Biology: Essay Question #1

Cellulose

Structure: Cellulose is a carbohydrate, that can be categorized as a structural polysaccharide with long chains of monosaccharides. It is never branched, instead it forms a straight line that are parallel to other cellulose, which are connected by hydrogen bonds. Because of the fiber's toughness, cellulose is difficult to digest. Function: The hydrogen bonds connecting several cellulose fibers together, create tough cellulose bundles that shape into an overlapping mesh that soon after form into the cell walls of plants.

A) Describe THREE types of chemical bonds/interactions found in proteins. for each type, describe its role in determining protein structures...

1. Peptide Bond 2. Hydrogen Bond 3. Ionic Bond

Hydrogen Bonds

DESCRIPTION: A hydrogen bond is a weak type of chemical bond common in living organisms. This type of bond involves a hydrogen atom from a polar covalent bond of another molecule (partial positive charge) that is attracted to a strong electronegative atom that also is apart of another molecule (partial negative charge) ROLE: Hydrogen bond is present in the secondary structure of a protein. The secondary structure of a protein includes alpha-helices and B-pleated sheets that are separately held together by hydrogen bonds. Alpha-helices have a curled shape while B-pleated sheets are folded alongside each other in an antiparallel shape.

Peptide Bond

DESCRIPTION: A peptide bond is a covalent bond found in the primary structure of a protein. The primary structure is the sequence of amino acids which is connected by the peptide bond. A peptide bond is formed between two amino acids when the carboxyl group of one amino acids reacts with the amino group of the other amino acid, releasing a molecule of water. This is the dehydration reaction and usually occurs between amino acids. ROLE: The peptide bond is the bond used by amino acids in the primary sequence. The sequence of amino acids connected by the peptide bonds is called a polypeptide chain. These chains are then folded due to various forces in order to become proteins.

Ionic Bonds

DESCRIPTION: Ionic bonds are formed between two oppositely charged ions, such as a cation and anion. Cations and anions are formed when a stronger electronegative atom steals the valence electrons from the weaker electronegative atom. The atom who lost electrons becomes a cation, a positively charged ion and the atom who gained electrons becomes a anion, a negatively charged ion. ROLE: The tertiary structure of a protein is fashioned by many stabilizing proteins due to bonding interactions of side chain groups of amino acids. Ionic bonds between the positively and negatively charged sites in amino acid side chains, help stabilize the tertiary structure of protein.

B) Choose ONE macromolecule from each of the following groups of macromolecules...for each of the three macromolecules you have chosen, describe its a)structure and b)function

Group 1: Phospholipids Group 2: Cellulose Group 3: DNA

DNA

Structure: DNA has two polynucleotides or "strands" that wind around on an imaginary axis and form a double helix. The two sugar phosphate backbones run 5' to 3' directions from each other which is referred to as the antiparallel arrangement. The sugar phosphate backbones are on the outside of the double helix, and the nitrogenous bases are paired in the interior of the double helix. The two strands are held together by hydrogen bonds between the paired bases, A=T and C=G which are complementary of the other. Function: It is these features that make it possible for DNA to generate two identical copies of each DNA molecule in the cell before it divides. The copies are distributed to the daughter cells after they've divided, making them genetically identical to their parent cells. Overall, it's function is to transmit genetic information whenever a cell reprieve.

Phospholipids

Structure: Phospholipids can be divided into three sections: the phosphate head, the glycerol center, and the two fatty acid tails. The phosphate head is hydrophilic and polar, enabling it to form bonds with water molecules. The two fatty acid tails are hydrophobic and non-polar, making them constantly reject any prospects of bonding with water molecules and instead choosing to create weak van der waal interactions with other molecules like lipids. Function: Phospholipids like to line up and arrange themselves into two parallel layers called phospholipid bilayers. This layer makes up a cell membrane and is critical to a cell's ability to function as it regulates what enters and exits.