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Chemistry

of LifePrepared by: Jerome A. Bigael,

Leyte Progressive High School

The Chemistry of CarbonThe emphasis of this

section is more on molecules containing carbon bonded to itself or other atoms.

We call these C-containing compounds as organic compounds

Since there are 4 valence electrons or outermost electrons in carbon, it is capable of covalently bonding with four more atoms to form straight

chains, branches or even rings.

All these three forms make-up the biological

molecules in all living things.

Organic Compound that contain only hydrogen and carbon are called

hydrocarbons.The covalent bonds

between carbon and hydrogen are rich in energy, making them applicable as fuels.

Hydrocarbons

Hydrocarbons are considered nonpolar compounds, and the equal distribution of electrons maybe attributed to similar electronegativities of hydrogen and carbon atoms.

However, most organic molecules inside a cell contain atoms other than hydrogen and carbon.

are molecules that is present in living organisms, including large macromolecules such as proteins, carbohydrates, lipids, and nucleic acids.

Generally, these follow the same

laws of nature like other chemical molecules. However,

biomolecules have specific functions, especially in a living system where they commonly act

as a building material.They are arranged from smaller

and simpler molecules, called subunits, until they form a more complex structure called a

macromolecule.

Aim: Understand the basis of how these biomolecules function.

Since water is composed of H and O, it is not surprising that these elements are among the most abundant elements in our body.

However, it is also important to note that another reason for the abundance of C, H, O and N is that these make up important biological molecules.

Element Percentage

H 63 %

O 25.5 %

C 9.5 %

N 1.4 %

Ca 0.31 %

P 0.22 %

CL 0.08 %

K 0.06 %

S 0.05 %

Na 0.03 %

Mg 0.01 %

Distribution of Selected Elements in the Human Body

Carbohydrates Are chains of small organic molecules with a 1:2:1

mole ratio of carbon, hydrogen and oxygen.

The simplest formula for carbohydrates is (CH2O)n where the subscript n refers to the number of carbon atoms.

Carbohydrates act as energy storage or food reserves in plants and animals, and this role is attributed to the many carbon-hydrogen bonds contained in a carbohydrate molecule.

Carbohydrates are important source of energy needed for many metabolic activities.

Because of abundance of polar in its structure, carbohydratesare highly polar molecules which can make them solublein many body fluids especially in blood through which they are carried to all parts of the body.

Carbohydrates are generally classified

into 3

Simple carbohydrates or monosaccharides, being small and therefore may be easily dissolved, provide instant source of energy.

These are sugars that cannot be hydrolysed/dissolve to give a simpler sugar.

Examples of monosaccharides include glucose (dextrose), fructose (levulose) and galactose.

Examples: fructose or sugar found in fruits

Disaccharides A disaccharide (also called a double sugar or

biose) is the sugar formed when two monosaccharides (simple sugars) are joined by glycosidic linkage. Like monosaccharides, disaccharides are soluble in water. Three common examples are sucrose, lactose, and maltose.

Example of a disaccharide molecule is milk.

Complex or Polysaccharides

Are composed of simple carbohydrates covalently bonded to each other

Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidiclinkages and on hydrolysis give the constituent monosaccharides or oligosaccharides.

Complex carbohydrates or polysaccharides, serves as structural building for cells.

For example, chitin, it serves as structural building material in insects and many fungi.

Polysaccharide is the main ingredient on the exoskeletons of athropodsand crustaecans and also in cell walls of fungi.

LipidsLipids are biomolecules that contain large

hydrophobic structures that are commonly not soluble in water.

The primary function of lipids are storage of energy and building material for cell membranes.

Cell membranes are selectively permeable, partly because of the lipid bilayer.

Examples of lipids are :

Fats, Oil and Waxes

Polynucleotides

Are chains of nucleotides that play a role in the storage of information.

Structurally, a nucleotide is composed of a heterocyclic base, a pentose (ribose or deoxyribose) unit, and a phosphate group.

The heterocyclic base can have either a purine (adenine, guanine) or a pyrimidine (Uracil, cytosine, thymine).

These nucleotides are associated as the monomeric units of deoxyribonucleic acid (RNA), which are important carriers of information inside the cell.

The presence of genes, inheritance, and protein synthesis are possible because of DNA and RNA molecules.

DNA is a doubled-stranded long chain of unbranched polymer, composed of four types of bases.

These bases are adenine= A, cytosine=C, guanine= G, and thymine= T.

In DNA, A-T and C-G pairings

are followed.The DNA carries all genetic

information of an individual.

On the other hand, RNA is important in the transcription and translation of genetic code.

RNA is a single stranded long chain of unbranched polymer composed of four types of subunits, namely, adenine= A,

uracil= U, cytosine= C and guanine= G.

Base-pairing in RNA occurs during transcription when RNA strand pairs up with DNA template strand or when RNA strand coils up and temporarily pairs up with the base pairs either in the same or in another RNA strand

In such cases the A-U and C-G base pairs

are followed.

Write the complementary base sequence for the matching strand in the DNA section shown below.

1. CGTAAGCGCTAATTA

2. TCTTAAATGATCGATC

3. AATGAATAGCTAGCTT

4. GGCATTCGCGATCATG

5. CGTTAGCATGCTTCAT

6. ACTAACGGTAGCTAGC

7. ATGTCGCTGATACTGT

8. GAAGCGATCAGTTACG

9. AATGAATAGCTAGCTT

10. GGCATTCGCGATCATG

11. CGTTAGCATGCTTCAT

12. ACTAACGGTAGCTAGC

Proteins

ProteinsProteins constitute more

than half of the cell’s dry weight. The biomolecule serves many functions, which includes structural support(collagen), movement (muscle), defense(antibody), catalyst in a reaction(enzyme), and transport.

Proteins generally contain C, H, N,

and O.Amino acids are the building blocks

of protein.

They are bi-functional product containing both a carboxylic group (-COOH) and a basic group (-NH2) attached to a carbon atom.