BIO 101 Ch.3: Organic Chemistry

Why is there thought to be an unlimited amount of structures formed by carbon?

Carbon has four valence electrons, and can therefore bond with up to four elements.

Hydrocarbons

A “backbone” structure that contains long chains of carbon atoms, with hydrogen atoms bonding where there are open spaces

Isomers

Varying structures with the same chemical formula

Functional groups

The combinations of atoms attached to the backbone that account for the reactivity of the molecule

• They chemically behave the same regardless of the backbone.

What does an R represent?

The location of functional groups attaching to the chain

Molecules containing carboxyl groups are…

• Polar (hydrophilic)

• Weakly acidic

Which functional group do proteins and amino acids have?

NH2 (amino group)

Which functional group may make a hydrocarbon water-soluble (hydrophilic)?

Hydroxide

Fats form when…

Molecules that contain alcohol and carboxyl groups react

Proteins form when…

Amino and carboxyl groups are linked.

Dehydration synthesis

• Allows for polymers to be built

• Molecules release water when they combine to form polymers

Hydrolysis

Water breaks down polymers

• an OH group binds to one monomer, and the H bonds to the other.

How many carbon atoms are in the backbone of a simple sugar (monosaccharide) molecule?

3-7

When do carbohydrates take a ringlike form?

When in water

• Hydroxyl allows to be soluble

Glucose formula

C6H12O6

Isomers of glucose

• Fructose

• Galactose

Examples of disaccharides

• Maltose

• Sucrose

• Lactose

How many glucose units does Maltose have?

2

Sucrose

• Collected from beets and sugar

• Used as sweetener

• Two units = glucose and fructose

What happens to fructose when digested?

It is converted to glucose (preferred energy source (for use by cells)

• If glucose is not needed, it is metabolized into fat

Lactose

• Contains glucose and galactose

Polysaccharides

• Branched structure —> easy to break down —> good short term energy source

Starch

• Slightly branched or unbranched

• Energy storage of glucose for plants

Glycogen

• Branched

• Energy storage of glucose for animals

Cellulose

• most abundant carbohydrate

• found in all tissues of a plant as cell walls

• unbranched molecules

• held together parallel by hydrogen bonds for extra strength

Chitin

• glucose contains functional group of aminos (NH2)

• present in exoskeletons

• medicinal applications (antiviral)

• used in cosmetics and food

Properties of lipids

• Hydrophobic

• Insoluble in water

Why are lipids insoluble in water?

Nonpolar hydrocarbons present in lipids lack hydrophilic groups

Fats

• solid at room temperature

• used for insulation and storing energy

Oils

Monomer composition of oils and fats

• glycerol

  • 3 OH groups

• Fatty acids

  • hydrocarbon chain ending in carboxyl group

How is an oil/fat formed?

Carboxyl group (at end of hydrocarbon chain of fatty acid) bonds with glycerol’s OH parts.

• Dehydration synthesis = 3 waters released along with fat molecule

Fatty acids in cells typically contain ____ carbon atoms per molecule.

16-18

Unsaturated fatty acid

Carbon chain contain double bonds where there are fewer hydrogens

Saturated fatty acid

More hydrogens, no double bonds

Trans fat

• unsaturated fat

• double carbon bond with hydrogen atoms on either side (basically doubled up)

• more solid fat

Phospholipids

Lipids that contain a phosphate functional group

• similar in structure to triglycerides, except 3rd fatty acid bonded to glycerol is replaced by ionic phosphate group that typically connects to another polar group

  • end with polar head = hydrophilic, soluble; end with tail (hydrocarbon) = hydrophobic, insoluble

Steroids

• Lipid

• Carbon skeleton has four fused rings

• Lack fatty acids, but are still insoluble

• ex. cholestrol

Amino acid composition

• Special skeleton (hydrocarbon chain)

  • Single center carbon atom

  • Carbon atom bonded to H, amino functional group, carboxyl functional group, and side chain (R-group)

How do amino acids bond?

Carboxyl group bonds with another’s amino group

How can hydrogen bonding occur within amino acids?

Between the double bond of C and O in one amino acid and the single bond of N and O in a polypeptide

Protein primary structure

Sequence of amino acids

Protein secondary structure

• Spatial location/orientation of amino acids

• Varied by # of amino acids in a polypeptide + which are present

• Alpha helix, beta-pleated sheet

• May be numerous in a polypeptide, even on the same segment

Protein tertiary structure

• overall 3D shape of the protein

• held together by R-groups on amino acids

• protein can turn denatured (inactive) when this structure is affected

What happens to side chains when their R-groups are hydrophobic?

They densely pack together

Quaternary structures

Multiple tertiary structures (multiple polypeptide chains)

Fibruous protein

• rodlike structure

• helical secondary structures

• ex. keratin, collagen

• often takes structural roles

Globular protein

• rounded/irregular tertiary structure

• ex. enzymes

Composition of nucleotides

• phosphate functional group

• sugar (deoxyribose in DNA, ribose in RNA) containing 5 carbon atoms

• nitrogen-containing base (adenine, guanine, cytosine, thymine)

Structure of DNA

• double helix shape

• each strand (molecule) has a backbone containing phosphates bonded to sugars

• bases orient towards inside of helix

• guanine of one strand is paired with the cytosine of another; same with adenine and thymine (complementary base pairing)

Function of RNA

Translate the many sequences of DNA into proteins

• Instead of thymine, RNA uses uracil

Adenosine

• Adenine + ribose

  • 3 phosphate groups connect = ATP