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102 Cards in this Set

  • Front
  • Back
- Energy source and storage
- Cell membrane component (intercellular communication)
- Structural compoentns (plants, fungi)
- Major role in immune system
- Major role in blood clotting
Functions of carbohydrates
These sugars have an aldehyde as their most oxidized functional group
Aldose
These sugars have a ketone as their most oxidized functional group
ketose
A linear chain of three or more carbon atoms, one of which forms a carbonyl group through a double bond with oxygen
Carbohydrate
Sugars oxidized by Fehling's, Tollen's or Benedict's reagent
Reducing sugars
Sugars not oxidized by Fehling's, Tollen's or Benedict's reagent
Nonreducing sugars
- Have the same order and types of bonds (chemical formula)
- Different spatial arrangements
- Different properties
Stereoisomers
What is the difference between two sugar epimers?
Epimers differ in stereo configuration at only one position
OH on the right

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

Based on position of the OH group on the chiral carbon farthest from the carbonyl group
L enatiomer
OH is trans to the CH2OH

What anomer is the glucose?
Alpha

36%
OH is cis to the CH2OH

What anomer is the glucose?
Beta

63%
Two stereoisomers that are mirror images of one another
Enantiomers

D-enantiomers are most common in nature
An adlehyde can react with an alcohol to form a _______
hemiacetal
A ketone can react with an alcohol to form a
hemiketal
Isomeric forms of monossacharides that differ only in their configuration about the hemiacetal or hemiketal carbon atom
Anomers
Enzymatic oxidation of anomeric C (glucose oxidase)
Specific for anomeric carbon

Previous tests only oxidized the C1 of any molecule in the blood.
Replacement of an OH group with an H: forms what molecule?
Deoxysugar
Reduction of the anomeric carbon creates what molecule?
Polyol
Oxidation of C6 - what name change occurs?
Becomes 'uronic acid'

"glucuronic acid"
Oxidation of carbonyl carbon: what name changes occur?
"onic acid"

Example: "gluconic acid"
aldohexoses cyclize by forming a ______ ring
Pyranose (six membered)
Aldopentoses and ketohexoses cyclize by forming a ________ ring
Furanose (five membered)
Usefulness of glucose mutarotation
Glycogen is synthesized from alpha-D-glucopyranose.

Cellulose is synthesized (by plants) by beta-D-glucopyranose
Ketoses are ______ (reducing/nonreducing) sugars.
nonreducing.

Can be isomerized by a base to be reduced.
Disaccharide of glucose and galactose
Lactose
Fructose and glucose disaccharide

Both anomeric carbons are invovled in the glycosidic bond
Sucrose

a-D-glucopyranoside (a1<->B2) b-D-fructofuranosyl
- Minimizes osmotic effects
- Highly branched structure permits rapid glucose release from glycogen stores
Advantages of glycogen storage in polymeric form
Has a-1-4 glycosidic bonds with a-1-6 glycosidic bonds every 24-30 residues
Amylopectin
- Hyaluronic acid
- Chondroitin sulfate
- Heparin

All are examples of....
Glycosaminoglycans

an example of heteropolysaccharides.
A molecule is considered a proteoglycan if......
covalently bound to 1 or more glycosaminoglycan chains
A molecule is considered a glycoprotein if...
More than 1 oligosaccharide is bound
- Cell to cell recognition and adhesion
- Cell migration
- Blood clotting
- Immune responses
- Hormones
- Genetic information**
Functions of glycoproteins and glycolipids

** - Function of nucleotides
- Starch
- Sucrose
- Lactose
Major dietary polysaccharides
Cleaves starch by breaking a-1-4 glycosidic bonds.

Products: dextrins (linear and branches oligosaccharides)
a-amylase in mouth

Inactivated by acid in stomach
Lumen of intestine
Pancreatic a-amylase- cleaves a-1,4 glycosidic bonds

Pancreatic secretions: bicarbonate (raises pH) and activates enzymes

What are the products?
Dissaccharides, trisaccharides (maltotriose), oligosacchrides (limit dextrins, with a-1,4 and a-1,6 bonds)
Intestinal epithelium

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

Final product
Monosaccharides

Indigestible polysaccharides (cellulose, fiber)
- Provide ATP
- Generate intermediates for:
- Hexose monophosphate pathway
- Glycogen synthesis
- Pyruvate dehydrogenase
Fatty acid synthesis
TCA cycle
- Glycerol-phosphate (TAG synthesis)
General functions of glycolysis
Which tissues use glycerol-phosphate for TAG synthesis

and

acetyl-Coa for FA synthesis?
Adipose and liver
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
Found in RBC's

It lowers the affinity of hemoglobin for oxygen

Catalyzed by bisphosphoglycerate muatese (BPGM)
GAPDH forms what product in glycolysis?
NADH
____ is reoxidized in the cytosol.

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

Lactate dehydrogenase reduces pyruvate to lactate, which in turn oxidizes NADH, forming NAD+
Liver Pyruvate Kinase affectors:
Negative:
- ATP
- Alanine
- Phosphorylation

Positive
- Fructose 1,6 bisphosphate (feedforward)
Name the transporter:

Blood brain barrier and RBC

- Low Km and always saturated
- Present in very high concentrations (5% of membrane proteins)
GLUT-1
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
GLUT-2
Name the transporter:

Brain neurons

- Low Km. Always saturated
GLUT-3
Name the transporter:

Muscle and Adipose

Sensitive to insulin
- Low Km
GLUT-4
Name the transporter:

Intestinal epithelium and spermatozoa

- Fructose transport
GLUT-5
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
acetyl CoA
Allosteric regulation of the pyruvate dehydrogenase complex
Inhibition by:
- AcCoa is a competitive inhibitor of E2
- NADH is a competitive inhibitior of E3

Activators
- AMp
- CoA
- NAD+
Pyruvate dehydrogenase complex

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

Is the enzyme on or off?
Off!
Pyruvate dehydrogenase is inactivated when it is phosphorylated or dephosphorylated?
Phosphorylation deactivates PDC

NADH and AcCoA stimulate PDH kinase (phosphorylates PDC)
- Citrate synthase
- Isocitrate dehydrogenase
- alpha-ketoglutarate dehydrogenase
Regulated steps of TCA cycle
Rate limiting step of Oxidative phase - Pentose phoshate pathway
Glucose-6-phosphate dehydrogenase

Most common deficiency in man
Unique feature of Glutathione molecule (ie, peptide bond)
No peptide bond between glutamate and cysteine
- ATP
- DNA
- RNA
- CoA
- NAD
- FAD
Products synthesized from non-oxidative phase of pentose phosphate pathway
Thiamine (B1) deficiency can be assayed by what activity?
transketolase activity.
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
NADPH only
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
NADPH and ribose-5-P
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
Ribose-5-P only
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
NADPH + pyruvate
Reactions of the non-oxidative phase: Sugar interconversions.

The donor is always ______

The acceptor is always ______
Donor: ketose

Acceptor: aldose
Fructose metabolism is inhibited by high levels of ______
citrate.
(glucose-a(1,2)-fructose
Sucrose
Galactose-B(1,4)-glucose
Lactose
Glycogenin is primed by _____-______ with UDP-glucose and tyrosine residue
self-glucosylation

Needs at least four residues for substrate activity
How many reducing ends are on a glycogen molecule?
Only one.

Bound to glycogenin.
Glycogenin and UDP-glucose is coupled with which ion?
Mn2+
What is the name of the branching enzyme for glycogenesis?
1,4 alpha-glucan branching enzyme
After 7 residues, the 1,4 alpha-glucan branching enzyme...
Sticks the residue to another residue to form an alpha 1-6 glycosidic bond.
Debranching enzyme has two activities:
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)
Reasons why calcium stimulates glycogenolysis
Stimulates Phosphorylase kinase, which has a calmodulin receptor.
Mechanism of cAMP action
Binds to regulatory subunits and liberates the catalytic subunits
Glycogen synthase is active when phosphoylated/dephosphorylated?
Dephosphorylated.

Adenylate cyclase stimulates phosphorylation of Glycogen synthase (inactivates), which promotes gluconeogenesis
What molecules prolong the cAMP response?
- Methylzantines
- Caffeine
- Theophyline
These tissues primarily/can only utilize glucose:

- RBC
- Brain and nervous tissue
- Kidney medulla
- Eye lens and cornea
Need gluconeogenesis by liver in order to function
- 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)
Precursors of glucose synthesis
2 lactate + 4 ATP + 2 GTP = 1 glucose
The Cori cycle

Located in RBC
2 alanine + 8 ATP + 2 GTP = 1 glucose
The Alanine Cycle

Located in muscle cells.

Glucagon signals pyruvate to be turned into alanine

Alanine goes to the liver
- Fasting
- Prolonged exercise
- High protein/low carbohydrate diet
- Stress
Physiological factors favoring gluconeogenesis
Principle carbon skeletons come from TCA cycle
Any reaction is gluconeogenic
Primary energy source of gluconeogenesis
Fatty acids

- Give carbon skeleton and ATP for gluconeogenesis
Is PFK-2 involved in flux of carbons?
No.

Sole function is the mediation of side reactions

Controls the amount of Fructose 1,6 bisphoshate available
Allosterics and regulation:

Pyruvate carboxylase
Stimulated by:
- acetyl-CoA (from FA oxidation)
Allosterics and regulation:

Phosphoenolpyruvate carboxylase (PEPCK)
Stimulated by:
- Glucagon
- Epinephrine
- Glucocorticoids
Allosterics and regulation:

Fructose bisphosphatase
Stimulated by:
- Citrate
- Fasting

Inhibited by:
- F-2-6 bisP
- AMP
Allosterics and regulation:

Glucose-6-phosphatase
Stimulated by:
Fasting conditions
Allosterics and regulation:

Pyruvate kinase
Stimulated by:
- F-1,6 BisP

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

PFK-2
Stimulated by:
- Unphosphorylation

Inhibited by
- Phosphorylation
Allosterics and regulation:

PFK-1
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
Allosterics and regulation:

Hexokinase
Inhibited by:
- G-6-P
Allosterics and regulation:

Glucokinase (liver)
Stimulated by:
- Glucose
- Insulin

Inhibited by:
F-6-P
Allosterics and regulation:

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

Inhibited by:
- NADH
- Acetyl-CoA
- ATP
Allosterics and regulation:

Citrate synthase
Stimulated by:
- ADP

Inhibited by:
- NADH
- Succinyl CoA
- Citrate
- ATP
Allosterics and regulation:

Isocitrate DH
Stimulated by:
- ADP
- Ca2+

Inhibited by:
- ATP
- NADH

Rate limiting step for TCA
Allosterics and regulation:

alpha-Ketoglutarate DH
Stimulated by:
- Ca2+
-ADP/ATP ratio

Inhibited by:
- Succinyl CoA
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
Glucose-mediae insulin release

GLUT 2 expressed in liver, kidney, pancreatic B-cells and serosal side of intesinal mucosa
Protein phosphorylation and gene expression are mediated through which two hormones?
- Glucagon
- Epinephrine
Activated gene expression via cyclic AMP response element binding protein (CREB)
A DNA-binding transcription factor that activates gene expression in response to increased cAMP
Does this occur before or after food intake?

- Glycolysis
- Glycogenesis
- Pentose Phosphate pathway
- FA and TAG synthesis
- Protein synthesis
- Cholesterol synthesis
- Nucleotide synthesis
After a meal (anbolic processes)
Does this occur before or after a meal?

- Gluconeogenesis
- Glycogenolysis
- Fatty acid oxidaton
Before a meal (catabolic processes)
Nucleoside diphosphate kinase is used in the TCA cycle and uses Mg2+ as a cofactor.

What reaction does it catalyze?
GTP + ADP <--> GDP + ATP