L1 Molecules Of Life

Front 1

What is the Chemical composition of a bacterial cell?

Back 1

• A cell maycontain c.1000different typesof small organicmolecule.

• But many ofthese can beclassified into 4families:

Sugars, amino acids, fatty acids and nucleotides

Front 2

What do the 4 families form?

Back 2

Four main families of small organic molecules formmomomeric building blocks for the formation of biologicalmacromolecules

Front 3

What functions do the monomers also have?

Back 3

Monomers may also have distinct functions:

• Sugars and fatty acids: energy source

• Nucleotide (ATP): energy carrier

Front 4

What are the features of carbohydrates?

Back 4

• Monosaccharides (simplesugars) are the building blocks ofcarbohydrates

• Molecular formula oftenn x C H2O

– n = 3, 4 ,5 or 6– e.g. C6H12O6

• Functional groups: carbonyl andhydroxyl

• Hydrophilic, polar, water soluble

Front 5

How are monosaccharides classified?

Back 5

Monosaccharides are classed as aldoses or ketoses,depending on whether they contain an aldehyde ora ketone group.

Front 6

How does ring formation occur in carbohydrates?

Back 6

• in aqueous solution, 5 and 6 carbon sugarsspontaneously form ring structures

• the carbonyl (aldehyde or keto) group reacts with ahydroxyl group

Front 7

What isomers do monosaccharides form?

Back 7

• Monosaccharides can occur as optical isomers or enantiomers (DorL-isomers) – mirror image forms

• Most naturally occurring sugars are D-isomers

• D-glucose (dextrose), but not L-glucose, can be metabolised by cellsin the glycolysis pathway

Front 8

What are the other isomers of glucose?

Back 8

Other isomers of glucose differ in the relative spatialarrangement of the carbonyl and hydroxyl groups, andare given different names:

Epimers: stereoisomersthat differ in configurationat a single asymmetriccarbon

Structural isomer

Front 9

What are the two isomers of glucose in ring formation?

Back 9

When glucose is in the ring structure, the hydroxylattached to carbon 1 (the aldehyde carbon) has twopossible positions (α- and β-).

• The α- and β-forms interconvert rapidly in solution

Front 10

what is C1 in ring structure termed?

Back 10

C1 in the ringstructuretermed theanomericcarbon.

Front 11

What are anomers?

Back 11

α and β-D-glucoseare anomers(stereoisomers thatdiffer in configurationof the anomericcarbon)

Front 12

How are complex carbohydrates formed?

Back 12

Complex carbohydrates are formed by glycosidic bondsbetween monosaccharides

Front 13

What happens to the a or B configuration when the bond is formed?

Back 13

The α- or β-configuration is “locked” when the bond isformed

α 1→4 linkage

β 1→4 linkage

Front 14

What are disaccharides?

Back 14

two monosaccharides linkedby a glycosidic bond

Front 15

What are Polysaccharides: “many” saccharides?

Back 15

Polymers of glucose act as energy stores

– Starch (amylose and amylopectin) in plants

– Glycogen in animals

Front 16

What is the structure of glycogen similar to?

Back 16

Glycogen has asimilar chemicalstructure toamylopectin, butwith morebranches

Front 17

What can complex oligosaccharides form?

Back 17

Complex oligosaccharides (a “few” saccharides) canform recognition molecules on cell surfaces e.g. bloodgroup determinants

Front 18

How can sugars be changed?

Back 18

Sugars can be modified, and linked to lipidsor proteins

Front 19

What are lipids and fats?

Back 19

Lipids: molecules in cells that are waterinsoluble(hydrophobic) but soluble inorganic solvents

– Triacylglycerols (fats and oils)

– Glycerophospholipids and other membranelipids

– Steroids and cholesterol

Front 20

What are fatty acids?

Back 20

Fatty acids are the monomeric building blocks oftriacylglycerols and glycerophospholipids

Front 21

What does the length and structural formula of the fatty acid carbon chain determine?

Back 21

The length and structural formula (saturated orunsaturated) of the fatty acid carbon chaindetermines its physical properties (shape, meltingpoint)

Front 22

How are triacylglycerols fomed?

Back 22

Triacylglycerols (triglyceride fats) are formed byester linkages between fatty acids and glycerol

Front 23

What are triacylglycerols useful for?

Back 23

• Important energy storagemolecules

• Hydrophobic (insoluble)so stored as fat dropletswithin cells

Front 24

what are Glycerophospholipids?

Back 24

• Also based onglycerol, but onefatty acid isreplaced by aphosphate group

• The phosphategroup is also linkedto a hydrophilic“head group”

Front 25

What are the characteristics of glycerophospholipids?

Back 25

• Glycerophospholipids are amphipathic (have ahydrophilic “head” and hydrophobic “tails”)

• This causes them to aggregate in an aqueousenvironment

• The phospholipid bilayer forms the cell membrane

Front 26

What is the steroid template the basis for?

Back 26

The steroid template (fused alkyl rings) is the basis forsteroid hormones and the sterol lipid, cholesterol.

Front 27

What is the role of cholesterol in cell membranes?

Back 27

• Cholesterol is a necessary component of animal cellmembranes

• Rigid structure inserts between glycerophospholipids

––modulates membrane fluidity

Front 28

What is the role of nucleic acids?

Back 28

Ribonucleic acid and deoxyribonucleic acid (RNA andDNA), act as information molecules for the cell

Front 29

What do nucleotides consist of?

Back 29

• Nucleotides, the building blocks of RNAand DNA, consist of:

– a pentose sugar

– a nitrogenous base

– phosphate

Front 30

What does the base-pair sequence form?

Back 30

The base-pair sequence of DNA forms the genetic code

Front 31

What is another function of nucleotides?

Back 31

Nucleotides also have other functions, particularly ATP,which carries chemical energy in its phosphoanhydridebonds

Front 32

What is the main function of proteins?

Back 32

Proteins carry out the mechanical, structural andtransport functions of the body.

Front 33

What is their other crucial role?

Back 33

They also play a crucial role as enzymes (biologicalcatalysts).

Front 34

What varieties do proteins come in?

Back 34

Different proteins display a wide variety of shapes andsizes.

Front 35

What determines the structure of each protein?

Back 35

Each protein structure is unique and is determined bythe information in the DNA sequence of the gene.

Front 36

How do proteins fold up?

Back 36

Proteins fold up spontaneously from linear chainsof amino acids

Front 37

What are the building blocks of proteins?

Back 37

Amino acids are the building blocks of proteins

Front 38

How many amino acids are there?

Back 38

20 amino acids - common to all living organisms

Front 39

What are the characteristics of amino acids?

Back 39

Amino acids are water soluble and electricallycharged at physiological pH

Front 40

How does each amino acid differ?

Back 40

Each amino acid differs in the properties of itsside chain (R group)

Front 41

How are amino acids linked in proteins?

Back 41

In polypeptides (proteins), amino acids are linked bypeptide bonds

Front 42

What are not involved in peptide bonding?

Back 42

Side chains (R groups) are not involved in peptidebonding

Front 43

How are amino acids grouped?

Back 43

Amino acids can be grouped according tothe characteristics of their side chains.

Front 44

What are the Amino acids with side chains that are basic (positivelycharged) at physiological pH?

Back 44

Front 45

What determines protein folding?

Back 45

• Side chains of amino acids are not involved in peptidebonding

• Interactions of side chains determine protein folding

Front 46

What are the amino acids that are acidic (negatively charged) at physiological pH?

Back 46

Front 47

What are the non-polar, uncharged amino acids?

Back 47

Front 48

What are the amino acids need to learn?

Back 48