AP Biology Midterm Review (2025) PDF

AP Biology Midterm Review (2025) 1.​ Compare passive transport (simple diffusion, facilitated diffusion, osmosis) with active transport. Discuss concentration gradients and give examples. 2.​ What is the function of proteins that are embedded into the cell membrane of cells? S...

AP Biology Midterm Review (2025) 1.​ Compare passive transport (simple diffusion, facilitated diffusion, osmosis) with active transport. Discuss concentration gradients and give examples. 2.​ What is the function of proteins that are embedded into the cell membrane of cells? Some can act as channel proteins, carrier proteins - for polar or charged molecules that cannot easily pass on their own. Glucose or ions need a protein to pass the phospholipid bilayer. 3.​ Explain what happens to red blood cells (normally contain.9% NaCl) when placed in the following solutions and provide an explanation for each: a)​ Hypotonic solution (100% distilled water): Water will diffuse into the cells. Water will move from a high to low concentration (to where there is more solute, less water). Cells will swell and burst. b)​ Isotonic solution (.9% NaCl): Water will diffuse in and out at an equal rate. Equal solute and water on each side. No net change in mass. Cells remain the same size. c)​ Hypertonic solution (90% water, 10% salt): Water will diffuse out of the cells; water moves from a high to low concentration (to where there is more solute, less water). Cells will shrink in size. 4. Use the following diagram to determine whether the concentration of the following molecules will remain the same, increase or decrease in the bag after 30 minutes. Amount of starch in the bag will _______remain the same______________________. Amount of glucose in the bag will _____decrease_______________________. Amount of iodine in the bag will _______increase_______________________. Amount of water in the bag will ________increase______________________. 5. A sweet potato was peeled and cut into 18 identical cubes. The initial mass was recorded. Three of each cube was soaked in a different sucrose solution overnight at a temperature of 25 degrees Celsius. The cubes were then removed and the final mass was recorded. The percent change in mass was calculated for each cube and the results are shown in the graph below.  a)​ Calculate the water potential (in bars) of the sweet potato at 25 degrees Celsius. Give your answer to one decimal place. Water Potential: 6. For each of the following organic compounds, list the elements they contain and describe the function of that organic compound. Choose from the following list of elements: Elements= Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur Organic compounds:  a)​ Carbohydrates= C,H,O b)​ Lipids= C,H,O c)​ Proteins= C,H,O,N,S d)​ Nucleic Acids= C,H,O,P,N 7. What process does the following diagram illustrate? Label the amino groups, carboxyl group and peptide bond. Dehydration Synthesis - removal of a water molecule to form covalent bonds. 2 amino acids (A and B) joining together to form a dipeptide (C). D represents water. Hydrolysis is the opposite process - addition of a water molecule to break covalent bonds. 8. Distinguish between the following: a)​ Primary Protein Structure: The sequence or order of amino acids in a polypeptide. Peptide bonds join amino acids. b)​ Secondary Protein Structure: Hydrogen bonding occurs between oxygen of a carboxyl group and hydrogen of an amino group. As a result of the hydrogen bonding, alpha helices and beta pleated sheets occur. c)​ Tertiary Protein Structure: R group interactions occur such as ionic bonds, hydrogen bonds, hydrophobic interactions (amino acids will orient away from water) and disulfide bridges. Proteins take on a 3D structure. d)​ Quaternary Protein Structure: Occurs when there are 2 or more polypeptide chains. 9. What is the name of this molecule? Phospholipid 10. What does the term amphipathic mean? Has hydrophobic & hydrophilic properties 11. How does this molecule interact with water? Hydrophilic head or polar head orients toward water; forms hydrogen bonds with water molecules and hydrophobic tails/nonpolar tails orient away from water 12. What are the two main components of the cell membrane? Lipids and Protein 13. Fill in the tables below that review the structure of function of various organelles found in eukaryotic cells. Organelle Structure Function RER Interconnected membranes; has Transport; protein ribosomes attached. synthesis Mitochondria Outer membrane; inner membrane Cellular respiration; ATP highly folded (cristae) production Lysosome Vesicle (sac) with digestive enzymes. Breakdown molecules;  waste materials with enzymes; cell lysis; break down old worn out organelles. SER Interconnected membranes; without Synthesis of lipids; ribosomes. detoxification of proteins. Chloroplasts 2 membranes; flattened sacs Site of photosynthesis (thylakoids) Golgi Bodies Series of flattened sacs Modification and packaging of molecules Vacuole Vesicle (sac) Water balance; water and nutrient storage. Function Prokaryotes Eukaryotes Stores genetic Circular Linear DNA information Cellulose Provides structure Peptidoglycan Chitin Cell Wall & support Synthesizes protein small large Ribosome 14. Membrane bound organelles. Which type of cells have them and why are they important in these types of cells? Eukaryotic cells have membrane bound organelles. Makes the cell more efficient in carrying out different chemical reactions. 15. Describe how the following structures work together: Rough ER, Golgi, Vesicle, and Cell Membrane. Protein is synthesized at the RER. Travels in a vesicle to the Golgi where processing occurs and then the vesicle travels to the cell membrane where exocytosis occurs and protein is secreted from the cell. Or the protein can be incorporated into the cell membrane. 16. Describe the endosymbiotic theory and the evidence that supports it. Theory that mitochondria and chloroplasts were once free living prokaryotic cells that were engulfed by a larger cell and evolved into the organelles they are today. Evidence: Both organelles have their own circular DNA like bacteria Both have small ribosomes like bacteria Both divide by binary fission like bacteria Both have a double membrane indicating they may have been a cell engulfed by another cell. 17. Surface area to volume ratios affect a biological system’s ability to obtain necessary resources or eliminate waste products. Data: Cube #1 SA/Vol Ratio=.4:1 Cube #2 SA/Vol Ratio=.8:1 Cube #3 SA/Vol Ratio=.73:1 Which cube would be most efficient in exchanging materials with the environment? Explain. Cube #2 would be most efficient. You want a high surface area to volume ratio. High SA/Vol ratio means more efficient. A high surface area to volume ratio is considered efficient because it allows for faster and more effective exchange of materials with the surrounding environment. Villi of the small intestine increase surface area for nutrient absorption. Root Hairs of roots increase surface area for water absorption Cristae (folds) of mitochondria increase surface area for cell respiration Alveoli (air sacs) of the lungs increase surface area for gas exchange of oxygen and carbon dioxide 18. Which organic macromolecule category does an enzyme belong to? Proteins that act as biological catalysts because they lower activation energy of a reaction. 19. How does temperature affect enzyme activity? High temperature denatures enzymes. This change in shape will not allow it to interact with its substrate and no reaction takes place. 20. What is the difference between competitive and noncompetitive inhibition? Competitive Inhibitors bind to the active site of the enzyme, preventing the substrate from binding. You can try to reverse this by increasing the concentration of substrate. Substrate will be more likely to bind to the active site and outcompetes the competitor. Noncompetitive inhibitors bind to the allosteric site and changes the shape of the active site. Substrate can no longer bind. Increasing substrate concentration will have no effect. 21. Explain why adding more substrate (with fixed enzyme concentration) will not increase the rate of enzyme activity. If you have 5 enzymes, they can only work at a maximum rate. Adding more substrate would not change this rate. 22. What is the difference between a catabolic process and an anabolic process? Catabolic process is the breakdown of substances while an anabolic process is the building of molecules. 23. Write the equation for photosynthesis: a)​ Which reactant is used for the light dependent reaction? Water b)​ Which reactant is used for the light independent reaction (Calvin Cycle)? Carbon dioxide  c)​ Which product is produced in the light reaction? Oxygen d)​ Which product is produced in the light independent reaction (Calvin Cycle)? Glucose *** Light reactions occur within the thylakoid membrane of the chloroplast. Calvin Cycle occurs within stroma of chloroplast. 24. Describe the role of water in photosynthesis. The splitting of water helps to replenish or donate electrons to the electron transport chain. Adds protons to contribute to the proton gradient. Proton gradient is important to generate ATP (Chemiosmosis). Splitting of water also produces oxygen. 25. How is the Calvin cycle dependent on the light reaction? Products of the light reaction - ATP and NADPH are used in the Calvin cycle, along with carbon dioxide to produce glucose. 26. Write the formula for cellular respiration. 27. Chemiosmosis in mitochondria and chloroplasts is using a proton gradient to generate ______ATP___. 28) Read the paragraph describing an event in cell respiration. Fill in the blanks: ​ As electrons move down the electron transport chain, they provide energy to pump ___protons_____________ from the matrix to the ___intermembrane_________________ space of the mitochondria (this is active transport). At the end of the electron transport chain, ___________oxygen______ acts as the final electron acceptor. As a result, ____water_________ is produced. Protons re-enter the matrix. As they diffuse down the gradient through ATP Synthase, they provide the energy that is needed to convert ADP to ___ATP______. The inner mitochondrial membrane allows for the establishment of a proton gradient. The electron transport chain is located there as well as ATP synthase. It separates the matrix from the intermembrane space. 29) Place the following steps of aerobic respiration in order. Write the main purpose of each step and where that step occurs in the mitochondria. ​ Oxidative Phosphorylation (ETC & Chemiosmosis)-produces water, ATP ​ Glycolysis - produces pyruvate, NADH, ATP ​ Krebs Cycle (Citric Acid Cycle)-produces NADH, FADH2, ATP, carbon dioxide ​ Oxidation of pyruvate - produces acetyl Co-A, carbon dioxide, NADH Glycolysis → Oxidation of Pyruvate → Kreb’s Cycle → Oxidative phosphorylation 30) Which step in cellular respiration occurs when both oxygen is present and absent in the cell? Glycolysis 31) Why must fermentation occur in anaerobic organisms? To regenerate NAD+ so that glycolysis can continue. 32) What are some properties of water that make it such an important compound in all living things? Water is a polar molecule - electrons are not shared equally. Oxygen has a slight negative charge and hydrogen has a slight positive charge. Hydrogen bonding is responsible for water bonding to other water molecules. Within a water molecule are polar covalent bonds. Examples of Properties: Cohesion: water molecules bonding to other water molecules Adhesion: water molecules bonding to other polar or charged molecules High Specific Heat Excellent Solvent High Surface Tension Solid Water is less dense than liquid water 33) The effect of fertilizer was investigated on the height of plants. You had 3 group set ups, 20 pots for each set up with an equal number of seeds planted in each pot. After one generation, the average height of the plants for each set up was calculated. The first group received 0% fertilizer, the second group received.2% fertilizer and the third group received.4% fertilizer. The data is shown below:  Group Mean Height (cm) Standard Error of the Mean (SEM) I 8.8 1.3 II 13 1.5 III 20 1.5 a)​ State the null hypothesis. There is no statistical difference between the means of the samples. b)​ State the control group. State the experimental group(s). Control - received 0% fertilizer; Experimental - received.2% and.4% fertilizer c)​ On the axes provided, create a graph to illustrate the means of the 3 groups. Label axes and create an appropriate scale with units. Include error bars for each group using the formula: mean∓2*SEM  d)​ Based on your calculations, identify the group that is the most likely to have a statistically significant difference in the mean height compared to the other groups. Justify your answer. Group 3. Error bars do not overlap. There is a statistical difference between Group 3 and the other groups..4 % fertilizer has an effect on plant height. e)​ Identify the independent and dependent variables for this experiment. Fertilizer concentration - IV Plant Height - DV f)​ How can we improve the reliability of this experiment? Increase the number of plants, use more concentrations, repeat experiment 34. A wildlife conservation organization is monitoring the distribution of four different species of birds in a national park. Based on previous studies, the expected distribution of the bird species in the park is as follows: ​ Species A: 40% ​ Species B: 30% ​ Species C: 20% ​ Species D: 10% In a recent survey, a sample of 500 birds was observed, and the actual number of birds for each species was counted as: ​ Species A: 210 birds ​ Species B: 140 birds ​ Species C: 90 birds ​ Species D: 60 birds Using a significance level of 0.05, perform a Chi-Square test to determine if the actual distribution of the bird species significantly differs from the expected distribution. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ X2= ______________ a)​ State the null hypothesis. There is no statistical difference between the observed and expected values. b)​ Do you accept or reject the null hypothesis? Justify your answer. ___ Our chi square value is less than the critical value. We accept the null hypothesis. There is no statistical difference between the observed and expected values. Structure of DNA: 1.​ What are the three components of a nucleotide? Sugar, phosphate (negatively charged) and a nitrogenous base 2.​ What are the names of the bonds that hold  ​ hold together the nitrogenous bases? Hydrogen bonds 3.​ What is the name of the bonds that hold together the phosphates and sugars in this model? Phosphodiester bonds 4.​ How does DNA differ from RNA? DNA - A,T,C,G​ ​ RNA - A,U,C,G Double Stranded​ ​ Single Stranded Deoxyribose​ ​ ​ Ribose Antiparallel strands Purines: adenine, guanine (double ring nitrogenous bases) Pyrimidines: cytosine, thymine and uracil (single ring nitrogenous bases) DNA Replication: 1.​ Name the enzymes involved in this process, and describe their function. Helicase - unwinds and unzips DNA Topoisomerase - prevents supercoiling of DNA DNA Polymerase - builds DNA Ligase - binds together the Okazaki fragments 2.​ Describe how the new strands of DNA are made during this process. The leading strand is continuous built in the 5’ to 3’ direction. The lagging strand is discontinuous built in the 5’ to 3’ direction but in fragments and ligase will be needed. Transcription: 1.​ What is transcription? What enzyme is involved? Base pairing rules? Direction? DNA nucleotide sequence is transcribed to the mRNA nucleotide sequence. SInce DNA is built in the 5 to 3’ direction , it uses the 3’ to 5’ template strand of DNA. RNA polymerase builds mRNA. DNA​ RNA A U C​ G G​ C T​ A mRNA is produced in the nucleus and travels to a ribosome attached to the RER or free ribosome both of which are found in the cytoplasm of the cell. 2) Describe the differences between prokaryotic and eukaryotic transcription. Prokaryotes: transcription occurs in cytoplasm; no RNA processing occurs Eukaryotes: transcription occurs in nucleus; RNA processing occurs in the nucleus; pre-MRNA contains introns and exons before exiting nucleus as mature mRNA with only exons 3) Use the following 2 diagrams to describe the process of RNA processing. A 5’cap and poly A tail is added to the pre-mRNA before the removal of introns. Pre-mRNA is processed to form mature mRNA. Introns are removed and exons are spliced together. A spliceosome is considered a ribonucleoprotein enzyme that catalyzes the removal of introns from pre-mRNA. Translation: DNA: 3’ TAC CGG ATA GCG GAA ACT 5’ mRNA 5’ AUG GCC UAU CGC CUU UGA 3’ AA: Met - Ala- Tyr- Arg- Leu- (Stop) (Start Codon) The amino acid sequence is based on the mRNA sequence. Every 3 bases of mRNA, known as a codon, can be looked up in the codon 89ikchart to see what amino acid they code for.