DYNAMIC STUDY For Bio CHAP 4-8
If a cell begins meiosis with a 2n (diploid) number of 16, how many chromosomes are there in the cell at prophase I?
16 Prophase I is the initial stage of meiosis, when duplicated chromosomes first become visible but no division of chromosomes or cell division has yet occurred; so, 16 chromosomes (the diploid number) are present. if the diploid number of chromosomes is 16, then each haploid daughter cell would contain 8 chromosomes. There are 16 total chromatids. The answers of 32, 64, and 128 are multiples of two of the original set of chromosomes (2n = 16), which do not occur during meiosis.
Why does the phospholipid bilayer form the way it does?
Because the phospholid heads are hydrophilic and the tails are composed of lipids which are hydrophobic. The phospholipid bilayer forms because the phospholipids heads are hydrophilic, arranged to face outward. They are therefore exposed to the aqueous solution on the inside and outside of the membrane. The tails are composed of lipids and are hydrophobic, arranged so the tails face inward and away from the aqueous solutions inside and outside of the membrane.
Which of the following is characteristic of all prokaryotes?
Lack of a membrane-bound nucleus bound by a membrane, as well as any other membrane-bound organelles. By definition, prokaryotic cells are cells whose DNA is not enclosed within a nucleus. All prokaryotes lack a membrane-bound nucleus.. Eukaryotes have membrane-bound organelles, including a true nucleus.
Which organelle is the recycling center of the cell?
Lysosome The lysosome utilizes powerful hydrolytic enzymes to digest specific substances. Mitochondria are the primary sites of energy conversion in eukaryotic cells and do not participate in the recycling of substances. The nucleus is the operations center of the cell, dealing mainly with the synthesis and storage of DNA. The smooth endoplasmic reticulum is the site where various lipids are synthesized and a site where potentially harmful substances within the cell are detoxified. The Golgi complex is a network of membranes that processes and distributes proteins and is linked to the rough and smooth endoplasmic reticulum.
Which of the following allows sexual reproduction to occur generation after generation?
Meiosis Because meiosis is a reduction division that produces haploid (n) gametes, each time fertilization occurs, the diploid condition (2n) is restored. If gametes were not haploid, then the chromosome number would increase in each generation, for example, from 2n to 4n to 8n to 16n, and so on, with each fertilization. With the exception of some plants, most species do not tolerate expanding numbers of chromosome sets. Mitosis results in cells that are diploid and genetically identical to the parent cells.
Which of the following is the building site for cellular proteins?
Ribosome The nucleolus is a special section of the nucleus that is devoted to the synthesis of ribosomal RNA. The smooth endoplasmic reticulum is a network of membranes that is the site for the synthesis and modification of various lipids. It is also the site where potentially harmful substances within the cell are detoxified. DNA contains the information for putting proteins together from a set of the building blocks called amino acids. Mitochondria are organelles that are the primary sites of energy conversion in eukaryotic cell
In reference to movement of molecules across a membrane, what is the difference between diffusion and passive transport?
There is no difference. When substances diffuse across a membrane, we call the movement passive transport. Passive transport is so named because it does not require an input of energy. Whether it is called diffusion or passive transport, the process is spontaneous, and the net movement of molecules is down a concentration gradient. Movement of molecules up a concentration gradient is called active transport and requires an input of energy.
How do enzyme inhibitors work?
They bind to an enzyme, which alters the active site so a substrate cannot bind. Some enzyme inhibitors work by binding to an enzyme (at a different site than the active site), changing the shape of the active site. When the active site changes, it no longer fits perfectly with its appropriate substrate, so the substrate is not able to bind. Other enzyme inhibitors, called impostors, bind to the active site and keep the substrate from binding while the site is occupied. In either case, the action of the enzyme's active site is altered. An enzyme inhibitor affects the enzyme directly and does not alter the characteristics of the substrate.
Heat is defined as .
the total amount of energy associated with the movement of atoms and molecules in a substance
Which of the following conditions represent(s) stored (potential) energy: (1) table sugar ready to be ingested, (2) a diver about to dive off the ten-meter platform at the Olympics, or (3) a gerbil running on its exercise wheel in its cage?
1 and 2 Table sugar (sucrose) can be digested by living organisms through a series of chemical reactions; the energy stored within its covalent bonds is then released. A diver about to dive off a high platform also represents stored (potential energy) due to the location and mass of the person. When the diver jumps, potential energy is converted to kinetic energy, the energy of movement. A gerbil running on its exercise wheel represents kinetic energy, the energy of movement.
Why are no two gametes exactly alike genetically?
Because each gamete has a different combination of parental chromosomes that is the result of both crossing over and independent assortment
Why are enzymes so critical to cell functioning?
Enzymes enable and regulate cellular reactions.
The induced fit model of enzyme catalysis states that __________.
the active site of the enzyme changes shape after substrate binds to it
Put the following steps of ATP phosphate transfer in the correct order:
1. ATP transfers a phosphate group to a protein 2. ATP energizes a molecule in a cell 3. A protein changes shape 4. ATP enables transport of ions across cell membrane
A Calorie displayed on the nutritional label of a candy bar is equal to .________
1000 calories Energy is measured in units called calories (with a lowercase c). A calorie is defined as the amount of energy required to raise the temperature of 1 gram of water by 1° Celsius. Because calories are relatively tiny units of energy, on nutritional labels the fuel content of food is described in kilocalories (units of 1000 calories each). However, the prefix kilo- is dropped, and a kilocalorie is referred to as a Calorie (with a capital C).
(chap8) If a cell begins meiosis with a 2n (diploid) number of 16, how many chromosomes are there in the cell at prophase I?
16 Prophase I is the initial stage of meiosis, when duplicated chromosomes first become visible but no division of chromosomes or cell division has yet occurred; so, 16 chromosomes (the diploid number) are present. if the diploid number of chromosomes is 16, then each haploid daughter cell would contain 8 chromosomes. There are 16 total chromatids. The answers of 32, 64, and 128 are multiples of two of the original set of chromosomes (2n = 16), which do not occur during meiosis.
If a cell begins meiosis with a 2n (diploid) number of 16, how many chromosomes are there in the cell at anaphase I?
16 The correct answer is 16 because, although the homologous chromosomes are separated during anaphase I, telophase I and cytokinesis have not yet occurred to produce the two haploid daughter cells that are the final product of meiosis I. The answer of 8 chromosomes indicates that the process of meiosis I has been completed, resulting in two haploid cells. The answers of 32, 64, and 128 represent successive multiples of two of the original number of chromosomes (2n = 16), which do not occur during meiosis.
If a cell has 30 chromosomes before mitosis, how many does each daughter cell have afterward?
30
If a cell begins meiosis with a 2n (diploid) number of 16, how many chromosomes are there in each cell at metaphase II?
8 Homologous chromosomes are separated in meiosis I, producing two haploid daughter cells containing duplicated chromosomes. Metaphase II, when the chromosomes individually line up at the cell equator, therefore, occurs in cells that are already haploid, with a chromosome number of 8.
A human skin cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain in total?
92 A sister chromatid is one of the two identical DNA molecules that make up a duplicated chromosome. A cell in prophase of mitosis has already undergone chromosomal duplication (DNA replication). Each chromosome will consist of a pair of sister chromatids. Therefore, if the cell has 46 chromosomes, there will be a total of 92 chromatids. Because each pair of sister chromatids is held together in a single chromosome, the chromosome count remains the same, in this case 46. Human gametes (sperm and egg), produced by meiosis, contain 23 chromosomes.
Which of the following is a true statement about ATP and cellular work?
ATP consists of adenosine and three phosphate groups. ATP loses a phosphate group during the transfer and ADP is created. However, ADP can be converted to ATP again by adding another phosphate group.
How are combustion and cellular respiration similar?
At the end of both chemical reactions, carbon dioxide and water are produced. Chemical energy can be released by a chemical reaction due to the arrangement of atoms. In cars, combustion engines utilize octane and oxygen to release kinetic energy in the form of motion. In cellular respiration, glucose and oxygen are reactants in a reaction that releases ATP. In both, heat is given off as a byproduct and carbon dioxide and water are products.
Which of the following is a true statement about cilia and flagella?
Bacteria can have flagella but not cilia. Prokaryotic cells do not have the cell structures that make up cilia but they can have flagella. Many plants and animals do not have cells that have flagella or cilia whereas many protist cells do.
Cellular respiration involves the breakdown of food molecules to produce ATP. What other molecule(s) is/are produced by cellular respiration?
Carbon dioxide and water In cellular respiration, the chemical energy in energy-rich food molecules such as glucose is harvested using oxygen. So glucose and oxygen are reactants, not products, in cellular respiration. Carbon dioxide and water are waste products of cellular respiration and are energy-poor.
Which of the following is found in bacteria, plant, and animal cells?
Cell membrane Plants and some bacteria have chlorophyll whereas all plants and bacteria have cell walls. Both of these features (cell walls and chlorophyll) are not found in animal cells.
Which of the following eukaryotic organelles is specific to plant cells?
Chloroplast found only in plant cells. Similar to the chloroplast, cell walls are found in plants cells but not animal cells. However, the cell wall is not considered to be an organelle. Cell walls of varying composition can be found in other groups, including domain Bacteria, kingdom Protista and kingdom Fungi. Mitochondria are found in both plant and animal cells. They are the energy production sites of these cells. The lysosome is present in animals, but not in most plants. Both plant and animal cells have an endoplasmic reticulum.
Plant cells do not have which of the following?
Chloroplasts function in photosynthesis. Mitochondria break down sugar that is made in photosynthesis to release energy. The central vacuole is a distinctive feature of plant cells, allowing for storage of nutrients, water and waste materials.
____________and____________ can reproduce themselves. They have their own DNA that evolved from .
Chloroplasts; mitochondria; prokaryotes Chloroplasts and mitochondria contain their own DNA that is similar in structure to prokaryotic chromosomes. These organelles evolved from ancient free-living prokaryotes that established residence in larger host prokaryotes.
Genetics plays a role in how fast different people can "burn" their food. The rate of food energy consumption by your body is called metabolic rate. How could genetics account for different metabolic rates in different people?
Different people inherit different versions of the same metabolic enzymes.
How do enzymes affect activation energy?
Enzymes lower the amount of energy required to activate a chemical reaction.
After collecting samples of the material found growing on last month's leftovers at the back of your fridge, you realize that you have discovered a new type of organism. You find that the cells have distinct microscopic subunits within them. Further, several of these subunits seem to be involved in the production and transfer of certain molecules. One molecule appears after a messenger molecule is sent from a subunit to another one. The first molecule then travels to another location, where it is covered in membrane and (eventually) released from the cell. What type of cells do you think these are?
Eukaryotic
Which type of passive diffusion is involved in ion transport across cell membranes?
Facilitated diffusion Facilitated diffusion passively carries charged molecules, such as ions, from areas of higher concentration to areas of lower concentration across cell membranes. Ions cannot penetrate the inner layers of phospholipid "tails" to enter a cell by diffusion. Active transport does transport some ions (sodium and potassium), but it uses energy to transport them. Osmosis refers only to the transport of water. Receptor-mediated transport facilitates the transport of larger molecules, and it uses energy.
How does meiosis generate genetic diversity?
Homologous chromosomes cross over during prophase I, and during metaphase I, chromosomes align randomly.
(Chap5) ________molecules generally can pass directly through the plasma membrane more readily than_________ molecules.
Hydrophobic; hydrophilic The plasma membrane that surrounds cells is composed of a phospholipid bilayer. The interior of the bilayer is hydrophobic. This means that hydrophobic substances can dissolve in the membrane and pass through it more easily than hydrophilic substances. Small, hydrophobic (nonpolar) molecules such as oxygen and carbon dioxide can dissolve in the hydrophobic interior of the plasma membrane and pass through the membrane more readily than hydrophilic (polar) molecules. Larger molecules, charged molecules, and ions cannot cross the lipid bilayer on their own and must move through proteins embedded in the membrane.
Which of the following is true about prophase I?
It involves pairing up of homologous chromosomes. Prophase I is the first step in the process of meiosis I when DNA condenses into chromosomes and homologous chromosomes pair up. Understanding this is critical to understanding how meiosis creates genetic diversity because prophase I involves exchange of genetic information between homologous chromosomes (crossing over). Wound healing requires production of body cells and involves mitosis, not meiosis. Division of the cytoplasm occurs during cytokinesis, which occurs at the end of meiosis I, meiosis II, and mitosis. Condensation of chromosomes, not uncoiling of chromosomes, occurs during prophase I.
Which of the following is true about meiosis II?
It results in the production of four haploid cells.
Imagine that you synthesize a molecule that resembles the substrate of a particular enzyme but has a different chemical composition. You discover that this "substrate imposter" can bind to the enzyme's active site. What effect will the "substrate imposter" have on the reaction that is normally catalyzed by the enzyme?
It will inhibit the reaction. Certain molecules can inhibit a reaction by binding to an enzyme and disrupting its function. The region of the enzyme where the substrate binds is called the active site. "Substrate imposters" like the one you've synthesized bind to the active site and plug it up so that the normal substrate cannot bind. This will inhibit the reaction. Blocking the active site with a "substrate imposter" so that the normal substrate cannot bind will not accelerate an enzyme-catalyzed reaction.
Which of the following is common to both plant and animal cells?
Mitochondria Other structures found in both plant and animal cells are a nucleus (with a nucleolus), the smooth and rough ERs, and a cytoskeleton. Animal cells don't have a protective cell wall. Animals tend to have specialized tissues for whole-organism protection. Plasmodesmata, central vacuoles, and chlorophyll are found in plants but not in animals
(chap4) Which organelle(s) provide(s) the energy you use to read this sentence?
Mitochondria The mitochondria are also known as the "powerhouses" of the cell and are the primary sites for the formation of ATP.
Mitosis and Cytokinesis
Mitosis is divided into four phases: prophase, metaphase, anaphase, and telophase. At the start of mitosis, the chromosomes coil up and the nuclear envelope breaks down (prophase). Next, a mitotic spindle made of microtubule tracks moves the chromosomes to the middle of the cell (metaphase). The sister chromatids then separate and are moved to opposite poles of the cell (anaphase), where two new nuclei form (telophase). Cytokinesis overlaps the end of mitosis. In animals, cytokinesis occurs by cleavage, which pinches the cell in two. In plants, a membranous cell plate divides the cell in two. Mitosis and cytokinesis produce genetically identical cells.
Comparing mitosis and meiosis
Mitosis—which provides for growth, tissue repair, and asexual reproduction—produces daughter cells that are genetically identical to the parent cell. Meiosis, needed for sexual reproduction, yields genetically unique haploid daughter cells—cells with only one member of each homologous chromosome pair
Which of the following terms describes a failure of chromosomes to sort properly during meiosis?
Nondisjunction Nondisjunction can occur at two critical phases of meiosis. Homologous chromosomes may fail to separate during anaphase I, or sister chromatids may fail to separate in anaphase II. Nondisjunction results in offspring with too many or too few chromosomes.
Which of the following lists the structures involved in protein synthesis and release in the correct order?
Nucleus, mRNA, and ribosome Protein synthesis begins in the nucleus, where an mRNA copy of the gene is made. The mRNA then moves to the cytoplasm where it attaches to a ribosome, and the protein is assembled and released into the cell or into a vesicle for expulsion from the cell.
Which of the following best describes the process of facilitated diffusion?
Passive movement of solutes across a membrane down their concentration gradients with the involvement of membrane proteins
Which of the following features explains why plant cells do not explode as a result of osmosis?
Plant cells have a cell wall that prevents the cell from absorbing too much water.
What is the structural difference between rough endoplasmic reticulum (ER) and smooth ER?
Rough ER has ribosomes, but smooth ER does not. Rough ER is also located closer to the nucleus and plays a central role in protein synthesis. The rough ER is rough because it is studded with ribosomes. Both rough and smooth ER are lipid-membrane-bound organelles and do not contain DNA. Neither rough nor smooth ER are located within the nucleus.
During which phase of the cell cycle does DNA replication occur?
S during S phase of the cell cycle. The cell cycle is the repeating pattern of growth, genetic duplication, and division seen in most cells. There are two main phases in this cycle: First, there is interphase, when the cell simultaneously carries out its work and, in preparation for division, duplicates its chromosomes. Second, there is the mitotic phase (or M phase), which includes both mitosis and cytokinesis. Interphase can be separated into three phases: G1, S, and G2. G1, standing for "gap-one," includes normal cell operations and cell growth. The cell then enters the S, or "synthesis" phase, where DNA is copied, resulting in the duplication of the chromosomes. Next is G2 ("gap-two") phase, during which there is more cytoplasmic growth and preparation for cell division (M phase).
Which of the following is a site for lipid synthesis?
Smooth endoplasmic reticulum The smooth endoplasmic reticulum is also the site where harmful substances such as alcohol are detoxified within the cell. Lysosomes are organelles found in animal cells that digest worn-out or unneeded cellular materials and foreign materials that enter the cell. The rough endoplasmic reticulum is a network of membranes important for protein synthesis. The nucleus is the site where DNA exists and is copied. The plasma membrane is the outer covering of the cell.
What types of eukaryotic cells are flagellated?
Sperm Sperm use their flagella to travel to an unfertilized egg. Motile bacteria are not eukaryotic but do use flagella to move. An egg is a type of eukaryotic cell, but it does not have flagella and is nonmotile. A virus is not a cell, does not have flagella, and is nonmotile. The nucleus is an organelle within a cell and does not possess flagella.
Which of the following is the last stage of mitosis?
Telophase
Which part of a reaction is changed by an enzyme?
The activation energy To understand activation energy, think about that little push that will send a boulder at the top of a hill rolling downward. In a cellular reaction, substrates (reactants) will not react unless they are aligned properly and their bonds are stressed, decreasing the amount of initial energy required to break the bonds. Enzymes can decrease this activation energy barrier—for example, by binding substrates and changing shape, which puts stress on substrate bonds. The energy difference between products and the reactants is not changed by an enzyme. Kinetic energy is the energy of movement and is not changed by an enzyme. Alteration energy is not a term used in reference to chemical reactions.
The enzyme lactase participates in what reaction?
The breakdown of lactose Enzymes are usually named for the reaction they catalyze and end in the suffix -ase. The enzyme lactase is specific for its substrate lactose. The enzyme's active site can fit only the lactose molecule. Fructose is a carbohydrate similar to lactose, but the enzyme lactase cannot react with fructose. Glucose is also a carbohydrate, but it cannot react with lactase because glucose does not fit lactase's active site. The enzyme lactase cannot participate in reactions that result in the formation of protein or lipids because it is specific for the carbohydrate substrate lactose.
Which of the following is a false statement about prokaryotic and eukaryotic cells?
The cytoplasm is similar in size and function in eukaryotic and prokaryotic cells. Prokaryotic cells have a cytoplasm that occupies the entire interior of the cell whereas eukaryotic cells have a cytoplasm that occupies the region between the nucleus and the plasma membrane.
For what purpose(s) might a cell transport materials across its plasma membrane?
To import nutrients, to get rid of wastes, or to secrete proteins
While working in a medical clinic, you are asked to assist in the care of a 16-year old female patient who has not yet begun menstruating. You also notice that she is small in stature and has a wider than average neck. You suspect that she might have __________.
Turner syndrome The patient's physical features—short stature, wide neck and possible fertility issues—suggest that she might have Turner syndrome. Turner syndrome occurs when there is only one X chromosome present in a female. Turner syndrome can result from mistakes in meiosis that produce gametes (sperm or egg) lacking an X chromosome. If such gametes are involved in fertilization, the offspring may be female with only one X chromosome (XO) instead of the normal two (XX). Red-green colorblindness and hemophilia are X-linked disorders that are due to a disease allele on the X chromosome. These diseases are found more often in males. Sickle-cell anemia and Huntington's disease are caused by disease alleles on autosomal chromosomes. These diseases are as likely to affect males as females.
If a house is an analogy for a cell, what part of a house corresponds to the cytoskeleton?
Walls The garbage would be similar to the lysosome, which breaks down no longer needed items. Chloroplasts would be analogous to solar panels and hallways to the endoplasmic reticulum
Cancer Cells: Dividing Out of Control
When the cell cycle control system malfunctions, a cell may divide excessively and form a tumor. Cancer cells may grow to form malignant tumors, invade other tissues (metastasize), and even kill the host. Surgery can remove tumors, and radiation and chemotherapy are effective as treatments because they interfere with cell division. You can increase the likelihood of surviving some forms of cancer through lifestyle changes and regular screenings.
Two types of nondisjunction
Within the human body, meiosis occurs repeatedly as the testes or ovaries produce gametes. Almost always, chromosomes are distributed to daughter cells without any errors. But occasionally there is a mishap, called a nondisjunction, in which the members of a chromosome pair fail to separate at anaphase. Nondisjunction can occur during meiosis I or II (Figure 8.20). In either case, gametes with abnormal numbers of chromosomes are the result
Which of the following situations represents released energy:
a dart shot out of a dart gun, active transport of a substance across a cellular membrane? Conditions 1 and 3 represent released energy. Compressing a spring (condition 2) requires energy; as a result, the coiled spring represents stored (potential) energy, much like ATP in a living cell. Stored energy can be converted to released energy, such as when the energy in a compressed spring is released to shoot a dart out of a dart gun or when the energy stored in ATP is released to pump a substance across a cellular membrane (active transport).
The energy stored in ATP (adenosine triphosphate) can drive cellular work by energizing other molecules. This process occurs when________.
a phosphate group is transferred from ATP to another molecule The energy stored in ATP can be released and transferred to other molecules this way, driving cellular work. For example, when energy is needed for a reaction, a phosphate group is transferred from ATP to another molecule, energizing that molecule through the energy release. ATP (adenosine triphosphate) stores energy in its phosphate groups, not in its adenosine (sugar plus nitrogenous base) component. The transfer of a phosphate group from another molecule to ATP would energize ATP, not the other molecule. This is how energy is stored in, not released by, ATP.
The region on an enzyme where a substrate binds is called the .
active site The active site has a shape and amino acid composition that fits the substrate molecule. When the substrate binds to the active site, the enzyme may change shape slightly to envelop the substrate. This shape change can place stress on the bonds of the substrate, making them easier to break. This is one way an enzyme lowers the activation energy of a reaction. Enzymes lower the activation energy of reactions, but the site where substrate binds is not called the "activation energy site." "Activation site" and "reaction site" are not terms used to describe where a substrate binds an enzyme
Which of the following is not a eukaryote?
bacterium Bacteria are prokaryotes. They are characterized by their few internal structures and their lack of a distinct membrane-bound nucleus. Trees, birds, and dogs are all multicellular eukaryotic organisms. Fungi are also eukaryotes even though they can be microscopic.
If phospholipids are dropped into water, .
bilipid structures form with the hydrophilic heads pointing outward and the hydrophobic tails pointing inward Phospholipids are composed of a molecule of glycerol linked to two fatty acid chains and a charged phosphate group. The fatty acid chains are hydrophobic; the phosphate group is hydrophilic. Phospholipids arrange themselves into bilayers, with the fatty acid "tails" of each layer pointing inward and the phosphate "heads" pointing outward. These structures resemble cell membranes, but are not, in fact, membranes. The structures formed may resemble tiny droplets, but they have the molecular orientations listed above. Due to their fatty acid components, phospholipids are mostly hydrophobic and do not dissolve in water.
Homologous chromosomes __________.
carry the same genes Different versions of the same gene are called alleles and arise from mutations that change the DNA sequence of the chromosome. The DNA sequences are not alike, because each member of a pair of homologous chromosomes is inherited from a different source—that is, one from the father and one from the mother.
Crossing over between homologous chromosomes normally occurs __________.
during prophase I The resulting structure has four chromatids. Non-sister chromatids (chromatids of homologous chromosomes) exchange corresponding segments, resulting in chromatids that that contain parts from both maternal and paternal chromosomes. Mitosis does not normally involve crossing over between homologous chromosomes, which normally remain unpaired throughout. Anaphase II is when separation of sister chromatids occurs in a haploid cell containing only one member of each pair of homologous chromosomes. Fertilization is a random joining of gametes that have slightly different genetic information. It contributes to variation among organisms.
What structure is unique to animal cells?
extracellular matrix The extracellular matrix is a sticky structure composed of collagen fibers that holds cells together. It also provides protection and support. The mitochondria and cell membrane are shared between plants and animals. The cell membrane is common to bacteria, plants, and animals whereas the chloroplast is not found in animal cells.
Results of alternative arrangements of chromosomes at metaphase of meiosis I
illustrates one way in which meiosis contributes to genetic variety. The figure shows how the arrangement of homologous chromosomes at metaphase of meiosis I affects the resulting gametes. Once again, our example is from a hypothetical diploid organism with four chromosomes (two pairs of homologous chromosomes), with colors used to differentiate homologous chromosomes (red for chromosomes inherited from the mother and blue for chromosomes from the father)
A karyotype __________.
is a picture of chromosomes arranged in ordered pairs If you isolate chromosomes from a cell in metaphase of mitosis (e.g., a human cheek cell), stain the chromosomes with dyes, take a picture in a microscope, and arrange the chromosomes in matching pairs, you produce a display called a karyotype. A normal human cell has 46 chromosomes matched up as 23 pairs. The 23rd pair contains the sex chromosomes: XX for women, XY for men. A karyotype will only show chromosomes from one species.
The number of chromosomes found in a somatic eukaryotic cell __________.
is constant during its entire life
The fluid-mosaic model is ultimately the best depiction of the cell membrane because .
it shows that the phospholipids and proteins within the layers are able to move. The fluid-mosaic model views the plasma membrane as a fluid, phospholipid bilayer that has a mosaic of proteins either fixed within it or capable of moving laterally across it. The plasma membrane is not similar to a sandwich with either proteins or lipids on the inside. The fluid mosaic model does not have the hydrophobic layer facing the cytoplasm. Proteins are both an integral and peripheral component of the model. More proteins and lipids compose the membrane model than carbohydrates.
Diploid cells become haploid during __________.
meiosis I At anaphase I, homologous chromosomes are separated from each other, followed by telophase I and cytokinesis, which produce two daughter cells. At this point, the cells are haploid because each daughter cell contains only one copy of each member of a homologous pair of chromosomes.
Plant cells divide by __________
mitosis followed by cytokinesis by cell plate formation Mitosis is the division of the cell nucleus that results in daughter cells that are genetically identical to each other and to the parent cell. Cytokinesis is the division of the cytoplasm that occurs after the last stage of mitosis. Cytokinesis in plants involves building a new cell wall, an inflexible structure surrounding the plant cells. During cytokinesis, plant cells form a cell plate that grows down the middle of the cell, which eventually forms a new cell wall. Cell division in plants and animals involves both mitosis and cytokinesis. Bacterial cells divide by binary fission.
DNA is located in the______________ , and its message reaches the ribosome via the______________ .
nucleus; nuclear pores DNA's instructions are copied onto mRNA, which leaves the nucleus through the nuclear pores and enters the cytoplasm. Cytoplasm is organelle-containing region surrounding the nucleus. The vesicles and microfilaments are found in the cytoplasm. The cell membrane marks the border of the cell, separating the cell contents from its immediate environment.
You decide to try your hand at canning pickles. You immerse freshly picked cucumbers in a solution that has a solute concentration twice that found in the cucumber cells. You allow your preparation to cure for several months in a sealed jar. When you later open the jar, you find that the fluid surrounding the pickles is more dilute than when you started. This change in concentration is due to_______
pickles in a hypertonic solution losing water through osmosis Osmosis is responsible for much of the movement of fluids into and out of cells. Osmotic imbalances can cause cells either to dry out from losing too much water or, in the case of animal cells, to break from taking too much water in. Plant cells generally do not have the latter problem because their cell walls limit their uptake of water. Cells gain or lose water relative to their surroundings in accordance with the solute concentration inside the cell versus outside the cell. When the surrounding solution is hypertonic to the cytoplasmic fluid, the cell loses water; when the surrounding solution is hypotonic, the cell gains water. When the surrounding fluid and cytoplasmic fluid are isotonic to each other, water flow is balanced between the cell and its surroundings. In this scenario, the pickling solution contains high amounts of solute, so water moves from the pickle cells into the surrounding solution. Water leaves the plant cells along its concentration gradient. Solute cannot cross the cell membrane. The process involves the movement of water; active transport is not involved.
Chloroplasts are found in__________ .
plants Chloroplasts contain chlorophyll and allow plants to use photosynthesis to store the sun's energy as carbohydrates. Among the organisms and structures listed, only plants have chloroplasts, which they use for photosynthesis. Yeast cells do not carry out photosynthesis and, therefore, do not have chloroplasts. Viruses and prions are not living and do not have chloroplasts.
If you are shipwrecked, it is not a good idea to drink seawater because_________ .
seawater is hypertonic to the body's cells and tissues; therefore, the cells will lose water through osmosis, making you even more thirsty
The sex of a human fetus is determined by the __________.
sex chromosome found in the sperm
In meiosis II, __________.
sister chromatids are separated into different daughter cells
