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Which of the following is NOT a concept of the cell theory?
The activity of an organism depends on both the individual and the collective activities of its cells.
The biochemical activities of cells are dictated by the relative number of their specific subcellular structures.
Cells are given life through a process known as spontaneous generation.
A cell is the basic structural and functional unit of living organisms.

Cells are given life through a process known as spontaneous generation.
All cells arise from pre-existing cells through cell division. Thus, continuity of life from one generation to another has a cellular basis. The other three major concepts of cell theory are as follows. (1) A cell is the basic structural and functional unit of living organisms. When you define cell properties you are, in fact, defining the properties of life. (2) The activity of an organism depends on both the individual and the collective activities of its cells. (3) According to the principle of complementarity of structure and function, the biochemical activities of cells are dictated by the relative number of their specific subcellular structures.

Which of the following names the three main parts of a human cell?
cytoplasm, nucleus, and lysosome
mitochondria, lysosome, and centriole
cytoplasm, plasma membrane, and nucleus
plasma membrane, mitochondria, and nucleus

cytoplasm, plasma membrane, and nucleus
Human cells have three main parts: the plasma membrane, the cytoplasm, and the nucleus.

Which of the following molecules might change over time in a cancer cell?
membrane glycolipids
membrane glycoproteins
glycocalyx sugars
all of the above

all of the above
DNA can be considered the "cell's blueprint," which contains the instructions for making all of the cellular organelles and the plasma membrane.

Which set of membrane proteins in the figure depicts the transport of solute molecules?

Panel A shows both passive and active transport processes mediated by integral membrane proteins.

What molecular structure is shown in D, but NOT in A, B, or C? membrane phospholipids
an integral membrane protein
a carbohydrate molecular group
a peripheral membrane protein

a carbohydrate molecular group
Panel D includes a membrane glycoprotein molecule. The carbohydrate components of this molecule are recognized by receptors present in the membranes of other cells.

Which of the following statements correctly describes the plasma membrane?
It is a dynamic fluid structure that is in constant flux.
It is a unique, solid barrier custom designed for each type of cell.
It is a flexible protein barrier supported by cholesterol rods.
It is a solid structure formed by phospholipids and cholesterol designed to be stable against pressure.

It is a dynamic fluid structure that is in constant flux.
The fluid mosaic model of membrane structure depicts the plasma membrane as an exceedingly thin structure composed of a double layer, or bilayer, of lipid molecules with protein molecules "plugged into" or dispersed in it. The proteins, many of which float in the fluid lipid bilayer, form a constantly changing mosaic pattern. The model, a dynamic fluid structure that is in constant flux, is named for this characteristic.

Which of the following factors act to bind cells together?
specialized junctions, wavy membrane contours, and glycoproteins
lipid-rafts, cholesterol, and glycolipids
glycoproteins, specialized junctions, and cholesterol
glycoproteins, lipid-rafts, and cholesterol

specialized junctions, wavy membrane contours, and glycoproteins
Typically, three factors act to bind cells together: (1) glycoproteins (and glycolipids) in forming the glycocalyx, which acts as an adhesive, (2) the wavy contours of the membranes of adjacent cells fitting together in a tongue-and-groove fashion, and (3) the formation of special membrane junctions.

Which of the following describes tight junctions?
junctions where cells are held together by cadherins
junctions within electrically excitable tissues, such as the heart and smooth muscle
junctions among epithelial cells lining the digestive tract
cell junctions in areas that are subjected to great mechanical stress, such as the skin and heart muscles

junctions among epithelial cells lining the digestive tract
In a tight junction, a series of integral protein molecules (including occludins and claudins) in the plasma membranes of adjacent cells fuse together, forming an impermeable junction that encircles the cell. Tight junctions help prevent molecules from passing through the extracellular space between adjacent cells. For example, tight junctions between epithelial cells lining the digestive tract keep digestive enzymes and microorganisms in the intestine from seeping into the bloodstream.

Which of the following would NOT diffuse through the plasma membrane by means of simple diffusion?
oxygen
glucose
a steroid hormone
a lipid soluble vitamin

glucose
Glucose, a small polar solute, uses a membrane transporter (a protein carrier) to cross the plasma membrane via facilitated diffusion. In simple diffusion, small nonpolar and lipid-soluble substances (including gases) diffuse directly through the lipid bilayer.

Which of the following is characteristic of cilia?
They are used for cellular adhesion.
They are substantially longer than flagella, and are most easily seen in human sperm cells.
They are whiplike, motile cellular extensions that occur in large numbers on the exposed surfaces of certain cells.
They move substances in any direction across cell surfaces.

They are whiplike, motile cellular extensions that occur in large numbers on the exposed surfaces of certain cells.
Cilia are whiplike, motile cellular extensions that occur, typically in large numbers, on the exposed surfaces of certain cells. Ciliary action moves substances in one direction across cell surfaces. Centrioles forming the bases of cilia and flagella are commonly referred to as basal bodies.

What process is indicated by C? digestion of food particles
export of RNA from the cell
release of ribosomes from the cell
exocytosis of secreted proteins

exocytosis of secreted proteins
The event indicated by C includes the fusion of a secretory vesicle with the plasma membrane and the subsequent release of the vesicle contents to the extracelluar space.

In a patient with severely burned skin, the damaged cells that have lost fluid cannot be properly rehydrated because_________.
selective permeability prevents water molecules from entering these damaged cells
selective permeability allows too many water molecules to enter these damaged cells, resulting in ionic imbalances within these cells
the absence of selective permeability allows water molecules that enter these damaged cells to also leave the cytoplasm

the absence of selective permeability allows water molecules that enter these damaged cells to also leave the cytoplasm
Skin is an organ made up of tissues, and tissues are made up of cells. Selective permeability requires an intact cell membrane.

Which of the following solutions may be infused intravenously to help rehydrate a severely dehydrated patient (i.e., a patient suffering from cellular dehydration)?
0.45% saline
5% saline
5% glucose
0.9% NaCl

0.45% saline
This solution is hypotonic (lower concentration of nonpenetrating solutes than in the cytoplasm).

This figure illustrates which of the following descriptions?
the use of the energy derived from the breakdown of glucose to power the sodium-potassium pump
the facilitated diffusion of both sodium and glucose through the same carrier protein
the use of a sodium concentration gradient to power the pumping of glucose into the cell
the reaction between sodium and glucose catalyzed by a membrane-bound enzyme

the use of a sodium concentration gradient to power the pumping of glucose into the cell
The sodium ion gradient is generated by the Na+-K+ pump at the left. Diffusion of sodium ions through the Na+-glucose symport (shown at the right) provides the energy necessary to actively transport glucose into the cell. Such a mechanism is used by intestinal cells (to absorb nutrients) and kidney cells (to recover glucose from urine prior to excretion).

How is the energy from ATP used most directly in the illustrated processes? to transport glucose across the membrane
to power a chemical reaction between sodium and glucose
to power a chemical reaction between sodium and potassium
to generate a sodium concentration gradient

to generate a sodium concentration gradient
The energy from ATP hydrolysis is used to transport sodium and potassium ions across the membrane and thereby establish concentration gradients for each of those ions.

Why are protein channels and carriers required for the movement of glucose into or out of the cell?
Glucose is a relatively large chemical structure.
Glucose is repelled by the polar heads of the membrane phospholipid molecules.
Glucose is a hydrophilic molecule.
The phospholipid region of the membrane is impermeable to all organic molecules.

Glucose is a hydrophilic molecule
Glucose and other monosaccharides are polar hydrophilic molecules that are not able to traverse the hydrophobic region of the phospholipid bilayer.

By which mechanism would a steroid molecule diffuse into the cell?

Steroid molecules are nonpolar fat-soluble molecules, which would be expected to diffuse directly across the phospholipid bilayer. Such solutes do not require a membrane protein to facilitate transport.

Which mechanism requires energy input by the cell in the form of ATP hydrolysis? A
B
C
none of the mechanisms require energy input

All three mechanisms are forms of diffusion. Transport by diffusion of a molecule down its concentration gradient is a spontaneous process that requires no energy input.

The mechanism depicted in B would most likely mediate the diffusion of which of the following solutes? a sodium ion
a protein
an oxygen molecule
an amino acid

an amino acid Mechanism B depicts the selective transport of a polar molecule such as an amino acid or sugar.

Why is the selective permeability of the plasma membrane essential for normal cell function?
Selective permeability allows cells to communicate with each other by sharing large and small molecules.
Selective permeability allows cells to exclude some substances and allow others to pass into or out of the cell.
Selective permeability allows cells to determine which proteins they should produce and retain.
Selective permeability allows cells to bind to one another in a fluid environment.

Selective permeability allows cells to exclude some substances and allow others to pass into or out of the cell.
Selective permeability of the plasma membrane ensures that the continual traffic across the membrane does not include undesirable substances. It also ensures that desirable cell contents are retained within the cell.

What is the difference between active and passive transport across the plasma membrane?
Active transport means that the cell is actively going after substances that it wants to bring into the cell, whereas passive transport means that the cell just waits for the substance to cross the membrane.
Active transport implies that the cell is working with other cells, whereas passive transport implies that the cell does not cooperate with other cells.
Active transport is ATP dependent, whereas passive transport uses only the kinetic energy of the particles for movement across the plasma membrane.
Active transport is used to move substances down their concentration gradient, whereas passive transport is used to move substances against their concentration gradient.

Active transport is ATP dependent, whereas passive transport uses only the kinetic energy of the particles for movement across the plasma membrane.
In active transport, the cell provides the metabolic energy (ATP) needed to move substances across the plasma membrane (against their concentration gradient). In passive transport, substances cross the plasma membrane (down their concentration gradient) using kinetic energy, without any energy input from the cell.

________ is the diffusion of a solvent, such as water, across a selectively permeable membrane.
Simple diffusion
Unassisted diffusion
Facilitated diffusion
Osmosis

Osmosis
A special name, osmosis, is given to the unassisted diffusion of a solvent, usually water, through a selectively permeable membrane.

Solutions with a higher concentration of solutes than the concentration inside the cells are __________.
hypoosmotic
isotonic
hypertonic
hypotonic

hypertonic
Hypertonic solutions have a higher concentration of nonpenetrating solutes than seen in the cell (for example, a strong saline solution). Cells immersed in hypertonic solutions lose water and shrink, or crenate.

Which of the following is a difference between primary and secondary active transport?
Primary active transport is used to transport sugars and amino acids across the plasma membrane, while secondary active transport includes the sodium-potassium pump.
Primary active transport is driven by secondary active transport.
Energy is required for primary active transport, but energy is not required for secondary active transport.
In primary active transport, the transport protein gets phosphorylated; in secondary active transport, the transport protein is not phosphorylated.

in secondary active transport, the transport protein is not phosphorylated
In primary active transport, energy comes directly from the hydrolysis of ATP and the subsequent phosphorylation of the primary active transporter. In secondary active transport, the solute (usually Na+) concentration gradient produced by primary active transport provides the (kinetic) energy to move other solutes, such as ions and glucose, against their concentration gradients. For example, glucose can be transported against its concentration gradient through a Na+-glucose symporter as Na+ moves down its concentration gradient (a gradient produced by the Na+-K+ pump).

Which of the following statements is TRUE?
During endocytosis, substances from inside the cell are moved outside.
During exocytosis, substances from inside the cell are moved outside.
Endocytosis cannot occur unless exocytosis has occurred.
Endocytosis and exocytosis are passive transport mechanisms.

During exocytosis, substances from inside the cell are moved outside.
Vesicular transport processes that eject substances from the cell interior into the extracellular fluid are called exocytosis. Exocytosis is a form of active transport, thus it requires energy, usually in the form of ATP.

Which of the following processes allows cells to concentrate material that is present only in very small amounts in the extracellular fluid?
phagocytosis
pinocytosis
receptor-mediated endocytosis
transcytosis

receptor-mediated endocytosis
Receptor-mediated endocytosis is the main mechanism for the specific endocytosis and transcytosis of most macromolecules by body cells, and it is exquisitely selective. The mechanism also allows cells to concentrate material that is present only in very small amounts in the extracellular fluid.

Which of the following forms of vesicular transport processes are used by flu viruses, diphtheria, and cholera toxins to enter our cells?
diffusion
pinocytosis
receptor-mediated endocytosis
fluid-phase endocytosis

receptor-mediated endocytosis
Flu viruses, diphtheria, and cholera toxins use receptor-mediated endocytosis to enter and attack our cells.

The plasma membrane is made primarily of ________.
water
amino acids
phospholipids
nucleic acids

phospholipids
The plasma (cell) membrane is a phospholipid bilayer, composed of two parallel sheets of phospholipid molecules lying tail to tail, with their polar heads exposed to water on either side of the membrane. Each lollipop-shaped phospholipid molecule has a polar "head" that is charged and is hydrophilic (hydro = water, philic = loving), and an uncharged, nonpolar "tail" that is made of two fatty acid chains and is hydrophobic.

What is the primary function of the mitochondria?

They are the main site of ATP production.
Mitochondria are threadlike or lozenge-shaped membranous organelles. In living cells they squirm, elongate, and change shape almost continuously. They are the power plants of a cell, providing most of its ATP supply.

Which organelle is responsible for synthesizing proteins?
mitochondria
Golgi apparatus
smooth endoplasmic reticulum
ribosomes

ribosomes
Proteins are synthesized at ribosomes. Free ribosomes float freely in the cytoplasm and produce soluble proteins that function in the cytosol, as well as those imported into mitochondria and some other organelles. Fixed ribosomes, which stud the rough endoplasmic reticulum, synthesize proteins destined either for incorporation into the cell membrane or lysosomes, or for export from the cell.

Which of the following events might the solid arrow at the bottom of B represent?


the conversion of a chemical messenger molecule into a specific product
the movement of a specific protein from the membrane to the cytoplasm
the transport of specific chemical messengers into the cell
the activation of specific cytoplasmic enzymes

the activation of specific cytoplasmic enzymes
Once activated by the binding of a specific chemical messenger, such as a hormone, the receptor initiates cellular responses by activating specific signal transduction pathways. These pathways include the activation of enzymes, such as kinases, that lead to specific cellular responses.

What is a membrane potential?
the ability of the cells to perform their specialized functions
a voltage or electrical charge across the plasma membrane
the possibility of cell activity
cooperation between cells

a voltage or electrical charge across the plasma membrane
The membrane potential is the electrical potential energy (measured in millivolts) resulting from the separation of oppositely charged particles (ions) across the plasma membrane. At rest, membrane potentials are typically negative, ranging from -50 to -100 mV, with more anions (than cations) concentrated along the internal surface of the membrane, and more cations (than anions) concentrated along the external surface.

Which of the following is NOT a characteristic of peroxisomes?
They contain powerful enzymes called acid hydrolases.
They contain powerful enzymes called oxidases.
They aid in the neutralization of dangerous free radicals.
They contain powerful enzymes called catalases.

They contain powerful enzymes called acid hydrolases.Lysosomes (not peroxisomes) contain digestive enzymes that work best in acidic conditions and so are called acid hydrolases.

Describe a mitochondrion

Mitochondria are characterized by a oblong shape with a double membrane.

What is the inner lining of the mitochondria composed of?
phospholipids
triglycerides
carbohydrates
DNA

Phospholipids are a major component of all cellular membranes, including the mitochondrial inner (A) and outer (B) membranes.

The folded membranes indicated by B are the site of ______. phagocytosis
intracellular digestion
endocytosis
enzymes involved in cellular respiration

enzymes involved in cellular respiration The folded membranes that comprise the cristae and the spaces between them (the matrix) are the locations of cellular respiration.

The small circular structure indicated by the letter C represents a ______.

ribosome
DNA molecule
secretory vesicle
centriole The mitochondria each have a small circular DNA chromosome that contains genes for several mitochondrial proteins. These proteins are translated within the mitochondria (on the ribosomes indicated by the small red dots). Most of the DNA in a cell is found in the nuclear chromosomes. Several muscular and nervous system diseases are associated with defects in mitochondrial DNA.

What major function occurs on the specific membranes indicated by A? production of most of the cell's ATP
digestion of food particles
replication of DNA
synthesis of secreted proteins

synthesis of secreted proteins
Structure A is the rough endoplasmic reticulum (ER). The figure illustrates how proteins are synthesized on ribosomes bound to the rough ER, sorted in the Golgi, and delivered to the plasma membrane for secretion or packaged into lysosomes.

The structure indicated by B is ______. the plasma membrane
the rough endoplasmic reticulum
the Golgi apparatus
the smooth endoplasmic reticulum

the Golgi apparatus
Note how the location of the Golgi apparatus within the endomembrane system is consistent with its functions of sorting and modifying proteins being transported to various cellular locations.

The membrane-bound compartment indicated by structure D contains which of the following? oxidases and catalases
ribosomes
nucleic acids
hydrolytic enzymes

hydrolytic enzymes Structure D is a lysosome, which stores enzymes that catalyze the hydrolysis (digestion) of organic cellular materials.

Which cell organelle provides the majority of the ATP needed by the cell to carry out its metabolic reactions?
ribosome
mitochondrion
lysosome
Golgi apparatus

Mitochondria are the site of the majority of ATP production because of the specialized enzymes on their cristae.

Which of the following is a function of the rough endoplasmic reticulum?
storage of calcium ions

synthesis of the cell's membranes
lipid metabolism, cholesterol

synthesis, and synthesis of the lipid components of lipoproteins

absorption, synthesis, and transport of fats

synthesis of the cell's membranes The rough ER synthesizes all proteins secreted from the cell; it also functions as the cell's "membrane factory" because integral proteins and phospholipids that form part of all cellular membranes are manufactured there.

Which cell component helps to maintain the structural integrity of the cell?
ribosome
centriole
peroxisome
cytoskeleton

The cytoskeleton acts as the cell's "bones," "muscles," and "ligaments" by supporting cellular structures and providing the machinery to generate various cell movements.

The nucleolus ________.
is the site of lipid production in a cell
is a dark-staining spherical body found within the mitochondria
is the site of ribosome assembly in a cell
is the primary site of protein synthesis

is the site of ribosome assembly in a cell Nucleoli ("little nuclei") are the dark-staining spherical bodies found within the nucleus where ribosomal subunits are assembled. They are not membrane bounded. Typically, there are one or two nucleoli per nucleus, but there may be more. Nucleoli are usually large in growing cells that are making large amounts of tissue proteins.

Some types of cells move freely through the body, while others are bound into tightly knit communities.
True
False

True
Although certain cell types (blood cells, sperm cells, and some phagocytic cells, which ingest and destroy bacteria and other substances) are "footloose" in the body, many other types, particularly epithelial cells, are knit into tight communities.

Diffusion is a form of active transport.
True
False

False
Diffusion is a form of passive, not active, transport. Diffusion results from substances moving down their concentration gradient, a form of kinetic energy. In order to move, or actively pump, substances against their concentration gradient, energy must be used. ATP directly, or indirectly, provides the energy for active transport.

Babies with Tay-Sachs disease cannot be treated by injecting the missing enzyme into their blood because_________.
the enzyme is a protein and, therefore, is not soluble in the blood
the enzyme is a protein that is digested by glycolipids in the blood
blood is not capable of delivering substances directly to nerve cells
the enzyme functions only in lysosomes and not in the blood

the enzyme functions only in lysosomes and not in the blood
Brain tissue has a high metabolic rate, requiring the constant breakdown of glycogen and lipids. When lysosomes fail to perform this function, fatty substance builds up to toxic levels and affects the child's nerve cells.

Phagocytosis is a form of exocytosis.
True
False

False
Phagocytosis is a form of endocytosis in which the cell engulfs some relatively large or solid material, such as a clump of bacteria, cell debris, or inanimate particles (asbestos fibers or glass, for example). When a particle binds to receptors on the cell's surface, cytoplasmic extensions called pseudopods form and flow around the particle, engulfing it.

In their resting state, all body cells exhibit a resting membrane potential; therefore, all cells are polarized.
True
False

True
All cells that have a resting membrane potential (RMP), such that the inside (interior surface) of the cell membrane has a net negative charge while the outside (external surface) of the membrane has a net positive charge. Given the different (opposite) charges on either side of the cell membrane, the cell is considered to be polarized. This RMP, which results from separation of charged particles (ions) across the cell membrane, can be measured in millivolts (typically ranging from -50 to -100 mV depending on the cell type).

Lysosomes perform digestive functions within a cell.
True
False

True
Born as endosomes that contain inactive enzymes, lysosomes are spherical, membranous organelles containing activated digestive enzymes. Lysosomes are large and abundant within phagocytes, the cells that dispose of invading bacteria and cell debris. Lysosomal enzymes can digest almost all kinds of biological molecules. They work best in acidic conditions and so are called acid hydrolases.

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