Intro to carbs and glycolysis Flashcards
When does de novo synethesis of glucose occur?
This is gluconogenosis and this occurs during fasting when blood glucose levels are falling and glucose is needed for certain organs
What and when does glycogenesis take place?
When glucose levels from diet are more than needed, the excess is stored as glycogen through glycogenesis
When need the glycogen is degraded through glycogenolysis
Go from Glycogen to lactate
What are the two minor pathways of glucose
Hexose monophosphate shunt- produces ribose-phosphate for nucleotide synthesis and NADPH that supplies power for bopsynthetic reactoin (making fatty acids)
Galatose and fructose metabolime– can sytnehsize sugar and sugar derivitatives.
Where can glucose be obtained from
Storage (glycogen) or diet
In storage glycogen is cnoverted to glucose or glucose 6-phosphate
Glcuose from diet has different sources. What are they? examples of each kind
Monosaccarides- honey and fruit- these can be easily absorbed by enterocytes
Disaccarides- milk sugar (lacatose) and table sugar (sucrose)- hudorlyzed by enzymes in the brush border of intestinal tract
Polysaccarides- starch (from plants) and glycogen(animals from their storage) and they contain alpha 1-4 glycosdies linkages and alpha 1-6 glycosidic linkages
What is lactose, sucrose and trehalose composed of
Lactose- glucose and galactose
Sucrose- glucose and fructose
Trehalose di-glucose
Where does the major daily caloric intake come from? How is each absorbed?
CARBS! mono, di and poly
- Monosaccharides are absorbed directly;
- disaccharides are digested by
intestinal surface enzymes - polysaccharides need to
be reduced to smaller molecules
Explain the absorption of strach and glycogen
- The amylose chains (1-4 glycosidic chain/ linear) are degraded by alpha-amylase in the saliva and pancreatic juices
making glucose, maltose (di) and maltotriose (tri). - The 1-6 glycosidic chains (amylopectin/branched) are hydolyzed by isomaltase
- Further digestion of oligiosaccharides occurs on the surface of the intestinal epithelial cells by alpha-glucosidases (maltases)
- Oligosacc not hydolyzed by amlyase or intesintal enzymes reach the ileum where bateriametablizes the sugas anerobically to short fatty acids, H2, methane and CO2
What happens in pathology of digestion? Explain oral tolerance test>
Undigested disaccharides go to the LI and they cause osmotic diarheea. Bacterial digestion results in production of large amounts of CO2, methane and hydrogen gas.
Oral tolerance test can measure the amout of hydrogen gas in a breath and can identify enzyme deficieny
What can cause disaccharide intolerance?
- Loss of brush cells in intestinal tract
- Intesitnal disease
- Drugs that damage the mucosa of the SI
Temp disorder can lead to severe diarhea
Explain what happens when someone is lactase intolerant
Latase definicity so lactose passes into the LI where it is digested by bacteria causing GI distress, cramping, bloating due to the CO2 and methane that is being produced.
What is isomaltase sucrose deficienty
Results in intolerance to sucrose. in about 10% of greenland eskimos and 2% of NAmericans are heterozygous
Where do intestinal cells obtain energy?
From glutamine metabolism— they don’t depend on glucose
How and by what are monosacc absorbed?
What is the exception?
By entercytes through facilitated diffusion
Pentoses and L-sugars enter through passive transport (so we can use xylose to test ability of mucosal cells for absorption)
How does glucose and ____ get absorbed?
Difference from mannose
Galatose!
Through the Na-monosaccharide (SGLT-1) co transporter driven by Na gradient and the hydrolyze of ATP, so the mono sacc can go against it’s gradient
** this is different from the Na-dependent transporter used for manose***
What does GLUT-5 transport?
Fructose!
What passes through GLUT-2?
Glut -2 transports all monosacc through the membrane of the lumen into the capillaries. CAn pas glucose, galactose, fructose
steps after monosacc have passed into the capillary through the Glut-2
Monosaccs. go to the liver. Gluocse is distributed into general circulation, while galactose, fructose and mannose are processed by the liver
Why can every cell use glycolysis? Names cells that only use it
Because its anerobic and doesn’t require O2
Scelera, retina, RBC, cornea– so they rely on the 2 ATPs formed by glycolysis
Name some functions of glycolysis
- Yields 2 atps (cells that have no mitochondria rely solely on these two ATPs)
- Sets the stage for aerobic oxidation because pyruvate can become Acytl CoA
- Stores glycogen which is an intermediate for carb storage
- Supplies intermediates for pentose phosphate pathway (making of NADPH and 4,5,7 Carbon sugars)
- Supplies intermediates for 2-3 BPG
- Supplies intermediates for special carbohydrate synthesis
- can take up glycerol from triacykygylercols
Where does glycolysis, TCA and oxidative phosphorylation take place
Glycolysis – in cytosol
TCA – in mitochondrial matrix
Electron transport and oxidative phosphorylation – in inner membrane and inter-membrane
Glucose–> pyruvate 2 ATP
Pyruvate–> CO2 2 ATP
NADH+H (FADH2)–>H2O 34 ATP
List organs
- Dependent on glucose that make pyruvate
- Dependent on glucose that make lactate
- Dependent on glycolysis b/c of low mitochondria
- Dependent on glucose that make pyruvate– brain
- Dependent on glucose that make lactate– No mitochondria so make pyruvate- RBC, retina, sclera, lens
- Dependent on glycolysis b/c of low mitochondria– renal medulla, testis, WBC, Whte mucle fibers
*** heart is aerobic but uses mostly fatty acids**
