Biological Chemistry & Cell Theory Overview DAT CH 1

Matter

Anything that takes up space and has mass.

Element

A pure substance with specific chemical/physical properties that cannot be broken down further.

Atom

Smallest unit of matter that retains the properties of an element.

Molecule

Two or more atoms bonded together.

Intramolecular Forces

Attractive forces between atoms within the same molecule.

Intermolecular Forces

Forces between different molecules that influence physical properties.

Monomer

A single molecule that can bond with others to form a polymer.

Polymer

A large molecule made by joining many monomers.

Dehydration (Condensation) Reaction

Reaction that joins monomers by covalent bonds while releasing water.

Hydrolysis

Reaction that breaks covalent bonds using water.

Carbohydrates

Molecules composed of carbon, hydrogen, and oxygen used for energy and structure.

Monosaccharide

Single sugar unit, e.g., glucose, fructose, ribose.

Disaccharide

Two monosaccharides joined by a glycosidic bond.

Polysaccharide

Long chain of monosaccharides.

Glycosidic Bond

Covalent bond between monosaccharides formed by dehydration.

Starch

Energy-storage polysaccharide in plants.

Glycogen

Energy-storage polysaccharide in animals.

Cellulose

Structural polysaccharide in plant cell walls.

Chitin

Structural polysaccharide in fungi cell walls and arthropod exoskeletons.

Proteins

Polymers of amino acids containing carbon, hydrogen, oxygen, and nitrogen.

Amino Acid

Monomer of proteins distinguished by its R-group side chain.

Peptide Bond

Covalent bond between amino acids formed via dehydration.

Primary Structure

Linear sequence of amino acids in a polypeptide.

Secondary Structure

α-helices or β-sheets formed by hydrogen bonding of the backbone.

Tertiary Structure

Overall 3-D folding of a single polypeptide due to R-group interactions.

Disulfide Bond

Covalent bond between sulfur atoms of cysteine side chains.

Quaternary Structure

Arrangement of multiple polypeptide chains into one functional protein.

Denaturation

Loss of secondary, tertiary, or quaternary protein structure and function.

Storage Proteins

Proteins that serve as reserves of amino acids.

Hormones

Protein or peptide signaling molecules that regulate physiology.

Receptors

Proteins that bind signaling molecules and initiate cellular responses.

Structural Proteins

Proteins that provide support to cells and tissues.

Immunity (Antibodies)

Proteins that recognize and neutralize foreign substances.

Enzymes

Protein catalysts that speed up biochemical reactions.

Catalyst

Substance that accelerates a reaction by lowering activation energy.

Transition State

Unstable intermediate between reactants and products.

Enzyme

Protein catalyst with a specific active site for its substrate.

Active Site

Region on an enzyme where the substrate binds.

Induced Fit Theory

Model stating that an enzyme molds around its substrate for optimal catalysis.

Ribozyme

RNA molecule with catalytic activity.

Cofactor

Non-protein helper (metal ion or molecule) required for enzyme activity.

Coenzyme

Organic cofactor, often a vitamin or vitamin-derived molecule.

Feedback Inhibition

End product of a pathway inhibits an earlier enzyme via an allosteric site.

Competitive Inhibition

Inhibitor competes with substrate for the active site; can be overcome by more substrate.

Noncompetitive Inhibition

Inhibitor binds to an allosteric site, reducing enzyme activity regardless of substrate concentration.

Vmax

Maximum reaction rate an enzyme can achieve.

KM (Michaelis constant)

Substrate concentration at which reaction speed is half of Vmax; reflects enzyme affinity.

Lipids

Hydrophobic molecules composed mainly of carbon, hydrogen, and oxygen.

Triglyceride

Three fatty acids ester-linked to glycerol.

Saturated Fatty Acid

Fatty acid with no double bonds; solid at room temperature.

Unsaturated Fatty Acid

Fatty acid with one or more double bonds; more fluid.

Phospholipid

Glycerol backbone with two fatty acids and a phosphate group; amphipathic.

Cholesterol

Amphipathic lipid that is a precursor to steroid hormones and vitamin D.

Lipoprotein

Protein-lipid complex that transports lipids through the bloodstream.

Waxes

Long-chain fatty acids esterified to long-chain alcohols.

Carotenoids

Pigment lipids with long conjugated carbon chains.

Sphingolipids

Lipids with an amino alcohol backbone involved in cell signaling.

Glycolipids

Lipids with an attached carbohydrate group.

Nucleic Acids

Polymers of nucleotides such as DNA and RNA.

Nucleoside

Sugar bound to a nitrogenous base, lacking phosphate.

Nucleotide

Sugar, nitrogenous base, and phosphate group combined.

Deoxyribose

Five-carbon sugar in DNA with an H on the 2′ carbon.

Ribose

Five-carbon sugar in RNA with an OH on the 2′ carbon.

Phosphodiester Bond

Linkage between 5′ phosphate and 3′ hydroxyl of adjacent nucleotides.

Sugar-Phosphate Backbone

Repeating sugar and phosphate units forming the framework of DNA/RNA strands.

Antiparallel

Orientation of the two DNA strands running in opposite 5′→3′ directions.

mRNA

Single-stranded RNA that carries the genetic message from DNA to ribosomes.

miRNA

MicroRNA that regulates gene expression by silencing mRNA.

rRNA

Ribosomal RNA that, together with protein, forms ribosomes.

tRNA

Transfer RNA that brings specific amino acids to the ribosome during translation.

dsRNA

Double-stranded RNA, often found in certain viruses; base pairs A=U and C≡G.

Reducing Atmosphere

Early Earth condition with little oxygen, favoring the formation of organic molecules.

Protobionts

Pre-cell aggregates of molecules formed on early Earth, considered precursors to living cells.

Anaerobic Prokaryotes

First living organisms that generated energy without oxygen (fermentation).

Cyanobacteria

Photosynthetic bacteria that released oxygen and changed Earth’s atmosphere.

Oxidizing Atmosphere

Atmosphere enriched in O₂ resulting from photosynthesis, altering planetary chemistry.

Endosymbiotic Theory

Hypothesis that mitochondria and chloroplasts originated from engulfed prokaryotes.

Miller-Urey Experiment

1950s experiment that simulated early Earth conditions and produced amino acids abiotically.

All Lifeforms Are Made of Cells

First tenet of modern cell theory stating that every living organism consists of one or more cells.

Cells Are the Basic Unit of Life

Second tenet of cell theory identifying the cell as the smallest unit that can carry out life processes.

All Cells Come From Preexisting Cells

Third tenet that new cells arise only by division of existing cells.

DNA Stores and Transmits Genetic Information

Modern addition to cell theory recognizing DNA as the hereditary material.

Cell Activity Equals Organism Activity

Principle that the collective activities of cells determine the overall functions of an organism.

Metabolism Occurs Within Cells

Concept that all biochemical reactions of life happen inside cells.

Similar Species Have Similar Cell Chemistry

Observation that organisms of related species share comparable cellular structures and biochemical pathways.