CARBON AND FUNCTIONAL GROUPS

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1 COURSE READINESS ASSESSMENT FOR PHYSIOLOGY CARBON AND FUNCTIONAL GROUPS

2 Carbon is an important and versatile element Carbon is one of the most abundant elements in organisms! A molecule that contains carbon is called an organic molecule A carbon atom has 4 unpaired valence electrons, so it can form a maximum of 4 covalent bonds: Pumbaa/ Wikimedia Commons / CC-BY-SA-3.0 / GFDL

3 Carbon is able to form single or multiple covalent bonds with another atom (often other carbon atoms). Examples: ethane ethylene ethyne Carbon atoms can also form long chains, such as in a fatty acid. Fatty acids are usually held together by single and sometimes double covalent bonds.

4 Carbon atoms can also form rings, such as in cyclohexane: These carbon rings are often simplified so that the carbon (and maybe other atoms) are not individually labeled. Cyclohexane again: Some rings have both single and double covalent bonds, such as in benzene: cacycle/ Wikimedia Commons / CC-BY-SA-3.0 / GFDL

5 Functional groups A functional group is a group of atoms that is commonly found together Functional groups are attached to larger organic molecules, giving them special properties

6 Some common functional groups -O-H hydroxyl C O carbonyl carboxyl amine phosphate -S-H sulfhydryl LeonardoG/ Wikimedia Commons / CC-BY-SA-3.0 / GFDL

7 Hydroxyl group: -O-H Molecules that contain this functional group are alcohols. Their names often end in -ol. Examples: ethanol glycerol cholesterol

8 Hydroxyl groups are polar. The oxygen atom has a slight negative charge and the hydrogen has a slight positive charge. Smaller alcohols like ethanol and glycerol are water soluble, or hydrophilic Larger alcohols like cholesterol are water insoluble, or hydrophobic.

9 Carbonyl group: C O Pronounced as car-bon-eel An aldehyde is a molecule with a carbonyl group at one end acetaldehyde A ketone is a molecule with a carbonyl group in the middle acetone Carbonyl groups are commonly found in carbohydrates and nucleic acids

10 Carboxyl group: A carboxyl group is basically a carbonyl group with a hydroxyl group attached! Molecules with a carboxyl group are called carboxylic acids acetic acid

11 These molecules are acids because they are proton donors - in solution, the hydrogen atom of a carboxyl group can detach to become a hydrogen ion (H + ): CH 3 COOH CH 3 COO - + H + acetic acid acetate hydrogen ion (proton) Carboxylic acids are the among the most acidic of all the organic, or carbon-containing, acids. Carboxyl groups are polar because of the presence of the hydroxyl. Thus, carboxylic acids are water soluble, or hydrophilic. Carboxyl groups are commonly found in proteins

12 Amine group: Can also be called an amino group Molecules that contain this group are called amines glycine (an amino acid in proteins) thymine (a nitrogenous base in DNA) Amines are bases because they are proton (H + ) acceptors they can pick up hydrogen ions from the surrounding solution: CH 3 NH 2 + H + CH 3 NH 3 + methyl amine hydrogen ion (proton) methylammonium ion

13 Amine groups are polar. Thus, molecules that are amines are water soluble, or hydrophilic. Amine groups are commonly found in nucleic acids and proteins

14 Phosphate group: Molecules that contain this group are called phosphates adenosine triphosphate, ATP (a cell s energy source)

15 The two hydrogen atoms can detach from a phosphate group, leaving it with a negative charge: -1 (or 1- ) if one of the two hydrogen atoms detach -2 (or 2- ) if both hydrogen atoms detach This net negative charge also makes a molecule water soluble, or hydrophilic. Phosphate groups are commonly found in nucleic acids

16 Sulfhydryl group: -S-H Molecules that contain this group are called thiols cysteine (an amino acid in proteins) The sulfur (S) atom in the group is capable of forming a covalent bond with a sulfur of another sulfhydryl group. This bond is called a disulfide bond or disulfide bridge. Example: Disulfide bond between two cysteine molecules CH 2 S S CH 2 Sulfhydryl groups are commonly found in proteins. Disulfide bonds between cysteines help to hold some proteins in their three-dimensional shapes.

17 Summary of Carbon and Functional Groups Carbon is an element that is important for life. Carbon atoms are versatile because they can form a maximum of four covalent bonds. Organic molecules are carbon containing molecules. Carbon atoms can form double and triple covalent bonds with other atoms. They can also form long chains and ring structures. Functional groups are groups of atoms that tend to be found together. They give organic molecules special properties. Six functional groups are among those commonly found in biological molecules: Hydroxyl, carbonyl, carboxyl, amine, phosphate, sulfhydryl.