HW: CH.3

In which stage of mitosis do the identical sets of chromosomes uncoil and resume their chromatin form? a. telophase b. prophase c. anaphase d. metaphase

a.

________ is a molecular "ferry" that brings amino acids to the ribosome to build a protein. a. DNA b. t-RNA c. mRNA d. rRNA

b. t-RNA serves as an adapter molecule; it ferries amino acids to the ribosome and participates in translation (the process by which amino acids are assembled into proteins).

Which of the following is not required for osmosis to occur? a. concentration gradient b. water c. cellular energy d. selectively permeable membrane

c. Osmosis is a special type of diffusion, which is always a passive process.

During which phase of mitosis do nuclear envelopes and the nucleoli reappear? a. Metaphase b. Prophase c. Telophase d. Anaphase

c. Telophase begins when the chromosomes stop moving. Nuclear envelopes form, and nucleoli reappear. Ultimately, the cell divides in two by a process known as cytokinesis.

Which of the following solutions contains the most solute? a. equilibrium b. isotonic c. hypertonic d. hypotonic

"Hyper" means "high," so a hypertonic solution has a higher solute concentration than the solution to which it is being compared.

Human cell division is commonly referred to as the Mitotic (M) phase, since most body cells only undergo mitosis. The M phase of the cell cycle includes mitosis and cytokinesis. Mitosis is the division of the cell's nucleus into two genetically identical daughter nuclei and consists of four separate phases. Place the four phases of mitosis in the correct order of occurrence from left to right.

1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

What phase matches with these descriptions? 1. Chromosomes uncoil to form chromatin. 2. Chromosomal centromeres split and chromosomes migrate to opposite ends of the cell. 3. Nuclear membrane and nucleolus disintegrate. 4. Chromosomes align on the spindle equator. 5. Centrioles move to opposite ends of the cell.

1. Telophase 2. Anaphase 3. Late prophase 4. Metaphase 5. Early prophase

1. Help prevent molecules from passing through the extracellular space between adjacent cells. 2. Type of anchoring junction. 3. Communicating junction. 4. Present in electrically excitable tissues. 5. Abundant in tissues subjected to great mechanical stress.

1. Tight junctions 2. Desmosomes 3. Gap junctions 4. Gap junctions 5. Desmosomes

Sort the following types of membrane transport mechanisms into active or passive processes: Facilitated diffusion Exocytosis Secondary active transport Simple diffusion Endocytosis Osmosis Primary active transport

Passive: Facilitated diffusion, Simple diffusion, and Osmosis Active: Exocytosis, Secondary active transport, endocytosis, and Primary active transport

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.

The region of mRNA that encodes a polypeptide is 24 nucleotides in length. Consider another such molecule with a coding region of 300 nucleotides. What is a reasonable estimate for the length of the corresponding polypeptide that will be produced during protein synthesis? a. 100 amino acids b. 300 amino acids c. 30 amino acids d. 900 amino acids

a. Each amino acid corresponds to a codon of 3 nucleotides. Therefore, a coding region of 300 nucleotides contains 100 codons and will produce a polypeptide of 100 amino acids in length.

Some transport processes use transport proteins in the plasma membrane, but do not require ATP. This type of transport is known as _____. a. facilitated diffusion b. exocytosis c. active transport d. simple diffusion e. endocytosis

a. Facilitated diffusion is a passive transport process during which molecules move down their concentration gradients through transport proteins.

What type of protein is associated with chromatin? a. histone b. collagen c. actin d. hemoglobin

a. Histone proteins are the major structural protein associated with chromatin.

Which of these is not a function of the plasma membrane? a. It prevents potassium ions from leaking out and sodium ions from crossing into the cell. b. It acts as a site of cell-to-cell interaction and recognition. c. It is selectively permeable but permits water and gases to cross. d. It encloses the cell contents in such a way that water in the body is divided into separate compartments.

a. It prevents potassium ions from leaking out and sodium ions from crossing into the cell.

Which of the following acts as the digestive system of the cell, breaking down materials? a. lysosome b. nucleus c. endoplasmic reticulum d. ribosome

a. Lysosomes use their enzymes to break down material, much as our digestive system breaks down the foods we consume. The root "lyse" means to loosen or separate, which is what the enzymes in lysosomes do to the chemical bonds in the items they digest.

What is the primary function of the mitochondria? a. They are the main sites of ATP production. b. They build cholesterol. c. They are the main sites of photosynthesis. d. They are the primary sites of protein production in a cell.

a. 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.

During which phase of mitosis do the nuclear envelope and nucleoli disappear? a. Prophase b. Telophase c. Anaphase d. Metaphase

a. Prophase is the first phase of mitosis. During this phase, the sister chromatids condense, the nuclear envelope and nucleoli disappear, and the spindle apparatus forms.

During which phase of mitosis do sister chromatids line up at the center of the cell? a. Metaphase b. Prophase c. Anaphase d. Telophase

a. Spindle microtubules from both poles of the cell attach to the sister chromatids and pull them in both directions. During metaphase, the sister chromatids are forced to the center of the cell.

During which of the following phases does DNA replication occur? a. Synthesis b. cytokinesis c. mitosis d. prophase

a. Synthesis is part of interphase, and is completed well before the cell actually divides.

How is the energy from ATP used most directly in active transport? a. to generate a sodium concentration gradient b. to power a chemical reaction between sodium and glucose c. to power a chemical reaction between sodium and potassium d. to transport glucose across the membrane

a. 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.

Which of the following is a function of the rough endoplasmic reticulum? a. synthesis of the cell's membranes b. lipid metabolism, cholesterol synthesis, and synthesis of the lipid components of lipoproteins c. storage of calcium ions d. absorption, synthesis, and transport of fats

a. 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.

The sodium-potassium pump uses ATP to move sodium and potassium ions across the plasma membrane. This statement describes _____. a. primary active transport b. secondary active transport c. simple diffusion d. facilitated diffusion e. exocytosis

a. The sodium-potassium pump is activated by ATP. This activation allows the pump to transport sodium and potassium ions against their gradients.

After DNA replication is completed, each DNA double helix consists of ______. a. one old parent strand and one new daughter strand b. either two old strands or two new strands c. two newly synthesized strands that replace the old parent strands d. strands that are mixtures of old and new nucleotides

a. This mechanism is called semiconservative replication and is based on the ability of each strand of the DNA double helix to function as a template for the synthesis of the opposite strand.

Each daughter cell resulting from mitotic cell division has exactly as many chromosomes as the parent cell. a. True b. False

a. True

Microtubules are hollow tubes made of subunits of the protein tubulin. a. True b. False

a. True

The orderly sequence of the phases of mitosis is prophase, metaphase, anaphase, and telophase. a. True b. False

a. True

If a tRNA had an AGC anticodon, it could attach to a(n) ________ mRNA codon. a. UCG b. TCG c. AUG d. UGA

a. UCG

Which vesicular transport process occurs primarily in some white blood cells and macrophages? a. phagocytosis b. exocytosis c. intracellular vesicular trafficking d. pinocytosis

a. phagocytosis

Which of the following is NOT a function of the smooth endoplasmic reticulum? a. protein synthesis in conjunction with ribosomes b. breakdown of stored glycogen to form free glucose c. lipid metabolism and cholesterol synthesis d. steroid-based hormone synthesis

a. protein synthesis in conjunction with ribosomes

Which of the following does not serve as a signal for cell division? a. repressor genes b. loss of contact inhibition c. shrinking surface-to-volume ratio d. joining of cyclins and Cdks

a. repressor genes

What organelle matches the description: a. site of synthesis of lipid and steroid molecules b. produces ATP aerobically c. site of enzymatic breakdown of phagocytized materal d. forms the mitotic spindle e. package proteins for insertion in the cell membrane or for exocytosis

a. smooth ER b. mitochondria c. lysosomes d. centrioles e. golgi apparatus

The membrane-bound compartment of a lysosome contains which of the following? a. ribosomes b. hydrolytic enzymes c. nucleic acids d. oxidases and catalases

b. A lysosome stores enzymes that catalyze the hydrolysis (digestion) of organic cellular materials.

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

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

Diffusion is a form of active transport. a. True b. False

b. 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.

During which phase of mitosis do the sister chromatids move apart? a. Telophase b. Anaphase c. Metaphase d. Prophase

b. During anaphase, the centromeres split and the spindle microtubules pull the sister chromatids to opposite poles of the cell. The single chromatids are now considered chromosomes.

What is the basic difference between simple diffusion and facilitated diffusion across a cell membrane? a. In simple diffusion, molecules move down the concentration gradient but in facilitated diffusion molecules move up the concentration gradient. b. In facilitated diffusion, molecules only move with the aid of a protein in the membrane. c. Simple diffusion requires molecules to move through special doorways in the cell membrane. d. Simple diffusion is passive but facilitated diffusion is an active process that uses energy.

b. Facilitated diffusion allows molecules that cannot pass through the lipid component of the membrane to pass through via a more compatible protein channel or carrier. This includes ions and polar molecules.

Which of the following is most likely to move through the cell membrane by facilitated diffusion? a. O2 b. Na+ c. CO2 d. small lipids

b. Ions move easily through water, which is polar, but cannot pass directly through the lipid (nonpolar) part of the cell membrane.

Phagocytosis is a form of exocytosis. a. True b. False

b. 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.

What are the two basic steps of polypeptide synthesis? a. protein coding and release b. transcription and translation c. transcription and DNA replication d. RNA production and DNA intron release

b. Polypeptide synthesis involves two major steps: (1) transcription, in which DNA's information is encoded into mRNA, and (2) translation, in which the information carried by the mRNA is decoded and used to assemble polypeptides.

Which organelle is responsible for synthesizing proteins? a. smooth endoplasmic reticulum b. ribosomes c. mitochondria d. Golgi apparatus

b. 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 processes allows cells to concentrate material that is present only in very small amounts in the extracellular fluid? a. phagocytosis b. receptor-mediated endocytosis c. transcytosis d. pinocytosis

b. 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 is NOT one of the three major components of a typical eukaryotic cell? a. plasma membrane b. ribosome c. cytoplasm d. nucleus

b. Ribosomes are organelles and they are located within one of the major components of the cell.

Which of the following is a characteristic of the cell membrane? a. fully permeable b. semipermeable c. impermeable d. not permeable

b. The cell membrane is semipermeable, or selectively permeable, because some things can easily pass through it while others cannot.

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

b. 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 is not a major function of proteins in the cell membrane? a. forming channels b. forming the entire glycocalyx c. acting as receptors d. anchoring cells to other structures

b. The glycocalyx is composed mostly of carbohydrates.

The cell cycle is divided into two main parts: interphase and cell division. Interphase is the period in which the cell is performing normal functions and not actively engaged in cell division. Most of your body's cells spend a lot of their time in interphase. Before a cell can divide, what must occur during interphase? a. The DNA relaxes into chromosomes. b. Each chromatin fiber is duplicated in the nucleus. c. The sister chromatids separate into chromosomes. d. The cell only performs its normal cell functions.

b. Unless the cell is in a state where it will not divide further, interphase prepares the cell to undergo cell division.

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

b. 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.

A gene can best be defined as ________. a. an RNA messenger that codes for a particular polypeptide b. a segment of DNA that carries the instructions for one polypeptide chain c. noncoding segments of DNA up to 100,000 nucleotides long d. a three-base triplet that specifies a particular amino acid

b. a segment of DNA that carries the instructions for one polypeptide chain

Which of the following would not be a constituent of a plasma membrane? a. glycolipids b. messenger RNA c. phospholipids d. glycoproteins

b. messenger RNA

The functions of centrioles include ________. a. serving as the site for ribosomal RNA synthesis b. organizing the mitotic spindle in cell division c. providing a whiplike beating motion to move substances along cell surfaces d. producing ATP

b. organizing the mitotic spindle in cell division

Once solid material is phagocytized and taken into a vacuole, which of the following statements best describes what happens? a. The vacuole remains separated from the cytoplasm and the solid material persists unchanged. b. A ribosome enters the vacuole and uses the amino acids in the "invader" to form new protein. c. A lysosome combines with the vacuole and digests the enclosed solid material. d. The phagocytized material is stored until further breakdown can occur..

c. A lysosome combines with the vacuole and digests the enclosed solid material.

During which phase of the cell cycle does DNA duplication, or replication, take place? a. Prophase b. Anaphase c. Interphase d. Metaphase

c. DNA replicates during interphase. This process provides each new daughter cell with a full complement of genetic material.

What is the name of the process by which the cytoplasm divides in two? a. Cytoplasmic streaming b. Segregation c. Cytokinesis d. Microtubule shortening

c. During cytokinesis, a ring of actin and myosin filaments contract to form a cleavage furrow and the cell divides in two.

When a double helix of DNA is replicated, two complete helices are formed. Together, these helices are called sister __________. a. telomeres b. centromeres c. chromatids d. chromosomes

c. Each new daughter cell receives one of the sister chromatids. After the chromatids separate, each is considered a new chromosome. At the end of cell division, each new cell contains 23 pairs of chromosomes.

In general, to maintain homeostasis the relationship between our intracellular and extracellular fluids should be which of the following? a. intracellular should be hypotonic to extracellular b. intracellular and extracellular should both be hypertonic c. isotonic to each other d. intracellular should be hypertonic to extracellular

c. In order to prevent the cells from either swelling or shrinking, the body fluids should be isotonic, meaning that they are at equilibrium.

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

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

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

c. 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.

Histones interacts with DNA to form the structural unit of chromatin called a ______. a. centriole b. vesicle c. nucleosome d. microfilament

c. The DNA helix wraps around a group of histone proteins to form a structural unit called a nucleosome.

During which of the following phases does chromatin condense and become chromosomes? a. anaphase b. prophase c. metaphase d. interphase

c. The chromatin condenses into rodlike chromosomes during prophase in preparation for dividing the DNA. Chromosomes are present from late prophase until telophase, when they relax and return to the chromatin state

mRNA and tRNA molecule are expected to interact within which of the following cellular locations? a. Golgi apparatus b. nucleus c. ribosome d. rough endoplasmic reticulum

c. The codons within the mRNA are recognized by corresponding tRNA molecules within cytoplasmic ribosomes during protein translation.

If a person is severely dehydrated, their extracellular fluids will become hypertonic to the intracellular fluid. What do you predict will happen to the person's cells? a. Extracellular fluids do not impact cell size, because cells contain intracellular fluid. b. The cells will rupture. c. The cells will lose water and shrink. d. The cells will swell.

c. The hypertonic extracellular fluid will draw water out of the hypotonic intracellular fluid, so the cells will shrink. This is called crenulation.

Where in a typical eukaryotic cell would you expect to find genes? a. in the nucleolus within the nucleus b. in chromosomes within the cytosol c. in the DNA within the cell's nucleus d. in the chromatin within the cell's cytoplasm

c. The nucleus houses the DNA, which contains the genes. Genes determine what proteins the cell can make, which in turn determines what the cell can do.

The electron microscope has revealed that one of the components within the cell consists of pinwheel array of 9 triplets of microtubules arranged to form a hollow tube. This structure is a ________. a. ribosome b. chromosome c. centriole d. centrosome

c. centriole

Which of the following is NOT a function of lysosomes? a. digesting particles taken in by endocytosis b. degrading worn-out or nonfunctional organelles c. forming acid hydrolases which are necessary to help form cell membranes d. breaking down bone to release calcium ions into the blood

c. forming acid hydrolases which are necessary to help form cell membranes.

Which structures are fingerlike projections that greatly increase the absorbing surface of cells? a. flagella b. primary cilia c. microvilli d. stereocilia

c. microvilli

Passive membrane transport processes include ________. a. the use of transport proteins when moving substances from areas of low to high concentration b. movement of water from an area of high solute concentration to an area of low concentration c. movement of a substance down its concentration gradient d. consumption of ATP

c. movement of a substance down its concentration gradient

A red blood cell placed in pure water would ________. a. neither shrink nor swell b. swell initially, then shrink as equilibrium is reached c. swell and burst d. shrink

c. swell and burst

Which of the following is the main component of the cell membrane? a. carbohydrates b. cholesterol c. water d. phospholipids

d. Although phospholipids have a polar head, the long fatty acid tails are nonpolar, making the membrane mostly nonpolar.

Which of the following best explains diffusion? a. exchange of nonpolar molecules for polar molecules b. movement of molecules from where there are fewer of them to where there are more c. movement of molecules farther away from equilibrium d. movement of molecules from an area of high concentration to an area of low concentration

d. By diffusion, molecules spread out to maximize their space.

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

d. 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 is the function of a histone protein? a. to catalyze the synthesis of the DNA molecule b. to unwind DNA during DNA replication c. to hold each strand of the DNA molecule together d. to allow DNA to form a compact structure

d. DNA forms chromatin by wrapping around nucleosomes formed by histone proteins and therefore becomes more condensed.

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

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

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

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

d. 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 statements about cells is FALSE? a. The cells in our bodies collectively carry out all of the functions necessary for us to stay alive. b. Although human cells are diverse in size, shape, and function, they have essentially the same organelles and general structure. c. Cells are the most basic units of life. d. Cells join together to form organelles, which then form our organs and organ systems.

d. Organelles are the functional parts of cells—they are inside the cells, in the cytoplasm. Cells join to form tissues, and the tissues then join to form the organs that work together in organ systems.

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

d. 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.

Which of the following statements is correct regarding net diffusion? a. Molecular weight of a substance does not affect the rate. b. The rate is independent of temperature. c. The lower the temperature, the faster the rate. d. The greater the concentration gradient, the faster the rate.

d. The greater the concentration gradient, the faster the rate.

Which of the following is least likely to increase the rate of diffusion? a. high temperature b. small molecule size c. higher concentration of molecules d. small concentration gradient

d. The larger the concentration gradient, the faster the rate of diffusion. Higher concentration means there are more collisions, so the molecules bounce away from each other more rapidly.

What part of a cell membrane is usually in contact with the interstitial fluid? a. cholesterol b. fatty acid tails c. hydrophobic molecules d. phosphate heads of phospholipids

d. The phosphate heads of the phospholipids are polar, so they are attracted to the polar water molecules.

The plasma membrane is made primarily of ________. a. amino acids b. water c. nucleic acids d. phospholipids

d. 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 major function occurs on the specific membranes of the Rough ER? a. digestion of food particles b. production of most of the cell's ATP c. replication of DNA d. synthesis of secreted proteins

d. The rough endoplasmic reticulum (ER) 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.

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

d. 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.

If the nucleotide or base sequence of the DNA strand used as a template for messenger RNA synthesis is ACGTT, then what would be the sequence of bases in the corresponding mRNA? a. ACGTT b. GUACC c. TGCAA d. UGCAA

d. UGCAA

Peroxisomes ________. a. sometimes function as secretory vesicles b. are also called microbodies, and contain acid hydrolases c. function to digest particles ingested by endocytosis d. are able to detoxify substances by enzymatic action

d. are able to detoxify substances by enzymatic action

Which type of cell junction acts as anchors and distributes tension through a cellular sheet and reduces the chance of tearing when it is subjected to great mechanical stress? a. connexons b. tight junctions c. gap junctions d. desmosomes

d. desmosomes

Which of the following describes the plasma membrane? a. a double layer of protein enclosing the plasma b. a membrane composed of tiny shelves or cristae c. a single-layered membrane that surrounds the nucleus of the cell d. the phospholipid bilayer surrounding the cell

d. the phospholipid bilayer surrounding the cell

In certain kinds of muscle cells, calcium ions are stored in ________. a. both smooth and rough ER b. the rough ER c. the cytoplasm d. the smooth ER

d. the smooth ER

A primary active transport process is one in which __________. a. the plasma membrane folds inward to form a vesicle containing extracellular material b. molecules pass directly through the phospholipid bilayer of the plasma membrane c. an intracellular vesicle fuses with the plasma membrane and releases its contents to the extracellular fluid d. molecules move across the plasma membrane without an input of energy e. molecules move through transport proteins that have been activated by ATP

e. Primary active transporters, such as the sodium-potassium ATPase (or pump), are activated when ATP is hydrolyzed. This activation allows for the transport of solutes across the plasma membrane against concentration gradients.

A vesicle fuses with the plasma membrane and releases its contents to the extracellular fluid. This statement describes _____. a. simple diffusion b. endocytosis c. facilitated diffusion d. active transport e. exocytosis

e. exocytosis: literally means "out of the cell"

The majority of water molecules moving across plasma membranes by osmosis do so via a process that is most similar to ____. a. active transport b. cotransport c. a process that requires energy from the cell d. simple diffusion e. facilitated diffusion

e. facilitated diffusion