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Macro
Exam I
87
Chemistry
Graduate
10/13/2010

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Term
Dangers of Sugar Consumption
Definition
-above 25%=decrease in Calcium, magnesium, zinc and iron
-added fructose increases BP and insulin resistance
Term
Monosaccharides
Definition
-3-9 carbon atoms
-hydroxyl groups (bind other groups)
-carbonyl group (aldehyde or ketone); carbonyl carbon most active
-contain chiral centers
Term
Chiral Carbon
Definition
-farther from carbonyl/anomeric carbon
-four different atoms attached
-determines L (opposite) vs. D (same)
Term
alpha vs. beta
Definition
alpha: OH below plane of ring
beta: OH above plane of ring
Term
Glucose
Definition
-found naturally in few foods
-product of starch digestion (starch->amylopectin->glucose)
Term
Lactose
Definition
glucose + galactose
Term
Sucrose
Definition
glucose + fructose
Term
Fructose
Definition
found in fruit and honey
Term
Galactose
Definition
not found in foods, by product of digestion
Term
Oligosaccharides
Definition
-2-10 monosaccharides
-disaccharide most abundant
-contain glycosidic bonds (alpha=digestible, beta=non-digestible)
Term
Maltose
Definition
malt product
Term
isomaltose
Definition
product of digestion
Term
lactose
Definition
milk products; oligo
Term
Sucrose
Definition
table sugar
Term
Lactulose
Definition
-beta 1,2 linkage; non-digestible
-lowers pH in gut by production of SCFA; kills pathogenic bacteria
-low pH keeps ammonia in gut instead of blood stream; important in advanced liver disease
-bulks stool
Term
Short Chain Fatty Acids
Definition
butyrate, acetate and proprionate
Term
Sucrose Polyester
Definition
-Olestra
-sucrose with 6-8 SCFA
-not recognized by lipase or amylase
-can cause anal leakage
Term
Sucralose
Definition
-Splenda
-3 OH replaced with Cl
-becomes 600x sweeter
Term
HFCS
Definition
-55-65% fructose to glucose
-metabolized in liver and enters below first key step in glycolysis (glucose->glucose-6-fructose)
-causes build up of glyceraldehyde-3-P which contributes to TG and FA
-lowers HDL and disrupts uric acid synthesis which increases BP
Term
Dextrose
Definition
-glucose hydrolyzed from corn starch
-used in IV
Term
Polysaccharides
Definition
-over 10 mono
-can be digestible or not
-has reducing (can donate e-) or non-reducing ends (can't donate e-)
Term
Starch
Definition
-70% amylopectin (branched) and 30% amalose
-used to thicken liquids
Term
Glycogen
Definition
-alpha 1,4 and 1,6 linkages
-digestible
Term
Cellulose
Definition
-non-digestible
-beta 1,4
-bulks up stool and exercises colonic muscles
Term
Arabinose
Definition
-beta 1,4
-xylose
Term
Pectin
Definition
-alpha 1,2 and 1,4; somewhat fermentable
-releases SCFA which decreases pH; energy source for colonisides and maintain healthy colon wall
-SCFA also shut down enzymes in cholesterol synthesis
Term
Mouth Digestion
Definition
-salivary amylase: alpha 1,4, operates in pH=7
-inactivated in stomach (too acidic)
-continues in neonates b/c pancreatic amylase doesn't develop until 6 mths.
Term
Upper GI Digestion
Definition
-chyme enters deodenum->secretin and CCK release
-Secretin causes pancreas to release bi-carbonate and CCK, amylase
Term
alpha-amylase
Definition
-digests 90% oligo into dextrins, maltriose and maltose
-binds to 5 glucose molecules and breaks between 2nd and 3rd molecule
-alpha 1,4 specific
-cannot digest alpha 1,6
Term
Sucrase
Definition
Principle Substrate: sucrose, malto-oligo (alpha 1,4 only)
Km=18 (S) and 3 (M)
Term
Alpha-Dextrinase
Definition
Principle Substrate: alpha dextrins (alpha 1,4 and 1,6)
Km=2-4
Term
Glucoamylase
Definition
Principe Substrates: malto-oligosaccharides, alpha dextrins (alpha 1,4 only)
Km=1-4(M) and 1 (D)
Term
Trehalase
Definition
Principle Substrate: Trehalose
Km=3
Term
Beta-Galactosidase Lactase
Definition
Principle Substrate: Lactose
Km=2
Term
SGLT1
Definition
-transfers glucose (or galactose) and Na (cotransport)
-on apical membrane
-Na is removed from enterocyte via Na/K Pump (2 come out, 3 K come in)
-against concentration gradient
Term
GLUT2
Definition
-found in liver, pancreatic beta cells, basal lateral surface of SI, kidney
-promotes absorption from enterocyte into portal circulation
-low affinity for mono, so need very high concentration for activation
-when levels are low, liver doesn't need, so goes to brain and RBC instead
-uses facilitated diffusion and doesn't discriminate between mono
Term
GLUT5
Definition
-found in SI, testes and kidney
-transports fructose from lumen into enterocyte
-uses passive diffusion (no energy use); moves downstream
Term
GLUT1
Definition
-found on RBC, brain and low levels on all cells
Term
GLUT3
Definition
-found on brain and low levels on all cells
Term
GLUT4
Definition
-found on heart, muscle, adipose tissue and brain
-dependent on insulin
-transported via vesicles stimulated by insulin
-translocation of genes into vesicles which are released in the presence of insulin
Term
Glucose and Muscles
Definition
-taken in via GLUT4 which is activated by insulin
-hexokinase catalyzes transformation from glucose to glucose-6-phosphate
-glucose trapped in muscle because glucose-6-phosphate can't be dephos
Term
Glucose and Liver
Definition
-enters via GLUT2 which requires very high concentrations to be active
-Glucokinase catalyzes transformation of glucose to glucose-6-phosphate; positively effected by insulin
-glucose can move back out via glucose-6-phosphotase
Term
Control of Glucose Flux
Definition
1. Availability of substrate
2. Activity of key enzymes
Term
Mechanisms of Enzyme Control
Definition
1. Allosteric Modification
2. Covalent Modification
3. Gene Expression
Term
Allosteric Regulation
Definition
-pathway intermediates that either aid or inhibit enzyme activity
-positive (T->R) or negative (R->T) effectors
-catalyze non-reversible rxns
-moderated by ATP and NAD)
Term
Covalent Modification
Definition
-reversible phosphorylation
-phosphate binding increases or decreases activity
-occurs b/c of hormonal changes
-mediated by kinase and phosphatases
-reversible
Term
Genetic Regulation
Definition
-slow acting through transcription or translation
-induction: increase mRNA transcription or translation at ribosome
Term
Key Control Point for Blood Sugar
Definition
LIVER
Term
High Plasma Glucose
Definition
-High insulin
-Low glucagon
-Liver: decreases glycogenolysis
decreases gluconeogenesis
decreases glycogen synthesis
-decreases glucose output by liver and decreases plasma glucose
Term
Glycogenolysis
Definition
conversion of glycogen polymers to glucose monomers
Term
Gluconeogenesis
Definition
produces glucose from non carbohydrate sources such as lactate and AA
Term
Glycogen
Definition
storage form of glucose in liver and muscles
Term
Low Plasma Glucose
Definition
-low insulin levels
-high glucagon levels
-Liver: increase glycogenolysis, gluconeogenesis; decreases glycogen synthesis
-Leads to increase in hepatic glucose output and increased plasma glucose
Term
Glucagon
Definition
hormone secreted from pancreas that raises blood glucose levels; opposite function of insulin
Term
Glucose Metabolism in Liver
Definition
-stores excess glucose as glycogen
-converts glucose to pyruvate
-releases glucose to other tissues via gluconeogenesis and glycogenolysis
Term
RBC and Glucose Metabolism
Definition
-no mitochondria
-rely on glycolytic pathway for energy
-requires oxygen
Term
Brain and Glucose Metabolism
Definition
-can completely oxidize glucose under aerobic conditions
Term
Muscle and Glucose Metabolism
Definition
-oxidize glucose and store for its own use
Term
Adipose and Glucose Metabolism
Definition
can completely oxidize glucose at low levels; uses glucose
Term
Glycolysis
Definition
-10 sequential steps that yields 38 possible ATP
-Pyruvate: 24 ATP
-2 ATP
-NADH: 6 ATP
-Glucose (if oxidized): 6 ATP
-generates glucose-6-phosphate for glycolysis, glycogen synthesis and pentose phosphate pathway
Term
Steps in Glycolysis
Definition
Glucose->glucose-6-phosphate->fructose-6-phosphate->fructose-1-6-phosphate->glyceraldehyde-3-phosphate->1,3-bisphosphoglycerate->3-phosphoglycerate->2-phosphoglycerate->phosphoenolpyruvate->pyruvate->lactate and ATP
Term
Glucokinase
Definition
-catalyzes transformation of glucose to glucose-6-phosphate
-high Km for glucose (needs lots of substrate)
-inactive when bound to regulatory protein (GKRP)
-high fructose-1-phosphate and low fructose-6-phosphate causes GKRP to dissociate and GK to become active
-fructose-1-phosphate only exists when fructose is high
-induced by insulin
Term
Glucose-6-Phosphatase
Definition
-high Km for glucose-6-phosphate (need lots of substrate)
-clips phosphate so glucogen can be used as glucose
-repressed by insulin and induced by cortisol (genetic)
Term
6-Phosphofructo-1-Kinase
Definition
-requires ATP and magnesium
-catalyzes transformation of fructose-6-phosphate to fructose-1-6-diphosphate (F16P2)
-first committed step of glycolysis
-induced by insulin and repressed by glucagon
-Positive Effectors: AMP/ADP, Fructose 2,6 diphosphate
-Negative Effectors: ATP, citrate
Term
Fructose 1,6 Diphosphatase
Definition
-catalyzes conversion of fructose-1-6-diphosphate to fructose-6-phosphate
-induced by glucagon and repressed by insulin
-Negative Effector: AMP/ADP, fructose 2,6 diphosphate
Term
Fructose-2,6-diphosphate
Definition
-synthesis and degredation determined by 6PF-2K or F2,6Pase respectfully
-modified covalently
Term
Activation of F2,6Pase
Definition
-occurs during fasting
-glucagon binds to receptor and causes dissociation of G alpha complex from G protein via GDP->GTP
-G alpha complex binds to adenylate cyclase which increases cAMP
-cAMP activates protein kinase A by binding to regulatory units
-Protein Kinase A phosphorylates bifunctional enzyme which inhibits 6PF-2K and activates F2,6Pase
-favors gluconeogenesis over glycolysis
Term
Activation of 6PF-2K
Definition
-occurs during fed state
-Insulin binds to receptors and activates secondary messengers that phosphorylate many proteins including phosphodiesterase (decreases cAMP) and protein phosphatase
-binding of insulin causes change in beta transmembrane protein
-activates tyrosine residues which autophosphorylate and serve as docking points for relay proteins that phosphorylate phosphodiesterase and protein phosphatase
-protein phosphatase dephosphorylates bifunctional enzyme and activates 6PF-2K and inhibits F2-6Pase
-favors glycolysis over gluconeogenesis
Term
Pyruvate Kinase
Definition
-need ADP
-catalyzes transformation of phosphoenolpyruvate to pyruvate
-only found in mitochondria
-Positive effectors: F-1-6P2
-Negative effectors: ATP, acetyl coA, alanine
-Induced by insulin
Term
Pyruvate Carboxylase and Phosphoenolpyruvate carboxykinase
Definition
-catalyze rxn of pyruvate to phosphoenolpyruvate and OAA
-needs ATP, CO2, biotin and GTP
-products are needed in more than one pathway
-Positive Effector: Acetyl CoA (PC)
-PEPCK induced by glucagon and repressed by insulin (use similar mechanism as 6FP-2K/F2-6Pase (PEPCK uses G protein and PK uses second messenger)
Term
Pyruvate Conversion
Definition
-changed to OAA in mitochondria using PC
-OAA converted to aspartate, malate and PEP
-crosses into cytosol through the use of ADH, MDH and PEPCK
-ADH and MDH release NADH to keep gluconeogenesis going
Term
Structural and Metabolic Differences between HFCS and sucrose
Definition
-HFCS contains glucose and fructose monomers vs. sucrose is a dissacharide
-HFCS monomers don't need to be broken down vs. sucrose that must be cleaved
Term
Metabolic Effects Associated with High HFCS Intake
Definition
1. Dyslipidemia
2. Hyperuricemia
3. Insulin Resistance
4. Appetite changes associated with weight gain
Term
Uric Acid Formation from Fructose
Definition
-when fructose is changed to F-1-P it releases ADP, AMP and uric acid
Term
Uric Acid Synthesis
Definition
AMP->IMP->Inosine->hypoxanthine->xanthine->urate
Term
Glycogenin
Definition
-acts as primer for growing chain on glycogen
-has glucosyl transferase: catalyzes bond between glucose and glycogen
-glucose linked via alpha 1,4 and 1,6 bonds at branched points
Term
Glycogen Synthesis in Liver
Definition
Glucose->G-6-P->G-1-P->glycogen primer->elongation using 2 UDP=glycogen
Term
Elongation of Glycogen
Definition
-UDP-glucose gives up glucose to non-reducing end
-forms alpha 1,4 glycosidic bond
-branching enzyme takes over and cleaves a bond 4-6 units from branch point
-forms alpha 1,6 bond which provides new site for elongation
Term
Carb Content of Foods
Definition
Milk: 12
Bread/Cereal: 15
Vegetables: 5
Fruit: 15
Deserts: 15
Term
Guidelines for Sugar Consumption
Definition
Dietary Guidelines for Americans: 6%
Institute of Medicine: no more than 25%
World Health Organization: no more than 10%
Average teen: 16%
Term
Cyclic Sugars
Definition
Formed by rxn of hydroxyl group of C-5 with anomeric carbon on C-1
Term
Salivary Amylase
Definition
specific for alpha 1,4 bonds
Term
Amylase Digestion Products
Definition
dextrins, maltriose and maltose
Term
Hypolactasia
Definition
as we get older we consume less lactose and lactase decreases as a result
Term
Range of Normal Blood Sugar
Definition
80-126 mg/dl
Term
Fate of G-3-P
Definition
Eventually turns into triglyceride backbone via glycerol-3-phosphatase
Term
Uses of Glucose-6-Phosphate
Definition
-glycolysis
-glycogen synthesis
-pentose phosphate pathway (ribose 5 phosphate synthesis)
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