Basic Biology Cheatsheet

Cheatsheet Content

Cell Structure and Function Prokaryotic Cells Lack a nucleus and membrane-bound organelles. Genetic material (DNA) is in the cytoplasm (nucleoid region). Examples: Bacteria, Archaea. Components: Cell wall, cell membrane, cytoplasm, ribosomes, DNA. Eukaryotic Cells Have a true nucleus and membrane-bound organelles. Examples: Plants, Animals, Fungi, Protists. Animal Cell Organelles: Nucleus: Contains genetic material (DNA), controls cell activities. Mitochondria: Powerhouse of the cell, produces ATP via cellular respiration. Ribosomes: Synthesize proteins. Endoplasmic Reticulum (ER): Rough ER: Studded with ribosomes, protein synthesis and modification. Smooth ER: Lipid synthesis, detoxification, calcium storage. Golgi Apparatus: Modifies, sorts, and packages proteins and lipids. Lysosomes: Contain digestive enzymes, break down waste. Cytoskeleton: Provides structural support, aids in cell movement. Cell Membrane: Regulates passage of substances in/out of cell. Plant Cell Organelles (additions to animal cell): Cell Wall: Rigid outer layer, provides support and protection. Chloroplasts: Site of photosynthesis. Central Vacuole: Stores water, nutrients, waste; maintains turgor pressure. Cellular Processes Photosynthesis Process by which plants convert light energy into chemical energy. Equation: $6CO_2 + 6H_2O + \text{Light Energy} \rightarrow C_6H_{12}O_6 + 6O_2$ Occurs in chloroplasts. Stages: Light-Dependent Reactions: Occur in thylakoid membranes, produce ATP and NADPH. Light-Independent Reactions (Calvin Cycle): Occur in stroma, use ATP and NADPH to fix $CO_2$ into glucose. Cellular Respiration Process by which cells break down glucose to produce ATP. Equation: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$ Occurs in cytoplasm (glycolysis) and mitochondria (Krebs cycle, oxidative phosphorylation). Stages: Glycolysis: Glucose $\rightarrow$ 2 Pyruvate, 2 ATP, 2 NADH (cytoplasm). Krebs Cycle (Citric Acid Cycle): Pyruvate derivatives broken down, produces ATP, NADH, FADH$_2$ ($CO_2$ released) (mitochondrial matrix). Oxidative Phosphorylation: Electron transport chain and chemiosmosis, produces large amounts of ATP (inner mitochondrial membrane). Cell Cycle Ordered sequence of events that a cell passes through to divide and duplicate. Interphase: Growth and DNA replication. $G_1$ phase: Cell growth, normal functions. S phase: DNA synthesis (replication). $G_2$ phase: Cell growth, preparation for mitosis. M Phase (Mitosis): Nuclear division. Prophase: Chromosomes condense, nuclear envelope breaks down. Metaphase: Chromosomes align at metaphase plate. Anaphase: Sister chromatids separate and move to opposite poles. Telophase: Chromosomes decondense, nuclear envelopes reform. Cytokinesis: Cytoplasm divides, forming two daughter cells. Meiosis Cell division that produces four haploid daughter cells (gametes) from a diploid parent cell. Involves two rounds of division: Meiosis I and Meiosis II. Important for sexual reproduction and genetic variation. Genetics and Heredity DNA Structure Double helix structure. Composed of nucleotides: Deoxyribose sugar, phosphate group, nitrogenous base. Bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T). Base pairing: A with T, G with C. RNA Structure Single strand. Composed of nucleotides: Ribose sugar, phosphate group, nitrogenous base. Bases: Adenine (A), Guanine (G), Cytosine (C), Uracil (U). Replaces Thymine with Uracil. Central Dogma of Molecular Biology DNA $\rightarrow$ RNA $\rightarrow$ Protein. Replication: DNA makes copies of itself. Transcription: DNA template used to synthesize mRNA. Translation: mRNA sequence used to synthesize proteins (occurs at ribosomes). Mendelian Genetics Gene: Unit of heredity. Allele: Different forms of a gene (e.g., 'T' for tall, 't' for short). Genotype: Genetic makeup (e.g., TT, Tt, tt). Phenotype: Observable physical traits (e.g., Tall, Short). Dominant Allele: Expressed even if only one copy is present. Recessive Allele: Only expressed if two copies are present. Homozygous: Two identical alleles (TT or tt). Heterozygous: Two different alleles (Tt). Punnett Square: Tool to predict offspring genotypes and phenotypes. Ecology Levels of Organization Organism: Individual living thing. Population: Group of individuals of the same species in the same area. Community: All populations of different species in an area. Ecosystem: Community plus its abiotic (non-living) environment. Biome: Large regions characterized by similar climate and dominant plant life. Biosphere: All parts of Earth where life exists. Food Chains and Webs Producers (Autotrophs): Make their own food (e.g., plants). Consumers (Heterotrophs): Obtain energy by eating other organisms. Primary Consumers: Herbivores, eat producers. Secondary Consumers: Carnivores/Omnivores, eat primary consumers. Tertiary Consumers: Carnivores/Omnivores, eat secondary consumers. Decomposers: Break down dead organic matter (e.g., bacteria, fungi). Food Chain: Linear pathway of energy flow. Food Web: Interconnected food chains, shows complex feeding relationships. Biogeochemical Cycles Water Cycle: Evaporation, condensation, precipitation, collection. Carbon Cycle: Photosynthesis (removes $CO_2$), respiration (releases $CO_2$), decomposition, combustion. Nitrogen Cycle: Nitrogen fixation, ammonification, nitrification, denitrification. Essential for proteins and nucleic acids. Phosphorus Cycle: Sedimentation, weathering, absorption by plants. Essential for ATP, DNA.