Catalog / Biology Essentials Cheatsheet
Biology Essentials Cheatsheet
A quick reference guide covering essential biology concepts, from cell structure to genetics and ecology. This cheat sheet provides concise summaries and key definitions for students and enthusiasts.
Cell Biology
Cell Structure
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Cell Membrane |
Phospholipid bilayer with embedded proteins; controls the movement of substances in and out of the cell. |
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Nucleus |
Contains DNA, controls cell activities through gene expression. |
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Mitochondria |
Site of cellular respiration; generates ATP. |
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Endoplasmic Reticulum (ER) |
Rough ER (with ribosomes): protein synthesis; Smooth ER: lipid synthesis and detoxification. |
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Golgi Apparatus |
Processes and packages proteins and lipids. |
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Lysosomes |
Contains enzymes for intracellular digestion. |
Cellular Processes
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Diffusion |
Movement of molecules from an area of high concentration to an area of low concentration. |
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Osmosis |
Movement of water across a semipermeable membrane from an area of high water potential to an area of low water potential. |
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Active Transport |
Movement of molecules against a concentration gradient, requiring energy (ATP). |
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Endocytosis |
Cellular uptake of large molecules or particles by engulfing them in vesicles. |
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Exocytosis |
Cellular secretion of large molecules by fusion of vesicles with the plasma membrane. |
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Cellular Respiration |
Process by which cells break down glucose to produce ATP. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP |
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Photosynthesis |
Process by which plants convert light energy into chemical energy. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ |
Cell Communication
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Cells communicate through chemical signals. Types of Signals:
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Signal Transduction: Process by which a cell converts one kind of signal or stimulus into another. |
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Receptor Proteins: Proteins that bind to specific signaling molecules and initiate a response. |
Genetics
Basic Genetic Terms
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Gene |
A unit of heredity; a sequence of DNA that encodes a protein or RNA molecule. |
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Allele |
A variant form of a gene. |
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Genotype |
The genetic makeup of an organism. |
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Phenotype |
The observable characteristics of an organism. |
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Homozygous |
Having two identical alleles for a gene. |
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Heterozygous |
Having two different alleles for a gene. |
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Dominant |
An allele that masks the effect of another allele. |
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Recessive |
An allele whose effect is masked by a dominant allele. |
DNA and RNA
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DNA |
Deoxyribonucleic acid; the genetic material containing instructions for cell function. |
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RNA |
Ribonucleic acid; involved in protein synthesis. Types include mRNA, tRNA, and rRNA. |
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Transcription |
Process by which RNA is synthesized from a DNA template. |
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Translation |
Process by which proteins are synthesized from mRNA. |
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Codon |
A sequence of three nucleotides that codes for a specific amino acid. |
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Central Dogma |
DNA → RNA → Protein |
Mendelian Genetics
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Law of Segregation: Allele pairs separate during gamete formation. Law of Independent Assortment: Genes for different traits assort independently during gamete formation. |
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Punnett Square: Diagram used to predict the genotypes and phenotypes of offspring. Example:
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Ecology
Basic Ecological Terms
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Ecosystem |
A community of living organisms (biotic) and their physical environment (abiotic) interacting as a system. |
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Habitat |
The natural environment where an organism lives. |
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Niche |
The role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. |
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Population |
A group of individuals of the same species living in the same area. |
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Community |
An interacting group of various species in a common location. |
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Biome |
A large naturally occurring community of flora and fauna occupying a major habitat, e.g., forest or tundra. |
Energy Flow
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Producers |
Organisms that produce their own food through photosynthesis or chemosynthesis. |
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Consumers |
Organisms that obtain energy by consuming other organisms. (Herbivores, Carnivores, Omnivores). |
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Decomposers |
Organisms that break down dead organic matter. |
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Food Chain |
A linear sequence of organisms through which nutrients and energy pass as one organism eats another. |
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Food Web |
A network of interconnected food chains. |
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Trophic Level |
Each step in a food chain or food web. |
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Energy Pyramid |
Graphical representation of energy flow through trophic levels. |
Biogeochemical Cycles
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The cycling of essential elements (e.g., carbon, nitrogen, water, phosphorus) through the biotic and abiotic components of ecosystems. Carbon Cycle: Photosynthesis, respiration, decomposition, and combustion. Nitrogen Cycle: Nitrogen fixation, nitrification, denitrification, and assimilation. Water Cycle: Evaporation, transpiration, condensation, precipitation, and runoff. |
Biochemistry
Macromolecules
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Carbohydrates |
Provide energy and structural support. Monosaccharides, disaccharides, and polysaccharides. |
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Lipids |
Store energy, form cell membranes, and act as hormones. Fats, oils, phospholipids, and steroids. |
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Proteins |
Perform a wide range of functions, including enzymes, structural components, and transport. Amino acids are the building blocks. |
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Nucleic Acids |
Store and transmit genetic information. DNA and RNA. |
Enzymes
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Enzyme |
A biological catalyst that speeds up chemical reactions by lowering the activation energy. |
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Substrate |
The reactant on which an enzyme acts. |
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Active Site |
The region of an enzyme where the substrate binds. |
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Cofactor |
A non-protein chemical compound or metallic ion that is required for an enzyme’s activity. |
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Inhibitor |
A substance that decreases the activity of an enzyme. (Competitive and Non-competitive). |
Important Concepts
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pH: A measure of the acidity or alkalinity of a solution. Buffers: Substances that resist changes in pH. ATP (Adenosine Triphosphate): The main energy currency of the cell. |