Question

*Why was carbon chosen as the atomic backbone of life?

*Define a functional group and explain their importance to life.

*Describe the complete structure, classification and functions of the carbohydrates.

*List and describe in detail the 4 protein structures.

*Define an enzyme and explain how they work and their importance to living things.

*Compare the different types of triglycerides and indicate which are not healthy and those that are healthy. Also, indicate why some are and are not healthy choices.

*List all the macromolecules and describe the monomers of each and how each can be identified through testing.

*List and describe all of the accessory organs of the digestive system and explain how they assist with the process of digestion.

*Explain at least 5 ways in which the small int. is capable of increasing its surface area to perform greater absorption of nutrients.

*Describe in detail the movement of food from the mouth to the anus.

*Compare the similarities and differences between the large intestine and the large intestine.

*Compare the similarities and differences between the wall of the sm. int. and the lg. int.

Answer 1

1). Carbon is the back bone of life living organisms consists mostly carbon based compounds . Carbon can bind to each other molecules . Election confihurstion is the key to an atoms characteristics . Electron configuration determines the kinds and number of bonds sn atom will form with the other atom.

2). Functional groups are the groups of the atom that occur in organic molecules and confer specific chemicsl properties to those molecules . Functional groups are found along the carbon backbone of macromolecules which I'd formed by chains and/ or rings of carbon atoms with occasional substitutions of an element such as nitrogen and oxygen.

Functional groups in biological molecules plays an important role in the formation of molecules like DNA, proteins , carbohydrates and lipids.

Functional groups include hydroxyl,methyl, amino, phosphate, sulfhydryl.

3). Structure: the general empirical structure for carbohydrates is (CH2O)n. Monosaccharides, which are simple sugars that serves as fuel as well as fundamental constituents of living organisms,are the simplest carbohydrates, and are required as energy sources. The most commonly known ones are perhaps glucose and fructose.

Classification:on the basis of their degree of polymerization they can classified as

Simple _mono and disaccharides (also known as sugars) and tri_and tetrasaccharides( oligosaccharides).

Complex :the polysaccharides.

Functions :

. They are used as material for energy storage and production .starch and glycogen ,respectively in plants and animals are stored carbohydrates from which glucose can be mobilized for energy production .

. They exert protein _saving action .

. Their presence is necessary for the normal lipid metabolism .

. They take part in detoxifying process .

. They are also found linked to many proteins and lipids.

4).The term structure when used in relation to proteins, takes on a much more complex meaning than it does for small molecules. Proteins are macromolecules and have four different levels of structure – primary, secondary, tertiary and quaternary.

Primary Structure

There are 20 different standard L-α-amino acids used by cells for protein construction. Amino acids, as their name indicates, contain both a basic amino group and an acidic carboxyl group. This difunctionality allows the individual amino acids to join together in long chains by forming peptide bonds: amide bonds between the -NH2 of one amino acid and the -COOH of another. Sequences with fewer than 50 amino acids are generally referred to as peptides, while the terms protein or polypeptide are used for longer sequences. A protein can be made up of one or more polypeptide molecules. The end of the peptide or protein sequence with a free carboxyl group is called the carboxy-terminus or C-terminus. The terms amino-terminus or N-terminus describe the end of the sequence with a free α-amino group.

The amino acids differ in structure by the substituent on their side chains. These side chains confer different chemical, physical and structural properties to the final peptide or protein. Each amino acid has both a one-letter and three-letter abbreviation. These abbreviations are commonly used to simplify the written sequence of a peptide or protein.

Depending on the side-chain substituent, an amino acid can be classified as being acidic, basic or neutral. Although 20 amino acids are required for synthesis of various proteins found in humans, we can synthesize only 10. The remaining 10 are called essential amino acids and must be obtained in the diet.

The amino acid sequence of a protein is encoded in DNA. Proteins are synthesized by a series of steps called transcription (the use of a DNA strand to make a complimentary messenger RNA strand - mRNA) and translation (the mRNA sequence is used as a template to guide the synthesis of the chain of amino acids which make up the protein). Often, post-translational modifications, such as glycosylation or phosphorylation, occur which are necessary for the biological function of the protein. While the amino acid sequence makes up the primary structure of the protein, the chemical/biological properties of the protein are very much dependent on the three-dimensional or tertiary structure.

Secondary Structure

Stretches or strands of proteins or peptides have distinct characteristic local structural conformations or secondary structure, dependent on hydrogen bonding. The two main types of secondary structure are the α-helix and the ß-sheet.

The α-helix is a right-handed coiled strand. The side-chain substituents of the amino acid groups in an α-helix extend to the outside. Hydrogen bonds form between the oxygen of the C=O of each peptide bond in the strand and the hydrogen of the N-H group of the peptide bond four amino acids below it in the helix. The hydrogen bonds make this structure especially stable. The side-chain substituents of the amino acids fit in beside the N-H groups.

The hydrogen bonding in a ß-sheet is between strands (inter-strand) rather than within strands (intra-strand). The sheet conformation consists of pairs of strands lying side-by-side. The carbonyl oxygens in one strand hydrogen bond with the amino hydrogens of the adjacent strand. The two strands can be either parallel or anti-parallel depending on whether the strand directions (N-terminus to C-terminus) are the same or opposite. The anti-parallel ß-sheet is more stable due to the more well-aligned hydrogen bonds.

Tertiary Structure

The overall three-dimensional shape of an entire protein molecule is the tertiary structure. The protein molecule will bend and twist in such a way as to achieve maximum stability or lowest energy state. Although the three-dimensional shape of a protein may seem irregular and random, it is fashioned by many stabilizing forces due to bonding interactions between the side-chain groups of the amino acids.

Under physiologic conditions, the hydrophobic side-chains of neutral, non-polar amino acids such as phenylalanine or isoleucine tend to be buried on the interior of the protein molecule thereby shielding them from the aqueous medium. The alkyl groups of alanine, valine, leucine and isoleucine often form hydrophobic interactions between one-another, while aromatic groups such as those of phenylalanine and tryosine often stack together. Acidic or basic amino acid side-chains will generally be exposed on the surface of the protein as they are hydrophilic.

The formation of disulfide bridges by oxidation of the sulfhydryl groups on cysteine is an important aspect of the stabilization of protein tertiary structure, allowing different parts of the protein chain to be held together covalently. Additionally, hydrogen bonds may form between different side-chain groups. As with disulfide bridges, these hydrogen bonds can bring together two parts of a chain that are some distance away in terms of sequence. Salt bridges, ionic interactions between positively and negatively charged sites on amino acid side chains, also help to stabilize the tertiary structure of a protein.

Quaternary Structure

Many proteins are made up of multiple polypeptide chains, often referred to as protein subunits. These subunits may be the same (as in a homodimer) or different (as in a heterodimer). The quaternary structure refers to how these protein subunits interact with each other and arrange themselves to form a larger aggregate protein complex. The final shape of the protein complex is once again stabilized by various interactions, including hydrogen-bonding, disulfide-bridges and salt bridges.