Chapter 3 - Chemistry of Life part 1

Biomolecules

Carbohydrates, lipids, proteins, and nucleic acids

Organic compounds

Made up of carbon and hydrogen at the same time, with or without any another element.

Carbon Atoms

form up to four covalent bonds to complete its octet:

• single, double, or triple

• straight or branched chains

• rings

What is an isomer?

Types of isomers

Structural, geometric, and enantiomers

Structural isomers

same molecular formula but

different structural formulas (different

covalent arrangements)

Geometric isomers

(cis–trans isomers) ; different spatial arrangements

Enantiomers

mirror images

Hydrocarbons

• carbon and hydrogen only

• Nonpolar

• hydrophobic

Non-polar Covalent Bond

A bond between 2 non-metal atoms that have the same electronegativity and therefore have equal sharing of the bonding electron pair.

Polar Covalent Bond

A bond between 2 non-metal atoms that have different electronegativities and therefore have unequal sharing of the bonding electron pair.

Electronegativity

Ability to attract electrons

Functional Groups

• Polar (hydroxyl and carbonyl)

• Acidic (carboxyl and phosphate)

• Basic (amino)

Hydrophilic

associate strongly with

polar water molecules

Acidic group

• release hydrogen ions

• become negatively charged

Basic group

• accepts a hydrogen ion

• become positively charged

Polymers

• long chains of monomers

• linked through condensation reactions

Macromolecules

• large polymers

• polysaccharides, proteins, and DNA

• broken down by hydrolysis reactions

Monosaccharide

• simple sugar (one sugar unit)

• typically contain three to seven carbon atoms.

•hydrophilic due to the large number of polar hydroxyl group.

Disaccharide

• 2 monosaccharides (two sugar units)

• joined by glycosidic linkage (usually between carbon 1 of the molecule and carbon 4 of the other molecule)

What functional group is formed when one carbon in a monosaccharide is double-bonded to an oxygen atom?

A carbonyl group (C=O).

What functional group is bonded to each carbon in a monosaccharide, except one?

A hydroxyl group (–OH).

What type of monosaccharide is formed when the carbonyl group is at the end of the carbon chain?

An Aldehyde

What type of monosaccharide is formed when the carbonyl group is located at any other position in the carbon chain (not at the end)?

A Ketone

Alpha glucose and beta glucose are

isomers

Polysaccharides

• Is a macromolecule

•Long chains (simple or branched) of repeating units of simple sugar, usually glucose.

The 3 Types of Polysaccharides

. Starch

. Glycogen

. Cellulose

Storage polysaccharides

• starch in plants

• glycogen in animals (For humans, it is

stored in muscles and liver)

Structural polysaccharide

• cellulose, cell walls of plants (serve as

fibers to the digestive system)

Starch

• Energy storage in plants

• Polymers of α-glucose (α-1-4 glycosidic linkage)

• Can exist in two forms:

- Amylose: simpler form “Un-branched”

- Amylopectin: more common form “branched”

• In Plants, the synthesized starch is stored inside

the “Amyloplast”

Which type of glycosidic linkage can be broken down by all organisms?

True or False: Starch consists of highly branched chains that form coils or helices.

True, the chains are stabilized by hydrogen bonds between hydroxyl groups of glucose subunits, forming a helical structure.

Glycogen

Cellulose

What structural change leads to the formation of amino sugars?

Replacing one hydroxyl group (–OH) with an amino group (–NH₂) in a carbohydrate molecule forms amino sugars like glucosamine and galactosamine (found in cartilage).

How do carbohydrates and proteins interact in the cell membrane?

They associate to form glycoproteins—proteins with carbohydrate chains attached. These are found on the outer surface of the cell and are common in secreted proteins like mucus.

How do carbohydrates and lipids interact in the cell membrane?

They form glycolipids through glycosidic linkage. Glycolipids act as markers for cellular recognition.