasmodesmata. Plant cell walls are usually perforated by channels between adjacent cells called plasmodesmata. The cytoplasm of one plant cell is continuous with the cytoplasm of its neighbors via plasmodesmata, which are cytoplasmic channels through the cell walls.
Cell junctions in plant cells are called __________, and communicating junctions in animal cells are called __________.
plasmodesmata; gap junctions
Evidence that supports the prokaryotic origins of mitochondria and chloroplasts are all of the following except __________.
Answer: that mitochondria and chloroplasts have multiple copies of linear DNA molecules associated with their inner membranes -that mitochondria and chloroplasts have multiple copies of linear DNA molecules associated with their inner membranes -that the ancestral prokaryote had two outer membranes, which became the double membranes of the mitochondria and chloroplasts -that mitochondria and chloroplasts have multiple copies of circular DNA molecules associated with their membranes -that mitochondria and chloroplasts can grow and reproduce within a cell -that mitochondria and chloroplasts are somewhat independent within a cell
Which of the following is false in respect to cells' chromosomes?
Answer: Chromosomes are only visible as a cell is about to divide. -Chromosomes are only visible as a cell is about to divide. -Chromosomes contain DNA and proteins. -Chromosomes are present throughout a cell's reproductive cycle. -Chromosomes exist even when cells are not actively synthesizing proteins.
Basal bodies are most closely associated with which of the following cell components?
Cilia
In terms of cellular function, what is the most important difference between prokaryotic and eukaryotic cells?
Eukaryotic cells are compartmentalized, which allows for specialization. A major difference between prokaryotic and eukaryotic cells is the location of their DNA. In a eukaryotic cell, most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane. In a prokaryotic cell, the DNA is concentrated in a region that is not membrane-enclosed, called the nucleoid. In addition, within the cytoplasm of a eukaryotic cell, suspended in cytosol, are a variety of organelles of specialized form and function. These membrane-bounded structures are absent in prokaryotic cells. Thus, the presence or absence of a true nucleus is just one aspect of the disparity in structural complexity between the two types of cells.
Cilia and flagella move due to the interaction of the cytoskeleton with which of the following?
Motor proteins In flagella and motile cilia, flexible cross-linking proteins, evenly spaced along the length of the cilium or flagellum, connect the outer doublets to each other and to the two central microtubules. Each outer doublet also has pairs of protruding proteins spaced along its length and reaching toward the neighboring doublet; these are large motor proteins called dyneins, each composed of several polypeptides. Dyneins are responsible for the bending movements of the organelle. A dynein molecule performs a complex cycle of movements caused by changes in the shape of the protein, with ATP providing the energy for these changes.
__________ are membrane-bound metabolic compartments that specialize in the production of hydrogen peroxide (H2O2) and its conversion to water.
Peroxisomes Peroxisomes are membrane-bound metabolic compartments that specialize in the production of hydrogen peroxide (H2O2) and its conversion to water. The peroxisome is a specialized metabolic compartment bounded by a single membrane. Peroxisomes contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen (O2), producing hydrogen peroxide (H2O2) as a by-product (from which the organelle derives its name).
Which of the following is present in a prokaryotic cell?
Ribosomes
What is the functional connection between the nucleolus, nuclear pores, and the nuclear membrane?
Subunits of ribosomes are assembled in the nucleolus and pass through the nuclear membrane via the nuclear pores.
Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why?
The intestinal cells are bound together by tight junctions.
The organelle that is a plant cell's compartment for the storage of inorganic ions such as potassium and chloride is the __________.
central vacuole
Animal cells have unique organelles called __________ that are composed of structures called __________.
centrosomes; centrioles Animal cells have unique organelles called centrosomes that are composed of structures called centrioles. In animal cells, microtubules grow out from a centrosome, a region that is often located near the nucleus. These microtubules function as compression-resisting girders of the cytoskeleton. Within the centrosome is a pair of centrioles, each composed of nine sets of triplet microtubules arranged in a ring. Although centrosomes with centrioles may help organize microtubule assembly in animal cells, many other eukaryotic cells lack centrosomes with centrioles and instead organize microtubules by other means.
A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized __________.
in the rough endoplasmic reticulum
The walls of plant cells are largely composed of polysaccharides and proteins that are synthesized __________.
in the rough endoplasmic reticulum and in the Golgi apparatus
The network of fibers that organizes structures and activities in a cell __________.
is the cytoskeleton
Microfilaments function in cell motility including __________.
muscle contraction, amoeboid movement, and cytoplasmic streaming in plants
The endoplasmic reticulum is part of the endomembrane system, which also includes the __________.
nuclear envelope, the Golgi apparatus, lysosomes, and vesicles
The region of a bacterial cell that contains the genetic material is called the __________.
nucleoid
The function of the rough endoplasmic reticulum (RER) is __________.
to synthesize proteins that are secreted as glycoproteins
Cell motility, which includes changes both in cell location and in the movement of cell parts, requires interactions of the cytoskeleton __________.
with motor proteins
Which statement about the cytoskeleton is true?
Answer: Components of the cytoskeleton often mediate the movement of organelles within the cytoplasm. -Components of the cytoskeleton often mediate the movement of organelles within the cytoplasm. -Intermediate filaments are hollow tubes of protein that provide structural support. -Microtubules are chains of proteins that resist stretching. -Microfilaments are more permanent structures in cells compared to intermediate filaments and microtubules. -Plant cells lack a cytoskeleton because they have a rigid cell wall.
The extracellular matrix of the animal cell has all of the following molecular components except __________.
Answer: a middle lamella -a middle lamella -collagen -proteoglycans -fibronectin -integrins Animal cells lack walls akin to those of plant cells, but animal cells do have an elaborate extracellular matrix (ECM). "Collagen," "proteoglycans," "fibronectin," and integrins" are all components of the extracellular matrix of animal cells.
Bacterial cells are prokaryotic. Unlike a typical eukaryotic cell they __________.
have no membrane-bounded organelles in their cytoplasm In a eukaryotic cell, most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane. In a prokaryotic cell, the DNA is concentrated in a region that is not membrane-enclosed, called the nucleoid. Within the cytoplasm of a eukaryotic cell, suspended in cytosol, are a variety of organelles of specialized form and function. Lacking a true nucleus and the other membrane-enclosed organelles of the eukaryotic cell, the prokaryotic cell is much simpler in structure.
The endosymbiont theory explains the origins of __________.
mitochondria and chloroplasts The endosymbiont theory explains the origins of mitochondria and chloroplasts. Mitochondria and chloroplasts display similarities with bacteria that led to the endosymbiont theory. This theory states that an early ancestor of eukaryotic cells engulfed an oxygen-using, nonphotosynthetic prokaryotic cell. Eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont (a cell living within another cell). Indeed, over the course of evolution, the host cell and its endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion. At least one of these cells may have then taken up a photosynthetic prokaryote, becoming the ancestor of eukaryotic cells that contain chloroplasts. This is a widely accepted theory of the origins of mitochondria and chloroplasts.
Cells are small because __________.
of the geometric relationships between surface and volume "Area is proportional to a dimension cubed (X3), whereas volume is proportional to a dimension squared (X2)" is incorrect because area is proportional to a dimension squared (X2) while volume is proportional to a dimension cubed (X3).
You would expect a cell with an extensive Golgi apparatus to __________.
secrete a lot of protein After leaving the ER, many transport vesicles travel to the Golgi apparatus. We can think of the Golgi as a warehouse for receiving, sorting, shipping, and even some manufacturing. Here, products of the ER, such as proteins, are modified and stored and then sent to other destinations. Not surprisingly, the Golgi apparatus is especially extensive in cells specialized for secretion.
