Physiology of Water, Buffers, Surfactants, and Proteins

Vocabulary flashcards covering key concepts from notes on water properties, surfactant function, buffer systems, homeostasis, and protein chemistry in physiology.

Organic molecules

Molecules that contain carbon; water is treated as organic here because it is the milieu of all biological processes.

Water polarity

Water is polar and bent due to the electron pull by oxygen, enabling hydrogen bonding.

Hydrogen bonds

Weak bonds between partially positive hydrogen and partially negative oxygen; collectively give water high surface tension and cohesion.

Polarity

Property of having partial positive and partial negative charges, enabling hydrogen bonding.

Universal solvent

Water’s polarity allows it to dissolve polar substances like salts; water arranges around ions with oxygen facing positive ions and hydrogens facing negative ions.

Hydrophilic

Polar molecules that dissolve in water (e.g., proteins, salts).

Hydrophobic

Non-polar molecules that do not dissolve in water (e.g., oils, lipids, steroid hormones such as aldosterone, hydrocortisone, estrogen, progesterone).

Surfactants

Molecules that interfere with hydrogen bonding, reducing surface tension; important in cleaning and in lung function.

Alveoli

Air sacs in the lungs lined with a thin water film, which tends to cause collapse via hydrogen bonding unless surfactant reduces surface tension.

Surfactant

A phospholipid produced around 32 weeks of gestation that reduces surface tension in alveoli to prevent collapse.

Respiratory distress syndrome (RDS)

Condition in premature babies lacking surfactant, leading to breathing difficulty and requiring ventilation/CPAP.

Buffer

A system that maintains pH by neutralizing excess H+ ions; bicarbonate is a key buffer in blood.

Bicarbonate buffer

HCO3− system that maintains blood pH by reacting with H+ to form carbonic acid.

Bicarbonate ion (HCO3−)

A buffer that helps stabilize pH by neutralizing added acids or bases.

Carbonic acid (H2CO3)

Formed from bicarbonate and H+; converted to water and CO2 by carbonic anhydrase.

Carbonic anhydrase

Enzyme that converts carbonic acid into water and CO2, aiding pH regulation.

CO2 elimination

CO2 produced from carbonic acid is expelled by breathing, helping regulate pH.

Kidneys

Organs that help eliminate water and regulate CO2 to stabilize pH, contributing to homeostasis.

Homeostasis

Dynamic constancy of the body's parameters within narrow, healthy ranges.

Normal ranges

Examples include blood pH 7.35–7.45, resting heart rate 62–80 bpm, body temperature 36.5–37.5°C, BP 100–120/60–80 mmHg.

Prefixes: hyper/hypo/contra/ipsi

Hyper = too much, hypo = too little, contra = opposite side, ipsi = same side.

Glomerulonephritis

Inflammation of kidney glomeruli (capillary balls).

Functional groups

Groups of atoms that move together and are sites for reactions; key groups include amino (NH2), carboxyl (COOH), and phosphate (PO4^3−).

Amino group

NH2 functional group found in amino acids and proteins.

Carboxyl group

COOH functional group; participates in peptide bonds and amino acid properties.

Phosphate group

PO4^3− functional group important in nucleotides and energy transfer.

Proteins

Long chains of amino acids linked by peptide bonds; perform hormonal, receptor, enzyme, antibody, and structural roles.

Amino acids

Building blocks of proteins; alpha carbon attached to an amino group, a carboxyl group, a hydrogen, and an R group.

Peptide bonds

Bonds between amino acids formed by dehydration synthesis; hydrolyzed during digestion.

Dehydration synthesis

Reaction that forms peptide bonds by removing water.

Hydrolysis

Reaction that adds water to break peptide bonds, releasing amino acids.

Digestion

Enzymatic hydrolysis of peptide bonds in the small intestine; intact proteins (e.g., insulin) are not absorbed orally.

Dipeptide

Two amino acids linked by a single peptide bond.

Tripeptide

Three amino acids linked by peptide bonds.

Oligopeptide

4–10 amino acids in a chain.

Polypeptide

11–99 amino acids in a chain.

Protein (by amino acid count)

A polypeptide with >100 amino acids that functions as a protein.

Insulin

Example of a protein that cannot be taken orally because digestive enzymes break it down.