Carbohydrate Metabolism

Front 1

In what organ does glycolysis occur?

Back 1

LIVER

Front 2

Describe the pathway lactose takes to reach the enterocytes (and what has it become)?

Back 2

Lactose is converted to Galactose (lactase)

Galactose crosses the outer endothelial layer of the enterocyte capillary by facilitated diffusion (sodium-dependent co-transport)

Galactose diffuses into the enteroyte

Front 3

Describe the pathway starch takes to reach the enterocytes (and what does it become)?

Back 3

Starch is converted into one of these by amylase:

isomaltose, maltose, maltriose, alpha-limit destrin

which are converted to glucose by alpha-glucosidases

glucose crosses the outer capillary membrane by sodium-dependent co-transport and the inner membrane by diffusion

Front 4

What is the only monosaccaride that crosses BOTH sides of the enterocyte capillary by simple diffusion?

Back 4

FRUCTOSE

Front 5

What enzyme converts sucrose to fructose?

Back 5

SUCRASE

Front 6

What enzyme is responsible for maintaining the Na+ gradient necessary to drive glucose uptake?

Back 6

Na+/K+ ATPase

Front 7

Na+/K+ ATPases are the targets for what category of drugs and give an example

Back 7

cardiac glycosides

e.g.: digoxin digitoxigenin

Front 8

What are the primary and secondary effects of lactose intolerance?

Back 8

Accumulation of lactose in the gut

Water retention and diarrhea

Front 9

Define GLYCOLYSIS

Back 9

Sequence of enayme catalyzed reactions that convert GLUCOSE to PYRUVATE (aerobically) or LACTATE (anaerobically)

Front 10

Which types of cells carry out glycolysis?

Back 10

ALL OF THEM

Front 11

What two tissue types are completely dependent on glycolysis?

Back 11

CNS

RBCs

Front 12

How many ATP/glucose does glycolysis produce under ANaerobic conditions?

Back 12

2

Front 13

How many ATP/glucose does glycolysis produce under aerobic conditions?

Back 13

38

Front 14

Glycolysis, Step 1

Back 14

Glucose --> glucose - 6 - phosphate
ATP --> ADP

Enzyme: Hexokinase (glucokinase in liver)

Front 15

Glycolysis, Step 2

Back 15

Glucose - 6- phosphate --> Fructose - 6- phosphate

Enzyme: Phosphoglucose isomerase (PGI)

Front 16

Glycolysis, Step 3

Back 16

Fructose-6-phosphate --> Fructose-1-6-phosphate
ATP-->ADP

Enzyme: Phosphofructokinase (PFK)

Front 17

Glycolysis, Step 4

Back 17

F-1,6-P --> GAD or --> DHP, where
GAD <--> DHP

Enzymes: aldolase, triosephosphate isomerase

Front 18

Glycolysis, Step 5

Back 18

GAD --> 1,3-bisphosphoglycerate
NAD+ + Pi --> NADH

Enzyme: glyceraldehyde 3-P dehydrogenase

Front 19

Glycolysis, Step 6

Back 19

1,3-bisphosphoglycerate --> 3-phosphoglycerate
ADP --> ATP

Enzyme: Phosphoglycerate kinase (substrate level phosphorylation!)

Front 20

Glycolysis, Step 7

Back 20

3-phosphoglycerate --> 2-phosphoglycerate

Enzyme: phosphoglyceromutase

Front 21

Glycolysis, Step 8

Back 21

2-phosphoglycerate --> phosphoenolpyruvate

Enzyme: Enolase (dehydration)

Front 22

Glycolysis, Step 9

Back 22

Phosphoenolpyruvate --> Pyruvate
ADP --> ATP

Enzyme: pyruvate kinase (PK)
(substrate level phosphorylation)

Front 23

Glycolysis, Step 10

Back 23

Pyruvate --> Lactate
NADH --> NAD+

Enzyme: lactate dehydrogenase (LDH)

Front 24

Describe allosteric regulation of the 1st step of glycolysis

Back 24

Hexokinase/glucokinase allosterically inhibited by GLUCOSE-6-PHOSPHATE

*NEGATIVE FEEDBACK

Regulates: (1) amount sugar available for glycolysis and (2) controls sugar uptake and BGL

Front 25

Three phases of glycolysis

Back 25

1) Energy utilization

2) cleavage

3) Energy producing

Front 26

Three highly regulated steps in glycolysis

Back 26

Step 1: glucose --> G-6-P (hexokinase)

Step 3: F-6-P --> F-1,6-P (PFK)

Penultimate step: PEP --> pyruvate (PK)

Front 27

Warburg Effect

Back 27

increased glycolytic rate of CA cells compared to normal surrounding cells

b/c tumors have decreased supply of O2, they adapt by increasing rate of glucose utilization

Front 28

Cori Cycle

Back 28

recycling of lactate produced by muscles during anaerobic metabolsim

lactate sent to liver and converted to glucose before being sent back to the muscles

Front 29

Overall glycolysis REACTION

Back 29

1 glucose + 2 NAD+ + 2 ADP --> 2 pyruvate + 2 ATP + 2 NADH + 2H+

Front 30

Comparative properties of Hexokinase and Glucokinase

Back 30

SEE CP 194

Front 31

3rd step of Glycolysis involves the isomerization of a ______ ( ______) to a ______ (______)

Back 31

an ALDOSE (G-6-P) to a KETOSE (F-6-P)

Front 32

What regulates Step 3 of Glycolysis?

Back 32

Cellular metabolites

Hormones

Front 33

What cellular metabolites positivelyand negatively regulate Step 3 of glycolysis?

Back 33

Positive regulation: AMP, ADP+Pi, F-2,6-bisP

Negative regulation: ATP, citrate

Front 34

What hormones positively and negatively regulate Step 3 of glycolysis

Back 34

Positive: INSULIN

Negative: GLUCAGON

Front 35

What does regulation of Step 3 of Glycolysis ensure?

Back 35

that glycolysis and gluconeogenesis can't happen in the same cell at the same time

Front 36

How does F-2,6-bisP ensure the mutual exclusivity of glycolysis and GNG?

Back 36

SEE CP 196

Front 37

CP 197

Back 37

CP 197

Front 38

Define SUBSTRATE LEVEL PHOSPHORYLATION

Back 38

oxidation of substrate --> energy

energy stored in bond

bond broken to make ATP

Front 39

Where is energy stored following the

Glyceraldehyde-3-phosphate --> 1,3-bisphosphoglycerate

step in glycolysis

Back 39

PHOSPHOANHYDRIDE BOND of 1,3-bisphosphoglycerate

Front 40

REVIEW CP 198

Back 40

REVIEW CP 198

Front 41

What are the positive and negative effectors of the PEP to Pyruvate step of glycolysis?

Back 41

Positive effector: F-1,6-P (feed forward activation)

Negative effector: ATP

Front 42

What does PK deficiency result in?

Back 42

anemia, due to the premature lysis of RBCs

Front 43

REVIEW CP 200

Back 43

REVIEW CP 200

Front 44

What is the first committed step in glycolysis?

Back 44

PFK-catalyzed (Step 3)

Front 45

What is COMMITTED STEP?

Back 45

First dedicated reaction in which a substrate becomes committed to that pathway

Front 46

Whyis the hexokinase-catalyzed step of glycolysis not the committed step?

Back 46

Becuase G-6-P can go to glycogen synthesis or PPP - therefore, product not committed to the glycolysis pathway

Front 47

Fructose metabolism pathway

Back 47

LOOK UP IN TEXT

Front 48

Fructose ingested as...

Back 48

SUCROSE or FRUCTOSE

Front 49

Fructose processed by (enzyme)...

Back 49

Fructokinase (FK) - converts to Fructose-1-Phosphate

Front 50

What is the usual cause of fructose intolerance?

symptoms?

Back 50

defective F-1-P aldolase

sequesters Pi since F-1-P cannot be turned over

Leads to: hypoglycemia, vomiting and liver failure

Front 51

Diets high in fructose can lead to _____ due to ____

Back 51

liver damage

excess loss of ATP

Front 52

GALACTOSE

Ingested as:
Processed by:

Back 52

ingested as LACTOSE

processed by GALACTOSE 1-P-URIDYLTRANSFERASE

Front 53

GALACTOSE METABOLISM

Back 53

SEE CP 203

Front 54

Classical G-1-P UDT deficiency leads to ____

Causes ....

Back 54

leads to EXCESS Galactose-1-Phosphate

causes glactosemia and galactoseuria
accumulation of G-1-P leads to liver damage, mental retardation and cataracts

Front 55

CLINCICAL CASE - PK deficiency

Back 55

SEE CP 204

Front 56

GNG PATHWAY

Back 56

LOOK UP IN TEXT

Front 57

G6PD pathology

Back 57

SEE CP 208

Front 58

Three reasons PPP is important

Back 58

(1) NADPH ---> reducing power for synthesis

(2) ribose-5-P --> to make DNA & RNA

(3) Specific tissue requirements

Front 59

What are the 5 tissues with specific requirements obtained from PPP?

Back 59

(1) RBCs - protect against ROS

(2) quickly-dividing cells - nucleic acid synthesis

(3) synthetic tissue- FA synthesis

(4) liver - drug detoxification

(5) phagocytes - killing bacteria

Front 60

Overall PPP reaction

Back 60

1 glucose-6-P +2NADP+ + 2H2O

-->

2NADPH + Ribose-5-P + CO2