AP Biology Difficult Topic Review

Some of the hardest AP bio topics and questions.

What is the ligand of a GPCR?

It could be a wide variety of things; hormones, steroids, pheromones, etc.

What happens to the alpha subunit once the receptor is activated in a GPCR?

It stops holding GDP and starts holding GTP. Then, it breaks away from the beta-gamma dimer.

What is the end result of one cell undergoing meiosis?

4 haploid gametes

What is the end result of one cell undergoing mitosis?

2 diploid daughter cells

What is the difference between the alignment of genetic material in mitosis metaphase vs. meiosis metaphase 1?

In mitosis metaphase, chromosomes align individually at the cell's equatorial plane, while in meiosis metaphase 1, homologous chromosome pairs align together side by side.

What is the difference between mitosis and meiosis prophase?

Mitosis prophase involves the condensation of chromatin into individual chromosomes, with the spindle apparatus beginning to form. In contrast, meiosis prophase I includes homologous chromosomes pairing up to form tetrads and crossing over may occur, increasing genetic diversity.

What happens to the nucleus in mitosis and meiosis?

The nucleus breaks and reappears. The nucleus breaks because it stops the spindles from attaching from either end and eventually pulling the chromatids apart.

Saturated vs unsaturated lipid

Saturated lipids contain no double bonds between carbon atoms, making them solid at room temperature, while unsaturated lipids have one or more double bonds, resulting in a liquid state at room temperature. Unsaturated lipids pack together less tightly than saturated lipids.

How do nitrogenous bases bond with each other? hydrogen or covalent bond?

Nitrogenous bases bond to each other with hydrogen bonds, and bond to their backbone with covalent bonds.

In which direction does RNA polymerase work?

RNA polymerase synthesizes RNA in the 5' to 3' direction, adding nucleotides to the growing strand.

In what form is genetic material during interphase?

Genetic material is in the form of chromatin during interphase, which is less condensed than chromosomes, allowing for transcription and replication.

Law of Segregation

States that during the formation of gametes, the two alleles for a trait separate from each other so that each gamete carries only one allele for each gene.

Law of Independent Assortment

States that the alleles for different traits are distributed to gametes independently of one another during meiosis, leading to genetic variation.

Law of Dominance

States that when two different alleles for a trait are present, one allele can mask the expression of the other, leading to a dominant phenotype.

Lamarck’s Theory

Posits that organisms can pass on traits acquired during their lifetime to their offspring, suggesting evolution occurs through adaptation to the environment.

Bottleneck Effect

A genetic phenomenon in which a population's size is significantly reduced for at least one generation, resulting in a loss of genetic diversity and alteration of allele frequencies.

Founder Effect

A genetic phenomenon that occurs when a small group of individuals establishes a new population, leading to a reduction in genetic diversity and different allele frequencies compared to the original population.

Heterozygous Advantage, and why does it occur?

A situation where individuals with two different alleles for a given gene (heterozygotes) have a higher fitness than those with two identical alleles (homozygotes). This phenomenon often occurs in environments where heterozygotes can better tolerate stressors such as disease or environmental changes. This advantage can maintain genetic diversity within a population, as seen in cases like sickle cell anemia resistance to malaria.

Allopatric vs sympatric speciation

Allopatric speciation occurs when populations are geographically isolated, leading to reproductive isolation and divergence, while sympatric speciation occurs without geographic barriers, often through mechanisms like polyploidy or behavioral differences.

What kind of animal has a higher mass-specific metabolic rate? Small or large?

Small

Why do smaller animals have a higher metabolic rate?

Smaller animals have a higher metabolic rate because they lose heat more quickly due to their larger surface area-to-volume ratio, necessitating a faster metabolism to maintain body temperature and support their energy needs.

How does UV damage DNA?

It causes unauthorized bonds (pyramidine dimers) between adjacent thymines, causing “lesions"/bumps in the DNA sequence. Cancer forms when something goes wrong in the process of fixing it.

What is a polypeptide?

Sequence/chain of amino acids.

What molecules can undergo diffusion (passive transport)?

Small, nonpolar molecules (O2, CO2, etc.) and lipids (steroids/fats)

What is a thylakoid membrane and what is its purpose?

The thylakoid membrane is a membrane-bound structure within chloroplasts containing chlorophyll. Its primary purpose is to conduct the light-dependent reactions of photosynthesis, converting solar energy into chemical energy.

What is hydrolysis?

A chemical reaction that involves the breakdown of a compound by reaction with water, often resulting in the release of energy. Water is added to cleave bonds within the compound.

What is dehydration synthesis?

A chemical reaction that involves the joining of two molecules by removing a water molecule, thus forming a covalent bond and typically resulting in the storage of energy.

Dehydration Synthesis vs Hydrolysis

Dehydration synthesis is the process of joining two molecules by removing water, while hydrolysis is the breakdown of a compound with the addition of water.

How do signaling cascades amplify signals?

One signaling molecule can activate many other signaling molecules in the next step.

Why can’t eukaryotic genes be expressed in prokaryotic organisms?

Eukaryotic genes have introns, and only eukaryotic organisms can remove those introns. Prokaryotic DNA does not have introns, and so they cannot remove introns from DNA.

What are the benefits of compartmentalization?

1. Allows for different environments inside/outside organelles

2. Increases internal surface area, useful for things like the rough ER/ribosomes.

What is osmolarity?

How “crowded” a solution is with dissolved particles (solutes).

Hypertonic vs hypotonic

Hypertonic is a solution with a higher concentration of solutes compared to another solution, while hypotonic is a solution with a lower concentration of solutes.

Input/output of the Calvin Cycle

Input: CO2, ATP, NADPH
Output: ADP, NADP+, G3P (sugar)

Input/output of the Krebs Cycle

Input: Acetyl-CoA (from link reaction, pyruvate to Acetyl-CoA)

Output: ATP, NADH, FADH2, CO2

Input/output of glycolysis

Input: Glucose

Output: ATP, NADH, pyruvate

What is the difference between guanine-cytosine bonds and adenine-thymine bonds?

G-C bonds have 3 hydrogen bonds, A-T bonds have 2 hydrogen bonds.

What is oxygen’s role in cellular respiration?

It is the final electron acceptor, in oxidative phosporylation.

Key similarities between prokaryotes and eukaryotes

1. Both have RNA

2. Both have ribosomes

NADH vs FADH2 contribution to ETC

NADH electrons travel through 4 complexes, FADH2 electrons travel through 3 complexes.