HW_ Set 1

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Pitt Community College *

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110

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Biology

Date

Feb 20, 2024

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HW 1: Introduction 1) What is the name for the formal process through which scientific research is checked for originality, significance, and quality before being accepted into scientific literature? ➢ Peer Review 2) What is a suggested and testable explanation for an event called? ➢ Hypothesis 3) Why are viruses not considered living? ➢ Viruses are obligate parasites & require a host 4) The presence of a membrane-enclosed nucleus is a characteristic of what? ➢ Eukaryotic cells 5) Which of the following sequences represents the hierarchy of biological organization from the most inclusive to the least complex level? ➢ Organism, Organ, Tissue, Organelle, Molecule 6) What is a characteristic that is not present in all living things? ➢ Nucleus containing DNA 7) Consider all levels of organization of the biological world and place each of these items in order from smallest to most encompassing level of organization: skin, cell, elephant, water molecule, planet Earth, tropical rainforest, hydrogen atom, wolf pack, liver ➢ Hydrogen Atom, Water Molecule, Skin Cell, Liver, Elephant, Wolf, Pack, Tropical Rainforest, planet Earth 8) Which of the following structures is conserved in all living organisms and points to a common origin? ➢ Store genetic material in DNA/RNA 9) VOCAB: ➢ Biosphere - collection of all the ecosystems on Earth ➢ Biology - the study of life ➢ Homeostasis - ability of an organism to maintain constant internal conditions ➢ Organ System - level of organization that consists of functionally related interacting organs ➢ Deductive Reasoning - form of logical thinking that uses a general inclusive statement to forecast specific results ➢ Inductive Reasoning - form of logical thinking that uses related observations to arrive at a general conclusion ➢ Organelle - small structures that exist within cells and carry out cellular functions 10) The scientific method consists of a series of well-defined steps. If a hypothesis is not supported by experimental data, a new hypothesis can be proposed. ➢ True 11) The scientific method is a method of research with defined steps that include experiments and careful observation. ➢ True

12) “If there are no kids there wouldn’t be adults,” what characteristic of life does this saying refer to. ➢ Grow & Reproduction 13) There is enough scientific proof that viruses can jump from bats to humans ➢ True

HW 2: Chemical Nature 1) Which of the following statements is false? ➢ Ionic bonds are generally stronger than covalent bonds 2) Which type of bond exemplifies a weak chemical bond? ➢ Hydrogen bonds 3) What are atoms that vary in the number of neutrons found in their nuclei called? ➢ Isotopes 4) If xenon has an atomic number of 54 and a mass number of 131, how many neutrons does it have? ➢ 77 5) Why do hydrogen and oxygen form polar covalent bonds within water molecules? ➢ Oxygen is more electronegative than hydrogen, generating a partial negative charge near the oxygen atoms 6) What happens to the pH of a solution when acids are added? ➢ The pH of the solution decreases 7) Which of the following functional groups is not polar? ➢ Methyl 8) Why can some insects walk on water? ➢ Insects can walk on water because of its high surface tension 9) What property of carboxyl makes carboxyl containing molecules hydrophilic? O II [ carboxyl group - CH - C - OH ] ➢ Carboxyl groups release H+, making its parent molecule hydrophilic 10) ATP is the energy molecule, it is made of nucleotides and involves a phosphate group chemistry. ➢ True 11) What is electronegativity? ➢ property of an atom to pull shared pair of electrons towards itself 12) Isotopes have many applications in biology, like carbon dating, PET scanning. ➢ True 13) Vander Waals bond is weaker than Hydrogen bond which is weaker than covalent bond. ➢ True 14) Hydrogen bonding forms the basis of DNA and Protein structure which is so important for their function. ➢ True

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HW 3: Proteins/Carbs 1) An example of a monosaccharide is ________. ➢ Fructose, Glucose, & Galactose 14) Cellulose and starch are examples of: ➢ Polysaccharides 15) Lactose is a disaccharide formed by the formation of a ________ bond between glucose and ________. ➢ Glycosidic; Galactose 16) The monomers that make up proteins are called ________. ➢ Amino Acids 17) The α-helix and the β-pleated sheet are part of which protein structure? ➢ Secondary 18) Amino acids have the generic structure seen below, where R represents different carbon- based side chains. ➢ True 19) The carboxyl group of one amino acid is linked to the amino group of the incoming amino acid. In the process, a molecule of water is released. It appears like Peptide bond formation is a dehydration synthesis reaction. ➢ True 20) Protein synthesis is directional, occurs from N to C terminal ➢ True 21) Polymer chains can adopt “α-helix” or "β-sheet” structures because of hydrogen bonding between carbonyl and amino groups in the peptide backbone. ➢ True 22) Polymer chains that adopt “α-helix” or "β-sheet” can further fold upon itself. Variety of chemical interactions involved. - hydrogen bonding - hydrophobic interactions, - ionic bonding, and - disulfide linkages ➢ True 23) What is the hierarchy in protein structure? ➢ Primary, Secondary, Tertiary, & Quaternary 24) In sickle cell hemoglobin, this glutamate is replaced by a valine. This change is termed mutation ➢ True 25) Chaperones maintain functional proteins (proteome) in living organisms and prevents diseases ➢ True 26) Carbohydrates could be grouped into ketosis, alcoves,

➢ True 27) Glycogen and starch are storage polysaccharides while cellulose is a structural polysaccharide. ➢ True 28) Alpha and beta isomer is according to the hydroxyl group's arrangement on anomeric carbon? ➢ True 29) Cellulose is a linear polymer while amylopectin is branches and glycogen is highly branched polymer of monosaccharides. ➢ True 30) What is the normal, and pre-diabetic level of fasting blood sugar in humans ➢ 100 mg/dL; 100-125 mg/dL 31) Cellulose is called a dietary fiber because it cannot be digested by the body. However, in bacteria Symbiotic bacteria help them digest cellulose. ➢ True 32) Proteins and carbohydrates have isomers and our body only uses L-amino acids and D- sugars isomers to build these macromolecules. ➢ True

HW 4: Lipids 1) What is cholesterol specifically classified as? ➢ A Steroid 2) Which hormones are made from cholesterol? ➢ Estradiol & Testosterone 3) Which of the following characteristics is not true for saturated fats? ➢ They tend to dissolve in water easily 4) Which fat has the least number of hydrogen atoms? ➢ Unsaturated Fat 5) Of what are phospholipids important components? ➢ The plasma membrane of animal cells 6) What is the basic structure of a steroid? ➢ 4 fused hydrocarbon rings 7) Besides its use in hormone production, for what does the body use cholesterol? ➢ Production of bile salts 8) What are the four classes of lipids and what is an example of each? a) lipids like margarine b) wax like the coating on feathers c) phospholipids like cell membrane constituents d) steroid like cholesterol 9) Why have trans fats been banned from some restaurants? How are they created? ➢ Trans fat is produced by the hydrogenation of oil that makes it more saturated and isomerized. It increases LDL amounts. 10) The fatty acids of triglycerides are classified as saturated, unsaturated, or trans fats. What is it about the structure of these compounds that gives them their physical characteristics? ➢ Unsaturated fats and trans fats have some double bonded carbon atoms, while saturated fats do not. 11) In phospholipids, the glycerol backbone is attached to two fatty acid molecules and one phosphate group. ➢ True 12) Fats have predominantly saturated fatty acids and oils have predominantly unsaturated fatty acids ➢ True 13) Omega 3 is an essential fatty acid because it is not synthesized by the body ➢ True 14) Unsaturated fatty acids can exist in cis and trans configuration. ➢ True 15) Cis fatty acids have kinks and are major constituents of liquid oils.

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➢ True 16) Saturated fats can be hydrogenated to form saturated fatty acids. ➢ True 17) LDL is bad cholesterol and HDL is good cholesterol ➢ True 18) Waxes are a class of lipids that consist of long chain alcohols esterified to long chain fatty acids. This is different from triglycerides where fatty acids are esterified with glycerol backbone ➢ True 19) Phospholipids in animals can be of only four types: namely 1) PtdCho, phosphatidylcholine 2) PtdEth, phosphatidylethanolamine 3) PtdSer, phosphatidylserine 4) PtdIns, phosphatidylinositol ➢ True 20) Triglycerides have fatty acids that are esterified with glycerol backbone, and phospholipids are triglycerides where one fatty acid chain is replaced by a phosphate group. ➢ True 21) Choline, ethanolamine, serine and inositol are four organic molecules that are attached to phosphate groups in the phospholipids and only serine is negatively charged, others are neutral. ➢ True

HW 5: Nucleic Acids 1) What are the building blocks of nucleic acids? ➢ Nucleotides 2) What may a nucleotide of DNA contain? ➢ Deoxyribose, Thymine, and a Phosphate Group 3) What is found in RNA that is not in DNA? ➢ Ribose & Uracil 4) Where is the largest amount of DNA found in a eukaryotic cell? ➢ In the Nucleus 5) If DNA of a particular species was analyzed and it was found that it contains 27% A, what would be the percentage of C? ➢ 23% 6) Meselson and Stahl’s experiments proved that DNA replicates by which mode? ➢ Semi-Conservative 7) The experiments by Hershey and Chase helped confirm that DNA was the hereditary material on the basis of the finding of what? ➢ Radioactive phosphorus was found in the cell 8) What are some differences between DNA and RNA? ➢ DNA contains deoxyribose and thymine, while RNA contains ribose and uracil 9) Which molecule carries information in a form that is inherited from one generation to another? ➢ Hereditary information is stored in DNA 10) What do RNA and DNA have in common? ➢ Both contain four different nucleotides 11) Explain how the components of DNA fit together. ➢ DNA is composed of nucleotides, consisting of a 5 carbon sugar, a phosphate, and a nitrogenous base. DNA is a double helical structure in which complementary base pairing occurs. Adenine pairs with thymine and guanine pairs with cytosine. Adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. The two individual strands of DNA are held together by covalent bonds between the phosphate of one nucleotide and sugar of the next. The two strands run antiparallel to each other 12) The bond between sugar molecule and Nitrogenous base is called glycosidic linkage in DNA but not in RNA ➢ False 13) Phosphoric acid molecules form a bridge between 5' carbon of one nucleotide with 3' carbon of another molecule. This establishes 5' to 3' directionality in the DNA synthesis. ➢ True 14) RNA is single stranded, has uracil in place of thymine, contains ribose sugar and not deoxyribose sugar and is of following three types, mRNA, tRNA and rRNA.

➢ True 15) Over the last two decades RNA has been found to be of further types based on size; miRNA (micro RNA) and siRNA (small interfering RNA. miRNA are usually 20 nucleotides long and have biological functions. siRNA are again small RNA molecules but they interfere with metabolic processes. Do you think in the coming years these RNA will prove to be biologically more involved than we know now? ➢ Yes 16)

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HW_ Set 1

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