Physiology Chapter 3
The concentration of cyclin D proteins within the cell rise and act to move the cell quickly through the ________ phase of the cell's cycle. A) G1 B) S C) G2 D) M
A) G1 (Growth) They do this by activating a group of otherwise inactive enzymes called cyclin-dependent kinases, therefore the overactivity of the gene that codes for cyclin D might be predicted to cause uncontrolled cell division as occurs in cancer.
Which of the following processes results in the formation of a food vacuole within the cell that will subsequently be digested from the lysosome? A) phagocytosis B) pinocytosis C) receptor-mediated endocytosis D) exocytosis
A) Phagocytosis Phagocytosis is a type of cellular "eating" in which the cell uses pseudopods to surround and engulf particles. The pseudopods join together and fuse, pinch off from the cell membrane, and become a food vacuole. See Figure 3.3 Scanning electronmicropah of phagocytosis.
Most, if not all, organelles in the cell have a limited life span, and thus must be continuously destroyed and replaced. A) True B) False
A) True Because of autophagy-the process that destroys worn out organelles- organelles can be continually replaced.
DNA helicase is responsible for unwinding the DNA molecule prior to DNA replication. A) True B) False
A) True DNA helicases are enzymes that break the weak hydrogen bonds between complementary bases to produce two free strands at a fork in the double stranded molecule.
Arriving in the cytoplasm, the mRNA can pass through a number of ribosomes to form a "string-of-pearls" structure called a polyribosome, or polysome, for short. A) True B) False
A) True Figure 3.18 An electronmicrograph of a polyribosome.
In the human body, cilia are found along the apical surface of epithelial cells of the respiratory and female reproductive tracts. A) True B) False
A) True In the respiratory tract, the cilia transport strands of mucus to the throat and in the female reproductive tract, ciliary movements draw the ovum into the fallopian tube and move it toward the uterus.
A protein that is synthesized for secretion begins with a leader sequence that permits the entry of these proteins into the cisternae of the rough endoplasmic reticulum. A) True B) False
A) True See Figure 3.22 How secretory proteins enter the endoplasmic reticulum
In the human body, cilia and flagella are composed of protein microtubules arranged in a characteristic "9 + 2" pattern. A) True B) False
A) True See Figure 3.5 Electron micrograph of cilia
The organelle that stores calcium (Ca2+) in striated muscle cells and is involved in steroid hormone metabolism is the ________________. A) endoplasmic reticulum B) lysosome C) Golgi complex D) mitochondria
A) endoplasmic reticulum The lysosome is involved in phagocytosis, the Golgi complex packages molecules into vesicles, and mitochondria are involved in ATP production.
Capsases are _________. A) enzymes that are activated during apoptosis B) enzymes that become activated when the mitochondria become "leaky" C) regulators of the cell cycle D) regulators of necrosis
A) enzymes that are activated during apoptosis Both intrinsic and extrinsic pathways of apoptosis result in the action of a group of previously inactive cytoplasmic enzymes known as capsases.
The plasma membrane is composed primarily of protein molecules embedded in a double layer of ________ molecules. A) phospholipid B) carbohydrate C) nucleic acid D) amino acid
A) phospholipid See Figure 3.2 The fluid-mosaic model of the plasma membrane.
The Human Genome Project has shown that there appear to be __________ genes in the genome. A) 3,000 to 4,000 B) 20,000 to 30,000 C) 100,000 D) 300,000 to 400,000
B) 20,000-30,000 Humans have 25,000 genes that code for polypeptide chains rather than the 100,000 genes that scientists had previously believed.
A stack of flattened sacs that receive, modify, and repackage proteins into new vesicles best describes the endoplasmic reticulum of the cell. A) True B) False
B) False A stack of flattened sacs that receive, modify, and repackage proteins into new vesicles best describes the Golgi complex. See Figure 3.12 The Golgi Complex.
Apoptosis refers to a type of cell death in which the cell swells, ruptures its membranes, and bursts. A) True B) False
B) False Apoptosis is a type of cell death in which the cell shrinks whereas necrosis is a type of cell death in which the cell swells, ruptures, and bursts.
DNA exists as one continuously long molecule that resides in the nucleus in each body cell. A) True B) False
B) False DNA exists as 23 pairs of chromosomes in each body cell, with the exception of sperm and egg cells that contain only 23 chromosomes.
Identical twins have identical gene expression because of epigenetic inheritance. A) True B) False
B) False Epigenetic inheritance refers to the inheritance of gene silencing from the gametes or early embryo that is carried forward by cell division into all cells of the body. Because of epigenetic changes that occur in response to differences in their environments, identical twins can have differences in gene expression.
Growth due to an increase in cell number as a result of mitotic cell division is called hypertrophy. A) True B) False
B) False Hypertrophy is an increase in the size of a cell whereas hyperplasia is growth due to the increase in cell number as a result of mitosis.
In anaphase of mitosis, the chromosomes line up in single file along the equator of the cell. A) True B) False
B) False In anaphase, the centromere splits and the sister chromatids separate and each is pulled to an opposite pole. In metaphase, the chromosomes line up in single file along the equator of the cell. See Figure 3.27 The stages of mitosis.
Individual genes code for only one protein. A) True B) False
B) False Individual genes code for an average of 3 different proteins. To a large degree, this is accomplished by alternative splicing of exons. Depending on which lengths of the gene's base pairs are removed as introns and which function as exons to be spliced together, a given gene can produce several different mRNA molecules coding for several different proteins.
Smooth endoplasmic reticulum would be abundant in cells that are active in protein synthesis and secretion, such as those of many exocrine and endocrine glands. A) True B) False
B) False Rough endoplasmic reticulum would be abundant in cells that are active in protein synthesis as these organelles contain ribosomes, which are the sites for protein synthesis.
The genes from DNA in the nucleolus located within the nucleus of the cell code for the specific production of transfer RNA (tRNA). A) True B) False
B) False The genes from DNA in the nucleolus located within the nucleus of the cell code for specific production of ribosomal RNA (rRNA)
Within the nucleus, DNA forms chromatin when it interacts with _______. A) a nucleosome B) proteins C) a double helix D) nucleoli
B) Proteins The proteins are called histones and they are spool-like in shape in which DNA wraps around. A nucleosome is a histone protein plus 2 turns of DNA, a double helix is the conformational shape of a DNA molecule, and nucleoli are dark areas in the nucleus that contain genes that code for rRNA. See Figure 3.14 The structure of chromatin.
Worn-out organelles and phagocytic by-products are characteristically found within the ____________, located in the cytoplasm. A) primary lysosome B) secondary lysosome C) residual body D) secretory vesicle
B) Secondary lysosome A primary lysosome contains only digestive enzymes in an acidic environment, a residual body is a lysosome that contains undigested wastes, and a secretory vesicle contains a product that is either secreted to the outside of the cell or used in another location within the cell.
Which of the following share identical base sequences? A) two homologous chromosomes B) two chromatids C) DNA transcribed into mRNA D) MRNA translated into tRNA
B) Two chromatids The two chromatids are identical in base sequences because they are produced by the semiconservative replication of DNA. See Figure 3.24 The replication of DNA.
The RNA type that diffuses through the nuclear pores to direct the assembly or synthesis of new protein molecules at the ribosomes in the cytoplasm is ______________. A) pre-mRNA B) mRNA C) rRNA D) tRNA
B) mRNA Once the pre-mRNA that has been cut of it's introns and spliced back together, it becomes mRNA that diffuses through the nuclear pores to direct the assembly or synthesis of new protein molecules at the ribosomes in the cytoplasm.
The ___________ are structures that greatly increase the surface area of cell membranes and thereby promote the rapid diffusion of molecules. A) cilia B) microvilli C) flagella D) microtubules
B) microvilli Cilia and flagella are for locomotion and microtubules are the thin proteins found in cilia and flagella. See Figure 3.6 Microvilli in the small intestine.
Which of the following is not a function of protein in the cell membrane? A) structural support B) synthesis of DNA C) enzymatic control of chemical reactions D) receptors for hormones and other arriving regulatory molecules
B) synthesis of DNA The synthesis of DNA occurs on ribosomes in the cytoplasm or on the ribosomes of the rough endoplasmic reticulum.
The cytoplasm is the fluid portion of the cytosol. A) True B) False
B)False The cytosol is the fluid portion of the cytoplasm. cannot be removed by centrifugation.
In terms of telomerase, cancer cells are most like which of the following cell types? A) muscle cells B) red blood cells C) germinal cells D) cartilage cells
C) Germinal cells Germinal cells that give rise to gametes can continue to divide indefinitely because they produce an enzyme called telomerase which duplicates the telomere DNA. Telomerase is found in most cancer cells [as well as stem cells] because of their ability to divide indefinitely.
The phase of the cell cycle during which DNA replicates itself is known as ______ phase. A) G2 B) G1 C) S D) M
C) S During G1, the cell performs the physiological functions characteristic of the tissue in which the cell is found. During G2, the chromatin condenses to form short, thick structures. During M, are the phases of mitosis.
One very important tumor suppressor gene that has been found to be mutated in more than 50% of all cancers is known as __________. A) an oncogene B) a centromere C) p53 D) cyclin D
C) p53 Normally, p53 protects against cancer by indirectly blocking the ability of cyclins to stimulate cell division.
Translation is best defined as the synthesis of ________________. A) mRNA, tRNA, and rRNA from DNA in the nucleus B) pre-mRNA only from DNA in the nucleus C) specific proteins from the mRNA base sequence code D) new, complementary strands of DNA in the nucleus
C) specific proteins from the mRNA base sequence code See Figure 3.21 The translation of messenger RNA (mRNA)
Which of the following statements about meiosis is false? A) Each daughter cell is genetically identical to the parent cell. B) Final daughter cells are gametes, either 4 sperm or a single ovum. C) Each daughter cell contains a total of 23 chromosomes [haploid]. D) Crossing-over of mixing of maternal and paternal chromosomes may occur.
D) Crossing-over of mixing of maternal and paternal chromosomes may occur Because of crossing-over of maternal and paternal chromosomes, the resulting daughter cells are all genetically unique. See Figure 3.31 Crossing over.
Which of the following organic molecules is not commonly found in the cell membrane? A) carbohydrates B) protein C) cholesterol D) nucleic acids
D) Nucleic acids Nucleic acids are found in the nucleus as well as in the cytoplasm of cells.
The mechanism whereby some viruses, including HIV and polioviruses, enter cells is called _________. A) phagocytosis B) endocytosis C) exocytosis D) receptor-mediated endocytosis
D) Receptor-mediated endocytosis See Figure 3.4 Receptor-mediated endocytosis.
Centrioles ___________. A) replicate during prophase of a dividing cell B) are DNA sequences that act as caps on the end of genes C) are compromised of microfilaments D) interact with spindle fibers to assist in moving chromosomes during mitosis
D) interact with spindle fibers to assit in moving chromosomes during mitosis See Figure 3.27 The stages of mitosis and Figure 3.28 The centrioles.
Membranes folded into cristae, with matrix, and energy production, are characteristics of an organelle known as the _____________. A) ribosome B) lysosome C) Golgi complex D) mitochondria
D) mitochondria A ribosome is the site of protein synthesis, a lysosome is involved in phagocytosis, and the Golgi complex packages molecules into vesicles.
DNA molecules can be found both in the nucleus and in the ______________. A) ribosomes B) lysosomes C) Golgi complex D) mitochondria
D) mitochondria The DNA in mitochondria consists of a circular small double-stranded molecule that leads many scientists to believe that mitochondria evolved from separate organisms related to bacteria that invaded the ancestors of animal cells and retained as an organelle.
Anticodons are characteristic of _______________. A) pre-mRNA B) mRNA C) rRNA D) tRNA
D) tRNA Translation of the codons [every 3 nucleotides in a strand of mRNA] is accomplished by tRNA that has a specific anticodon, which is 3 nucleotides that are complementary to a specific codon in mRNA. See Figure 3.20 The structure of transfer RNA (tRNA).
Cytokinesis occurs during _____________. A) prophase B) metaphase C) anaphase D) telophase
D) telophase See Figure 3.27 The stages of mitosis
The RNA type characterized by bending on itself to form a cloverleaf structure that twists further into an upside down "L" shape is called __________. A) pre-mRNA B) mRNA C) rRNA D) tRNA
D)tRNA Both pre-mRNA and mRNA are single stranded and linear in structure and rRNA is composed of 4 molecules of rRNA and 82 proteins arranged to form 2 subunits equal in size. See Figure 3.20 The structure of transfer RNA (tRNA).
Which of the following cannot pass through nuclear pores? A) water B) potassium ions C) glycerol D) DNA
DNA- DNA is too large to pass through nuclear pores. During protein synthesis, a copy is made of DNA in the form of mRNA, which can exit through the nuclear pores into the cytoplasm.
What is epigenetic inheritance?
Epigenetic inheritance refers to the inheritance of gene silencing from the gametes or early embryo that is carried forward by cell division into all cells of the body. Because of epigenetic changes that occur in response to differences in their environments, identical twins can have differences in gene expression.
In order for genes that are packaged in chromatin to be expressed, the chromatin must undergo the process of ___________.
acetylation The acetylation of chromatin produces a more open structure that can be activated by transcription factors, producing mRNA. See Figure 3.15 Chromatin structure affects gene expression.
Aminoacyl-tRNA synthetase is a group of enzymes that join a specific ____ molecule to the end of its complementary tRNA molecule
amino acid This makes sure that a tRNA with a given antiocodon can bind to only one specific amino acid.
Introns and exons are found within _____________.
pre-mRNA Pre-mRNA contains stretches of base pairs [introns] that do not contribute to the protein code whereas the coding regions in the pre-mRNA are called exons. See Figure 3.17 The processing of pre-mRNA into mRNA.
