Chapter 3: Biological Molecules

This set of vocabulary flashcards covers the chemical elements, roles, structures, and diagnostic food tests for major biological molecules including carbohydrates, fats, and proteins as outlined in the Chapter 3 notes.

Carbohydrates

Organic molecules composed of carbon, hydrogen, and oxygen, serving as an immediate source of energy with a general formula of $C_n H_{2m} O_m$ and a 2:1 ratio of hydrogen to oxygen.

Fats

A type of lipid used for insulation and long-term storage of energy, containing much less oxygen in proportion to hydrogen compared to carbohydrates.

Proteins

Organic molecules made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur, used for the growth and repair of cells.

Monosaccharides

The basic unit of carbohydrates, small enough to pass through cell membranes, including glucose ($C_6 H_{12} O_6$) and fructose.

Disaccharides

Double sugars formed when two single sugars are joined together, such as maltose and sucrose.

Reducing Sugars

Sugars like glucose, fructose, and maltose that act as reducing agents by donating electrons via an aldehyde group (-CHO) or ketone group (-CO-).

Starch

A complex carbohydrate consisting of several thousand glucose molecules joined together; it is the storage form of carbohydrates in plants.

Cellulose

A complex carbohydrate that makes up plant cell walls to protect cells and serves as dietary fiber to prevent constipation.

Glycogen

A branched complex carbohydrate made of many glucose molecules, serving as the storage form of carbohydrates in animals, stored in the liver and muscles.

Glycosidic bonds

Bonds that join monosaccharides or longer sugar chains to other carbohydrates to form disaccharides or polysaccharides.

Triglyceride

A fat molecule made up of one glycerol molecule and three fatty acid chains; an example is tristearin ($C_{37} H_{110} O_6$).

HDL (High-density lipoprotein)

Known as 'good cholesterol,' it transports cholesterol to the liver to be released from the body, reducing the likelihood of buildup in the arteries.

LDL (Low-density lipoprotein)

Known as 'bad cholesterol,' it takes cholesterol to the arteries where it can collect in walls as plaque, potentially leading to atherosclerosis.

Atherosclerosis

A buildup of plaque in the arteries caused by excess cholesterol, which can increase the risk of blood clots, strokes, or heart attacks.

Amino Acids

The basic unit of proteins, consisting of a main chain and a side chain called an R group; there are 20 naturally occurring types in the human body.

Peptide Bond

A bond formed between the amino group of one amino acid and the carboxyl group of another to link them into a polypeptide chain.

Protease

An enzyme required to break the peptide bonds between amino acids through the process of hydrolysis.

Benedict’s Test

A test for reducing sugars that involves heating a sample with Benedict’s solution; a positive result ranges from green to red precipitate as $Cu^{2+}$ reduces to $Cu^+$.

Iodine Test

A test for starch where iodine in potassium iodide solution turns from brown to blue-black if starch is present.

Ethanol-emulsion Test

A test for fats where a specimen is dissolved in ethanol and then added to water, forming a cloudy white emulsion if lipids are present.

Biuret Test

A test for proteins using biuret reagent or sodium hydroxide and copper sulfate; a positive result is a color change from blue to violet.

Emulsion

A mixture of tiny dispersed droplets formed when lipids dissolved in ethanol are added to water, scattering light to appear white and cloudy.