Science Practice 1
DNA is composed of ____________.
two short parallel polynucleotide chains one coiled polynucleotide chain two long polynucleotide chains twisted in a double helix two long parallel polynucleotide chains DNA is a nucleic acid and is one of the major groups of biological molecules. All nucleic acids are made up of nucleotides which are linked in polynucleotide chains. DNA molecules have an antiparallel structure - the two strands of the helix run in opposite directions of one another. Each strand has a 5′ end and a 3′ end.
Which of the following is an example of a redox reaction?
A. Acid-base neutralization B. Combustion C. Single replacement reaction D. Synthesis The answer is B Rationale: A redox reaction is one that involves the transfer of electrons between two species. The substance that gives away electrons is said to be oxidized. The substance that receives the electrons is said to be reduced. During combustion, elemental oxygen (O2) reacts with a compound to form products that contain oxygen. This requires oxygen to transition from a neutral oxidation state (0) to an oxidation state of -2. (The oxygen has been reduced.) In the other reaction choices, the oxidation states of atoms do not necessarily change.
Which of these statements is true about pH?
A. Adding an acid to a solution will increase the pH B. Blood has an acidic pH C. Higher pH values indicate a higher [H+] D. A pH of 6 is more acidic than a pH of 8 The answer is D Rationale: Lower pH values indicate a more acidic solution, thus 6 is more acidic than 8. This occurs because acids increase [H+] of a solution, which lowers the pH of a solution. Thus, higher pH values would have a lower [H+]. Blood has a pH between 7.35 and 7.45, so it is slightly basic.
Which of the following enzymes is responsible for breaking down a polysaccharide to a disaccharide?
A. Amylase B. Cobalamin C. Catalase D. Trypsin The answer is A Rationale: Amylase is an enzyme that is secreted by the salivary glands and the pancreas to break down starch to maltose, which is a disaccharide. Trypsin is found in the digestive system of many vertebrates, where it hydrolyzes proteins. Cobalamin is a water-soluble vitamin that plays a role in DNA synthesis, and is involved in both fatty acid and amino acid metabolism. Catalase catalyzes the decomposition of hydrogen peroxide to water and oxygen.
Which of the following accessory structures is not correctly paired with its function?
A. Arrector pili / odor production B. Ceruminous glands / earwax production C. Hair follicle / hair production D. Apocrine glands / sweat production The answer is A Rationale: Arrector pili is a bundle of smooth muscle responsible for the appearance of "goose bumps," particularly during cold temperatures in order to trap a layer of warm air in the surface of the skin. Please see the diagram below as a visual reference for the anatomy of the arrector pili referenced in the question above.
Filtration of blood occurs in the renal corpuscles. Which of the following is not part of the renal corpuscles?
A. Bowman's capsule B. Glomerular Basement Membrane C. Glomerulus D. Vasa Recta The answer is D Rationale: A renal corpuscle is made up of the loop of capillary networks called the glomerulus, and the blind end of the nephron which is called the bowman's capsule. The combined basement membrane of these two structures makes up the glomerular basement membrane. The Vasa recta, on the other hand, is a capillary loop in the renal medulla, running parallel to the loop of Henle.
Fatty acids are organic acids that have a __________ group joined to a hydrocarbon tail.
A. Carbonyl B. Carboxyl C. Hydroxyl D. Amino The answer is B. Rationale: Generally, a fatty acid is a long straight chain of carbon atoms with hydrogen atoms along its length. At the end of the chain is a carboxyl group (-COOH). The amino group is (-NH2). A hydroxyl group consists of one hydrogen and one oxygen atom and is written as ( -OH). Aldehydes and ketones are organic compounds which incorporate a carbonyl functional group, (C=O).
Which of the following shows a relationship between the immune system and another system of the body?
A. Dilation of blood vessels in response to histamine B. Introduction of antibodies through breastfeeding C. Destruction of a pathogen by the hydrochloric acid in the stomach D. Phagocytosis of pathogens by macrophages The answer is D Rationale; The main function of hydrochloric acid in the stomach is not for immunity but for digestion. However, in relation to immune system, it also destroys pathogens that enter the body through food and drinks.
Which of the following digestive organs contains vitamin-producing bacteria?
A. Liver B. Stomach C. Large intestine D. Small intestine The answer is C Rationale: The large intestine contains healthy gut bacteria that are responsible for producing Vitamin K, a fat-soluble vitamin that plays a role in blood clotting. Often-times newborns are given a Vitamin K shot to aid in blood clotting due to any trauma during the birthing process. This is done because the gut bacteria has not yet populated and synthesized Vitamin K.
HIV is a virus that destroys the body's defense against diseases by inserting itself into the host's DNA. In which part of the infected host cell will HIV virus be found?
A. Ribosomes B. Peroxisomes C. Nucleus D. Lysosomes The answer is C HIV infects a host cell by integrating its genetic material with the genetic material of the host cell. Genetic material is located in the nucleus. Ribosomes are the sites for protein synthesis. Peroxisomes break down fatty acids to be used for forming membranes and as fuel for respiration. They also transfer hydrogen from compounds to oxygen to create hydrogen peroxide and then convert hydrogen peroxide into water. Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out cell parts, food, and engulfed viruses or bacteria.
Which of the following correctly describes anatomical position?
A. Seated, arms at sides, palms facing posteriorly B. Supine, arms at sides, palms facing posteriorly C. Prone, arms at sides, palms facing anteriorly D. Upright, arms at sides, palms facing anteriorly The answer is D Rationale: Anatomical position is described as standing erect, arms at sides, face and palms are facing anteriorly (facing to the front).
Which of the following is the result of deficient production of thyrotropin-releasing hormone?
A. The thyroid gland will produce an insufficient amount of thyroid hormones B. The parathyroid gland will be stimulated to overproduce parathyroid hormone C. The pituitary gland will produce excessive amounts of thyroid-stimulating hormone D. There will be insufficient production of growth hormone Rationale: The Thyrotropin-releasing hormone (TRH) stimulates the pituitary gland to release TSH (thyroid-stimulating hormone), which in turn stimulates the thyroid gland to secrete the thyroid hormones, T3 and T4. Deficient production of TRH will result in an insufficient production of thyroid hormones in the thyroid.
Which of the following types of tissues functions in the covering, lining, and protection of surfaces and body cavities?
A. Connective tissue B. Nerve tissue C. Muscle tissue D. Epithelial tissue The answer is D Rationale: Epithelial tissue functions as the lining and covering of body surfaces and cavities. Muscle tissue functions in facilitating voluntary and involuntary movements. Connective tissue is responsible for the support and protection of tissues and organs. Nerve tissue is responsible for transmitting nerve impulses.
Which of the following is the name of the imaginary vertical plane that equally divides the body into left and right?
A. Coronal B. Transverse C. Horizontal D. Sagittal The answer is D Rationale: The sagittal plane is also a vertical plane but it equally divides the body into left and right. The Coronal plane is an imaginary vertical plane that divides the body into front (anterior) and back (posterior). The horizontal, or transverse, plane is an imaginary plane at right angle with coronal and sagittal planes and it divides the body into superior and inferior.
The basic function of the renal system includes filtration, secretion, reabsorption, and excretion. Which of the following substances is secreted by the nephrons and can be found in the filtrate that is eventually excreted?
A. Creatinine B. Glucose C. Sodium D. Amino Acids Rationale: Amino acids, sodium and glucose are normally reabsorbed in the proximal portion of the renal tubules. Creatinine, which is used to assess glomerular filtration, is filtered in the glomerulus and also secreted by the tubules.
Which of the following organ systems is correctly paired with its function?
A. Digestive/ waste elimination B. Circulatory/ obtaining nutrients necessary for growth, energy and normal body processes C. Excretory/ transport of substance to all tissues of the body D. Endocrine/ regulation of homeostasis through hormone signaling The answer is D Rationale: The Endocrine system is responsible for regulating homeostasis through hormone signaling. The Digestive system is responsible for obtaining nutrients through the breakdown and absorption of food. The Circulatory system is responsible for transport of substance to all tissues of the body. The Excretory system is primarily responsible for waste elimination.
Which of the following proteins makes up the hair and nails?
A. Elastin B. Vinculin C. Keratin D. Collagen The answer is C Rationale: Hair and nails are made of dead epidermal cells that are rich in keratin. Collagen and elastin are the main structural proteins found in the dermis of the skin. Vinculin is a protein that functions in cellular adhesion.
The head is _________ to the neck.
A. Superior B. Proximal C. Inferior D. Superficial The answer is A Rationale: Superficial means that the structure is closer to the surface of the body. Superior indicates that the structure is located at a relatively higher position while inferior denotes a relatively lower position. Proximal denotes a position that is relatively closer to the center of the body or the point of attachment.
Which of the following processes correctly describe the formation of new cells in order to replace worn-out and damaged cells during injury?
A. Endocytosis B. Exocytosis C. Mitosis D. Meiosis The answer is C Rationale: Mitosis and meiosis are two types of cell division. Mitosis is a process where a single cell divides into two identical daughter cells. The major purpose of mitosis is to replace worn-out and damaged cells. Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. The purpose of meiosis is to create sex cells - sperm in males, eggs in females. Exocytosis is the cellular process of transporting substances out of the cell. Endocytosis is the cellular process of taking substance into the cell.
Which of the following can be classified as an extensive property?
A. Entropy B. Malleability C. Melting point D. Luster The answer is A Rationale: An extensive property is one in which a physical quantity (amount) is impacted by the size of the system it describes or by the amount of matter within that system. One example of an extensive property is entropy. Since entropy can be defined as the amount of "randomness" or "disorder" in a system, it is directly impacted by both the size of the system and the amount of matter within it. Malleability is a substance's ability to deform under pressure (compressive stress). If malleable, a material may be flattened into thin sheets by hammering or rolling. A substance's ability to change form under pressure is not dependent on the size of the system or the amount of matter within it. The melting point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure, not on the size of the system or the amount of matter within it. Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. There are two main types of luster: metallic and nonmetallic. This quality of a substance is not affected by the size of a system or the amount of matter within it.
Which of the types of tissue is responsible for providing the matrix that supports and connects other tissues of the body?
A. Epithelial tissue B. Connective tissue C. Nerve tissue D. Muscle tissue The answer is B Rationale: Connective tissue is responsible for providing the matrix that supports and connects other tissues of the the body. Nerve tissue is responsible for transmitting nerve impulse. Epithelial tissue functions as lining and covering of body surfaces and cavities. Muscle tissue functions in facilitating voluntary and involuntary movements.
Which of the following describes the function of Rough Endoplasmic Reticulum?
A. Facilitates movement of substance in and out of the cell B. Conversion of nutrients to ATP C. Intracellular digestion of damaged structures, macromolecules, and bacteria D. Synthesis and transport of proteins The answer is D Rationale: The Rough Endoplasmic Reticulum is studded with ribosomes and, as such, assists in the synthesis and transport of proteins.
Which of the following does not correctly describe a cell membrane?
A. Fat soluble substances such as oxygen, carbon dioxide, and alcohol can easily pass through the membrane. B. The phospholipid component has hydrophilic heads and hydrophobic tails. C. It is composed of a single layer of lipids interspersed with proteins. D. It is composed entirely of proteins and lipids. The answer is C Rationale: The cell membrane is a lipid bilayer primarily made up of lipids and proteins. The phospholipid component has hydrophilic heads and hydrophobic ends. The hydrophobic ends make up the middle portion of the membrane and this layer makes it easy for fat soluble substances, such as oxygen, carbon dioxide, and alcohol to pass through.
Which of the following is true of insulin and glucagon?
A. Insulin and glucagon maintain normal levels of blood glucose in the fasting state. B. Insulin and glucagon regulate the level of calcium in the blood. C. Insulin and glucagon have opposite effects on blood glucose but work together to maintain homeostasis. D. Secretion of insulin and glucagon is regulated by the pituitary gland. The answer is C Rationale: Insulin and glucagon are both secreted by the pancreas and function in the homeostatic maintenance of the blood's glucose level. Insulin decreases the level of the blood's glucose during a fed state and glucagon increases levels of glucose during a fasting state.
Which of the following describes cellular respiration?
A. It is a reductive anabolic activity B. It is an oxidative anabolic activity C. It is a reductive catabolic activity D. It is an oxidative catabolic activity The answer is D Rationale: An anabolic reaction is a reaction that uses energy to build molecules the organism needs. A catabolic reaction breaks down complex molecules into smaller molecules to create energy for the organism to use. Oxidation is when an element loses one or more electrons to oxygen. Reduction is when an element gains one or more electrons. Cellular respiration is the process in which a cell takes in oxygen and uses it to break down glucose to create energy in the form of ATP. In the final stage of cellular respiration (called the electron transport chain), oxygen accepts electrons and picks up protons to form water. So, because elements lose electrons to oxygen and it is a reaction in which energy is created, cellular respiration is both an oxidative and catabolic activity.
Which organelle is responsible for storing DNA?
A. Lysosomes B. Nucleus C. Rough Endoplasmic Reticulum D. Golgi Apparatus The answer is B Rationale: The genetic material, DNA, is found within the membrane-bound nucleus. The Rough Endoplasmic Reticulum is where synthesized proteins are processed and sorted. The Golgi Apparatus is responsible for the transport of proteins within and out of the cell. Lysosomes are responsible for digesting molecules/ substances being transported inside the cell from the outside.
Which of the following cell organelles is correctly paired with its function?
A. Lysosomes/ ATP production B. Ribosome/ Protein synthesis C. Nucleus/ Intracellular digestion D. Mitochondria/ Cell division The answer is B Rationale: Ribosomes are responsible for synthesis of proteins. The nucleus houses the genetic material and is responsible for cellular division, not intracellular digestion. The mitochondria are the powerhouse of the cell, wherein ATP is generated. They are not involved in cell division. Lysosomes contain digestive and hydrolytic enzymes which is essential for breaking down of molecules. Lysosomes are not involved in ATP production.
Which of the following is not located on the anterior region of the human body?
A. Mandible B. Vertebral column C. Clavicle D. Sternum The answer is B Rationale: The vertebral column is located posteriorly (at the back). The mandible, sternum, and clavicle are all located anteriorly (front).
Which of the following can be classified as an intensive property?
A. Mass B. Density C. Entropy D. Volume Rationale: An intensive property is any characteristic of matter that does not depend on the amount of the substance present. Examples of intensive properties are density and color. This is because no matter how much or little you have of a substance, the color and the density of that substance are the same. If you have one ounce of orange juice or three gallons of orange juice, it will still be the color orange and will have the same density. An extensive property is any characteristic of matter that depends on the amount of matter being measured. Examples of extensive properties are mass and volume. If you have one ounce of orange juice, the mass and volume of the orange juice would be different than if you had three gallons of orange juice. Entropy refers to the degree of disorder within a system (how random and unpredictable something is). It is measured by the amount of energy unavailable in a closed thermodynamic system. Entropy can change depending on the size of the system and the amount of matter within it which makes it an extensive property.
Osteoblasts are specialized cells that secrete the protein collagen and other substances necessary for bone formation. Which of the following organelles is more likely to be predominant in osteoblasts?
A. Mitochondria B. Ribosomes C. Lysosomes D. Nucleus The answer is B Rationale: Ribosomes are the organelles responsible for protein synthesis, so it is expected to be predominant in protein-secreting cells such as osteoblasts. Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out cell parts, food, and engulfed viruses or bacteria. Mitochondria are responsible for ATP production and are considered the powerhouse of the cell. The nucleus is the "control center" that is responsible for directing the overall activity of the cell. The nucleus contains most of the cell's DNA
Which of the following is a carbohydrate?
A. Myosin B. Collagen C. Cellulose D. ATP Rationale: Cellulose is a polysaccharide (a sugar) that is made up of a linear chain of several hundred to many thousands of β linked D-glucose molecules. Carbohydrates are built from simple sugars. Adenosine triphosphate (ATP) is a complex organic chemical that provides energy to drive many processes in living cells, (e.g. muscle contraction, nerve impulse propagation, and chemical synthesis). Collagen is the main structural protein in the extracellular space in the various connective tissues in the body. Myosins are a family of motor proteins that play roles in muscle contraction as well as a range of other motility processes in eukaryotic organisms.
Which of the following organ systems is not correctly paired with its function?
A. Nervous/ collecting, analyzing and integrating information that regulates intrinsic body conditions and maintains behavioral patterns B. Circulatory/ transport of substance to all tissues of the body C. Digestive/ provide defense against infectious diseases D. Respiratory/ breathing and gas exchange The answer is C Rationale: The Immune system is responsible for providing defense and immunity against infectious diseases. The Digestive system is responsible for the breakdown and absorption of food. The Respiratory system facilitates breathing and gas exchange. The Nervous system is responsible for collecting, analyzing and integrating information that regulates intrinsic body conditions and maintains behavioral patterns. The Circulatory system is responsible for transport of substance to all tissues of the body.
Which of the following is the correct order of structures from simple to most complex?
A. Neurons, mitochondria, nerve tissues, brain B. Mitochondria, neurons, nerve tissues, brain C. Brain, neurons, mitochondria, nerve tissues D. Mitochondria, nerve tissues, neurons, brain The answer is B Rationale: Neurons are the basic cells that make up the nervous system. Since the mitochondria is an organelle that you would find inside a neuron, it is going to be the simplest structure in the list. Multiple neurons are needed to form nervous tissue, which in turn makes up the brain.
Which of the following statements is true?
A. Nucleotides are made up from DNA B. Codons are made up from nucleotides C. Codons are made up from DNA D. DNA makes up nucleotides The answer is B Rationale: A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis. The DNA molecule is made from nucleotides.
The respiratory system is composed of organs that facilitate gas exchange between the blood and the external environment. Which of the following describes the group of organs that function during gas exchange?
A. Organ System B. Organelle C. Organ D. Tissue The answer is A Rationale: Tissues are a collection of specialized cells that perform a specific functions (e.g. protection, support, nerve conduction and movement). A group of tissues that has a specialized function is referred to as an organ. A group of organs that work together to perform several related functions is an organ system. Below is a model representing the hierarchy of the structure of the human body:
Which of the following statements about osmosis is false?
A. Osmosis involves the movement of water from an area of high concentration of water to an area of low concentration of water B. Osmosis involves a selectively permeable membrane C. Osmosis moves water molecules mostly through the phospholipid heads of the cell membrane D. Osmosis is the spontaneous net movement of water molecules The answer is C Rationale: Osmosis is the spontaneous movement of water molecules through a selectively permeable membrane. The water moves along a concentration gradient, which means that it moves from areas of higher water concentration to areas of lower water concentration. (When considering solutes - the substance dissolved in the water - the water moves from a region of low solute concentration to a region of high solute concentration.) The water moves across the membrane until there are equal concentrations of water and solute on each side. The water molecules achieve this by moving across a selectively permeable membrane that transports the water through proteins called aquaporins.
Fragile bones due to production of deficient or defective collagen as a result of a genetic defect is a characteristic of which of the following conditions?
A. Osteoporosis B. Kyphosis C. Tetany D. Brittle Bone Disease The answer is D Rationale: Brittle Bone Disease is a congenital disorder that involves defective or deficient collagen synthesis due to genetic mutations. Osteoporosis is an imbalance in bone remodeling wherein bone resorption exceeds bone formation resulting to porous and fragile bones. Tetany is characterized by spastic muscle contractions due to calcium deficiency.
In order to break apart a polysaccharide into disaccharides, what type of reaction needs to occur?
A. Oxidation-reduction B. Hydrolysis C. Glycosidic D. Condensation The answer is B Rationale: Hydrolysis reactions add water to break glycosidic bonds between the monomers in a polysaccharide. Disaccharides are formed by the condensation reactions of two simple sugar molecules coming together. Two OH groups, one from each sugar molecule, come together and form an oxygen bridge between. There is no such thing as a "glycosidic reaction" but rather a glycosidic bond forms by a condensation reaction, which means that one water molecule is produced during formation of a glycosid. An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species.
Which of the following endocrine glands has an exocrine function that aids in regulating levels of glucose in the blood?
A. Pancreas B. Adrenal C. Hypothalamus D. Pineal The answer is A Rationale: The Pancreas is both an endocrine and exocrine gland. As an exocrine gland, it produces bicarbonate and the enzymes necessary for the digestion of foods in the small intestine. As an endocrine gland, it produces the hormones insulin and glucagon, which regulate the level of glucose in the blood. The Hypothalamus, pineal, and adrenal glands are all endocrine glands that produce releasing and inhibiting hormones, melatonin, and cortisol and aldosterone, respectively.
Which of the following is the largest organ of the human body?
A. Pancreas B. Kidney C. Lung D. Skin The answer is D Rationale: Skin is the largest single organ of the body that is mainly responsible for covering and protection of internal structures.
Newborn babies are given several types of vaccines in order to protect them from acquiring diseases. Which of the following is responsible for this immunity process?
A. Passive immunity B. Active immunity C. Autoimmune disease D. Innate immune system Rationale: Vaccination is an active immunity which involves exposure to a killed or weakened form of the disease in order to trigger production of antibodies. Passive immunity is a temporary protection from diseases brought by introduction of antibodies from another person. The innate immune system is comprised of non-specific barriers and cellular responses that acts immediately following infection. An autoimmune disease refers to a condition wherein immune cells function abnormally and attack molecular components of the body's own organs.
Which of the following is a heterotrophic organism with a genome stored in DNA?
A. Plants B. Algae C. Human D. Virus The answer is C Rationale: Humans are heterotrophic organisms, which means that they cannot make their own food. Instead, they rely on other sources of nutrition, such as plants and animals. Humans have their genome stored in DNA. Plants and algae are autotrophic (they can create their own food/nutrition) and have their genome stored in DNA. A virus, on the other hand, is neither autotrophic nor heterotrophic, and has RNA as genetic material.
Which of the following steps of protein synthesis occurs in the nucleus?
A. Replication B. Elongation C. Translation to amino acid D. Transcription to mRNA The answer is D Rationale: Protein synthesis is comprised of two main steps, transcription of DNA to mRNA and translation of mRNA codons to amino acids. In the nucleus, the mRNA transcribes the genetic instruction from the DNA. mRNA then diffuses to the cytoplasm through the nuclear pores. Translation to amino acid and elongation to a particular protein molecule occur in the cytoplasm, particularly in the ribosomes.
80a. Which of the following organelles plays a vital role in the breaking down of macromolecules? 80b. Which of the following organelles is responsible for digesting damaged cellular structures, as well as macromolecules and bacteria ingested by the cell?
A. Ribosomes B. Lysosomes C. Golgi Apparatus D. Rough Endoplasmic Reticulum The answer is B Rationale: Ribosomes are the sites of protein synthesis. Ribosomes are attached to the Rough Endoplasmic Reticulum, where the synthesized proteins are processed and sorted. The Golgi Apparatus is then responsible for transporting and delivering synthesized proteins to other regions of the cell or to the plasma membrane for exocytosis into the extracellular fluid. Lysosomes, on the contrary, are responsible for digesting molecules/ substances being transported inside the cell from the outside, such as during phagocytosis by macrophages.
Which of the following incorrectly describes neurons?
A. Sensory neurons carry information away from the brain. B. Motor neurons carry efferent impulses. C. Sensory neurons carry afferent impulses. D. Motor neurons cause muscle contractions. Rationale: Sensory neurons carry afferent impulses or stimuli toward the brain and spinal cord. Motor neurons carry efferent information away the brain which cause muscle contractions.
Which of the following scenarios would result in a monkey zygote containing 47 chromosomes instead of the typical 46 chromosomes?
A. The chromatid does not separate properly during mitosis. B. This gives improved protein functions to the new organism. C. The chromosomes do not separate properly during meiosis. D. The ovum degrades. The answer is C Rationale: When a zygote has more or less than the normal 46 chromosomes, it is referred to as aneuploidy. A common form of aneuploidy is trisomy, which is when there is an extra chromosome in cells. Different numbers of chromosomes are caused by nondisjunction. Nondisjunction happens when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis I or II.
Which of the following statements is true about covalent bonds?
A. The covalent bond between H-Cl is nonpolar B. Covalent bonds aren't affected by the electronegativity of the atoms C. Sigma bonds are the weakest covalent bonds D. Covalent bonds form from the sharing of electrons between atoms The answer is D. Rationale: A covalent bond is a chemical bond that is formed when two atoms share electrons in their outermost shells. These shared electrons are called shared pairs. Sigma bonds are the strongest covalent bonds and are due to head-on overlapping of orbitals on two different atoms. A single bond is usually a sigma bond. Covalent bonds are also affected by the electronegativity of the connected atoms, which determines the polarity of the bond. Two atoms with equal electronegativity will make nonpolar covalent bonds such as H-H. A molecule that does not share electrons "equally," such as H2, creates a polar bond. A polar bond is characterized by one of the atoms in the molecule having a stronger "pull" on the shared electrons. This results in some atoms in the molecules having a slightly negative charge and others having a slightly positive charge. In the case of water, the oxygen atom end sup with a slight negative charge because it pulls the shared electrons with Hydrogen closer to itself. This results in the hydrogen atoms having a slightly positive charge do to the imbalance.
Which of the following is true?
A. The female gametes are called ova and contain full set of chromosomes. B. The male gametes are called sperm and contain half of a set of chromosomes. C. The female gametes are called ovaries and contain half of a set of chromosomes. D. The male gametes are called eggs and contain full set of chromosomes. Rationale: The ova, or eggs, are the female gametes and contain half of a set of chromosomes, while sperm are the male gametes which also contain half of a set of chromosomes. Ovaries are the female reproductive organs, which produce the female gametes. In males, the reproductive organs responsible for producing gametes are the testes.
Which of the following would an electron microscope be used to measure?
A. The strength of chemical bonds B. 20-nm polymer films C. Aquatic samples D. Insect samples The answer is B Rationale: Electron microscopes are powerful tools for obtaining images of incredibly small objects that cannot be observed by regular optical microscopes. Electron microscopes are capable of imaging samples that are only several nanometers in size, such as thin polymer films. Biologists sometimes examine insects, but they generally do this with optical microscopes since the insects are so large. Aquatic samples cannot be used in an electron microscope because the technique is performed in a vacuum.
Which of the following anatomical terms is correctly matched with its meaning?
A. carpal/foot B. cervical/wrist C. cranial/skull D. inguinal/neck The answer is C Rationale: Cranial refers to the bone comprising the skull. Carpal refers to the bone comprising the wrist. Cervical refers to the region of vertebrae in the neck. Inguinal is the superior region of the thigh.
A decrease in the amount of hemoglobin in the blood would result in __________________.
A. decreased blood pressure B. increased oxygen-carrying capacity C. decreased oxygen-carrying capacity D. increased blood viscosity The answer is C Rationale: The function of hemoglobin is to bind oxygen molecules in order to transport oxygen in the blood. If hemoglobin levels are decreased, this would directly result in a limited ability to carry and deliver oxygen. Blood viscosity may increase if the number of red blood cells increases. However, if hemoglobin is decreased, blood viscosity would likely not change. Blood pressure may also increase if the number of red blood cells was increased. However, decreased hemoglobin would not affect blood pressure.
White blood cells contain many _________ because they need to dispose of harmful intruders such as bacteria and viruses. Which of the following options correctly completes the statement above?
A. ribosomes B. Golgi C. mitochondria D. lysosomes The answer is D Rationale: White blood cells contain a larger number of lysosomes because they need to dispose of harmful intruders such as bacteria and viruses. Lysosomes are responsible for digesting and removing waste from a cell. This means they can digest bacteria and viruses that are engulfed by white blood cells in order to protect the body. Mitochondria are the organelles responsible for generating energy-rich molecules for the cell. The Golgi apparatus collects small molecules and combines them to make more complex molecules within the cell. Then it packages up the complex molecules to either store or to send out of the cell. Ribosomes are responsible for protein synthesis. mRNA is translated into proteins by the ribosomes.
Which of the following types of muscles are involuntary?
A. skeletal only B. skeletal and visceral C. cardiac and visceral D. cardiac and skeletal Rationale: Cardiac and visceral muscles are both involuntary, while skeletal muscles operate under voluntary control. An involuntary muscle is a muscle that contracts without conscious control (like the heart). A voluntary muscle contracts when we consciously tell it to contract (like your biceps).
Which of the following is a function of the epidermis?
A. storage of fat B. contains many blood vessels that can constrict or dilate for thermoregulation C. protects underlying tissues from abrasions, heat, microbes, and chemicals D. functions as a major component of the adaptive immune system The answer is C Rationale: The epidermis, as the outermost layer of the skin, protects underlying tissues from abrasions, heat, microbes, and chemicals. It functions as a major component of the innate immune system (the "general" immune system that targets anything seen as "foreign"). It is avascular, so it does not contain blood vessels. Lipid-containing cells are found in the subcutaneous layer.
