Glycolysis (carbohydrate metabolism I)

what is the type of dietary carbs found in animals?

glycogen

three types of dietary carbs in plants?

starches, fibers and sugars

what are the three types of starches in plants (which are different combinations of amylose and amylopectin)?

rapidly digested, slowly digested and resistant starch

which enzyme is glycogen digested by?

alpha amylase

which enzyme are rapidly and slowly digested starches digested by?

alpha amylase

resistant starch cannot be digested because of its GRANULAR STRUCTURE but what happend in the gut?

it is fermented by gut microbiota

what are the two types of fibers found in plants and fruits?

insoluble and soluble

both soluble and insoluble fibers are not digestable but are…?

fermentable by gut microbiota

example of soluble and insoluble fibers, respectively?

inulin and cellulose

three types of simple sugars found in plants and fruits?

mono, di and trisaccharides

example of trisaccharide?

maltotriose

example of disaccharide?

maltose

example of monosaccharides?

glucose and fructose

what is the monomer for both maltose and maltotriose?

glucose

name of the 6 membered ring of simple glucose?

glucopyranose

which glucose form (L or D) is synthetic?

L

which glucose form is this?

L

which glucose form is this?

D

which glucose form is this?

alpha D glucopyranose

which form of glucose is this?

beta D glucopyranose

which form (alpha or beta) of D glucopyranose is more common?

beta (2/3)

name of sugars which contain a ketone group?

ketoses

examples of ketoses?

fructose, ribulose, xylulose and sedoheptulose

name of sugars with an aldehyde group?

aldoses

out of ribose and ribulose which is an aldose?

ribose

out of ribose and ribulose which is a ketose?

ribulose

examples of aldoses?

glucose, galactose, glyceraldehyde and ribose

what monomers is sucrose made of and what is the bond connecting them?

glucose and fructose (alpha 1,2)

what monomers is maltose made of and what is the bond connecting them?

glucose (alpha 1,4)

what monomers is lactosemade of and what is the bond connecting them?

glucose and galactose (beta 1,4)

examples of two branched glucose polysaccharides?

glycogen and amylopectin

which bonds in glycogen and amylopectin confer linearity?

alpha 1,4 glycosidic

which bonds in glycogen and amylopectin confer branching?

alpha 1,6 glycosidic

which is more branched glycogen or amlyopectin?

glycogen

is amylose branched or unbranched?

unbranched

two examples of unbranched glucose polysaccharides

amylose and cellulose

bonds in amylose?

alpha 1,4 glycosidic

bonds in cellulose?

beta 1,4 glycosidic

bonds in inulin?

beta 1,2 glycosidic

what monomers is inulin made of?

beta fructose

beta 1,4 and beta 1,2 glycosidic bonds in cellulose and inulin confer what?

compactness

what type of bonds form between hydroxyl groups within and between chains of cellulose?

hydrogen bonds

which bonds are the reason amylose adapts a helical structure?

hydrogen bonds

starch consumption shapes our genetic makeup by?

increasing amylase gene duplication

what is the main glucose transporter in animals?

GLUT1

what does the Michaelis constant Km represent?

it represents the concentration of substrate at which the enzyme works at half its max velocity

does glut1 have a low or high Km?

low

what does low Km mean in terms of affinity for substrate?

it means the enzyme has a high affinity for the substrate

what is the Km for glut1?

1mM

where in the body is glut1 found?

everywhere

where in the body is glut2 found? leap card

liver, kidneys, intestines and pancreas (LIPK)

does glut2 have a low or high Km?

high

glut2’s high Km and low affinity for glucose allow it to act as…?

a glucose sensor

what is the Km for glut2?

15-20mM

“low Km meaning high sensitivity allowing it to constantly take up glucose across the physiological range” —> which glucose transporters is this about?

glut1 and glut3

“high Km meaning low sensitivity allowing it to be a glucose sensor” —> which glucose transporter is this about?

glut2

where is glut3 found?

mainly neurons

which has a higher affinity for glucose, glut1 or glut3?

glut3

Ensures a constant glucose supply to cells (especially where glucose is the main energy source) —> which glucose transporter?

glut1

Ensures neurons get enough glucose even when blood sugar is low —> which glucose transporter?

glut3

where is glut4 found? mama

muscles and adipose tissue

which glucose transporter is highly regulated by insulin?

glut4

glut4 moves from intracellular vescicles to the cell surface in response to which hormone?

insulin

what happens to glut4 on cell surface when insulin levels drop?

it moves back to the cell’s interior

what is the Km for glut4?

5mM

what is the Km for glut5?

5mM

where is glut5 found?

jejunum

which sugar does glut5 transport?

fructose

what is the main glucose transporter in the gut?

SGLT1

SGLT1 full name

sodiu glucose transporter 1

does sglt1 use atp?

no

what other transporter does sglt1 rely on?

Na/K ATPase

which two sugars does sglt1 transport from the gut lumen?

glucose and galactose

is sglt1 located on the apical or basolateral side of enterocytes?

apical

what is the transporter located on the basolateral side of enterocytes and transports glucose from enterocytes into the bloodstream?

glut2

is the sodium concentration higher in the intracellular or extracellular space in enterocytes?

extracellular

in enteroendocrine cells what channels does a high level of glucose (and thus atp) inhibit?

ATP gated potassium channels

inhibition of K channels in enteroendocrine cells leads to what?

depolarisation of the cells and calcium influx

influx of calcium in enteroendocrine cells leads to what?

hormone secretion

GLP1 stimulates secretion of which hormone?

insulin

GLP1 inhibits secretion of which hormone?

glucagon

which glucose transporter transports glucose into pancreatic beta cells?

glut2

describe the general mechanism of how high blood glucose level results in secretion of insulin in pancreatic beta cells

glut2 transports glucose from the bloodstream into pancreatic beta cells, high levels of glucose in the cells results in high levels of ATP, ATP inhibits ATP gated potassium channels, this results in the depolarisation of the cell, which results in the release of insulin

describe the general mechanism of how insulin stimulates glucose absorption in muscle cells via glut4

when insulin binds to the insulin receptor, glut4 vescicles fuse with the plasma membrane to translocate glut4 from the cell’s interior to the surface, when insulin levels fall glut4 vescicles are retrieved back into the cell

what does AMPK stand for?

AMP activated protein kinase

is AMPK insulin dependent or independent?

independent

what are the two molecules which stimulate glut4 translocation to the cell surface?

insulin and AMPK

when is AMPK activated and responsible for glut4 translocation?

during exercise

generally describe the mechanism through which glucose uptake stimulates GLP1 release in enteroendocrine cells

glucose is transported into the cell by sglt1, a higher level of glucose means a higher level of ATP, ATP then inhibits the ATP gated potassion channel, this leads to the depolarisation of the cell, which in turn leads to the uptake of calcium, calcium then stimulates secretion of GLP1

which enzyme converts pyruvate to lactate?

lactate dehydrogenase

what coenzyme is used by lactate dehydrogenase?

NADH

what is pyruvate converted to in yeast cells under anaerobic conditions?

ethanol

what are the two enzymes used in conversion of pyruvate to acetaldehyde and then ethanol?

pyruvate decarboxylase and alcohol dehydrogenase

what coenzyme is used in conversion of pyruvate to ethanol (and what is released as a side product)?

NADH and CO2

first step of glycolysis

glucose to glucose 6 phosphate (hexokinase)

second step of glycolysis

glucose 6 phosphate to fructose 6 phosphate (phosphoglucose isomerase)

third step of glycolysis

fructose 6 phosphate to fructose 1,6 bisphosphate (phosphofructokinase)

fourth step of glycolysis (last in the investment phase)

fructose 1,6 bisphosphate to dihydroxyacetone phosphate and glyceraldehyde 3 phosphate (aldolase)

which enzyme converts dihydroxyacetone phosphate to glyceraldehyde 3 phosphate

triose phosphate isomerase

how many molecules of ATP are used in the investment phase of glycolysis and which enzymes use them?

2, hexokinase and phosphofructokinase