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Topics Most Likely to Show Up on 2020 AP Biology Exam

The AP Biology exam is coming up in just a few weeks and at this point, hopefully you are doing some practice FRQs every week to prepare. As you work through the past years’ FRQs, you may have noticed that certain topics show up more often than others.

This is a list of the topics and associated processes and vocabulary that are most likely to show up on the 2020 AP Biology exam. It is important that you feel comfortable with all of the material covered (Ch 1 through 22 in the Campbell & Reece AP Biology textbook), but also make sure you know the topics below extra well.

Commonly Tested AP Biology Topics

Cellular Respiration:

  • The sequence of steps in cellular respiration: glycolysis → pyruvate conversion to acetyl-CoA → Krebs Cycle → Electron transport chain and ATP synthesis

  • The location of each step. Definitely know that all of the steps above occur in the mitochondria except glycolysis. Glycolysis occurs in the cytoplasm

  • What important role does oxygen play? What happens if oxygen is not present? Oxygen is the final electron acceptor in the electron transport chain. If oxygen is not present, cellular respiration cannot occur and the cell switches to anaerobic respiration (fermentation)

  • The inputs and outputs of each step. The diagram below will help you refresh that:

  • What would happen to the pathway or the outputs if one of the enzymes were damaged? For instance, which steps would be affected if pyruvate dehydrogenase complex (PDC) were damaged? What would happen to the ATP outputs if the proton pumps in the electron transport chain were nonfunctional? Questions like these are common on the exam


  • The sequence of steps in photosynthesis: light reactions → Calvin cycle

  • Where each step occurs. The light reactions occur in the thylakoid membranes and the Calvin cycle occurs in the stroma. Both are inside the chloroplast.

  • What important role does water play? It acts as the electron donor in the light reactions.

  • At what step does carbon fixation occur, and which enzyme catalyzes the first step? Carbon fixation occurs in the Calvin cycle and rubisco catalyzes the first step in the cycle

Protein Synthesis

  • The sequence of steps in the process: transcription → mRNA preprocessing → translation This short video clearly shows each step

  • Where each step occurs. In prokaryotes, both transcription and translation occur in the cytoplasm since they don’t have a nucleus. In eukaryotes, transcription and mRNA preprocessing occur in the nucleus. Translation occurs in the cytoplasm

  • The roles of tRNA, ribosomes, and mRNA in protein synthesis.

  • The differences between the DNA template strand, RNA transcript (before preprocessing), and mRNA. The RNA transcript has both introns and exons. The introns do not code for any products so they are spliced out, resulting in a much shorter mRNA strand


  • How to construct Punnett squares and use them to calculate probabilities of getting a certain genotype or phenotype. These short videos explain how to do this

  • How to read and interpret pedigrees. Each shape represents an individual. If the shape is shaded in, the individual has the condition or phenotype of interest. The purpose of pedigrees is to use family history to predict the probability of an individual having a particular phenotype or condition of interest. Below is an example of a pedigree:

Gene Expression

  • How is prokaryotic gene expression different from eukaryotic gene expression?

  • What ways are there to increase or decrease the expression of certain genes? Histone acetylation can increase expression, while DNA methylation can decrease expression. Alternative RNA splicing can also change which genes are expressed

Running Experiments

  • This isn’t a chapter from the Campbell textbook, but it is a very important topic and is almost guaranteed to show up on the exam

  • What is a control and what is its purpose? What should be the same between the control and the experimental groups? A control is included as a baseline. All factors should be exactly the same between the control and the experimental groups except the factor of interest.

  • How to run and interpret Chi-square tests for experiment results. Refer to this article for a step-by-step outline on this

  • Understand the experiment itself. The purpose of an experiment will vary greatly from question to question. It is important to identify what the experiment is trying to test or find out. Is it the influence of sunlight on plant growth? Is it the impact of an additional nutrient in the petri dish on bacteria growth? Is it how the density of bacteria in a petri dish affects their population growth?

If there are any particular topics you would like a detailed explanation on, please comment below and I will put something together.

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