Macromolecules, Enzymes, and the Human Digestive System

Comprehensive vocabulary flashcards covering macromolecules, chemical indicators, enzyme mechanisms and regulation, anatomy and physiology of the human digestive tract, digestive enzymes, and accessory organs.

Organic Molecules

Carbon-based molecules that serve as the foundational building blocks of life.

Monomer

An individual molecular building block that bonds with other subunits to synthesize larger molecules.

Polymer

A large molecule composed of repeating structural subunits known as monomers.

Carbohydrates

Organic macromolecules composed of carbon, hydrogen, and oxygen ($CHO$) in a $1:2:1$ ratio; their chemical names frequently end in "-ose" and they function as an energy source and for short-term energy storage.

Monosaccharide

The monomer of carbohydrates, also referred to as a simple sugar, which typically exhibits a hexagonal or pentagonal ring structure.

Polysaccharide

A carbohydrate polymer formed from chains of monosaccharides; stored as starch in plants and as glycogen in animals.

Lipids

Non-polar, hydrophobic macromolecules composed of $CHO$ that do not dissolve in water; examples include fats, waxes, oils, and steroids.

Triglyceride

The most common form of lipid, composed of a single glycerol backbone bonded to $3$ fatty acid chains.

Saturated Fatty Acid

A fatty acid chain lacking double bonds whose carbon atoms are saturated with hydrogen; its flat shape permits dense packing, rendering it solid at room temperature (e.g., butter, lard, bacon grease).

Unsaturated Fatty Acid

A fatty acid chain possessing one or more double bonds, resulting in bends that prevent tight molecular packing.

Protein

A macromolecule composed of carbon, hydrogen, oxygen, and nitrogen ($CHON$); each protein possesses a specific shape determining functions such as transport, catalyzing reactions, membrane transport, immune defense, and structural support.

Amino Acid

The monomer of proteins, consisting of a central carbon atom bonded to a carboxyl group, an amine group, a hydrogen atom, and a variable R-group.

Primary Protein Structure

The linear sequence of amino acids within a polypeptide chain, strictly determined by genetic instructions.

Secondary Protein Structure

The initial conformational folding of a polypeptide chain into alpha-helices (coils) and beta-pleated sheets (zig-zags).

Tertiary Protein Structure

The complete three-dimensional folding of a polypeptide chain into a specific, biologically active shape.

Quaternary Protein Structure

The multi-subunit structural assembly formed when two or more distinct polypeptide chains come together.

Nucleic Acid

A macromolecule composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus ($CHONP$) whose sequence stores and transmits genetic instructions for assembling proteins.

Nucleotide

The monomer of nucleic acids, consisting of a 5-carbon sugar, a phosphate group, and a nitrogenous base ($A$, $T$, $C$, $G$, or $U$).

Indicator

A chemical compound used to detect the presence of other specific chemical compounds by undergoing an observable color change.

Benedict's Solution

A light blue reagent that tests for simple sugars, changing to yellow, orange, green, or red in a positive test; sucrose (table sugar) is a notable exception that does not cause a color change.

Lugol's / Iodine Solution

An indicator that begins clear and turns bluish-black when in the presence of starch (complex carbohydrates).

Biuret's Solution

A light blue reagent that indicates the presence of proteins by shifting to a purple color.

Sudan IV

A red indicator used to identify lipids; a positive reaction produces red clumps or a distinct red layer floating on top.

Reactants

The starting molecules present prior to a chemical reaction that undergo rearrangement.

Products

The end-result molecules produced after a chemical reaction has taken place.

Catalyst

A substance that accelerates the rate of a chemical reaction without being consumed or permanently changed by the process.

Enzyme

A biological catalyst composed of protein that accelerates specific metabolic reactions; enzyme names typically terminate with the suffix "-ase".

Activation Energy

The initial quantity of energy required to begin a chemical reaction and break the chemical bonds within the reactants.

Catabolism

The metabolic process of breaking down large, complex molecules into smaller constituent units.

Anabolism

The metabolic process of building larger, more complex molecules from smaller constituent units.

Active Site

The specific catalytic pocket on an enzyme that is complementary in shape to its targeted substrate.

Coenzymes

Organic molecules, such as vitamins, that assist enzymes in folding correctly and functioning properly.

Cofactors

Inorganic substances, such as minerals or hydrochloric acid ($HCl$), that help enzymes fold and maintain catalytic functionality.

Competitive Inhibitors

Inhibitory molecules that bind directly to an enzyme's active site, physically blocking the substrate from entering.

Non-Competitive Inhibitors

Inhibitory molecules that bind to an alternative site (allosteric site), causing a conformational change in the enzyme and active site so the substrate can no longer bind.

Allosteric Site

A distinct location on an enzyme separate from the active site where non-competitive inhibitors attach.

Protein Denaturation

The structural unraveling of an enzyme caused by adverse environmental factors (such as extreme heat over $105^\circ\text{F}$ or extreme pH), which permanently eliminates catalytic function.

Mechanical Digestion

The physical process of breaking food down into smaller pieces without breaking chemical bonds.

Chemical Digestion

The enzymatic hydrolysis of polymeric food macromolecules into dimers and absorbable monomers.

Saliva

Oral secretion produced by salivary glands containing $99\%$ water, mucus to lubricate food, and salivary amylase.

Peristalsis

Involuntary, wave-like contractions of smooth muscle that propel food along the gastrointestinal tract.

Chyme

The semi-fluid mixture of mechanically disrupted food and acidic gastric juices generated in the stomach.

Duodenum

The initial section of the small intestine where secretions from the pancreas and liver enter to carry out the majority of chemical digestion at an optimal pH of approximately $8$.

Jejunum

The middle section of the small intestine involved both in continuing chemical digestion and absorbing nutrients.

Ileum

The terminal section of the small intestine primarily dedicated to nutrient absorption.

Sodium Bicarbonate

An alkaline chemical secreted by the pancreas into the duodenum that neutralizes acidic gastric chyme and raises the local pH to approximately $8$.

Villi

Microscopic, finger-like projections lining the small intestine that increase surface area for nutrient absorption, each housing capillaries and a lacteal.

Lacteal

A lymphatic vessel embedded within each intestinal villus that absorbs digested lipid subcomponents.

Large Intestine

The digestive organ consisting of the ascending, transverse, and descending colon; responsible for water reabsorption to maintain balance and home to mutualistic Escherichia coli ($E.\text{ coli}$) that synthesize Vitamin K.

Salivary Amylase

An enzyme produced by the salivary glands and active in the mouth at a pH of approximately $7$ that breaks complex carbohydrates (starch) down into maltose.

Pepsin

A gastric enzyme produced and active in the stomach at an optimum pH of approximately $2$ that utilizes $HCl$ as a cofactor to cleave proteins into smaller peptides and amino acids.

Trypsin

A proteolytic enzyme synthesized by the pancreas and active in the small intestine at a pH of approximately $8$ to break proteins down into peptides and amino acids.

Pancreatic Amylase

An enzyme produced by the pancreas that hydrolyzes starch into maltose and glucose within the small intestine.

Lipase

A pancreatic enzyme active in the small intestine that digests lipids into glycerol and fatty acids.

Accessory Organs

Organs (liver, gallbladder, and pancreas) that assist digestion by discharging secretions into a common duct emptying into the duodenum, without food ever traveling through them.

Liver

The body's largest internal organ (weighing about $3\text{ pounds}$ and divided into $4\text{ lobes}$) that manufactures bile, detoxifies the blood, and synthesizes glycogen from surplus blood glucose.

Gallbladder

A small organ that stores and concentrates bile produced by the liver before releasing it into the duodenum.

Gallstones

Hardened, crystallized deposits of cholesterol or bilirubin that form inside the gallbladder and can cause severe pain if they obstruct the bile duct.

Cirrhosis

A chronic liver disease marked by the accumulation of scar tissue that obstructs blood flow and impairs hepatic function; commonly triggered by hepatitis, alcoholism, drugs, or fatty liver.

Jaundice

A clinical condition marked by yellowing of the skin and eyes caused by a buildup of bilirubin, a yellow pigment released when red blood cells break down.

Hepatitis A

An acute viral infection of the liver transmitted through the fecal-oral route.

Hepatitis B & C

Chronic, bloodborne and bodily fluid-transmitted viral infections of the liver that can lead to cirrhosis and liver cancer.