AP Biology FRQ Predictions Study Guide

AP Biology Free Response Question (FRQ) Format

  • Time Allowed: 1 hour and 30 minutes
  • Total Questions: 6 Questions
      - Questions 1 & 2: Long free-response questions (25 minutes each)
      - Questions 3 to 6: Short free-response questions (10 minutes each)
  • Instructions:
      - Read each question carefully.
      - Answers must be in paragraph form (No outlines, bulleted lists, or diagrams).
      - Planning is allowed in the provided orange booklet (no credit for this material).
      - Credit is awarded only for responses in the Free Response booklet.

Question 1: GLP-1 Peptide Hormone Research

  1. Introduction to GLP-1:
       - GLP-1 is a modified peptide hormone that regulates blood glucose levels.
       - Mechanism: Binds to receptors on pancreatic cells and stimulates insulin secretion following food intake.
       - Problem: The naturally occurring GLP-1 is rapidly degraded by the enzyme Dipeptidyl Peptidase-4 (DPP-4), leading to a short half-life in the bloodstream.

  2. Role of DPP-4:
       - Definition: A hydrolytic enzyme that cleaves peptide bonds in proteins, inactivating hormones like GLP-1.
       - Activity Example: DPP-4 hydrolyzes GLP-1, thus reducing its levels and effects in the body.

  3. Synthetic Modification:
       - A synthetic analog of GLP-1 was developed by modifying the amino acid sequence at the DPP-4 recognition site.
       - Outcome:
         - Decreased cleavage by DPP-4.
         - Increased half-life in the bloodstream.
         - Prolonged binding to receptors, enhancing intracellular signaling and physiological response.

  4. Experimental Study:
       - Researchers cultured pancreatic β-cells and treated them with equal concentrations of GLP-1 and modified GLP-1 under elevated glucose conditions.
       - Measurement:
         - Intracellular cAMP concentration.
         - Insulin secretion over time is tracked.
       - Data Summary:
         - Concentration of cAMP and insulin in the presence of GLP-1 and modified GLP-1 over time intervals (0, 15, 30, 45, 60, 90, 120 minutes).

  5. Data Analysis Questions:
       - B. i. Independent Variable: Type of GLP-1 (naturally occurring vs. modified GLP-1).
       - B. ii. Justification for stopping at 120 minutes: To prevent confounding factors from longer-term exposure, ensuring clear and concise data collection related to initial spikes in signaling.
       - B. iii. Relationship: The higher the intracellular cAMP concentration, the greater the insulin secretion observed, which is attributable to enhanced receptor activation and signaling cascade by GLP-1.

  6. Second Experiment on Hormone Degradation:
       - C. i. Dependent Variable: Percentage of active hormone remaining after exposure to DPP-4.
       - C. ii. Identify the first time with noticeable differences in hormone degradation between GLP-1 and modified GLP-1.
       - C. iii. Importance of Constant DPP-4 Concentration: Ensures that any difference in hormone activity is due to variations in the hormone itself rather than fluctuations in enzyme concentration.

  7. Effect of Protein Phosphatases:
       - D. i. Predicted Effect: The addition of a protein phosphatase would likely decrease insulin secretion since it removes phosphate groups from proteins, leading to diminished activation of signaling pathways that promote secretion.
       - D. ii. Duration of Response: The addition of a phosphatase would shorten the duration of the cellular response to GLP-1, as dephosphorylation reverses the activation effects of phosphorylation in signaling.
       - Role of Phosphorylation/Dephosphorylation in Signal Transduction: Phosphorylation activates proteins, while dephosphorylation inactivates them; thus, this cycle regulates signaling intensity and duration.

Question 2: FOXP2 Gene and Speech Development

  1. Introduction to FOXP2:
       - FOXP2 is a gene associated with speech and language development; it encodes a transcription factor for multiple developmental genes.
       - Research Context: An investigation is presented concerning a family with a history of a speech disorder.

  2. Pedigree Analysis:
       - A. Mode of inheritance deduced from pedigree data. Likely autosomal dominant based on affected individuals distribution.

  3. Gene Expression Analysis:
       - Tissue was collected from unaffected and heterozygous (FOXP2+/m) family members. mRNA abundance for DCX and CNTNAP2 genes was measured using RT-PCR.
       - Data Summary:
         - Comparative expression values for DCX and CNTNAP2 are reported as mean ± 2SE.
         - DCX average reduced in affected group; CNTNAP2 expression is increased.

  4. Statistical and Graphical Representations:
       - B. i. Construct a bar graph based on the expression data provided.
       - B. ii. Independent Variable: FOXP2 genotype.
       - Relationship described between genotype and expression levels of DCX and CNTNAP2.
       - B. iii. Calculation of Percent Decrease: Percent decrease in DCX expression is derived from average differences between affected and unaffected groups:
          ext{Percent Decrease} = rac{1.00 - 0.58}{1.00} imes 100 = 42 ext{%}

  5. Haploinsufficiency Hypothesis:
       - C. i. Evidence Support: Evaluate pedigree and gene expression, showing functional copy insufficiency leads to disorders.
       - C. ii. Expression Increase: Decrease in FOXP2 can lead to upregulation of CNTNAP2 due to the compensation for reduced gene products.

  6. Mutational Impact Discussion:
       - D. Small Genetic Changes: Explain how minimal changes impact regulatory genes with large phenotype differences, considering developmental pathways and processes.

Question 3: Jack Pine Ecology

  1. Fire Adaptation:
       - Jack pine produces serotinous cones that require fire heat to release seeds. This adaptation promotes reproductive success in fire-prone environments.

  2. Population Dynamics:
       - (a) Describe how serotinous cones correlate with survival and establishment post-fire events.
       - (b) Explain how low fire frequency allows competitors to outcompete jack pine due to shaded resources, hindering their growth and establishment.
       - (c) Forests with high fire frequency lead to reduced diversity through uniformity in species at lower maturity levels.
       - (d) Justification for decreased diversity due to large biomass loss resulting from repeated fires, hindering regeneration specifics essential for variety.

Question 4: Aerobic Bacteria Research

  1. Glycolysis and Electron Transport in Aerobic Bacteria:
       - (a) Glycolysis: occurs in the cytoplasm; Electron transport: happens in the plasma membraneembedded proteins.
       - (b) Impact of Inhibition: An electron transport chain protein's inhibition halts proton pumping necessary for ATP synthesis leading to reduced ATP production.
       - (c) Endosymbiotic Theory Evidence: The structure of bacterial ETC is analogous to mitochondrial function suggesting evolutionary lineage.
       - (d) Efficient proton pump dynamics within the limited volume of the intermembrane space enhances ATP synthesis through the chemiosmotic gradient.

Question 5: Molecular Clock Analysis

  1. DNA Comparison Between Species:
       - Overview of using DNA sequences to estimate divergence times based on mutation rates.
       - (a) Calculate divergence time using non-coding region mutation rate leading to 12 nucleotide differences:
    extTime=122extmillionyears=6extmillionyearsext{Time} = \frac{12}{2} ext{million years} = 6 ext{million years}.
       - (b) Justify the use of non-coding regions as stable markers for evolutionary time estimates due to lower selective pressure compared to coding regions.
       - (c) Describe how strong selection on Region 2 diminishes reliability for measuring time due to adaptive mutations.
       - (d) Explain the utility of synonymous mutations for molecular clocks, providing stability in protein function across species divergence and time estimation reliability.

Question 6: Insulin Production in Bacteria

  1. Challenges in Gene Expression:
       - (a) Discuss why direct gene insertion from genomic DNA fails due to introns and bacterial machinery inability to process them.
       - (b) Reverse transcriptase synthesis of DNA from mRNA enables processing into a functional format for bacterial use, resulting in successful insulin production.
       - (c) Explain how muscle cells can harbor non-expressed genes due to regulatory mechanisms silencing transcription despite genomic presence.
       - (d) Discuss RNA processing including splicing and alternative splicing contributes to the vast array of possible protein outputs surpassing the number of genes within the genome.

 

  • End of Exam: Mark at the conclusion of presented questions and instructions for candidates to submit their responses accordingly.