AP BIO Study Guide- Water, Carbon, & Macromolecules
H2O = two hydrogen ions bonded* to an oxygen ion
*bond = “polar covalent”: the molecule has opposite charges on opposite ends; this is due to the electronegativity difference between the H’s and O, causing the H’s to have partial negative charges and the O to have a partial positive one; strong bond that keeps the water molecule together
H2O molecules bond to each other by “hydrogen bonding”: these are weaker bonds that are able to be broken and reformed frequently; this allows water its many emergent properties and to be the key to life
Four emergent properties:
1) Cohesion/Adhesion- This is the ability of water molecules to stick to one another due to hydrogen bonding as well as to other surfaces, respectively. This is what allows transpiration up the plant xylem and out the leaves to occur (this is also due to the difference in water concentrations between inside the plant and in the atmosphere, as water wants to go from a high concentration to a low concentration). Also, surface tension is considered a subtopic of this property.
2) Moderation of Temperature- Due to water’s high specific heat, it is able to absorb heat from the environment (breaking bonds) or release heat to it (forming bonds), without more than a slight change in its own temperature. This allows water to regulate to temperature of the environment around it and to make sure it is habitable enough for life. Water also has a high heat of vaporization. This results in “evaporative cooling”: as a surface is heated (heat is absorbed), the hydrogen bonds between water molecules break, and water changes from its liquid form to a gas, and is evaporated. This allows water to stabilize the temperatures of organisms and bodies of water.
3) Expansion upon Freezing- When water freezes and changes to its solid form, the H2O molecules form a crystal lattice, where the hydrogen bonds keep each water molecule a certain distance away from each other. Due to this further apart spacing, ice is less dense than liquid water. Therefore, ice floats on top of liquid water. This allows ice to insulate what is below it, and helps regulate life.
4) Versatility as a Solvent- Due to the partial pos. and partial neg. charges within an H2O molecule, when a solute is introduced into water, as long as that solute has charged ions, the H’s and O’s will be attracted to the oppositely charged ions, creating a hydration shell around the ions and pulling them away from the solute’s molecules, dissolving it (WATER IS PRETTY CLOSE TO A UNIVERSAL SOLVENT.)
An “acid” is any substance that increases the hydrogen ion concentration of a solution.
A “base” is any substance that reduces the hydrogen ion concentration of a solution.
pH = “percent (%) hydrogen”
[H+] and [OH-] have an inverse relationship. This means as one goes up in concentration, the other goes down. Their relationship always has a constant of 10 ^ -14.)
(In a neutral solution, pH is 7, which means [H+] = 10 ^ 7, and [OH-] = 10 ^ 7.)
*Know how to do a Mol equation/set-up*
Carbon can create up to four bonds with many different elements due to its “tetravalence” (has 4 valence electrons, and needs 4 more)
Ability to create long chains, often with hydrogen, resulting in organic molecules
Despite some organic molecules being isomers (same molecular formula), the variation in their carbon skeletons (brancing, double bonds, etc.) is what makes them completely different molecules.
Monomers are the “building blocks” of macromolecules, which, when linked together, create polymers.
Monomers are bonded together using “dehydration synthesis” (the removal of water molecules), and broken apart by “hydrolysis” (the addition of water molecules).
Carbohydrates are sugars that provide fiber and a quick source of energy for your body. The monomer of carbohydrates is called a monosaccharide. Glucose is most common monosaccharide.
The type of links within carbohydrates are called “glycosidic linkages”. Two monosaccharides linked together creates a disaccharide. For example, two glucose molecules bonded together would create maltose.
Many monosaccharides linked together creates a polysaccharide. In aqueous solutions they form rings.
Carbohydrates are used for many different purposes, such as energy storage in plants (starch) and animals (glycogen), as well as for structure within plants (cellulose, forms cell wall) and animals (chitin, forms exoskeletons).
Carbohydrates contain a carbonyl group
Carbs contain “alpha” or “beta” links. We are unable to digest beta links.
Lipids are not considered polymers because they are made up of a few monomers they are not made up of many. Usually lipids consist of a glycerol and three fatty acids (triglyceride). There are three types of lipids: fats, phospholipids, and steroids, but they all have one thing in common: they are hydrophobic. This is due to them being nonpolar and having no charge (fatty acids are basically really long chains of hydrogen and carbon with no charge).
The types of links within lipids are called “ester linkages”.
Saturated fats have a straight molecule and are solid at room temperature. These are bad for you, such as butter.
Unsaturated fats are “kinked” due to a carbon double bond and are liquid at room temperature. These are good for you, such as different types of oils.
Phospholipids contain a hydrophilic head (this is due to it actually having a charge due to its phosphate group’s neg. charge) and a hydrophobic tail. They make up the cell membrane of animal cells.
Steroids are made up of 4 carbon rings. One common type of steroid is cholesterol.
Amino acids are the building blocks, made from the ribosomes of cells. They can either be nonpolar, polar, electrically charged, or etc. There are 20 different amino acids in existence, but they can make up countless proteins.
Amino acids consist of an alpha carbon, a hydrogen, an R group/side chain, a carboxyl group (COOH), and an amino group (N3H+). The “R” group is the variable that makes the specific amino acid unique. All amino acids are distinguishable by their “N-C-C” backbone.
The types of bonds present between amino acids are called peptide bonds, and the polymers of amino acids are called “polypeptides” (proteins).
Amino acids sequences are controlled by DNA/genetics. Even one amino acid being out of place can cause serious issues.
There are 4 levels of conformation to creating a protein. CONFORMATION = STRUCTURE.
Primary structure consists of the unique amino acid sequence. Secondary structure is the “backbone” of a protein, where the curves and folding of polypeptide chains are created through the attraction of hydrogen bonding. Tertiary structure by the interactions (Ex: types of bonds) between the “R” groups. Quaternary structure is the creation of a macromolecule through two or more polypeptides.
Some examples of quaternary structures are collagen (found in hair) and hemoglobin (found in the blood, in RBC’s).
Monomers are called nucleotides.
There are two types, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
They consist of a phosphate group, a pentose sugar, and a nitrogenous base.
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