Biochemistry

The Chemistry of Life

What is an organic compound?

For our purposes, organic compounds are compounds

associated with living things and contain the elements carbon and

hydrogen

Examples of organic compounds: C6H12O6, CH4, C6H6

Examples of inorganic compounds: NaCl, CO2, H2O, CaCO3

the Carbon Atom (4 Valence Shell Electrons)

Several Factors Make Carbon Essential to Life:

1.The ease with which carbon atoms form bonds to other carbon atoms (single, double or triple bonds).2.The strength of both C-C bonds and the covalent bonds carbon forms to other elements (C,H,N,O,P,S).3.An almost infinite variety of different molecules can be formed using carbon.

Carbon’s Versatility Forms the Basis for its Importance in Living Things.

The Four Major Groups of Organic Compounds We Associate with Life:

1. Carbohydrates2. Lipids3. Proteins4. Nucleic Acids

• The above classes of organic compounds are both required by living things (found in foods) and comprise living things. They are needed for growth and energy.

• Nucleic acids are generally not needed in the diet because the human body can synthesize (make) the building blocks (monomers) of nucleic acids (from amino acid precursors).

Organic compounds are relatively large molecules called MACROmolecules.

• Macromolecules are relatively large molecules consisting of many atoms and chemical bonds.

• Some macromolecules are also polymers. Polymers are built from joining smaller units (monomers) together. Carbs, nucleic acids, proteins and lipids are all polymers.

I. Carbohydrates (CH2O)n:

a. Made up of the elements carbon, hydrogen and oxygen; usually in a 1:2:1 ratio of C:H:O.

b. Sometimes easily identified because the names end in ‘ose’ (glucose, sucrose, etc.).

c. Source: Plants form carbohydrates using sunlight during photosynthesis.

Living things use carbohydrates (like glucose) as their main source of energy. Plants, some animals, and other organisms use carbohydrates for structural

purposes.

Food Sources: Bread, fruits, pasta, grains, vegetables.

Categorizing the Carbohydrates

See Handout

MONOSACCHARIDES(SIMPLE SUGARS)

NOTE: Although the above monosaccharides have the same molecular formula (C6H12O6), they have different arrangements of atoms and bonds, and, therefore, different chemical properties.

The Disaccharides or Double Sugars(also considered simple sugars)

•Sucrose (table sugar) is found naturally in fruits.

•Lactose is found naturally in milk and milk products (yogurt, cheese).

• Maltose is a grain sugar and is used during the beer fermentation process.

POLYSACCHARIDES(THE COMPLEX SUGARS)

The polysaccharides (cellulose, chitin, glycogen and starch) are each comprised of over 300 glucose monomers or building

blocks linked together via glycosidic (covalent bonds).

Polysaccharides include:• Cellulose (plant cell wall fibers)• Chitin (found in fungal cell walls/exoskeleton of arthropods).

*Chitin is a nitrogen-containing carbohydrate.• Glycogen (an energy storage form of glucose found in

animal liver/skeletal muscle cells).• Starch (plant energy storage). Example: Potato.

Polysaccharides are more slowly digested by the body than the simple sugars. Why?

Examples of Polysaccharide Structure

SUMMARY OF THE STRUCTURES

Summary: Examples and Functions of Carbohydrates

Examples Use in Animals Use in Plants

Monosaccharides Glucose, Galactose, Fructose, Ribose,Deoxyribose

Glucose is carried by the blood to transport energy to cells.

Fructose is used to make fruits sweet-tasting, attracting animals to disperse seeds in fruit.

Disaccharides Maltose, Lactose, Sucrose

Lactose is the sugar in milk, providing energy to young mammals.

Sucrose is carried by a plant’s ‘circulatory system’ to transport energy to cells.

Polysaccharides Starch, Glycogen, Cellulose, Chitin

Glycogen is used as a short-term energy store in liver/muscles.

Cellulose is used to make strong fibers that construct plant cell walls.

II. The Functions of Lipids

Long term energy storage in the form of fat (humans) and oils (plants). A thin layer of thermal (heat) insulation under the skin.Form waterproof coverings (hydrophobic) – skin, bird feathers, etc. Form parts of biological (cell) membranesAct as chemical messengers (steroids)Allow for buoyancy (less dense than water) so animals can float on waterCushion and protect internal organs.

A Focus on the Fats

THERE ARE 3 TYPES OF FATS:1. Unsaturated Fats

a. Monounsaturatedb. Polyunsaturated

2. Saturated Fats3. Trans Fats (a modified

unsaturated fat).

NOT ALL FATS ARE CREATED EQUAL

the Basic chemical structure of fats

Some lipids, such as fats, are made up of one or more fatty acid chains and a glycerol backbone.

The Trans Fats(processed, artificial Fats)

Found in ‘foods’ like margarine. Margarines, with trans fats, are now thought to be far unhealthier than butter.

Trans fats are considered by many nutritionists to be ‘metabolic poisons’ because they:

a. Raise the levels of bad cholesterol (LDL) and lower the levels of good cholesterol (HDL)

b. Increase the risk of heart disease and stroke.

Ideally you should consume no trans fats. The recommendation is no more than 3 grams/day of trans fats.

NYC has banned the use of trans fats in restaurants.

TRANS FATS

Diets Rich in Fats:Characteristic Saturated Fatty

Acids & Polyunsaturated

trans (hydrogenated)

fatty acids.

Monounsaturated fatty acids and

polyunsaturated cis fatty acids (Omega-

3 and Omega 6)

Shape Straight Bent and Twisted

Origin Animals or Artificial Processing

Plants

State at Room Temperature

Solid Liquid

Why is the Shape of the Molecule Important?

Inside your blood vessels, fatty acids with a bent/twisted shape tend to more easily be picked up and carried away by blood flowing through your arteries. Saturated

fatty acids, which are straight, can lie flat against the walls of your arteries—resulting in deposits called plaque (plaques are deposits of saturated or trans fatty

acids that combine with cholesterol). Polyunsaturated fats tend to carry away cholesterol molecules.

Identifying Fatty Acids(Saturated or Unsaturated?)

Steroids

Includes molecules like cholesterol and chemical messengers like hormones (ex. estrogen in females, testosterone in males and the

stress hormone cortisol).

A focus on Cholesterol

TYPES OF CHOLESTEROL

High-Density Lipoprotein Low-Density Lipoprotein

HDL LDL

The “Good” Cholesterol The “Bad” Cholesterol

Elevated levels of HDL cholesterol are beneficial in that there is a low risk of

coronary artery disease.

Elevated levels of LDL cholesterol increase blood triglyceride (fat) levels, increase blood pressure, and increase

the risk of coronary artery disease.

A PHOSPHOLIPID BILAYER SURROUNDS & PROTECTS ALL CELLS

Phospholipids contain a polar head (hydrophilic) and two non-polar tails (hydrophobic). Because of this, phospholipids form

important cell coverings that protect the inside of the cell from its environment.

Comparing the use of carbohydrates and lipids in terms of energy storage

Carbohydrates Lipids

Storage: 4 Calories/Gram 9 Calories/Gram

Energy Released: 17 KJ/Gram 38 KJ/Gram

Stored As: Glycogen (Animals)Starch (Plants)

Fats (Animals)Oils (Plants)

Time: Short-Term Energy Storage

Long-Term Energy Storage

Metabolism: Quickly and Easily Broken Down into Glucose.

Slower to build up fat stores and/or break down into glycerol/fatty acids.

Energy Storage of carbs, lipids & proteins

• The main energy-storing bonds are those covalent bonds between carbon and hydrogen.

• Lipids have a higher ratio of C-H bonds to C-O bonds than either carbs or proteins.

One can eat lots of fresh fruits and vegetables without necessarily worrying about excess caloric intake because these items have only moderate amounts of carbs, little fat and are

high in undigestible fiber.

III. The Nucleic Acids

• Function: Store and transmit hereditary (genetic) information.

• Contain the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus.

• The monomers of nucleic acids are called nucleotides. Nucleotides are made up of 3 parts:a. 5-carbon sugar b Phosphate group, c. Nitrogen(ous) base.

Examples: 1. Deoxyribonucleic Acid (DNA)

2. Ribonucleic Acid (RNA)

IV. Proteins

THE FUNCTIONS OF PROTEINS•Form structures such as hair, fur, nails, muscle and bone.•Allow cell to cell communication.•Hormones (chemical messengers in the body).•Form antibodies to protect against infection.•Act as Catalysts (enzymes) to speed up chemical reactions in the body.•Can be a source of energy (last resort)

Proteins

Amino Acids(the monomers or Building Blocks of Proteins)

• Contain the elements nitrogen, carbon, hydrogen, and oxygen (some amino acids contain sulfur).

• The monomers of proteins/polypeptides are amino acids.

• Amino acids contain:a. An amino groupb. Carboxyl groupc. Variable R-group (side chain)

Another View

There are 20 different types of Amino Acids. Some of those Amino Acids mustbe acquired through the food we eat, while others can be synthesized (made) by

the body.

Polypeptides

When amino acids join, they form a polymer called a polypeptide. The monomers (amino acids) are

held together by covalent peptide bonds.

Protein Folding & Denaturation

Protein Shape (structure) and Function (Examples)