AP Biology Notes CRAMMMMM

Unit 1: Chemistry of Life

Atom: The smallest unit of matter that retains the chemical properties of an element. It consists of a nucleus containing protons and neutrons, surrounded by electrons.
Element: A substance consisting of only one type of atom, characterized by a specific number of protons. Elements cannot be broken down into simpler substances by chemical means.
Compound: A substance formed when two or more elements are chemically bonded together in a fixed ratio. Compounds have properties different from those of their constituent elements.
Covalent Bond: A chemical bond that involves the sharing of electron pairs between atoms. Covalent bonds are strong and common in organic molecules.
Ionic Bond: A chemical bond formed through the transfer of electrons from one atom to another, resulting in the formation of ions (charged particles) that are electrostatically attracted to each other.
Hydrogen Bond: A relatively weak bond formed between a hydrogen atom with a partial positive charge and an electronegative atom (such as oxygen or nitrogen) with a partial negative charge. Important in water and biological molecules.
Polar Molecule: A molecule with an uneven distribution of electrical charge, resulting in regions of partial positive and partial negative charge. Water is a classic example.
Nonpolar Molecule: A molecule with an even distribution of electrical charge, meaning there are no significant regions of positive or negative charge. Lipids like oils are nonpolar.
Cohesion: The attraction between molecules of the same substance. Water's cohesion is due to hydrogen bonds, contributing to surface tension.
Adhesion: The attraction between molecules of different substances. Water's adhesion to surfaces helps in capillary action.
Solvent: A substance that dissolves another substance, known as the solute, to form a solution. Water is a versatile solvent due to its polarity.
Solute: A substance that is dissolved in a solvent. Examples include salt or sugar when dissolved in water.
Solution: A homogeneous mixture of a solute dissolved in a solvent. The components are evenly distributed throughout.
pH: A measure of the hydrogen ion concentration in a solution, indicating its acidity or alkalinity. It ranges from 0 to 14, with 7 being neutral, below 7 acidic, and above 7 alkaline.
Buffer: A substance that minimizes changes in pH by absorbing or releasing hydrogen ions, helping to maintain a stable pH in solutions.
Macromolecule: A large, complex molecule, such as proteins, nucleic acids, carbohydrates, and lipids, which are essential for life processes.
Monomer: A small, repeating unit that can join with other monomers to form polymers. Examples include amino acids (for proteins) and nucleotides (for nucleic acids).
Polymer: A large molecule made up of many monomers bonded together. Proteins, nucleic acids, and polysaccharides are polymers.
Carbohydrate: An organic compound composed of carbon, hydrogen, and oxygen, typically in a ratio of 1:2:1. Carbohydrates serve as energy sources and structural components in organisms.
Lipid: A hydrophobic organic molecule composed mainly of carbon and hydrogen atoms. Lipids include fats, oils, phospholipids, and steroids, serving various roles in energy storage, insulation, and cell structure.
Protein: A macromolecule composed of amino acids linked together by peptide bonds. Proteins perform a wide range of functions, including catalyzing reactions, transporting molecules, and providing structural support.
Nucleic Acid: A macromolecule composed of nucleotide monomers. There are two types: DNA (deoxyribonucleic acid), which carries genetic information, and RNA (ribonucleic acid), which is involved in protein synthesis.

Unit 2: Cell Structure and Function

Prokaryote: A type of cell that lacks a nucleus and other membrane-bound organelles. Bacteria and Archaea are prokaryotes. Their DNA is typically found in a nucleoid region.
Eukaryote: A type of cell that has a nucleus and other membrane-bound organelles, such as mitochondria and endoplasmic reticulum. Eukaryotic cells are found in plants, animals, fungi, and protists.
Organelle: A specialized subunit within a cell that has a specific function, such as the mitochondria for energy production or the nucleus for storing genetic information.
Nucleus: The central organelle in eukaryotic cells that contains the cell's DNA, organized into chromosomes. It controls the cell's growth, metabolism, and reproduction.
Ribosome: A cellular structure responsible for protein synthesis. Ribosomes are found in both prokaryotic and eukaryotic cells and can be free in the cytoplasm or bound to the endoplasmic reticulum.
Endoplasmic Reticulum (ER): An extensive network of membranes in eukaryotic cells that is involved in the synthesis, modification, and transport of proteins and lipids. The rough ER has ribosomes attached, while the smooth ER does not.
Golgi Apparatus: An organelle in eukaryotic cells that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles. It consists of flattened sacs called cisternae.
Mitochondria: The "powerhouse" of the cell; an organelle in eukaryotic cells where cellular respiration occurs, producing ATP (adenosine triphosphate), the cell's main energy currency.
Chloroplast: An organelle found in plant cells and algae where photosynthesis occurs. Chloroplasts contain chlorophyll, which captures light energy to convert carbon dioxide and water into glucose.
Plasma Membrane: The outer boundary of a cell that controls the entry and exit of substances. It is composed of a phospholipid bilayer with embedded proteins.
Cell Wall: A rigid outer layer found in plant cells, bacteria, fungi, and algae that provides structure, support, and protection. In plants, it is primarily composed of cellulose.
Cytoplasm: The gel-like substance inside the cell, excluding the nucleus, where organelles are located and many metabolic reactions occur.
Cytoskeleton: A network of protein fibers in the cytoplasm that provides cell structure, shape, and movement. It includes microtubules, intermediate filaments, and actin filaments.
Selective Permeability: The property of the plasma membrane that allows certain substances to pass through while restricting others. This is crucial for maintaining cell homeostasis.
Passive Transport: The movement of substances across a cell membrane without the input of energy, driven by concentration gradients. Examples include diffusion and osmosis.
Active Transport: The movement of substances across a cell membrane against their concentration gradient, requiring energy input, usually in the form of ATP.
Osmosis: The diffusion of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.
Facilitated Diffusion: A type of passive transport where specific proteins in the cell membrane help transport molecules across the membrane, following their concentration gradient.
Endocytosis: The process by which cells engulf material from their external environment by forming vesicles from the plasma membrane. Types include phagocytosis and pinocytosis.
Exocytosis: The process by which cells expel material to their external environment by fusing vesicles with the plasma membrane.

Unit 3: Cellular Energetics

Metabolism: The sum of all chemical reactions that occur within an organism, including both catabolism (breakdown of molecules) and anabolism (synthesis of molecules).
Enzyme: A protein that acts as a biological catalyst, speeding up chemical reactions within cells without being consumed in the reaction.
Substrate: The reactant molecule on which an enzyme acts. The substrate binds to the enzyme's active site.
Active Site: The specific region on an enzyme where the substrate binds and where catalysis occurs.
Activation Energy: The minimum amount of energy required to initiate a chemical reaction. Enzymes lower the activation energy, making reactions easier to proceed.
Catalyst: A substance that speeds up the rate of a chemical reaction without being consumed in the reaction. Enzymes are biological catalysts.
Denaturation: The process by which a protein loses its native shape and function due to disruption of its chemical bonds, often caused by changes in temperature, pH, or exposure to certain chemicals.
ATP (Adenosine Triphosphate): The primary energy currency of the cell, used to power various cellular processes. ATP stores energy in its phosphate bonds, which are released when ATP is hydrolyzed to ADP (adenosine diphosphate) and inorganic phosphate (Pi).
Cellular Respiration: The process by which cells break down glucose and other organic molecules to produce ATP. It occurs in three main stages: glycolysis, the Krebs cycle, and the electron transport chain.
Glycolysis: The initial breakdown of glucose into pyruvate, occurring in the cytoplasm. It produces a small amount of ATP and NADH.
Krebs Cycle: A series of chemical reactions that further oxidize pyruvate, producing more energy carriers (NADH and FADH2) and releasing carbon dioxide. It occurs in the mitochondrial matrix.
Electron Transport Chain: A series of protein complexes in the inner mitochondrial membrane that uses electrons from NADH and FADH2 to pump protons across the membrane, creating a gradient that drives ATP synthesis.
Fermentation: An anaerobic process by which cells regenerate NAD+ from NADH, allowing glycolysis to continue in the absence of oxygen. It produces less ATP than cellular respiration. Examples include lactic acid fermentation and alcoholic fermentation.
Photosynthesis: The process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. It occurs in two main stages: the light-dependent reactions and the Calvin cycle.
Chlorophyll: The green pigment in chloroplasts that absorbs light energy to drive photosynthesis.
Light-Dependent Reactions: The initial reactions of photosynthesis, which occur in the thylakoid membranes of chloroplasts. They convert light energy into chemical energy in the form of ATP and NADPH.
Calvin Cycle: The second stage of photosynthesis, which occurs in the stroma of chloroplasts. It uses ATP and NADPH to convert carbon dioxide into glucose.

Unit 4: Cell Communication and Cell Cycle

Signal Transduction Pathway: A series of steps by which a signal on a cell's surface is converted into a specific cellular response. It typically involves a signal molecule (ligand), a receptor protein, and intracellular signaling molecules.
Ligand: A molecule that binds to a receptor protein, triggering a cellular response.
Receptor: A protein that receives signals from external sources and transmits them to the inside of the cell, often by binding to a ligand.
Second Messenger: A molecule that relays signals received by receptors on the cell surface to target molecules inside the cell. Examples include cyclic AMP (cAMP) and calcium ions (Ca2+).
Apoptosis: Programmed cell death, a normal process that eliminates damaged or unnecessary cells. It plays a crucial role in development and tissue homeostasis.
Cell Cycle: The life cycle of a cell, consisting of a series of stages through which a cell grows, replicates its DNA, and divides. The main phases include interphase (G1, S, G2) and mitosis (M).
Interphase: The phase of the cell cycle where the cell grows and replicates its DNA in preparation for cell division. It consists of three subphases: G1 (growth), S (DNA synthesis), and G2 (preparation for mitosis).
Mitosis: The division of the nucleus in eukaryotic cells, resulting in two daughter nuclei with identical genetic material. It consists of four main stages: prophase, metaphase, anaphase, and telophase.
Cytokinesis: The division of the cytoplasm, resulting in two separate daughter cells. It typically occurs immediately after mitosis.
Checkpoints: Control points in the cell cycle where the cell assesses whether conditions are right for cell division. These checkpoints help prevent errors in DNA replication and cell division.
Cyclins: Proteins that regulate the cell cycle by activating cyclin-dependent kinases (CDKs). Cyclin levels fluctuate during the cell cycle.
Cancer: A disease caused by uncontrolled cell division, resulting in the formation of tumors. Cancer cells often have mutations that disrupt the normal cell cycle checkpoints.

Unit 5: Heredity

Gene: The basic unit of heredity, consisting of a specific sequence of DNA that codes for a particular trait or protein.
Allele: Different forms of a gene. For example, a gene for eye color might have alleles for blue eyes, brown eyes, or green eyes.
Genotype: The genetic makeup of an organism, describing the specific alleles it carries for a particular trait.
Phenotype: The physical traits of an organism, which are determined by its genotype and environmental factors. For example, blue eyes are a phenotype.
Homozygous: Having two identical alleles for a particular gene. For example, BB or bb.
Heterozygous: Having two different alleles for a particular gene. For example, Bb.
Dominant: An allele that is expressed in the phenotype even when paired with a recessive allele. In heterozygous individuals, the dominant allele masks the effect of the recessive allele.
Recessive: An allele that is only expressed in the phenotype when paired with another recessive allele. In heterozygous individuals, the recessive allele is masked by the dominant allele.
Punnett Square: A diagram used to predict the possible genetic outcomes of a cross between two individuals by showing all possible combinations of alleles.
Monohybrid Cross: A cross involving one trait, where the parents differ in only one characteristic. For example, a cross between a plant with purple flowers and a plant with white flowers.
Dihybrid Cross: A cross involving two traits, where the parents differ in two characteristics. For example, a cross between a plant with round, yellow seeds and a plant with wrinkled, green seeds.
Mendel's Laws: Principles of inheritance discovered by Gregor Mendel, including the law of segregation (alleles separate during gamete formation) and the law of independent assortment (alleles of different genes assort independently).
Pedigree: A family tree of traits, showing the inheritance of a particular trait through multiple generations. Pedigrees can be used to determine whether a trait is dominant or recessive and whether it is sex-linked.
Sex-Linked Trait: A trait on a sex chromosome, usually the X chromosome. Sex-linked traits often affect males more than females because males have only one X chromosome.

Unit 6: Gene Expression and Regulation

DNA (Deoxyribonucleic Acid): The genetic material that carries the instructions for building and operating an organism. DNA is a double-stranded helix composed of nucleotides.
RNA (Ribonucleic Acid): A single-stranded nucleic acid that plays a role in protein synthesis. There are several types of RNA, including mRNA, tRNA, and rRNA.
Transcription: The process by which DNA is copied into RNA. It occurs in the nucleus and is catalyzed by RNA polymerase.
Translation: The process by which RNA is used to synthesize protein. It occurs on ribosomes in the cytoplasm.
mRNA: Messenger RNA, which carries genetic information from DNA to ribosomes.
tRNA: Transfer RNA, which brings amino acids to ribosomes during translation.
rRNA: Ribosomal RNA, which is a component of ribosomes.
Codon: A three-base sequence on mRNA that specifies a particular amino acid.
Anticodon: A three-base sequence on tRNA that is complementary to a codon on mRNA.
Mutation: A change in DNA. Mutations can be caused by errors in DNA replication or by exposure to mutagens.
Operon: A gene regulation unit in bacteria, consisting of a promoter, an operator, and a cluster of genes that are transcribed together.
Promoter: A DNA sequence that is the start site for transcription. RNA polymerase binds to the promoter to initiate transcription.
Enhancer: A DNA sequence that increases transcription by binding to activator proteins.
Silencer: A DNA sequence that decreases transcription by binding to repressor proteins.
Epigenetics: Gene expression changes without DNA change. These changes can be caused by DNA methylation or histone modification.

Unit 7: Natural Selection

Evolution: Change in the genetic makeup of a population over time. This change can be driven by various mechanisms, including natural selection, genetic drift, mutation, and gene flow.
Natural Selection: The process where individuals with favorable traits are more likely to survive and reproduce, passing those traits to their offspring. Over time, this process can lead to adaptation and evolution.
Adaptation: An inherited trait that increases an organism's chance of survival and reproduction in its environment. Adaptations can be structural, physiological, or behavioral.
Fitness: The ability of an organism to survive and reproduce in its environment. Fitness is often measured by the number of offspring an organism produces.
Gene Pool: The combined genetic information of all members of a population. The gene pool includes all of the alleles for all of the genes in the population.
Genetic Drift: Random changes in allele frequencies in a population, especially in small populations. Genetic drift can lead to the loss of genetic diversity.
Founder Effect: Reduced genetic diversity when a population is descended from a small number of colonizing ancestors. The founder effect can lead to the establishment of rare alleles in a new population.
Bottleneck Effect: A sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts or human activities such as intentional destruction. The bottleneck effect can lead to the loss of genetic diversity.
Speciation: The formation of new and distinct species in the course of evolution. Speciation can occur when populations become reproductively isolated from each other.
Allopatric Speciation: Speciation that occurs when biological populations are physically isolated by an external barrier. This can lead to genetic divergence and the formation of new species.
Sympatric Speciation: Speciation without physical separation of members of the population. This can occur through mechanisms such as polyploidy or disruptive selection.
Reproductive Isolation: Mechanisms that prevent species from mating with others. These mechanisms can be prezygotic (occurring before the formation of a zygote) or postzygotic (occurring after the formation of a zygote).
Hardy-Weinberg Equilibrium: Condition under which a population's allele frequencies remain constant from generation to generation. This equilibrium is maintained when there is no mutation, no gene flow, random mating, no natural selection, and a large population size. We can represent this mathematically with the following equations:-
- p + q = 1 (where p and q are the frequencies of the two alleles in the population)
- p^2 + 2pq + q^2 = 1 (where p^2 is the frequency of the homozygous dominant genotype, 2pq is the frequency of the heterozygous genotype, and q^2 is the frequency of the homozygous recessive genotype)
Phylogenetic Tree: A diagram showing evolutionary relationships among various species. Phylogenetic trees are based on shared characteristics, such as DNA sequences or morphological traits.

Unit 8: Ecology

Ecology: The study of interactions between organisms and their environment, including both biotic (living) and abiotic (non-living) factors.
Population: A group of individuals of the same species living in a specific area. Populations have characteristics such as population size, density, and age structure.
Community: Different populations living together in a defined area. Communities interact with each other in various ways, such as competition, predation, and symbiosis.
Ecosystem: A community of living organisms and their physical environment, including interactions between biotic and abiotic components. Ecosystems can be terrestrial or aquatic.
Biosphere: The global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere.
Biotic Factors: Living components of an ecosystem, such as plants, animals, fungi, and bacteria. Biotic factors can affect the distribution and abundance of organisms.
Abiotic Factors: Non-living physical and chemical elements in the ecosystem, such as temperature, sunlight, water, and nutrients. Abiotic factors can limit the growth and distribution of organisms.
Food Chain: A linear sequence of organisms through which nutrients and energy pass as one organism eats another. Food chains typically start with primary producers and end with top predators.
Food Web: A complex network of interconnected food chains, showing the feeding relationships among various organisms in an ecosystem. Food webs are more realistic representations of energy flow than food chains.
Trophic Levels: Hierarchical levels in an ecosystem, comprising producers and consumers. Primary producers are at the bottom of the food chain, followed by primary consumers, secondary consumers, and so on.
Primary Producer: Organisms that produce biomass from inorganic compounds (e.g., plants). Primary producers are the foundation of most food chains and food webs.
Primary Consumer: Herbivores that feed on primary producers. Examples include deer, rabbits, and grasshoppers.
Secondary Consumer: Carnivores that feed on primary consumers. Examples include snakes, foxes, and hawks.
Decomposer: Organisms that break down dead or decaying organisms, releasing nutrients back into the environment. Examples include bacteria and fungi.
Carrying Capacity: The maximum population size an environment can sustain given the available resources. Carrying capacity is determined by limiting factors.
Limiting Factor: Environmental factor that restricts population growth. Limiting factors can be density-dependent or density-independent.
Density-Dependent Factors: Factors whose effects on the size or growth of the population vary with population density. Examples include competition, predation, and disease.
Density-Independent Factors: Factors that affect population size regardless of population density. Examples include natural disasters, weather, and climate.
Succession: The process of change in the species structure of an ecological community over time. Succession can be primary (occurring on new, previously uninhabited land) or secondary (occurring on disturbed land).
Biodiversity: The variety of life in the world or in a particular habitat or ecosystem. Biodiversity includes genetic diversity,