Cell Bio Ch. 2

What is the size of small molecules in cells?

mol. weight 100-1000 Da, up to ~30 carbon atoms; 1/10 total mass of organic matter in a cell

2 major roles of small molecules in cells

monomer subunits to construct macromolecules; energy sources getting broken down and transformed into other small molecules

Sugars →

polysaccharides, glycogen, and starch (in plants)

fatty acids →

fats and membrane lipids

amino acids →

proteins

Nucleotides →

nucleic acids

Which 2 groups of small molecules are energy sources?

sugars and fatty acids

What are 2 roles of sugar?

energy sources and subunits of the larger carbohydrates

How can glucose be converted into different sugars?

By switching the orientation of specific -OH groups relative to the rest of the molecule.

How do sugars form rings?

in aqueous solution, the aldehyde or ketone group of a sugar molecule tends to react with a hydroxyl group of the same molecule, thereby closing the molecule into a ring

What are sugar derivatives?

chemically altered monosaccharides where one or more hydroxyl has been replaced by another functional group to alter their properties, reactivity, and function

Formation of a disaccharide

the carbon that carries the aldehyde or ketone reacts with any hydroxyl group on a second sugar via condensation reaction to make a glycosidic bond

Unsaturated fatty acids

• have one or more double bonds in their hydrocarbon tail to make a kink in the tail

• insoluble in water because of the hydrocarbon tail

• plant oils, liquid at room temperature

saturated fatty acids

• have no double bonds, so a straight tail

• amphipathic properties

• meat and dairy products

How are fatty acids linked together and the process?

• covalently linked via their carboxylic acids

• if free carboxyl group of a fatty acid will be ionized, but more often it is linked to other groups to form either esters or amides

triglycerides

• neutral (nonpolar and hydrophobic) lipid with 3 acyl chains and no polar head group

• fatty acids are stored in cells as an energy reserve (fats and oils) through an ester linkage to glycerol to form triacylglycerols

• can be packed tightly into dense droplets inside cells to store energy

Phosphoglycerides

• subunit of cell membrane

• 2 fatty acid tails linked to glycerol

• amphipathic containing a hydrophilic head and 2 hydrophobic fatty acid tails

Phosphoglyceride head groups

have 4 polar head groups; ethanolamine, choline, serine, and inositol that link to phosphate

Sphingolipids

• two hydrocarbon tails: 1 tail is a fatty acid, other tail is sphingosine; and a polar region

• no glycerol, only one true acyl chain

• amphipathic

• saturated hydrocarbon chains give them a waxy consistency

What forms a bilayer in an aqueous environment?

fatty acids form micelles, phospholipids, and sphingolipids

lipid micelle structure

• in water they form a lipid bilayer by having the hydrophilic heads face the water and hydrophobic tails inside

steroids

• have a different biologic pathway than fatty acids.

• have a common multiple-ring structure

• insoluble in water

• amphipathic with small hydrophilic areas

cholesterol

building blocks for steroids

roles of lipids

chemical energy source, signal molecules, structural

Amino acid structure

• central carbon attached to a carboxyl group, amino group, hydrogen, and R side chain

• they differ only by R group or side chain

• in water, they become ionized amino acids

• have general pattern N-C-C backbone with side chains

• have N terminus and C terminus

Peptide bonds

• in proteins, amino acids are joined together by an amide linkage called a peptide bond.

• link amino acids together to form peptide chains

• formed via condensation

Proteins

long polymers of amino acids linked by peptide bonds, and always written with the N-terminus towards the left

Peptides

shorter, usually fewer than 50 amino acids long

Nucleotides

• consists of a nitrogen-containing base, a 5 carbon sugar, and one or more phosphate groups

• subunits of nucleic acids

• link to sugars via glycosidic bonds

Pyrimidine bases

uracil, thymine, cytosine

Purine bases

adenine and guanine

_____ replaces _____ in RNA

uracil; thymine

Carbon functions on sugar molecule

• carbon 1: makes glyosidic bond with base

• carbon 2: oxy vs deoxy

• carbon 3: makes connection with nucleotide

• carbon 5: links to phosphate

How is DNA read?

5’ to 3’

2 types of pentoses

ribose and deoxyribose

differ by OH and H

Phosphates

• normally joined to the C5 hydroxyl of the ribose or deoxyribose sugar

• mono, di, and triphosphates are common

• the phosphate makes a nucleotide negatively charged

Nucleotides are joined together by _____ between the ___ prime and the ___ prime carbon atoms of adjacent sugars.

phosphodiester bonds; 3; 5

nucleoside

• base + sugar

• adenosine, guanosine, cytidine, uridine, thymidine

Nucleotide

• base + sugar + phosphate

• adenine, guanine, cytosine, uracil, thymine

Nucleotide functions

• as nucleoside di and triphosphates, they carry chemical energy in their easily hydrolyzed phosphoanhydride bonds; bonds are broken via hydrolysis to release energy

• they combine with other groups to form coenzymes

• they are used as small intracellular signaling molecules in the cell

Macromolecules

• polymers constructed from the addition of monomers, in sequence, to one end of the growing chain

• synthesis of biological polymers is driven by nucleotide hydrolysis

oligosaccharide examples

GAGs and complex oligosaccharides

Polysaccharide examples

cellulose, glycogen, and GAGs

Proteoglycans

• made of proteins and carbs

a and b links

• the hydroxyl group on the carbon that carries the aldehyde or ketone can rapidly change from one position to the other

• glycosidic link = carbon 1 and any available carbon with an OH or NH on 2nd molecule

• b = facing up

• a = facing down

• once one sugar is linked to another, the form is frozen

cellulose

structural; makes up cell wall in plants

starch

• plants store glucose in starch

• animals use glycogen instead of starch to store glucose

polysaccharide structure

macromolecules made from >10 monosaccharide subunits (usually thousands)

What makes up a cellulose microfibril?

a bundle of cellulose molecules

GAGs

• linear oligo and polysaccharides built from repeating disaccharide subunits

• used as structural molecules helping with ECM

Glycosylation

• adding a glycosidic bond or sugar to something else

• glycosidic bonds can occur between a glycan (carb) and something else with an available NH or OH not on terminus

Proteoglycan

• proteins glycosylated with GAGs

• found outsid of cell to form matrix, or on cell surface

• protein is typically elongated; along length of protein at certain amino acids are glycosylated GAGs

• covalently linked with glycosidic bonds to protein

• have same properties as normal GAGs

Complex oligosaccharides

• can be linear or branched

• non-repetivive sugar sequence usually linked to proteins or lipids