AP Biology Review May 2025

Dehydration

connecting monomers together by the removal of water

Hydrolysis

disassembling polymers by the addition of water

Disaccharides

glucose + glucose = maltose / glucose + fructose = sucrose / glucose + galactose = lactose

Polysaccharides

Plants: starch (energy) and cellulose (structure)

Animals: glycogen (energy) and chitin (structure)

*Lipids

hydrophobic (very non-polar), consist of long hydrocarbon chains

Fats

consist of glycerol and 3 fatty acids, store long term energy, saturated = no double bond in hydrocarbon tails (no kink), unsaturated = double bond (kink)

Phospholipids

consist of phosphate head, glycerol, and 2 fatty acid tails, tail is hydrophobic, head is hydrophillic

Protein structure and organization

composed of an amino group, a carboxyl group, hydrogen, and an R group, joined by peptide bonds and folded numerous times; 1) Primary (linear sequence) 2) Secondary (helix or pleat) 3) Tertiary 4) Quaternary (globular)

Protein functions (8)

1) enzymes 2) antibodies 3) storage proteins 4) transport proteins 5) hormones 6) receptor proteins 7) motor proteins 8) structural proteins

*Nucleic Acids

DNA (A+T, G+C) carries genetic info, RNA (A+U, G+C) manufactures proteins

Nuclear Envelope

double membrane enclosing the nucleus (where genetic info is stored) perforated with pores, continuous with ER

Chromatin

uncondensed DNA that forms chromosomes during cell division

Nucleolus

nonmembranous structure involved in production of ribosomes, a nucleus has one or more of these

Rough ER

covered in ribosomes, secretes and transports proteins produced by ribosomes

Smooth ER

metabollic processes (synthesis of lipids, metabolism of carbs, detoxification of drugs and poisons)

Golgi

stores, transports, and secretes cell products

Cytoskeleton

supports cell, maintains its shape, aids in movement of cell products

Centrosomes (2 centrioles)

only in animal cells, microtubules used for cell division

Lysosomes

only in animal cells, digestive organelles

Flagella

only in animal cells, cluster of microtubules for motility

Extracellular Matrix

only in animal cells, made of proteins that provide support for cells and relay information for communication between the environment and the cell

Central Vacuole

only in plant cells, stores water and sugar, breaks down waste, and used as a mechanism for plant growth (when it swells)

Prokaryotic vs. Eukaryotic

nucleoid / nucleus; only ribosomes / complex membrane-bound organelles; both have same genetic coding, sugars, and amino acids

Phospholipid Bilayer

tails of phospholipids are loosely packed and are in constant motion; membrane contains integral and peripheral proteins, cholestrol, and glycopreotins and glycolipids; cholesterol makes the membrane less permeable to water and other substances; non-polar and small polar molecules can pass through unadied

Passive trasport

movement of molecules without requirement of energy: 1) diffusion 2) osmosis (across a membrane) 3) facilitated diffusion (helped by transport proteins)

Active transport

movement of molecules that requires energy: 1) sodium-potassium pumps 2) exocytosis 3) endocytosis (phagocytosis, pinocytosis)

Membrane Potential

voltage across a membrane due to difference in positive and negative ions, electrons move from high to low concentration (ex. sodium-potassium pumps in neurons)

Electrochemical Gradient

diffusion gradient resulting in combination of membrane potential and concentration gradient

Hypertonic

solution with higher concentration of solutes, animal/plant cell in this solution would become shiveled/plasmolyzed

Hypotonic

solution with lower concentration of solutes, animal/plant cell in this solution would lyse/become turgid

Isotonic

equal levels of solute concentration, plant cell in this solution would become flaccid

When ΔG is negative...

...the reaction is exergonic (loss of free energy).

When ΔG is positive...

...the reaction is endergonic (gain of free energy).

*Enzymes

proteins that are biological catalysts, lower the activation energy required to start a chemical reaction (reactants at unstable transition state) can be used over and over

Substrate

the substance that an enzyme acts upon

Active Site

region of enzyme that binds to the substrate

Induced fit

change in the shape of an enzyme's active site induced by the substrate, helps to break down the substrate

The higher the substrate concentration...

...the faster the reaction until the enzyme becomes saturated.

Denaturation

the unraveling of an enzyme due to high temperatures or incompatible pH

Cofactors

nonprotein molecules that are required for proper enzyme function, cofactors made of organic molecules are called coenzymes

Enzyme inhibition may be irreversible if...

...the inhibitor attaches by covalent bonds (poisons, toxins)

Competitive Inhibitors

resemble a substrate and block enzymes' active sites, can be overcome with higher concentration of substrate

Noncompetitive Inhibitors

bind to a portion of the enzyme and change the shape of the active site so that it cannot match with substrates, used for regulating metabolic reactions

Feedback Inhibition

the product of a metabolic pathway switches off the enzyme that created it earlier in the process

Oxidation

loss of electrons (OIL)

Reduction

gain of electrons (RIG)

Oxidative Phosphorylation

ATP synthesis powered by redox reactions that transfer electrons to oxygen

Electron Acceptors

Cellular respiration: NAD+ and FAD (to NADH and FADH2)

Photosynthesis: NADP+ (to NADPH)

Glycolysis

Input: glucose, 2 ATP

Output: 2 pyruvic acid, 4 ATP (net 2), 2 NADH

Conversion Reaction before Kreb's

Input: 2 pyruvate

Output: 2 acetyl (w/ CoA), 2 NADH, 2 CO2

Krebs Cycle

Input: 2 acetyl ➝ citric acid

Output: 2 ATP, 6 NADH, 2 FADH2, 4 CO2 (after 2 turns of the cycle)

Electron Transport Chain

Input: NADH, FADH2, O2 (to accept e-)

Output: 34-38 ATP, H2O

Alcohol Fermentation

Input: glucose, 2 ATP, 2 NADH

Output: 2 NAD+, 2 ethanol, 2 CO2, 4 ATP (net 2)

Lactic Acid Fermentation

Input: glucose, 2 ATP, 2 NADH

Output: 2 NAD+, 2 lactate, 4 ATP (net 2)

Photosynthetic Equation

Chloroplast structure

Exciting chlorophyll: chlorophyll in thylakoids absorb light, which excites electrons to produce potential energy

Light Reactions

Input: H2O (2 e-), light energy, NADP+

Output: O2, ATP, NADPH

Calvin Cycle

Input: 6 CO2 (fixed to RuBP by Rubisco), ATP, NADPH

Output: 2 G3P = 1 glucose

Watson and Crick

built the first accurate 3D DNA model

Leading Strand vs. Lagging Strand

works toward replication fork / works away from replication fork; both always move in the 5' ➝ 3' direction

Steps of DNA Replication

1) helicase separates the DNA strands 2) SSB proteins prevent DNA from reanneling 3) primase creates RNA primer 4) DNA polymerase extends DNA strand from the primer 5) DNA polymerase I (RNase H) removes the primers 6) ligase joins the okazaki fragments of the lagging strand

3 types of RNA

1) mRNA messenger 2) tRNA transfer amino acids (20 kinds) 3) rRNA ribosomes

Transcription

1) Initiation: promoter site (TATA) is recognized 2) Elongation: RNA polymerase adds ribonucleotides in the 5' ➝ 3' direction 3) Termination: RNA strand separates, RNA polymerase recognizes termination sequence (AAUAAA)

RNA processing/splicing

splicesomes remove introns and put together exons, 5' cap and PolyA tail are added

Codon vs. Anticodon

codon = nucleotide sequence on mRNA

anticodon = nucleotide sequence on tRNA

Translation

1) Initiation: 5' cap attaches to ribosome which accepts an initiator tRNA at the P site (*AUG will always be 1st codon) 2) Elongation: codon/anticodon recognition and formation of peptide bond between A site amino acid and P site amino acid chain 3) translocation of the ribosome down the mRNA strand 4) Termination: ribosome will recognize stop codon and release the protein

DNA mutations

base-pair substitution; insertion/deletion; frameshift: 1) missense = different protein 2) nonsense = codes for a stop signal prematurely 3) silent = no harmful change

Prokaryotic cell division

binary fission: splits in 2, exact copies, quick and efficient with few mutations, but reduces amount of genetic variation

Somatic cell vs. Gamete

any body cell except gametes / reproductive cells (sperm, egg)

Interphase

(90% of cell's life) G1: 1st growth, normal metabolic activity (goes into G0 phase if it is not ready for next phase); S: synthesis, DNA replication; G2: 2nd growth, prepares for mitosis

Mitosis

1) Prophase: chromatin condenses into chromosomes, nucleus disappears 2) Metaphase: chromosomes line up at equator, kinetechore microtubules attach 3) Anaphase: sister chromatids move to opposite poles of the cell 4) Telophase and Cytokinesis: daughter cells separate, nucleus reforms, chromosomes decondense

Cyclin-dependent Kinases (Cdks)

a regulatory protein that depends upon the presence of cyclin to complete its function, MPF is a Cdk that triggers a cell's passage into the M phase

Meiosis I

1) Prophase I: homologous chromosomes pair up and synapsis occurs, crossing over segments of the chromosomes (chiasma) to create more genetic variation 2) Metaphase I: homologous chromosomes line up at the equator 3) Anaphase: homologous chromosomes move to opposite poles of the cell. 4) Telophase I...

Meiosis II

Prophase II - Telophase II act exactly like mitosis except that the resultant number of daughter cells is 4 instead of 2, each with their own unique combination of genetic information

4 mechanisms that contribute to genetic variation

1) Mutation 2) Independent Assortment: homologous chromosomes align randomly on one side of the equator or another 3) Crossing Over 4) Random Fertilization: a zygote can be any combination of a sperm and egg (64 trillion different combinations in humans)

Testcross

breed a homozygous recessive individual with an individual with a dominant phenotype but an unknown genotype to determine whether or not the individual is homozygous or heterozygous

Incomplete Dominance

heterozygous offspring have an intermediate phenotype of the parents, 1:2:1 ratio (ex. pink flower from red and white flowers)

Codominance

both alleles manifest themselves separately in an organism's phenotype (ex. roan cattle)

Multiple alleles

a trait controlled by two or more alleles (ex. blood type, eye color)

Blood Types

A: A antigen, B antibody

B: B antigen, A antibody

AB: A and B antigen, no antibodies (universal recipient)

O: no antigens, A and B antibodies (universal donor)

Linked genes phenotypic ratio

two large numbers (wild and mutant) and two much smaller numbers (recombinant phenotypes)

Genetic Map (Linkage/Cytological Map)

ordered list of the genetic loci along a particular chromosome, recombinant frequencies can be used to construct it (smaller the percentage = closer together)

X Inactivation

in females during embryonic development, one of the two X chromosomes in a cell becomes inactive (Barr body) (ex. calico cats)

3 stages in cell communication

1) Reception: cell detects a signal via connection of a ligand to a receptor protein 2) Transduction: the receptor protein converts the signal to a form that can cause a chemical response 3) Response: transduced signal triggers a specific cellular response

Types of cell signaling (3)

synaptic, paracrine, hormonal

Examples of cell signaling

G-protein coupled receptor, ligand-gated ion channels, steroid hormones (dissolved across plasma membrane, intracellular receptor)

Second Messengers and Phosphorylation cascade

second messengers and kinases spread throughout a cell that help amplify a cellular signal by a series of phosphorylation reactions (addition of phosphate)

Evidence for Evolution

1) Biogeography 2) Fossil Record 3) Comparative Anatomy 4) Comparative Embryology 5) Molecular Biology

4 conditions for Hardy-Weinberg Equilibrium (not evolving)

1) very large population 2) isolation from other populations 3) no mutations 4) no natural selection

Microevolution vs. Macroevolution

change in the gene pool of a population over several generations / large scale changes in a population that leads to the evolution of a new species

4 causes of Microevolution

1) genetic drift 2) gene flow 4) natural selection

Genetic Drift

random change in gene frequency of a small breeding population: 1) Founder Effect = small population of organisms colonizes a new area, 2) Bottleneck Effect = sudden decrease in population size due to disaster

Gene Flow

loss/addition of alleles from a population due to imigration/emigration

Nonrandom Mating

selection of mates for specific phenotypes: 1) Assortative Mating = when individuals select partners with simple phenotypic characters, 2) Inbreeding = more recessive traits likely to come together

3 Modes of Natural Selection

1) Stabilizing: favors intermediate, 2) Directional: favors one extreme phenotype, 3) Diversifying: favors both extremes

Heterozygote Advantage

heterozygotes for a trait are more likely to survive (ex. carriers of sickle cell anemia are immune to malaria)

Biological Species Concept

population whose members can create viable, fertile offspring (Problems: doesn't apply to extinct animals or asexually reproducing organisms)

Prezygotic Reproductive Barriers

1) Habitat Isolation 2) Behavioral Isolation (differing behaviors for attracting mates) 3) Temporal Isolation (mate at different times) 4) Mechanical Isolation 5) Gametic Isolation (unable to fertilize egg)

Postzygotic Reproductive Barriers

1) Reduced Hybrid Viability (disruption in embryonic stage) 2) Reduced Hybrid Fertility 3) Hybrid Breakdown (F1 is fertile, F2 is sterile or weak)

Allopatric Speciation

when populations become geographically isolated from the rest of the species and has the potential to develop a new species (ex. Adaptive Radiation: many diversely adapted species from common ancestor, Darwin's finches)