Module 3 ( Biomolecules) 3.1 Organic Molecules Organic Molecules contain both carbon and hydrogen atoms. Four classes of organic molecules (Biomolecu

Module 3 ( Biomolecules) 

3.1 Organic Molecules

Organic Molecules contain both carbon and hydrogen atoms. Four classes of organic molecules (Biomolecules) exist in living organisms. 

-carbohydrates

-lipids

-proteins

-nucleic acids

Functions of the biomolecules in the cell are diverse. 

Carbon and Life

Carbon and life. Carbon is the basis of life as we know it. The structure of carbon allows for the formation of (a) the lipids that store energy in this canola plant; (b) carbohydrates that provide structure for this tree; (c) the proteins that form the hemoglobin of red blood cells; and (d) the genetic material that the lioness has passed on to her offspring.

The Carbon Atom

Carbon can form four covalent bonds. Bonds with carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur. The C—C bond is very stable. Long carbon chains, hydrocarbons, can be formed. Besides single bonds,  double bonds, and triple bonds, ring structures are also possible. Branches may also form at a carbon atom, making complex carbon chains. 

The Carbon skeleton and functional groups

The carbon chain of an organic molecule is called skeleton, or backbone

Functional groups- Cluster of specific atoms bonded to the carbon skeleton with characteristic structures and functions. 

Functional groups determine the chemical reactivity and polarity of organic molecules. 

Isomers

Isomers are organic molecules that have identical molecular formulas but different arrangements of atoms. 

The Biomolecules of Cells

Four Classes of biomolecules are

-carbohydrates

-lipids-

-proteins

-nucleuic acids

Usually consist of many repeating units called monomers. A molecule composed of monomers is called a polymer (many parts). 

Example:

-Amino acids (monomer) are joined together to form a protein (polymer)

-Lipids are not polymers because they contain two types of subunits. 

Biomolecules

Carbohydrates

Characteristics:

Contains carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio. Monomers are monosaccharides.

Functions:

Energy source

Provide building material (structural role).

Varieties:

Monosaccharides

Disaccharides

Polusaccharides

Monosaccharides

Monosaccharide- single sugar molecule

-also called a simple sugar

-has a backbone of 3 to 7 carbon atoms

Examples:

Glucose (blood sugar), fructose (fruit sugar). And glactose are hexoses- six carbon atoms.

Ribose and deoxyribose (sugar contained in nucleotides, the monomer of DNA) are pentoses with five carbon atoms. 

Disaccharides

Disaccharide-  two monosaccharides joined together during a dehydration reaction.

Example: Lactose, Sucrose, and Maltose

Polysaccharides: Energy-Storage and Structural Molecules

A Polysaccharide is a polymer of monosaccharides

Example:

-Starch provides energy storage in plants.

-Glycogen provides energy storage in animals.

-Cellulose is found in the cell walls of plants. (most abundant organic molecule on earth.) (Animals are unable to digest cellulose.)

-Chitin is found in the cell walls of fungi and in the exoskeleton of some animals.

-Peptidoglycan is found in the cell walls of bacteria (monomers contain an amino acid chain.)

Lipids

Characteristics: Varied in structure, large, nonpolar molecules that are insoluble in water. 

Functions: Long-term energy storage, Structural components, heat retention, cell communication and regulation, and protection. 

Varieties: fats, oils, and phospholipids, steroids, and waxes. 

Types of Lipids

Triglycerides: Long-Term Energy Storage

Also Called Fats and Oils. 

Functions: Long-term energy storage and insulation

consist of one glycerol molecule linked to three fatty acids by dehydration synthesis. 

Fatty acids may be either unsaturated or saturated 

Unsaturates- One or more double bonds between carbons. Tend to be liquid at room temperature, for example, plant oils. 

Saturated- no double bonds between carbons. Tend to be solid at room temperature. Examples: butter and lard.

Trans- A triglyceride with at least one bond in a trans configuration. 

Phospholipids: Membrane Components

Consists of one glycerol molecule linked to two fatty acids and a modified phosphate group.

The fatty acids (Tails) are nonpolar and hydrophobic. The modified phosphate group (head) is polar and hydrophilic.
Function_ form plasma membranes of cells. In aqueous solutions, phospholipids aggregate to form a phospholipid bilayer (double layer). Polar phosphate heads are oriented towards the water. Nonpolar fatty acid tails are oriented away from water. 

Steroids: Four Fused Carbon Rings

Composed of four fused carbon rings. Various functional groups are attached to the carbon skeleton. 

Functions: Component of the animal cell membrane, hormonal regulation. 

Examples: Cholesterol, testosterone, estrogen

-Testosterone and estrogen are sex hormones differing only in the functional groups attached to the carbon skeleton.

-Cho;esterol is the precursor molecule for several other steroids. 

Waxes

Long-chain fatty acids are connected to carbon chains containing alcohol functional groups. Solid at room temperature, waterproof, and resistant to degradation. 

Function: Protection

Examples: Earswax (contains cerumen). Plant cuticle, beeswax. 

Proteins

Proteins are polymers of amino acids linked together by peptide bonds. 

• A peptide bond is a covalent bond between amino acids

• Two or more amino acids joined together are called peptides

• Long chains of amino acids joined together are called polypeptides. 

A protein is a polypeptide that has folded into a particular shape, which is essential for its proper functioning. 

Functions of Proteins

Metabolism- Most enzymes are proteins that act as catalysts to accelerate chemical reactions within cells. 

Support- Some proteins have a structural function, for example, keratin and collagen. 

Transport- Membrane channel and carrier proteins regulate what substances enter and exit cells. Hemoglobin protein transports oxygen to tissues and cells. 

Defense- Antibodies are proteins of our immune systems that bind to antigens and prevent them from destroying cells. 

Regulation- Hormones are regulatory proteins that influence the metabolism of cells. 

Motion- Microtubules move cell components to different locations. Actin and myosin contractile proteins allow muscles to contract. 

Amino Acids: Protein Monomers

There are 20 different common amino acids. Amino acids differ by their R, or variable groups,

which range in complexity.

Shape of Proteins and Levels of Protein Structure

Proteins cannot function properly unless they fold into their proper shape.  When a protein loses it proper shape, it said to be denatured. Exposure of proteins to certain chemicals, a change in pH, or high temperature can disrupt protein structure.

Proteins can have up to four levels of structure:

-Primary

-Secondary

-Tertiary

-Quaternary

Four Structures of Proteins

• Primary structure

Linear sequence of amino acids.

• Secondary structure

Polypeptide folds into repeating patterns - alpha helices and beta (pleated) sheets held in place with hydrogen bonds.

• Tertiary structure

Three-dimensional shape of a polypeptide.

• Quaternary structure

More than one polypeptide interacting with one

another

The Importance of Protein Folding and Protein-Folding Diseases

Chaperone proteins help proteins fold into their normal shapes and may also correct misfolding of new proteins.

-Defects in chaperone proteins may play a role in several human diseases, such as Alzheimer

disease and cystic fibrosis.

-Prions are misfolded proteins that have been

implicated in a group of fatal brain diseases 

Example: Mad cow diseasePrions are believed to cause other proteins to fold the wrong way.

Nucleic Acids

Nucleic acids are polymers of nucleotides.

Two varieties of nucleic acids:

DNA (deoxyribonucleic acid) Genetic material that stores information for its own replication and for the sequence ofamino acids in proteins.

RNA (ribonucleic acid) Performs a wide range of functions within cells which include protein synthesis and regulation of gene expression.

Structure of a Nucleotide

Each nucleotide is composed of three parts:

• A phosphate

• A pentose sugar

• A nitrogen containing (nitrogenous) base

There are rive types of nucleotides found in cucleic acids. 

• DNA contains adenine, guanine, cytosine, and thymine,

• RNA contains adenine, guanine, cytosine, and uracil.

Structure of DNA and RNA

Backbone of the nucleic aci strand is composed of alternarting sugar phosphate molecules.

• RNA is predomaminately a single stranded molecule, whereas DNA is Double stranded molecule

• DNA is composed of two strands held together y hydrogen bonds between the nitrogen containing bases. 

The two strands twist around each other forming a double helix.

The nucleotides may be in any order within a stand but between strands. 

–Adenine (purine) makes hydrogen bonds with thymine (pyrimidine)

-Cytosine (oyrimidine) makes hydrogen bonds with guanine (purine)

-The bonding between the nitrogen containing bases in DNA is referred to as complementary base pairing. 

Comparing DNA and RNA structure

ATP (Adenosine Triphosphate)

ATP is a nucleotide composed of adenine and ribose (adenosine) and three phosphates.

• High-energy molecule due to the presence of the last two unstable phosphate bonds

• Hydrolysis of the terminal phosphate bond yields:

-The molecule ADP (adenosine diphosphate).

-An inorganic phosphate, P.

-Energy to do cellular work.

ATP is therefore called the energy currency of the cell.