Biochemistry Exam Ii Carbohydrates

Front 1

- Energy source and storage
- Cell membrane component (intercellular communication)
- Structural compoentns (plants, fungi)
- Major role in immune system
- Major role in blood clotting

Back 1

Functions of carbohydrates

Front 2

These sugars have an aldehyde as their most oxidized functional group

Back 2

Aldose

Front 3

These sugars have a ketone as their most oxidized functional group

Back 3

ketose

Front 4

A linear chain of three or more carbon atoms, one of which forms a carbonyl group through a double bond with oxygen

Back 4

Carbohydrate

Front 5

Sugars oxidized by Fehling's, Tollen's or Benedict's reagent

Back 5

Reducing sugars

Front 6

Sugars not oxidized by Fehling's, Tollen's or Benedict's reagent

Back 6

Nonreducing sugars

Front 7

- Have the same order and types of bonds (chemical formula)
- Different spatial arrangements
- Different properties

Back 7

Stereoisomers

Front 8

What is the difference between two sugar epimers?

Back 8

Epimers differ in stereo configuration at only one position

Front 9

OH on the right

Based on position of the OH group on the chiral carbon farthest from the carbonyl group

Back 9

D enantiomer

Front 10

OH on the left

Based on position of the OH group on the chiral carbon farthest from the carbonyl group

Back 10

L enatiomer

Front 11

OH is trans to the CH2OH

What anomer is the glucose?

Back 11

Alpha

36%

Front 12

OH is cis to the CH2OH

What anomer is the glucose?

Back 12

Beta

63%

Front 13

Two stereoisomers that are mirror images of one another

Back 13

Enantiomers

D-enantiomers are most common in nature

Front 14

An adlehyde can react with an alcohol to form a _______

Back 14

hemiacetal

Front 15

A ketone can react with an alcohol to form a

Back 15

hemiketal

Front 16

Isomeric forms of monossacharides that differ only in their configuration about the hemiacetal or hemiketal carbon atom

Back 16

Anomers

Front 17

Enzymatic oxidation of anomeric C (glucose oxidase)

Back 17

Specific for anomeric carbon

Previous tests only oxidized the C1 of any molecule in the blood.

Front 18

Replacement of an OH group with an H: forms what molecule?

Back 18

Deoxysugar

Front 19

Reduction of the anomeric carbon creates what molecule?

Back 19

Polyol

Front 20

Oxidation of C6 - what name change occurs?

Back 20

Becomes 'uronic acid'

"glucuronic acid"

Front 21

Oxidation of carbonyl carbon: what name changes occur?

Back 21

"onic acid"

Example: "gluconic acid"

Front 22

aldohexoses cyclize by forming a ______ ring

Back 22

Pyranose (six membered)

Front 23

Aldopentoses and ketohexoses cyclize by forming a ________ ring

Back 23

Furanose (five membered)

Front 24

Usefulness of glucose mutarotation

Back 24

Glycogen is synthesized from alpha-D-glucopyranose.

Cellulose is synthesized (by plants) by beta-D-glucopyranose

Front 25

Ketoses are ______ (reducing/nonreducing) sugars.

Back 25

nonreducing.

Can be isomerized by a base to be reduced.

Front 26

Disaccharide of glucose and galactose

Back 26

Lactose

Front 27

Fructose and glucose disaccharide

Both anomeric carbons are invovled in the glycosidic bond

Back 27

Sucrose

a-D-glucopyranoside (a1<->B2) b-D-fructofuranosyl

Front 28

- Minimizes osmotic effects
- Highly branched structure permits rapid glucose release from glycogen stores

Back 28

Advantages of glycogen storage in polymeric form

Front 29

Has a-1-4 glycosidic bonds with a-1-6 glycosidic bonds every 24-30 residues

Back 29

Amylopectin

Front 30

- Hyaluronic acid
- Chondroitin sulfate
- Heparin

All are examples of....

Back 30

Glycosaminoglycans

an example of heteropolysaccharides.

Front 31

A molecule is considered a proteoglycan if......

Back 31

covalently bound to 1 or more glycosaminoglycan chains

Front 32

A molecule is considered a glycoprotein if...

Back 32

More than 1 oligosaccharide is bound

Front 33

- Cell to cell recognition and adhesion
- Cell migration
- Blood clotting
- Immune responses
- Hormones
- Genetic information**

Back 33

Functions of glycoproteins and glycolipids

** - Function of nucleotides

Front 34

- Starch
- Sucrose
- Lactose

Back 34

Major dietary polysaccharides

Front 35

Cleaves starch by breaking a-1-4 glycosidic bonds.

Products: dextrins (linear and branches oligosaccharides)

Back 35

a-amylase in mouth

Inactivated by acid in stomach

Front 36

Lumen of intestine
Pancreatic a-amylase- cleaves a-1,4 glycosidic bonds

Pancreatic secretions: bicarbonate (raises pH) and activates enzymes

What are the products?

Back 36

Dissaccharides, trisaccharides (maltotriose), oligosacchrides (limit dextrins, with a-1,4 and a-1,6 bonds)

Front 37

Intestinal epithelium

Oligo and dissachraridases attached to the brush border of the intestinal epithelial cells

Final product

Back 37

Monosaccharides

Indigestible polysaccharides (cellulose, fiber)

Front 38

- Provide ATP
- Generate intermediates for:
- Hexose monophosphate pathway
- Glycogen synthesis
- Pyruvate dehydrogenase
Fatty acid synthesis
TCA cycle
- Glycerol-phosphate (TAG synthesis)

Back 38

General functions of glycolysis

Front 39

Which tissues use glycerol-phosphate for TAG synthesis

and

acetyl-Coa for FA synthesis?

Back 39

Adipose and liver

Front 40

2,3 BPG is made in what cells?

It _____ the affinity of hemoglobin for oxygen so that hemoglobin can unload oxygen upon arriving at peripheral tissues

Back 40

Found in RBC's

It lowers the affinity of hemoglobin for oxygen

Catalyzed by bisphosphoglycerate muatese (BPGM)

Front 41

GAPDH forms what product in glycolysis?

Back 41

NADH

Front 42

____ is reoxidized in the cytosol.

Lactate dehydrogenase reduces ________ to _______ in order for GAPDH to continue producing ATP.

Back 42

NADH

Lactate dehydrogenase reduces pyruvate to lactate, which in turn oxidizes NADH, forming NAD+

Front 43

Liver Pyruvate Kinase affectors:

Back 43

Negative:
- ATP
- Alanine
- Phosphorylation

Positive
- Fructose 1,6 bisphosphate (feedforward)

Front 44

Name the transporter:

Blood brain barrier and RBC

- Low Km and always saturated
- Present in very high concentrations (5% of membrane proteins)

Back 44

GLUT-1

Front 45

Name the transporter:

Liver, B cells of pancreas, serosal side of intestine

- high Km and High Vmax
- Uses glucose when fed at rate proportional to glucose concentration

Back 45

GLUT-2

Front 46

Name the transporter:

Brain neurons

- Low Km. Always saturated

Back 46

GLUT-3

Front 47

Name the transporter:

Muscle and Adipose

Sensitive to insulin
- Low Km

Back 47

GLUT-4

Front 48

Name the transporter:

Intestinal epithelium and spermatozoa

- Fructose transport

Back 48

GLUT-5

Front 49

This molecule functions as:
- Input to the TCA cycle, where the moiety is further degraded to CO2

- Donor for synthesis of fatty acids, ketone bodies and cholesterol

Back 49

acetyl CoA

Front 50

Allosteric regulation of the pyruvate dehydrogenase complex

Back 50

Inhibition by:
- AcCoa is a competitive inhibitor of E2
- NADH is a competitive inhibitior of E3

Activators
- AMp
- CoA
- NAD+

Front 51

Pyruvate dehydrogenase complex

When the energy state of the cell is high or O2 is lacking.

Is the enzyme on or off?

Back 51

Off!

Front 52

Pyruvate dehydrogenase is inactivated when it is phosphorylated or dephosphorylated?

Back 52

Phosphorylation deactivates PDC

NADH and AcCoA stimulate PDH kinase (phosphorylates PDC)

Front 53

- Citrate synthase
- Isocitrate dehydrogenase
- alpha-ketoglutarate dehydrogenase

Back 53

Regulated steps of TCA cycle

Front 54

Rate limiting step of Oxidative phase - Pentose phoshate pathway

Back 54

Glucose-6-phosphate dehydrogenase

Most common deficiency in man

Front 55

Unique feature of Glutathione molecule (ie, peptide bond)

Back 55

No peptide bond between glutamate and cysteine

Front 56

- ATP
- DNA
- RNA
- CoA
- NAD
- FAD

Back 56

Products synthesized from non-oxidative phase of pentose phosphate pathway

Front 57

Thiamine (B1) deficiency can be assayed by what activity?

Back 57

transketolase activity.

Front 58

What is the cells need?

- Oxidative reactions produce NADPH from G-6-P
- Nonoxidative reactions convert ribulose-5-P to F-6-P and G-3-P, which are resnthesized to G-6-P by tthe gluconeogenic pathway to produce more NADPH

- In this mode, G-6-P is completely oxidized to CO2

Back 58

NADPH only

Front 59

What is the cells need?

- Oxidative reactions produce NADPH and ribulose-5-P from G-6-P
- Isomerase converts ribulose-5-P to ribose-5-P

Back 59

NADPH and ribose-5-P

Front 60

What is the cells need?

- No oxidavite reactions
- High NADPH inhibits G-6-P dehydrogenase
- Nonoxidative reations in reverse: transketolase and transaldolase used to convert F-6-P and G-3-P to ribose-5-P

Back 60

Ribose-5-P only

Front 61

What is the cells need?

- Both the oxidative and nonoxidative reactions are used.
- Oxidative reactions generate NADPH and ribulose-5-P from G-6-P
- nonoxidative reactions convert the ribulose-5-P to F-6-P and G-3-P, which are oxidized to pyruvate by the glycolytic pathway

Back 61

NADPH + pyruvate

Front 62

Reactions of the non-oxidative phase: Sugar interconversions.

The donor is always ______

The acceptor is always ______

Back 62

Donor: ketose

Acceptor: aldose

Front 63

Fructose metabolism is inhibited by high levels of ______

Back 63

citrate.

Front 64

(glucose-a(1,2)-fructose

Back 64

Sucrose

Front 65

Galactose-B(1,4)-glucose

Back 65

Lactose

Front 66

Glycogenin is primed by _____-______ with UDP-glucose and tyrosine residue

Back 66

self-glucosylation

Needs at least four residues for substrate activity

Front 67

How many reducing ends are on a glycogen molecule?

Back 67

Only one.

Bound to glycogenin.

Front 68

Glycogenin and UDP-glucose is coupled with which ion?

Back 68

Mn2+

Front 69

What is the name of the branching enzyme for glycogenesis?

Back 69

1,4 alpha-glucan branching enzyme

Front 70

After 7 residues, the 1,4 alpha-glucan branching enzyme...

Back 70

Sticks the residue to another residue to form an alpha 1-6 glycosidic bond.

Front 71

Debranching enzyme has two activities:

Back 71

1) Transferase (cleaves off last 3 glucose units and sticks them to non-reducing ends of adjacent amylose chain.
2) a-1,6 glucosidase (Liberates free glucose)

Front 72

Reasons why calcium stimulates glycogenolysis

Back 72

Stimulates Phosphorylase kinase, which has a calmodulin receptor.

Front 73

Mechanism of cAMP action

Back 73

Binds to regulatory subunits and liberates the catalytic subunits

Front 74

Glycogen synthase is active when phosphoylated/dephosphorylated?

Back 74

Dephosphorylated.

Adenylate cyclase stimulates phosphorylation of Glycogen synthase (inactivates), which promotes gluconeogenesis

Front 75

What molecules prolong the cAMP response?

Back 75

- Methylzantines
- Caffeine
- Theophyline

Front 76

These tissues primarily/can only utilize glucose:

- RBC
- Brain and nervous tissue
- Kidney medulla
- Eye lens and cornea

Back 76

Need gluconeogenesis by liver in order to function

Front 77

- Lactate (from RBC)
- Glycerol (from adipose TAGs)
- Amino acids (especially alanine, from muscle tissue)
- Propionate (3C molecule left over from odd-chain FA oxidation - minor)

Back 77

Precursors of glucose synthesis

Front 78

2 lactate + 4 ATP + 2 GTP = 1 glucose

Back 78

The Cori cycle

Located in RBC

Front 79

2 alanine + 8 ATP + 2 GTP = 1 glucose

Back 79

The Alanine Cycle

Located in muscle cells.

Glucagon signals pyruvate to be turned into alanine

Alanine goes to the liver

Front 80

- Fasting
- Prolonged exercise
- High protein/low carbohydrate diet
- Stress

Back 80

Physiological factors favoring gluconeogenesis

Front 81

Principle carbon skeletons come from TCA cycle

Back 81

Any reaction is gluconeogenic

Front 82

Primary energy source of gluconeogenesis

Back 82

Fatty acids

- Give carbon skeleton and ATP for gluconeogenesis

Front 83

Is PFK-2 involved in flux of carbons?

Back 83

No.

Sole function is the mediation of side reactions

Controls the amount of Fructose 1,6 bisphoshate available

Front 84

Allosterics and regulation:

Pyruvate carboxylase

Back 84

Stimulated by:
- acetyl-CoA (from FA oxidation)

Front 85

Allosterics and regulation:

Phosphoenolpyruvate carboxylase (PEPCK)

Back 85

Stimulated by:
- Glucagon
- Epinephrine
- Glucocorticoids

Front 86

Allosterics and regulation:

Fructose bisphosphatase

Back 86

Stimulated by:
- Citrate
- Fasting

Inhibited by:
- F-2-6 bisP
- AMP

Front 87

Allosterics and regulation:

Glucose-6-phosphatase

Back 87

Stimulated by:
Fasting conditions

Front 88

Allosterics and regulation:

Pyruvate kinase

Back 88

Stimulated by:
- F-1,6 BisP

Inhibited by:
- ATP
- Alanine
- Phosphorylation (cAMP by glucaon or epinephrine)

Front 89

Allosterics and regulation:

PFK-2

Back 89

Stimulated by:
- Unphosphorylation

Inhibited by
- Phosphorylation

Front 90

Allosterics and regulation:

PFK-1

Back 90

Stimulated by:
- AMP
- F 2,6 bisphosphate

Inhibited by:
- Mg-ATP
- Citrate

ATP and F6P regulate by two mechanisms:
1) Substrate concentration
2) Allosteric effectors

Front 91

Allosterics and regulation:

Hexokinase

Back 91

Inhibited by:
- G-6-P

Front 92

Allosterics and regulation:

Glucokinase (liver)

Back 92

Stimulated by:
- Glucose
- Insulin

Inhibited by:
F-6-P

Front 93

Allosterics and regulation:

Pyruvate DH

Back 93

Stimulated by:
- Pyruvate
- AMP
- CoASH
- NAD+
- Ca2+

Inhibited by:
- NADH
- Acetyl-CoA
- ATP

Front 94

Allosterics and regulation:

Citrate synthase

Back 94

Stimulated by:
- ADP

Inhibited by:
- NADH
- Succinyl CoA
- Citrate
- ATP

Front 95

Allosterics and regulation:

Isocitrate DH

Back 95

Stimulated by:
- ADP
- Ca2+

Inhibited by:
- ATP
- NADH

Rate limiting step for TCA

Front 96

Allosterics and regulation:

alpha-Ketoglutarate DH

Back 96

Stimulated by:
- Ca2+
-ADP/ATP ratio

Inhibited by:
- Succinyl CoA

Front 97

Increased ATP production closes the K+ channel

K+ wants to leave the cell.
Cell becomes more negative
Calcium ion enters the cell, releasing insulin via exocytosis

Back 97

Glucose-mediae insulin release

GLUT 2 expressed in liver, kidney, pancreatic B-cells and serosal side of intesinal mucosa

Front 98

Protein phosphorylation and gene expression are mediated through which two hormones?

Back 98

- Glucagon
- Epinephrine

Front 99

Activated gene expression via cyclic AMP response element binding protein (CREB)

Back 99

A DNA-binding transcription factor that activates gene expression in response to increased cAMP

Front 100

Does this occur before or after food intake?

- Glycolysis
- Glycogenesis
- Pentose Phosphate pathway
- FA and TAG synthesis
- Protein synthesis
- Cholesterol synthesis
- Nucleotide synthesis

Back 100

After a meal (anbolic processes)

Front 101

Does this occur before or after a meal?

- Gluconeogenesis
- Glycogenolysis
- Fatty acid oxidaton

Back 101

Before a meal (catabolic processes)

Front 102

Nucleoside diphosphate kinase is used in the TCA cycle and uses Mg2+ as a cofactor.

What reaction does it catalyze?

Back 102

GTP + ADP <--> GDP + ATP