Chapter 2- The Chemistry of Life: Organic Macromolecules Organic Molecules

Organic Molecules

molecules that contain carbon atoms covalently bonded to hydrogen atoms. Other elements can additionally be included, Carbon can form 4 chemical bonds with other atoms and can therefore form a great variety of molecules, It forms 4 bonds because it needs 4 electrons to fill its outermost electron shell, almost exclusively associated with organisms, They perform vital functions for cells.

Organic Macromolecules

The 4 organic macromolecules (large molecules) are constructed from joining together smaller building blocks, or subunits, The 4 organic macromolecules are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

composed of one or more carbon containing rings and contain 5 or 6 carbon atoms, contain hydrogen and oxygen, classified based on the number of rings (i.e., sugar units) present.

Monosaccharides and Structure

Monosaccharides are the building blocks (subunits) of polysaccharides, Structure: Composed of 1 sugar unit (or ring), Have the suffix -ose

Functions of Monosaccharides

Provide immediate energy (e.g., glucose), A component of nucleotides (nucleotides are the building blocks of DNA and RNA)

Disaccharides

Structure: Composed of 2 sugar units (or 2 rings) Functions: Provide immediate energy (e.g., sucrose, which is common table sugar)

 Polysaccharides

Structure: Composed of many sugar units (or many rings) Functions:

o   Branched polysaccharides serve as short-term energy storage

·       They store glucose. Glucose monosaccharides are released from the ends of branches when energy is needed.

·       Starch is used by plants and glycogen is used by animals.

o   Long, straight chain polysaccharides serve the function of strong, structural materials.

·       The straight chains can pack together tightly.

e.g., cellulose in plant cell walls and chitin in the strong exoskeleton of insects and crustaceans

Nucleotides

The building blocks (subunits) of nucleic acids are nucleotides, All nucleotides are composed of 3 components:a sugar (a monosaccharide)

·       the sugar is ribose in RNA

·       the sugar is deoxyribose in DNA, a phosphate, a base

·       DNA bases are called: cytosine (C), guanine (G), adenine (A) and thymine (T)

·       RNA bases are called: cytosine (C), guanine (G), adenine (A), and uracil (U)

RNA

There are multiple forms of RNA molecules with different functions, e.g., mRNA, rRNA, tRNA, RNA has various structural forms depending on the type of RNA, RNA molecules are involved in the processes of getting from DNA to polypeptide

DNA

genetic material of organisms, encodes the information of make polypeptides (which fold to form proteins), which produce our inherited traits, composed of segments called ‘genes’. Each gene encodes the information to make a polypeptide

Amino Acids

The building blocks (or subunits of proteins are _, There are 20 amino acids.

§  Amino acids have a central carbon atom (C) connected to:a hydrogen atom (H)

a carboxyl group (-COO) an amino group (-NH3), a side chain (the side chain is different in all amino acids and determines its properties

Amino Acids

The building blocks (or subunits of proteins), there are 20.

Structure of Amino Acids

a hydrogen atom (H), a carboxyl group (-COO), an amino group (-NH3), a side chain (the side chain is different in all amino acids and determines its properties)

Polypeptides

Polypeptides are long chains of amino acids linked together, Polypeptides don’t have function. Polypeptides must fold to form proteins, which have function.

Proteins

formed when polypeptides fold into a three-dimensional shape, i.e., a protein is a folded polypeptide chain that now has function.

What is the link between DNA and Proteins?

DNA encodes the order that amino acids are linked together to form polypetides, The order of amino acids in a polypeptide determines the specific way that a polypeptide will fold to form the final protein.

Proteins Functions

  Proteins are responsible for most structures and functions of cells  including,  Structural proteins, such as( Collagen protein in connective tissues   Keratin protein that forms our tough hair, nails and outer skin layer )Enzymes (Enzymes speed up chemical reactions in cells )Transport proteins(  Move substances into and out of cells)Muscle contraction  ( Muscles are composed of long protein filaments that bring about movement)

More about Lipids

insoluble (do not dissolve) in water, They have lots of nonpolar covalent bonds,They are therefore hydrophobic and unable to attract water molecules, There are 4 classes: fats, phospholipids, steroids, and waxes

Fat composition

Fats are composed of 1 glycerol molecule bonded to 3 fatty acid molecules.

Saturated Fats

In fats, all carbon-carbon bonds in fatty acid chains are single covalent bonds (C-C), Saturated fats are solid at room temperature, e.g., meat grease, butter, A diet high in saturated fat is a risk factor for coronary heart disease, Saturated fats contribute to atherosclerosis, which is narrowing of blood vessels,There are no double bonds linking any carbon atoms in the fatty acid chains

Saturated fats with Animals

Foods rich in saturated fats include many animal products (e.g., red meats and dairy products) as well as products produced from them (e.g., pastries, cakes, cookies, etc.), Animal products (which account for most dietary saturated fat) in moderation can be a source of important nutrients needed by the body including,Iron from red meats, essential amino acids (which are the amino acids that the body cannot make) from all animal products, calcium from dairy products, etc.

Unsaturated fats

In unsaturated fats there is one or more double covalent bonds linking carbon atoms in the fatty acid chains (C=C), There are 2 types of unsaturated fat:Unsaturated cis fats and Unsaturated trans fats

Unsaturated cis fats

both hydrogen atoms are on the same side of the double bond, occur naturally , They are called ‘oils’ and are liquid at room temperature, the ‘good fats’ in the diet and should account for most dietary fat, Foods rich in this include oils (olive, sunflower, canola, etc.), fish, avocado, and nuts.

Unsaturated trans fats

(commonly known as just trans fats),  In unsaturated trans fats, the hydrogen atoms are on opposite sides of the double bond, Until recently, trans fat in foods was mostly produced artificially by adding hydrogen to vegetable oil.

History of Unsaturated trans fats

Trans fats used to be present in a variety of baked goods, convenience foods, and the fast-food industry. Trans fats were added to foods to improve flavor and increase shelf life. Trans fats have shown a strong and consistent link to increased risk of coronary heart disease and other negative health outcomes (and they do not have any nutritive value).Their use is now heavily regulated in the food industry!  They are banned in some countries. In the US, use is restricted to less than 0.5g of trans fat per serving (in which case, the product can put 0g in the nutritional label, but it would still be listed as ‘hydrogenated oil’ in the ingredients if present).

Functions of Fats

Long-term Energy storage, Cushioning and insulation, Absorption of fat-soluable

Phospholipids

composed of 1 glycerol molecule bonded to 1 phosphate  molecules and 1 phosphate molecule.§  The resulting phospholipid is amphipath forms a bilayer in water Functions: Phospholipids form the 2-layer cell membrane that surrounds all cells

Amphipathic

(contain a region that is hydrophilic and a region that is hydrophobic

Steroids

Steroids have a backbone of 4 fused rings of carbon atoms

Waxes: Lipids

varied structures, but they are nonpolar molecules like other lipids, Their primary function is providing protective coatings, Other functions include structural roles (like beeswax) and protective functions (like earwax).

Cholesterol

  An important component of cell membranes that surround all cells, Needed to synthesize the hormones estrogen and testosterone (these hormones are made by modifications to cholesterol)

Estrogen and testosterone hormones

These are the so-called male and female sex hormones needed for gamete (egg or sperm) production and development of secondary sex characteristics