Basic Elements in Life

Flashcards covering the basic elements of life including water, carbohydrates, lipids, proteins, and nucleic acids based on the introductory biology chapter.

Molecules of Life

The five major classes of compounds that constitute life: Water, Carbohydrates, Lipids, Proteins, and Nucleic acids.

Water Polarity

The bent, bipolar nature of water molecules where oxygen has a partial negative charge ($\delta-$) and hydrogen has a partial positive charge ($\delta+$) due to electronegativity.

Cohesion

The tendency for water molecules to stick together due to hydrogen bonds, resulting in properties like surface tension and droplet formation.

Adhesion

The attractive forces between unlike molecules, such as water clinging to a leaf surface.

Capillary action

The upward movement of water in small or narrow spaces caused by the combined forces of cohesion and adhesion.

High specific heat capacity

A property of water that allows it to absorb heat and act as an effective temperature buffer to keep cell temperatures constant.

High latent heat of vaporisation

The large amount of heat energy ($540\,\text{calories g}^{-1}$) required to turn liquid water into vapor, aiding in heat dissipation through sweat.

Density of water at $4^{\circ}C$

The temperature at which water reaches its greatest density; ice is less dense and floats because hydrogen bonds keep molecules far apart.

Carbohydrate

An organic compound containing carbon, hydrogen, and oxygen in a $1:2:1$ ratio, with the general chemical formula $(CH_2O)_n$.

Monosaccharides

Simple sugars such as Glucose, Galactose, and Fructose that are sweet, water-soluble, and can be classified by carbon count (triose, pentose, hexose).

Alpha-glucose ($\alpha$-glucose)

A form of glucose where the hydroxyl ($OH$) group juts downwards from the first carbon atom.

Beta-glucose ($\beta$-glucose)

A form of glucose where the hydroxyl ($OH$) group juts upwards from the first carbon atom.

Disaccharides

Carbohydrates formed when two monosaccharides are linked together via a condensation process and the formation of a glycosidic bond.

Maltose

A reducing disaccharide known as malt sugar, composed of two glucose molecules linked by an $\alpha(1-4)$ glycosidic bond.

Sucrose

A non-reducing disaccharide known as cane sugar, composed of Glucose and Fructose linked by an $\alpha(1-2)$ glycosidic bond.

Lactose

A reducing disaccharide known as milk sugar, composed of Glucose and Galactose linked by an $\alpha(1-4)$ glycosidic bond.

Polysaccharides

Long chains of monosaccharide units bound by glycosidic bonds, which are generally not sweet, insoluble in water, and amorphous.

Amylose

A linear, unbranched component of starch ($10-30\%$) made of glucose subunits with $\alpha(1-4)$ bonds that forms a helix shape.

Amylopectin

A branched component of starch ($70-90\%$) containing glucose subunits with both $\alpha(1-4)$ and $\alpha(1-6)$ bonds.

Glycogen

The animal storage polysaccharide made of glucose subunits that is highly branched, occurring approximately every $10$ subunits.

Cellulose

A structural polysaccharide in plants made of glucose subunits in $\beta(1-4)$ bonds, arranged in a flip-flop manner to produce long, rigid molecules.

Lipids

Non-polar (hydrophobic) compounds formed from fatty acids and glycerol, containing $C, H$, and $O$ with a hydrogen-to-oxygen ratio much greater than $2:1$.

Phospholipids

Amphipathic lipids formed from one glycerol, two fatty acids, and one phosphoric acid, serving as the basis for biological membranes.

Steroids

Lipids with a basic skeleton of $17$ carbon atoms arranged in one $5$-C ring and three $6$-C rings, such as cholesterol and testosterone.

Saturated fatty acids

Hydrocarbon chains with only single bonds that are typically solid at room temperature and have higher melting points.

Unsaturated fatty acids

Hydrocarbon chains containing one or more double bonds ($C=C$) which cause the chain to bend, typically liquid at room temperature.

Amino Acid

The building block of proteins, consisting of a central carbon, an amino group, a carboxyl group, a hydrogen atom, and a variable R group.

Zwitterion

A dipolar ion formed by an amino acid in water where it has a net charge of zero at its isoelectric point.

Peptide bond

The covalent bond that links amino acids together via a condensation reaction between an amino group and a carboxyl group.

Primary structure

The linear sequence of amino acids in a polypeptide chain, determined by genes and held by covalent bonds.

Secondary structure

The folding or coiling of a polypeptide chain into $\alpha$-helices or $\beta$-pleated sheets due to hydrogen bonding.

Tertiary structure

The 3D globular shape of a single polypeptide chain formed by interactions like disulphide bonds, ionic bonds, and hydrophobic interactions.

Quaternary structure

A functional molecule formed by the association of two or more polypeptide chains, such as hemoglobin.

Conjugated protein

A protein composed of simple proteins combined with a non-proteinous substance known as a prosthetic group or cofactor.

Denaturation

The process where heat, acids, or bases destroy the weak bonds of a protein, changing its shape and making it inactive.

Nucleotide

The subunit of nucleic acids composed of a pentose sugar, a phosphate group, and a nitrogenous base.

Purines

Nitrogenous bases with a double-ring structure, specifically Adenine and Guanine.

Pyrimidines

Nitrogenous bases with a single-ring structure, including Cytosine, Thymine (DNA only), and Uracil (RNA only).

Phosphodiester bond

The bond formed between the phosphate group of one nucleotide and the hydroxyl group of the next, releasing water.

DNA vs. RNA sugars

DNA contains deoxyribose sugar, whereas RNA contains ribose sugar.