Glycerol and Fatty Acid Structure

Fatty Acids

• Palmitic acid is a saturated fatty acid, meaning it has no double bonds between carbons.
• Saturated fatty acids are likely to be solid at room temperature.
• Glycerol plus one fatty acid produces a monoglyceride.
• Glycerol plus two fatty acids produces a diglyceride.

Polarity

• Saturated fatty acids have no double bonds between carbons, making them "saturated" with hydrogens.
• When electrons are shared unevenly, the atom with a stronger attraction for electrons develops a slight negative charge (d+).
• The atom with a weaker attraction for electrons develops a slight positive charge (d-).
• Polar molecules have positive and negative ends, or poles.
• Hydrogen bonds may occur between atoms in neighboring molecules or between atoms in different parts of the same molecule.

Hydrogen Bonding

• Hydrogen bonding is responsible for the surface tension of water.
• Surface tension is the attractive force between water molecules that causes water to form spherical droplets when falling or to bead up when spilled onto a nonabsorbent surface.
• Hydrogen bonding between molecules makes it difficult to stretch or deform water.

Biological Solutions

• Life as we know it is established on water-based, or aqueous, solutions that resemble dilute seawater in their ionic composition.
• The adult human body is about 60% water.
• Na+, K+, and Cl- are the main ions in body fluids.

Molecular Shape

• Covalent bonds and weak bonds play a critical role in determining molecular shape.
• The three-dimensional shape of a molecule is difficult to show on paper, but many molecules have characteristic shapes due to the angles of covalent bonds between atoms.
• Double bonds in long carbon chain fatty acids cause the chains to kink or bend.

Proteins

• Proteins have a mix of beta strands and alpha helices.
• Protein secondary structure is illustrated by ribbon diagrams.
• The tertiary structure of a protein is its three-dimensional shape, created through spontaneous folding as the result of covalent bonds and noncovalent interactions.
• Globular proteins can be a mix of alpha helices, beta sheets, and amino acid chains that fold back on themselves.
• The tertiary structure of globular proteins arises partly from the angles of covalent bonds between amino acids and partly from hydrogen bonds, van der Waals forces, and ionic bonds that stabilize the molecule's shape.

Hydrogen Ions

• Hydrogen ions in body fluids come from the separation of water molecules (H2O) into H+ and OH- ions.
• Acids, molecules that release H+ when they dissolve in water, are also a source of hydrogen ions.
• Carbonic acid is made in the body from CO2 and water.
• When carbonic acid separates into a bicarbonate ion and a hydrogen ion, only free H+ contributes to the hydrogen ion concentration.

Buffers

• Buffers are substances that moderate changes in pH.
• Many buffers contain anions that have a strong attraction for H+ molecules.
• When free H+ is added to a buffer solution, the buffer's anions bond to the H+, thereby minimizing any change in pH.
• The bicarbonate anion, HCO3-, is an important buffer in the human body.