Biochemistry and Biological Macromolecules

Comprehensive vocabulary flashcards covering the structure, function, monomer units, synthesis reactions, and classification of lipids, carbohydrates, nucleic acids, and proteins.

Phospholipid

A lipid molecule composed of a glycerol molecule attached to a hydrophilic phosphate head and two hydrophobic fatty acid tails, forming the bilayer of cell membranes.

Hydrophobic

A property of non-polar molecules or chemical groups that do not interact with or dissolve in water ('water-fearing').

Hydrophilic

A property of polar or charged molecules or chemical groups that readily dissolve in or interact with water ('water-loving').

Waxes

Large lipid molecules consisting of chains or rings with $40$ to $600$ $C-H$ bonds that are water-repellent, solid at room temperature, and used by plants and animals for waterproofing and structural building (e.g., beeswax).

Steroids

Lipids characterized by a carbon skeleton composed of four fused rings that are hydrophobic and function as membrane components and hormones (e.g., cholesterol, testosterone).

Cholesterol

A steroid lipid found in cell membranes that preserves membrane fluidity at low temperatures, but can accumulate as arterial plaque leading to cardiovascular disease.

Saturated Fatty Acid

A fatty acid chain with no double bonds between carbon atoms ($C-C$ single bonds only), allowing it to pack tightly and remain solid at room temperature.

Unsaturated Fatty Acid

A fatty acid chain containing one or more carbon-carbon double bonds ($C=C$), introducing kinks that prevent tight packing and make the lipid liquid at room temperature.

Triglyceride

A lipid consisting of one glycerol molecule bonded to three fatty acid chains, serving as long-term energy storage, insulation, and protective organ cushioning.

Micelle

A spherical assembly formed by amphipathic lipid molecules in an aqueous solution, with hydrophobic tails secluded in the interior and hydrophilic heads oriented outward.

Monosaccharide

A single carbohydrate monomer unit with the empirical formula ratio of $1C:2H:1O$, functioning as an immediate energy source (e.g., glucose, fructose, galactose).

Glucose

A six-carbon monosaccharide ($C_6H_{12}O_6$) that circulates in blood and serves as the primary immediate fuel source for cellular respiration and brain activity.

Monomer

A small, single molecular subunit that can chemically bind to other identical or similar subunits to form a larger polymer.

Polymer

A large macromolecule formed by covalently linking many repeating monomer subunits together.

Disaccharide

A double sugar molecule formed when two monosaccharides join through dehydration synthesis via a glycosidic bond (e.g., maltose, sucrose, lactose).

Dehydration Synthesis

A chemical reaction that covalently bonds two smaller molecules together by removing a water molecule ($H_2O$).

Hydrolysis

A chemical cleavage reaction that breaks down a complex molecule into smaller subunits by adding a water molecule ($H_2O$).

Polysaccharide

A complex carbohydrate polymer composed of long chains of monosaccharides linked by glycosidic bonds, utilized for energy storage or structural support.

Monosaccharide

Glycogen

A highly branched polysaccharide of glucose stored in animal liver and muscle tissues to provide intermediate energy reserves.

Cellulose

An unbranched structural glucose polysaccharide found in plant cell walls that provides rigidity and serves as indigestible dietary fiber in humans.

Amylose

An unbranched, helical plant starch polysaccharide composed of glucose units linked together for energy storage.

DNA (Deoxyribonucleic Acid)

A double-stranded, antiparallel nucleic acid polymer containing deoxyribose sugar and bases $A$, $T$, $C$, and $G$, functioning in the permanent storage of genetic information.

RNA (Ribonucleic Acid)

A single-stranded nucleic acid polymer containing ribose sugar and bases $A$, $U$, $C$, and $G$, functioning in decoding genetic information for protein synthesis.

Antiparallel Strands

The orientation of the two complementary strands in a DNA double helix, where one strand runs in the $5' \rightarrow 3'$ direction and the other in the $3' \rightarrow 5'$ direction.

Phosphodiester Bond

The strong covalent linkage connecting the phosphate group of one nucleotide to the hydroxyl group on the sugar of the adjacent nucleotide, making up the nucleic acid backbone.

Nucleotide

The monomer subunit of nucleic acids, consisting of a five-carbon pentose sugar, a phosphate group, and a nitrogenous base.

Purines

Double-ring nitrogenous bases found in nucleic acids, consisting of Adenine ($A$) and Guanine ($G$).

Pyrimidines

Single-ring nitrogenous bases found in nucleic acids, consisting of Cytosine ($C$), Thymine ($T$), and Uracil ($U$).

Complementary Base Pairing

The specific pairing rule where Adenine forms $2$ hydrogen bonds with Thymine/Uracil ($A=T$ / $A=U$) and Guanine forms $3$ hydrogen bonds with Cytosine ($G\rightleftharpoons C$).

Primary Structure

The unique linear sequence of amino acids in a polypeptide chain held together by covalent peptide bonds, determined by genetic instructions.

Secondary Structure

Localized folding of the polypeptide chain into alpha helices or beta-pleated sheets, stabilized by hydrogen bonds between the carbonyl ($C=O$) and amino ($N-H$) backbone groups.

Tertiary Structure

The complex three-dimensional folding of a single polypeptide chain, stabilized by interactions among side-chain $R$-groups including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

Quaternary Structure

The overall macromolecular structure that results when two or more tertiary polypeptide subunits assemble into a single functional protein (e.g., hemoglobin).

Amino Acid

The monomer building block of proteins, containing an alpha carbon bonded to a hydrogen atom, an amino group ($-NH_2$), a carboxyl group ($-COOH$), and a variable $R$-group side chain.

Peptide Bond

The covalent bond formed between the carboxyl carbon of one amino acid and the amino nitrogen of another via a dehydration synthesis reaction.

Enzymes

Proteins that act as biological catalysts to speed up chemical reactions by lowering activation energy without being permanently altered.

Antibodies

Specialized defense proteins synthesized by the immune system to recognize, neutralize, and protect the body against pathogens and foreign invaders.

Hydrolysis

A chemical reaction in which polymers are broken down into individual monomers through the addition of a water molecule ($H_2O$).

Protein denaturation

The disruption and unfolding of a protein's secondary, tertiary, or quaternary structure caused by factors such as extreme heat or pH changes, leading to a loss of biological activity while leaving the primary amino acid sequence intact.

Saturated fat

A lipid composed of fatty acids containing only single carbon-carbon bonds, holding the maximum possible number of hydrogen atoms and typically remaining solid at room temperature.

Unsaturated fat

A lipid containing one or more carbon-carbon double bonds ($C=C$) in its hydrocarbon chain, which introduces bends that typically keep it liquid at room temperature.

Disaccharide

A carbohydrate molecule composed of two monosaccharide units joined together by a glycosidic bond through a dehydration reaction.