Biology 101 (Chapter 4 - Chapter 5) First Exam

Carbon is unique because it can form strong covalent bonds with other carbon atoms, allowing for the formation of long chains. These chains can vary in length, giving rise to different organic compounds. Additionally, carbon atoms can form bonds with other elements such as hydrogen, oxygen, and nitrogen, resulting in different shapes of organic compounds. Carbon-carbon double bonds can also be formed, and the number and location of these double bonds can vary, leading to even more diversity in organic compounds. Therefore, all of the given options are correct.

Saturated fats do not have cis double bonds. In fact, saturated fats have single bonds between all carbon atoms, which means they are saturated with hydrogen atoms. The absence of double bonds in saturated fats gives them a straight structure, allowing them to pack tightly together and usually exist as solid fats at room temperature.

When phospholipids are added to water, they have a unique property that allows them to self-assemble into a double-layered structure. This structure is called a bilayer. The hydrophilic (water-loving) heads of the phospholipids face outward towards the water, while the hydrophobic (water-fearing) tails face inward, creating a stable barrier. This bilayer formation is essential in many biological processes, including the formation of cell membranes. Therefore, the correct answer is bilayer.

Lactose is an example of a disaccharide because it is composed of two sugar molecules, glucose and galactose, bonded together. Disaccharides are carbohydrates made up of two monosaccharide units joined by a glycosidic bond. Starch and amylose are polysaccharides, not disaccharides, as they are composed of many sugar molecules. Galactose is a monosaccharide, not a disaccharide, as it consists of a single sugar molecule. Therefore, lactose is the only option that fits the definition of a disaccharide.

The correct answer is 3'TAACGT5'. In DNA, the two strands are complementary to each other, meaning that they have opposite sequences of bases. The given sequence 5'ATTGCA3' can be paired with its complementary sequence by replacing each base with its complementary base: A with T, T with A, G with C, and C with G. This gives us the sequence 3'TAACGT5', which is the complementary strand to the given sequence.

If a DNA sample is composed of 10% thymine, it means that the other three bases (adenine, cytosine, and guanine) must make up the remaining 90%. Since DNA is a double-stranded molecule, adenine pairs with thymine and cytosine pairs with guanine. Therefore, if thymine is 10%, guanine must also be 10% to maintain the complementary base pairing. Thus, the percentage of guanine in the DNA sample would be 40%.

Ovalbumin is a protein found in egg whites and is considered a storage protein. Storage proteins are responsible for storing amino acids and other nutrients for later use by the organism. Ovalbumin acts as a source of nutrition for the developing embryo inside the egg, providing it with the necessary amino acids and other essential nutrients for growth and development. Therefore, ovalbumin is an example of a storage protein.

The correct answer is "Random chain." Carbon chains can exist in various forms such as open (straight) chains, ring chains, and branched chains. However, a random chain is not a recognized form for carbon chains.

Peptide bonds are created during the formation of the primary structure of a protein. These bonds form between the amino acids in a protein chain, linking them together to create the linear sequence of amino acids. Peptide bonds are formed through a condensation reaction, where the carboxyl group of one amino acid reacts with the amino group of another amino acid, resulting in the formation of a peptide bond and the release of a water molecule. This process is repeated for each amino acid in the protein chain, ultimately forming the primary structure of the protein.

Hydrogen bonds stabilize the alpha helix and beta pleated sheet structures of proteins. These bonds form between the carbonyl oxygen of one amino acid and the hydrogen of the amino group of another amino acid. This interaction helps to maintain the secondary structure of proteins by holding the helix or sheet in place. Hydrogen bonds are relatively weak individually, but when many of them are present in a protein structure, they contribute significantly to its stability.

Atherosclerosis is not an example of steroids because it is a condition characterized by the buildup of plaque in the arteries, leading to narrowing and hardening of the blood vessels. Steroids, on the other hand, are a class of hormones that include cholesterol, estradiol, and testosterone, which play important roles in various physiological processes in the body. Atherosclerosis is not a hormone or a type of steroid, but rather a pathological condition.

The given statement "are macromolecules" is incorrect about fats. Fats are not considered macromolecules. They are classified as lipids, which are a diverse group of molecules that include fats, oils, and waxes. Lipids are hydrophobic and are composed of three fatty acids joined to a glycerol molecule, forming a triacylglycerol. Fats have two types, saturated and unsaturated, based on the presence of double bonds in the fatty acid chains.

Denaturation is the term used for a change in a protein's three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds. This disruption can be caused by factors such as heat, pH changes, or exposure to certain chemicals. Denaturation results in loss of the protein's biological activity, as the specific shape is crucial for its function. Hydrolysis, stabilization, and dehydration do not specifically refer to a change in protein conformation and are not the correct terms for this process.

A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another amino acid. In the given options, option C represents a peptide bond as it shows the connection between two amino acids, indicating the formation of a peptide bond.

Carbohydrates macromolecules are polymers called polysaccharides composed of many monosaccharides joined by glycosidic linkages. Polysaccharides are long chains of monosaccharide units that are linked together by glycosidic bonds. This arrangement allows for the formation of complex carbohydrates such as starch, cellulose, and glycogen. Disaccharides, on the other hand, are composed of only two monosaccharide units joined by a covalent bond, while hydrogen bonds are not involved in the formation of carbohydrates macromolecules.

Organic compounds with a sulfhydryl group are known as thiols. Thiols are characterized by the presence of a sulfur atom bonded to a hydrogen atom (-SH). They are often referred to as mercaptans as well. Thiols are important in various biological processes and have a strong odor. They are commonly found in garlic, onions, and other pungent substances. Thiols also play a significant role in the chemistry of proteins and enzymes.

The amino group is characterized by two of the above properties. It includes a nitrogen atom and can pick up H+ from the water in living organisms, making it act as an acid. Additionally, in its ionized form, the amino group carries a charge of -1.

Petroleum is a complex mixture of hydrocarbons, which are organic compounds composed of hydrogen and carbon atoms. These hydrocarbons are the main components of petroleum and are responsible for its energy-rich properties. Enantiomers are a type of stereoisomer and are not typically found in petroleum. Amino acids, on the other hand, are organic compounds found in living organisms and are not major components of petroleum. Therefore, the correct answer is hydrocarbons.

Carbon atoms do not form hydrogen bonds by sharing their four valence electrons. Hydrogen bonds occur when a hydrogen atom is bonded to a highly electronegative atom such as oxygen, nitrogen, or fluorine. Carbon atoms typically form covalent bonds by sharing electrons with other atoms, including other carbon atoms.

Sulfur is not a frequent bonding partner of carbon. While carbon commonly forms bonds with hydrogen, nitrogen, and oxygen, it does not typically bond with sulfur. This is because sulfur and carbon have different electronegativities, making their bonding preferences different.

The 5' end of a polynucleotide strand of DNA has a phosphate group attached to the number 5 carbon of pentose. This is because the numbering system of DNA starts from the carbon atom in the pentose sugar, and the phosphate group is attached to the 5th carbon atom in the pentose sugar. This phosphate group is important for the formation of phosphodiester bonds between nucleotides, which are crucial for building the DNA strand.

Starch is indeed found in plant cells in structures called "plastids". Plastids are specialized organelles that are responsible for storing various substances in plants. Starch, which is a complex carbohydrate, is synthesized and stored in plastids called amyloplasts. These amyloplasts are primarily found in plant tissues that require energy storage, such as roots, tubers, and seeds. Therefore, the statement "Starch is found in plant cells in structures called 'plastids'" is true.

The correct answer is "two of the above." Both glucose and fructose are aldoses and hexoses. Aldoses are a type of sugar that contains an aldehyde group, and hexoses are sugars with six carbon atoms. Therefore, both statements are true. However, the statement that they differ in molecular formula is incorrect because glucose and fructose have the same molecular formula, C6H12O6.

Cow harbors cannot digest cellulose by its enzymes. Instead, they rely on a symbiotic relationship with microorganisms in their rumen, which produce enzymes capable of breaking down cellulose. These microorganisms ferment cellulose into simpler compounds that the cow can then digest and utilize for energy. Therefore, the statement is false.

The correct answer is "All of the above". This is because structural isomers, cis-trans isomers, and enantiomers all refer to compounds that have the same molecular formula but different structures. Structural isomers have different connectivity of atoms, cis-trans isomers have different arrangements of groups around a double bond, and enantiomers are mirror images of each other. Therefore, all three options fit the definition given in the question.

Amylose and amylopectin are both types of starch, which are polysaccharides found in plants. They are not synthesized in animal cells. Both amylose and amylopectin are branched, but their branching patterns differ. Amylose has a linear structure with 1-4 glycosidic linkages, while amylopectin has a highly branched structure with both 1-4 and 1-6 glycosidic linkages. Potato tubers and grains are the major sources of starch, including both amylose and amylopectin. Therefore, the correct answer is that potato tubers and grains are the major sources of them.

Insoluble fiber refers mainly to cellulose. Cellulose is a type of fiber found in plant cell walls that cannot be broken down by the human digestive system. It adds bulk to the stool and helps promote regular bowel movements. Chitin is another type of fiber found in the exoskeletons of insects and crustaceans, while cytoskeleton refers to the network of protein filaments within a cell. Therefore, neither chitin nor cytoskeleton are the correct answers for insoluble fiber.

The question is asking how many different types of polypeptides can be synthesized using 20 common amino acids, with each polypeptide composed of 110 amino acids. The correct answer is 20^(110), which means raising 20 to the power of 110. This is because for each position in the polypeptide chain, there are 20 possible amino acids that can be placed. Since there are 110 positions, we multiply 20 by itself 110 times, resulting in a very large number of possible combinations.

The figure can make enantiomers, as it contains an asymmetric carbon (b). It can also make cis-trans isomers, as it contains a double bond that can have different spatial arrangements (a). Therefore, the correct answer is that it can make enantiomers and cis-trans isomers (two of the above).

When ten glucose molecules are linked together by dehydration reactions, a water molecule is removed for each linkage. Since there are ten glucose molecules, there will be nine water molecules removed. The molecular formula for glucose is C6H12O6, so for ten glucose molecules, the carbon (C) count would be 6 * 10 = 60, the hydrogen (H) count would be 12 * 10 = 120, and the oxygen (O) count would be 6 * 10 = 60. However, since nine water molecules are removed, the oxygen count will decrease by 9, resulting in C60H102O51.

The molecule illustrated in the figure is a saturated fatty acid. This can be inferred from the statement that a diet rich in this molecule may contribute to atherosclerosis, as saturated fats are known to increase the risk of atherosclerosis. Additionally, the statement suggests that molecules of this type are usually liquid at room temperature, which is not true for saturated fats as they are usually solid at room temperature. Therefore, the correct answer is A and B.

When a carbon atom forms four single bonds, it adopts a tetrahedral shape with bond angles of 109.5 degrees. This is because the four bonding pairs of electrons repel each other and try to maximize their distance from each other, resulting in a tetrahedral arrangement. This arrangement ensures the most stable and energetically favorable configuration for the carbon atom. Therefore, the correct answer is tetrahedral shape with 109.5 bond angles.

The statement is false because β glucose actually refers to the OH group attached to the first carbon being above the plane of the glucose ring, not the second carbon. In β glucose, the OH group attached to the first carbon is above the plane, while in α glucose, it is below the plane.

A disruption in hydrogen bonding would have the least effect on the primary level of protein structure. The primary level refers to the linear sequence of amino acids in a protein chain. Hydrogen bonding primarily occurs between the backbone atoms of the amino acids, stabilizing the secondary, tertiary, and quaternary levels of protein structure. However, the disruption of hydrogen bonding would not directly impact the linear sequence of amino acids, thus having the least effect on the primary level.

Hydrocarbons, such as fats and gasoline, are known to be hydrophobic compounds because their bonds are primarily nonpolar carbon to hydrogen linkages. This means that they do not dissolve in water, making the statement "dissolve in water" incorrect. Hydrocarbons can undergo reactions that release a relatively large amount of energy, which is a characteristic of their chemical structure. Therefore, the correct answer is "dissolve in water."

The electron configuration of an atom determines the number of valence electrons, which in turn determines the kind and number of bonds that an atom will form with other atoms. Additionally, the electron configuration is the key to an atom's chemical characteristics. Therefore, all of the statements provided are true about electron configuration, making "None of the above" the correct answer.

Glycine is the correct answer because it is the only amino acid among the options that does not have an asymmetric carbon at its α-carbon position. An asymmetric carbon is a carbon atom that is bonded to four different groups or atoms. In glycine, the α-carbon is bonded to two hydrogen atoms, an amino group, and a carboxyl group, making it the only option where the α-carbon is not asymmetric.

When a polymer with 741 monomers is broken by hydrolysis, it will result in the formation of 741 monomers and 740 water molecules. This is because hydrolysis breaks the bonds between the monomers in the polymer chain by adding a water molecule to each bond, resulting in the formation of individual monomers and water molecules. Therefore, the correct answer is "none of the above" as none of the options provided matches the expected outcome.

The two compounds in the figure are not related as geometric isomers, structural isomers, or enantiomers. Geometric isomers have the same connectivity of atoms but differ in the arrangement of substituents around a double bond. Structural isomers have the same molecular formula but differ in the arrangement of atoms. Enantiomers are mirror images of each other. Since none of these relationships apply to the given compounds, the correct answer is "none of the above".

Carbon dioxide is often considered inorganic because it is a very simple molecule and it lacks both nitrogen and hydrogen. Additionally, carbon dioxide does not have single bonds. These characteristics contribute to its classification as an inorganic molecule.

Starch and cellulose differ in all of the above aspects. They have different functions, with starch being a storage molecule in plants and cellulose providing structural support. They also have different glycosidic linkages, with starch having alpha linkages and cellulose having beta linkages. Furthermore, they have different three-dimensional shapes, with starch forming helical structures and cellulose forming straight chains. Therefore, all of the given options accurately describe the differences between starch and cellulose.

Acetone is the simplest ketone and consists of 3 carbons. However, it is not a structural isomer with Propanal, which means that the statement "structural isomer with Propanal" is false. Additionally, Acetone does not have a carboxyl group within the carbon skeleton. Therefore, the correct answer is "has a carboxyl group within the carbon skeleton".