Properties of Water

Overview

• O is more electronegative => Unequally shared e- between O and H => polar molecule

• Polarity: differences in atomic electronegativity

• Hydrogen bond: slightly negative O of one water molecule attracted to slight positive H of another molecule

Properties of H₂O

due to its polar and hydrogen bonds

1. Cohesion (co- : cooperate => alike molecules)

   • H-bonding between like molecules

   • Surface tension: hydrogen bonds between water molecules => increased force

2. Adhesion:

   • 2 different molecules form hydrogen bonds

   • High solvency ability in its liquid state

   • Emergent properties = cohesion + adhesion + surface tension

   • Transpiration: movement of water up plants

   • Capillary action: result of cohesion and adhesion

3. High sepcific heat:

   • Absorbs lots of thermal energy before changing states => resisting temp changes

   • Larger bodies => absorb and store more heat => moderation

   • Maintain stable temperature

4. Evaporative cooling:

   • Also used to moderate temperature

   • Cool plants, human sweat, homeostasis

5. Expansion upon freesing:

   • Unique H bond interactions when in its solid state => less dense than solid

   • Ice floating leaving water beneath maintains the stable environment below for aquatic life

   • Solution: liquid, homogenous mixture of 2+ mixture

   • Solvent: dissolving agent

   • Solute: dissolved substance

6. Solvent of life:

   Hydrophilic	Hydrophobic
   Polar, ions	Non-polar
   Cellulose, sugar, salt	Oil, lipids
   Blood	Cell membrane

pH = 14 - pOH

pH: concentration of hydrogen ions

pOH: concentration of hydroxide ions

Organic Chemistry

Carbon and the molecular diversity of life

1. Carbon:

• Organic compound: C and H

• Major elements of life: CHONPS

• 4 valence electrons: tetravalence => forms up to 4 covalent bonds => single, double, triple

• Form macromolecules: carbohydrates, lipids, proteins, nucleic acids

• Molecules can be chains, ring-shaped, or branched

Forms isomers:

• Have same molecular formula, but differ in atom arrangement

• Different structures => different functions

• Additional information (not really important):

Functional groups:

Ch 4 - Functional Groups.pdf

Organic Compounds:

1. Dehydration synthesis: make polymers, A+B => AB + H₂O

   • Subcomponents of H₂O (H and OH) are removed from interacting monomers then combined to create

2. Hydrolysis reactions: cleaves covalent bonds => hydrolyzed polymers into monomers

Carbohydrate:

1. Units of monosaccharides (simple sugar) linked together by a covalent bond called glycosidic linkages

2. Raito: 1C:2H:1O

3. Monosaccharides => disaccharides => polysaccharides

4. Function: energy storage and building blocks

5. Some polysaccharides need to know:

   • Storage: starch (plants), glycogen (animals, alpha linkages)

   • Building: cellulose (beta linkages, plants), chitin (animals, fungi cell walls, arthropod exoskeletons

Lipids:

• Very hydrophobic and nonpolar. Don’t form polymer

Fats/ Triglyceride:

• Source of energy in animals

• Made of 1 glycerol (3-C alcohol) and 3 fatty acid chains (long hydrocarbon chains that attach to the glycerol backbone)

• Fatty acids are connected to glycerol by ester linkage.

Phospholipids:

• Building blocks of cell membrane => creating lipid bilayer

• Has a phosphate group (the head), glycerol, 2 FA tails

• Heads are hydrophilic, tails are hydrophilic

Steroids:

• 4 fused carbon rings attached chemical groups

• Including steroid hormones/signaling molecules (e.g estrogen) and cholesterol

• Cholesterol: found in cell membrane, maintain membrane fluidity

Nucleic Acids:

• Repeating units of nucleotides linked together by covalent phosphodiester bonds between OH group and adjacent nucleotides

• Contain 3 parts: phosphate group, 5 carbon sugar, and nitrogenous base

• The more similar 2 sequences (nucleotides/ nitrogenous bases) are more related 2 organisms are

• E.g: DNA, RNA, ATP, cAMP, NADH, NADPH

DNA:

• the 5' phosphate group of one nucleotide and the 3'-OH group of another

RNA:

• mRNA (m for messenger): transmit protein building directions to ribosomes in cytoplasm

• tRNA: deliver + place amino acids into proteins that are built

• rRNA (r for ribosome): main building component of ribosomes

ATP (adenosine triphosphate)

• Single nucleotide: ribose + nitrogenous base (always adenine) + 3 phosphate group

• Store + transfer energy (power most activities)

• Made during cellular respiration

Proteins:

• Amino acids: building blocks of protein

• 20 unique amino acids => each has a unique side chain (R group) => unique chemical properties

• A wide range of functions:

  1. Enzymes: biological catalysts (e.g lactase, protease: breakdown)

  2. Defensive proteins (e.g antibodies)

  3. Structural support (e.g keratin)

  4. Transport (hemoglobin, ion channels)

  5. Hormones (insulin)

  6. Receptors 

  7. Motor proteins

• Polypeptides: polymers of amino acids

• Building blocks linked by peptide bonds between carboxyl group and amino group

Amino acids = R group + Carboxyl group (-COOH) + amino group (-NH2)

Primary:

• Amino acid sequence in peptide (bond) chain

• Indirectly determine 3D structure

Secondary:

• Hydrogen bonds form between the peptide chain backbone (carboxyl and amino)

• Alpha pleated sheets or beta-helix

Tertiary:

• Bondings between side chains (R groups)

• Bondings include hydrogen bonds, disulfide bridges (covalent bond between 2 S), van der Waals interactions, hydrophobic interactions

•  3D structure

  

Quaternary: 

• Multiple peptide chains join together

• Not all have this level

• Denaturation: unfold of protein if pH and temp are not optimal