Water, Carbon, and Life Flashcards

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Carbon valence

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Carbon has four valence electrons, which allows it to form up to four covalent bonds with other atoms. This tetravalence enables the formation of diverse carbon backbones and complex organic molecules.

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Hydrocarbon

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A hydrocarbon is an organic molecule composed only of carbon and hydrogen atoms, often forming the backbone of many biological molecules like fats. Hydrocarbons can vary in chain length and shape and release energy when they undergo combustion or metabolic reactions.

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Structural isomer

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Structural (constitutional) isomers share the same molecular formula but differ in the arrangement of their atoms, leading to distinct structures and often different physical and chemical properties. For example, $C_5H_{12}$ can exist as pentane and 2-methylbutane with different carbon backbones.

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Enantiomer

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Enantiomers are mirror-image isomers that cannot be superimposed on each other, like left and right hands. Two enantiomers of a drug can have different biological activities, and often only one enantiomer is biologically active.

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Hydrogen bond

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A hydrogen bond is an intermolecular attraction that occurs when a hydrogen atom covalently bound to an electronegative atom (such as oxygen or nitrogen) is attracted to another electronegative atom. Hydrogen bonds are weaker than covalent bonds but are crucial for properties like water cohesion and biomolecular structure.

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Specific heat

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Specific heat is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. Water has a high specific heat due to hydrogen bonding, which buffers temperature changes in organisms and environments.

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Universal solvent

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Water is called the universal solvent because its polarity allows it to surround and separate charged and polar molecules, forming aqueous solutions. This solvent property enables many biological solutes like $Na^+$ and $Cl^-$ to dissolve and participate in cellular processes.

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Cohesion and adhesion

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Cohesion is the attraction between water molecules via hydrogen bonds, while adhesion is the attraction between water and other polar or charged surfaces. Together they enable phenomena like surface tension and capillary action, which are important for water transport in plants.

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Atomic structure

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An atom consists of a dense nucleus containing protons and neutrons surrounded by an electron cloud of orbiting electrons. Protons are positively charged, neutrons are neutral, and electrons are negatively charged, with most of the atom's mass in the nucleus.

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Electron configuration

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Electrons occupy shells around the nucleus with defined capacities (e.g., 2, 8, 8). Valence electrons in the outermost shell determine an element's chemical reactivity—for example, carbon has four valence electrons enabling four bonds.

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Isotope

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Isotopes are atoms of the same element that differ in neutron number but have the same number of protons and electrons. Radioisotopes like carbon-14 are useful for dating and medical imaging because they decay predictably over time.

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Ionic vs covalent

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Covalent bonds form when atoms share electrons to fill outer shells, while ionic bonds form when one atom transfers electrons to another, creating oppositely charged ions held together by electrostatic attraction. Covalent bonds form discrete molecules; ionic bonds often form crystal lattices.

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Microbes

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Microbes are single-celled organisms—including bacteria, fungi, and protozoa—that play essential roles in ecosystems and human health. Many antibiotics are derived from microbes, and microbes can be beneficial or pathogenic depending on context.

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Antibiotic resistance

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Antibiotic resistance occurs when bacteria evolve mechanisms to survive exposure to antibiotics, often through mutation or horizontal gene transfer. This leads to treatment failures and is a growing public-health crisis exacerbated by overuse and lack of new antibiotics.

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Scientific method

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The scientific method is an iterative process for investigating phenomena that includes observations, hypothesis formation, experimentation, and revision. It underpins biological research such as antibiotic discovery and testing.

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Characteristics of life

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Living systems share key features: cellular organization, reproduction, energy processing, regulation/homeostasis, growth and development, response to the environment, and evolutionary adaptation. These criteria help distinguish living organisms from nonliving matter.