Ch.2 - The Molecules of the Cell

Four major families of organic molecules

• sugars

• fatty acids

• amino acids

• nucleotides

Condensation reactions (dehydration synthesis)

• subunits added to one end of growing chain

• subunits linked by covalent bonds

• creates water molecule

Polysaccharides in animals? plants?

animals: glycogen

plants: starch & cellulose

What are glycogen and starch used as?

energy stores

What is cellulose used for?

structural polysaccharide

Fatty acids

stored as energy reserves (fats & oils) through ester linkage to glycerol

What do fatty acids form by bonding to glycerol via ester linkage?

triacylglycerols

Saturated fatty acids

contain all H’s possible on chain

What do saturated fatty acids form?

solid aggregates & deposits inside blood vessels

Unsaturated fatty acids

• have less than max amount of H’s

• contain one or more double bond

Do cis unsaturated fatty acids form aggregates? Do trans?

cis: do not form aggregates because double bond forms kink

trans: behave similarly saturated fatty acids (tend to form aggregates)

Forming phospholipids

• two OH groups in glycerol linked to fatty acids & third OH group linked to phosphoric acid via condensation reactions

• phosphate group linked to small hydrophilic group

What do phospholipids in biological membranes contain:

• 1 saturated fatty acid

• 1 cis unsaturated fatty acid

How do the saturated and unsaturated fatty acids in phospholipids balance each other?

saturated acids make membrane harder/less fluid while cis unsaturated acids reduce membrane stability

What do phospholipids spontaneously form in water?

bilayers

Phosphodiester bond

phosphate group is bonded to 3’ carbon of one nucleotide and 5’ carbon of next nucleotide through 2 ester linkages

Electrostatic interactions

attractions between ionized (charged) groups

What mediates interactions between proteins and nucleic acids

weak, non-covalent bonds of compatible groups

cAMP

cyclic adenosine monophosphate; used for intracellular & intercellular signaling

How are ribosomes assembled?

1. ribonucleotides and amino acids subunits held by covalent bonds to create macromolecules (rRNA & proteins)

2. macromolecules held by noncovalent bonds to create ribosome