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• Spring 2025 BISC-220 Practice Exam 1 is available with an answer key.
• The lecturer for the course is Rita Barakat, PhD.
• The answer key corresponds to the practice exam posted on Brightspace, also the last spring's first exam.
• Exam takers must write their name and lab instructor's name on the exam sheet.
• Exam takers must not start the exam until instructed.
• Exam takers must ensure the exam has 14 pages.
• Continuing on the exam after the time is up will result in a zero grade.
• You must use a #2 pencil to fill in the Blue Scantron Answer Sheet.
• When filling out the answer sheet, bubble in your last name, leave an empty one for a space, and then bubble in your first name.
• You must enter your USC ID # as the identification number.
• Columns K & L should reflect the last two digits of the LECTURE section (13028 = 8:00 am Tuesday/Thursday, 13022 = 9:30 am Tuesday/Thursday).
• Columns O & P should reflect the last two digits of your LAB section (ie 62 for 13162).
• Bubble in all answers with a #2 pencil on SIDE 1, fully filling in the entire circle while fully erasing mistakes.
• The entire exam should be turned in when you are done with the Blue Scantron Answer Sheet inserted between the exam pages to the instructor.

Cell Membrane Transport

• Large polar or ionic molecules cannot directly cross the cell membrane because they aren't miscible or "mixable" with the hydrophobic medial layer of the membrane.
• If 30 mg of NaCl is dissolved in water, the compound will ionize becoming a sodium cation and a chloride anion.
• Forms of bulk transport don't require any energy expenditure.
• Transcription takes place in the nucleus while translation takes place at the ribosome in a plant cell.
• A plasma membrane enriched with saturated fatty acid tails is more viscous.

Microscopy and Cellular Structures

• If visualizing an onion root tip cell under a light microscope is difficult, lowering the stage completely before adjusting the height using the coarse adjustment knobs is necessary.
• Hydrogen bonds are relatively weak intermolecular bonds formed due to electrostatic forces.
• Hexokinase, which catalyzes the first reaction of glycolysis in the cytoplasm of prokaryotic and eukaryotic cells, would be synthesized at a ribosome floating freely in the cytoplasm of a eukaryotic cell.
• The structure labeled 11 in the image is the mitochondria, which play a key role in cellular respiration in animal and plant cells.
• The structure labeled 2 is the nucleolus, the location where the concentration of genetic material (DNA) is most dense in all cells, including prokaryotes.
• The organelle or structuring playing an important role in intracellular activity, specifically during cell division, is marked as 7 in the image.
• Structures 7 and 9 are not membrane-bound.

Macromolecules and Energy

• Carbohydrates are the major macromolecules essential for cell respiration and are typically utilized as an "immediate energy source" by cells.
• A long-term carbohydrate energy storage in animals typically requires converting glucose into glycogen polysaccharides.
• Starch is most likely the carbohydrate isolated from a plant cell broken down into glucose by pepsin.

Lipids and Fatty Acids

• Avocado oil is an example of an unsaturated cis fatty acid in our diet.
• Estradiol, a steroid hormone secreted by the ovaries in biological females, transport mechanism is most likely to occur via simple diffusion into the cell.

Protein Structure and Synthesis

• The monomer for proteins is H2N-C-COOH
• Hemoglobin is an example of a protein that has achieved a quaternary level of folding structure.
• Disulfide bonds form at the tertiary level of protein structure.
• Proteins that remain within the cell are most likely synthesized at a ribosome marked as 10 on the image.

Enzymes

• Hexokinase is an enzyme that catalyzes the first reaction of glycolysis, which takes place in the cytoplasm of all cells (prokaryotic and eukaryotic).
• An enzyme that binds a single substrate and produces two or more products is typically considered a catabolic enzyme.

DNA and RNA

• DNA contains the nitrogenous base Thymine whereas RNA contains the nitrogenous base Uracil.
• Messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA) participates in translation in prokaryotes and eukaryotes.

Signaling Pathways and Receptors

• Dopamine signaling via D2-type receptors results in inhibition of Adenylyl Cyclase, leading to a net decrease in movement.
• For G-protein Coupled Receptors and Receptor Tyrosine Kinases, the N-terminus of the protein is typically located on the extracellular side whereas the C-terminus is typically located on the intracellular side
• Excessive water consumption results in a hypotonic extracellular environment, causing cells to burst due to rapid influx of water.
• Signaling via D2-type receptors results in inhibition of Adenylyl Cyclase, leading to a net decrease in movement.
• All of the following statements are true about protein channels except Channel proteins are typically only selective for certain molecules based on the size of the channel pore.
• You are studying a protein channel that is known to flux (or allow for the movement of) Chloride ions along their concentration gradient. What type of amino acids would you expect to find in the inner lining of the channel pore?

Cellular and Molecular Processes

• The innermost valence shell of all atoms except Hydrogen and Helium is considered "full" if it contains two electrons.
• In the lac operon, the repressor will bind most strongly to the control region of the operon when the concentration of lactose within the cell is low.
• Cotransporters require energy in the form of favorable entropy from the movement of one molecule along its concentration gradient to function.
• When a G-protein becomes activated, there is an exchange of GDP for GTP which aids in the dissociation of the G-protein domains.
• For both, G-protein Coupled Receptors and Receptor Tyrosine Kinases, the N-terminus
• is typically located on/ in the extracellular side the whereas the C-terminus is typically located on/ in the intracellular side.

The Cell

• All of the following kingdoms are within the domain Eukarya except Archaea.
• Prokaryotic cells may contain some membrane-bound organelles, such as vesicles.
• Transcription factors are proteins that bind to the promoter regions of DNA to facilitate transcription of specific genes.

Signaling

• Autocrine signaling is common for cells in individual glands to require self-regulation as a means for maintaining intracellular homeostasis in the mammalian endocrine system.
• Ionotropic signaling mechanisms are faster than metabotropic signaling mechanisms.
• G-protein Coupled Receptor (GPCR) signaling cascades will result in a change in gene expression.
• All of the elements are considered to be essential for life on Earth, and are the most abundant elements in most living things, except Potassium.
• All of the following statements is/ are true about protein channels except C. Channel proteins are typically only selective for certain molecules based on the size of the channel pore.

Dialysis

• There was most likely a net movement of molecules into the dialysis tubing.

Isomers

• The image containing the "correct answer" (d.) depicts the trans geometric isomer of pentene.