Cmb-I Test 2 Pritchard

Front 1

What is the most aboundant of the four major classes of biological molecules?

Back 1

- out of proteins, nucleic acids, lipids, and carbohydrates, carbs are the most numerous

Front 2

Sugars are polyhydroxy ___________ or ___________. Biological sugars are in the _____ configuration, which is determined by ___________________________.

Back 2

- aldehydes or ketones

- D

- the absolute configuration at its highest numbered asymmetric carbon

Front 3

Define:
- stereoisomers
- enantiomers
- diastereomers

Back 3

- stereoisomers: same chemical formula but differ in atomic arrangement
- enantiomers: stereoisomers that are mirror images of each other (have identical chemical and physical properties)
- diastereomers: stereoisomers which are NOT mirror images (different chemical and physical properties)

Front 4

Most drugs today are resolved. What does this mean, and how is it done?

Back 4

- resolved means that you have separated out the enantiomers to either D- or L-
- Racemic mixtures can be separated out by derivatizing the mixture with another chiral reagent and then separating the D- and L- forms

Front 5

What is the Lobry de Bruyn-van Ekenstein reaction?

Back 5

- C-2 epimerization of sugars occurs under alkaline conditions
- you will get interconversion of an aldose to a ketose if you put a sugar in base

Front 6

Under physiological conditions, what types of sugars can be oxidized? What about under basic conditions?

Back 6

- only aldoses (NOT ketoses) can be oxidized (-CHO to -COOH)
- under basic conditions and in the presence of Ag+ or Cu2+, both ketoses and aldoses are oxidized

Front 7

What are some common mechanisms for oxidizing sugars?

Back 7

- (-CHO)+Br2 and H20 will give (-COOH)
- dilute HNO3 will create an aldaric acid, where both ends of the sugar now have COOH

Front 8

What are some common mechanisms for reducing sugars?

Back 8

- using NaBH4, can get (-CHO) to reduce to an alditol (-CH2OH)

Front 9

How are hemiacetals formed?

Why is this reaction important?

Back 9

- an alcohol (ROH) attacks an aldehyde (R-COH) and forms a hemiacetal (R-COH-OR')
- a hemiacetal is a C with two O's attached

- this is how aldose sugars are cyclized

Front 10

Looking at a Haworth projection formula, how can you tell if a cyclic sugar is in the alpha or beta form?

Back 10

- alpha: the OH on C1 is on the opposite side of the CH2OH
- beta: the OH on C1 is on the same side as the CH2OH

Front 11

A sugar with a 6-membered ring is called a ________ while a sugar with a 5-membered ring is called a _________. Two cyclic sugars that differ only in the configuration of the __________ are called __________.

Back 11

- pyranose
- furanose
- anomeric carbon atom (either a hemiketal or hemiacetal)
- anomers

Front 12

How are sugar hemiketals formed? How large is the ring?

Back 12

- the C4 alcohol end of the sugar (ROH) attacks the ketone end of the sugar (R'-C-CH2OH) to form the hemiketal
- this results in a 5-C ring

Front 13

Why does the optical rotation of a freshly prepared solution of D-glucose change?

Back 13

- due to mutarotation
- a-D-glucose: +112 deg
- B-D-glucose: +19 deg
- The two anomers of D-glucose are diastereomers and have different chemical and physical properties
- this sugar will mutarotate between the alpha and beta configuration to reach an equilibrium of about +52.5 deg for the optical rotation

Front 14

What are the total number of conformations of cyclic glucose?

Back 14

- 2 chairs
- 4 boats
- 6 skews
- 12 half chairs
- total of 24 possible conformations

Front 15

What are alditols?

What is the makeup of honey?

Back 15

- sugars that have (-CH2OH) on either ends

- ~18% H20
- ~38% fructose (B-D-Fructopyranose)
- ~31% glucose

Front 16

How do hemiacetals and hemiketals form acetals and ketals?

What are sugar acetals called? How can they be detected?

Back 16

- each 'hemi' is attacked by another alcohol (R-OH) so that you now have two (-OR) groups attached to the carbon
- GLYCOSIDES: sugar acetals
- can detect them because the C1 carbon is now stable (has an extra R group attached) and will not mutarotate in solution

Front 17

What two sugars are each of these common disaccharides made from?
- lactose
- sucrose
- maltose
- cellobiose
- isomaltose

Back 17

- lactose: gal-B-1,4-glc
- sucrose: glc-a-1,2-fru
- maltose: glc-a-1,4-glc
- cellobiose: glc-B-1,4-glc
- isomaltose: glc-a-1,6-glc

Front 18

What is unusual about sucrose in comparison to other disaccharides?

Back 18

- it is an a-1,2 linkage (backwards) meaning that there is no free anomeric carbon
- it is a non reducing sugar

Front 19

What is the reducing end of a sugar?

What are glycosidic bonds?

Back 19

- the free anomeric carbon end

- when a hemiacetal or hemiketal joins to another R group, this is a glycosidic bond (between the C and the OR groups)

Front 20

This sugar conjugate is found in bitter almonds, cherry kernels, peaches, and apricots.

Back 20

- Amygdalin

Front 21

What bean-derived acetal was claimed to be an anti-cancer agent?

Back 21

- Laetrile

Front 22

What sugar is a breakdown product of starch and is used in chromatographic separations?

Back 22

- cycloheptaamylose

Front 23

Why does stachyose give humans gas?

Back 23

- humans can break down the sucrose portion of the sugar, but cannot break down the gal-a-1,6-gal linkages
- bacteria in the lower intestine can, which releases CO₂

Front 24

What is dextratriose a component of?

Back 24

- sake and honeydew

Front 25

What does human milk contain besides lactose? What role do these sugars play?

Back 25

- contains a large number of oligosaccharides
- they don't serve any nutritional value, and it is thought that they help prevent bacterial adherence in babies (UTI prevention)

Front 26

What donates sugars in glycoconjugate biosynthesis?

Back 26

- glycosyl transferases steal a sugar from a nucleotide (base+sugar+PO₄)

Front 27

What is the major nucleoside di- or monophosphate to donate sugars?

Back 27

- UDP is attached to lots (glcNAc, galNAc, murNAc, gal, glc)
- GDP is attached to fucose and mannose
- CMP is attached to sialic acid (NeuNAc)

Front 28

What are the two monomers of lactose synthase?

Which monomer only works in lactating mammary glands?

Back 28

- B-D-galactosyl transferase and a-lactalbumin

- a-lactalbumin

Front 29

What reaction does each monomer of lactose synthase catalyze?

Back 29

- B-D-galactosyl transferase: UDP-gal + glcNAc-R to form B-D-gal-(1,4)-GlcNAc-R

- a-lactalbumin: UDP-Gal + Glc to form B-D-gal-(1,4)-glc [lactose]

Front 30

What causes lactose intolerance?

Back 30

- the enzyme B-galactosidase in the small intestine breaks down lactose to galactose and glucose
- as people get older, and if they aren't from a historically dairy-farming region of the world, this enzyme is lost
- lactose can't be broken down, and there is an influx of fluid into the small intestine
- lactose is broken down by the bacteria in the large intestine, causing gas (CO2 and H2)

Front 31

What is the most abundant biological molecule on Earth?

Back 31

- cellulose

Front 32

Why can't humans eat wood?

Back 32

- wood is made of cellulose
- linear glc-β(1,4)-glc
- human's can't digest this bond
- herbivores and termites have bacteria within their gut that produce cellulases that can degrade cellulose

Front 33

After cellulose, what is the most abundant biological molecule on earth?

Back 33

- chitin
- linear β(1,4) polymer of glcNAc

Front 34

If a patient comes into the ER and has lost a lot of blood, what are they normally given before blood/plasma?

Back 34

- dextran sulfate IV: causes fluid to come out of tissues and expands blood volume
- is a linear α(1,6) linked glucan that is water soluble
- produced by certain bacteria growing on sucrose

Front 35

What is starch composed of?

What keeps it from being totally soluble in water?

Where is each portion digested in the body?

Back 35

- α-amylose: linear α(1,4) glc polymer
- amylopectin: very large branched polymer of α(1,4)glc with α(1,6) branches every 24-30 residues
- amylopectin is insoluble in water

- amylopectin is in small intestine, while amylase is present in salivary secretions

Front 36

What is often used to thicken jams and jellies?

Back 36

- pectin, a "soluble fiber"
- heterogenous polymer of partially methylated α-D-galNAc

Front 37

What polysaccharide is used in salad dressings because it has high viscosity at low shear but low viscosity at high shear?

Back 37

Xanthan gum

Front 38

What is guar gum used for?

Back 38

- forms highly viscous solutions, and keeps water from leaching out of many foods
- found in hot dogs, cheese, ice cream, baked goods

Front 39

True or false:

- Alginate is from red seaweed, and carrageenan is from brown seaweed.
- Alginate is used to make dental impressions.
- Alginate is used to thicken foods, milk, and toothpaste.

Back 39

- FALSE: alginate=brown, carrageenan=red
- TRUE
- FALSE: carrageenan is used for these purposes. alginate is mainly used for low fat spreads, sauces, and pie fillings

Front 40

What is a water-soluble derivative of cellulose, that is widely used in food products and pharmaceuticals?

Back 40

- carboxymethylcellulose

Front 41

What is the only glycosaminoglycan that is not covalently bound to the protein? Where is this found?

Back 41

- Hyaluronan (hyaluronic acid)
- very important in ground substance, vitreous humor, synovial fluid
- forms very viscous solutions that are shear dependent

Front 42

Which has a larger volume: hyaluronan or chondroitin-4-sulfate?

Back 42

- hyaluronan

Front 43

_______________________ is a major component of the proteoglycans of cartilage and other connective tissues. Where do people get this in their diet?

Back 43

- chondroitin-4-sulfate

- from meat products (chicken skin, pigs feet, cartilage)

Front 44

Which residue of chondroitin-4-sulfate is sulfated?

What other position can be sulfated?

What other glycosaminoglycan is similar to chondroitin?

Back 44

- galNAc
- C6
- dermatan sulfate; difers by an inversion of the configuration at C5, and is commonly found in the skin

Front 45

How is keratan sulfate linked to a protein?

Back 45

- either through a ser/thr (O-linkage) or an asparagine (N-linkage)

Front 46

Even though heparin and heparan sulfate are similar, they are found in different locations in the body. Where?

What makes these two GAGs unique?

Back 46

- heparin: intracellular granules of mast cells
- heparan sulfate: basement membranes
- They both have N-sulfate groups on their glcNAc residues

Front 47

What is the most highly negatively charged biological polymer known?

What biological activity does this enzyme possess?

Back 47

- heparin

- enhances antithrombin III, which prevents thrombin from cleaving fibrinogen to fibrin (clot)
- its sulfate group is necessary for the tight binding to antithrombin III

Front 48

All GAGs (except one) are covalently linked to proteins via what unique linkage?

What GAG differs in its linkage depending on what tissue it's in?

Back 48

- gal-gal-xyl-O-(Ser/Thr)
- O-linked glycosylation

- keratan sulfate
- If in cartilage, linked via O-linkage to serine and galNAc
- If in cornea, linked via N-glycosidic linkage

Front 49

Describe the keratan sulfate linkages.

Back 49

- Cartilage: serine-O-GalNAc-(branches to keratan sulfate chain attached at C4; C5 has gal-NeuNAc attached); ser-O-GalNAc-Gal-NeuNAc
- cornea: asparagine-N-glcNAc-GlcNAc-Man-branches at C4 and C5 to join onto 2 other Man, each Man joins to a keratan sulfate chain

Front 50

How is chondroitin sulfate sulfated?

Back 50

- after the GalNAc residues have become part of the growing CS chain, a PAPS molecule donates a sulfate via a sulfotransferase

Front 51

What are the four major groups of proteoglycans?

Back 51

- hyalectans
- cell surface heparan sulfate-containing proteoglycans
- basement membrane proteoglycans
- small leucine-rich proteoglycans