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Biochem 385 Unit 1 > Lecture 7: Glycolysis: Regulation > Flashcards

Lecture 7: Glycolysis: Regulation Flashcards

1
Q

Glucokinase overview

A

glucose sensor

affects insulin secretion from pancreatic beta cells

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2
Q

phosphofructokinase 1 (PFK-1)

A

one of 3 metabolic valves in glycolytic pathway

allosterically regulated

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3
Q

disarcharide sugars

A

maltose, sucrose, lactose

give rise to monosacchardes sugars to enter glycoltic pathway

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4
Q

Regulated valves

A

rate-limiting enzymes in metabolic pathways

open and close in response to cell conditions

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5
Q

Regulation of glycolytic pathway (glycolysis and gluconeogenesis)

A

reversible steps in both regulate in both pathways (shown wide in pictures)

irreversible steps have actual changes in free energies (delta G) that are very negatie and require PATHWAY SPECIFIC ENZYMES (shown as skinny)

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6
Q

glucokinase and hexokinase

A

catalyze same reaction

differ in properties

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7
Q

Hexokinase I

A

high affinity for substrate (at low concs, enzyme has half activity)
phosphorylates a variety of hexose sugars
in ALL tissues
INHIBITED by product of reaction (glucose-6-P)

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8
Q

Glucokinase

A

low affinity for substrate (it takes a lot more substrate to reach half max enzyme activity)
Spefic for GLUCOSE
only in liver and pancreatic cells
NOT inhibited by glucose-6-P

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9
Q

Role of glucokinase in liver cells

A

high blood glucose levels-> hexokinase and glucokinase active in liver cells

hexokinase will become inhibited

traps glucose in liver cells more than in other tissues because glucokinase doesn’t become inhibited, which allows more glucose to be trapped as gluco-6-P

liver is where we store most glycogen

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10
Q

role of glucokinase in pancreatic beta cells

A

glucokinase sequesters glucose inside cells

initiate signaling pathway leading to release of INSULIN into blood

this makes glucokinase a glucose sensor

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11
Q

Km values

A

tells what substrate concentration is needed to reach half maximum activity

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12
Q

Glucose transporters are called

A

GLUC transporters

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13
Q

review slide 7

A

review slide 7

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14
Q

what happens to flux through glycolytic pathways when glucokinase is activated by glucose?

A

flux will increase because glucokinase is activated at high glucose levels (while hexokinase is inactivated)

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15
Q

what turns off glucokinase?

A

a lack of glucose

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16
Q

what effect would a mutation in glucokinase have on insulin secretion

A

insulin secretion will decrease, but won’t go away because hexokinase can still get some to be secreted

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17
Q

How would you treat diabetes that is cauased by glucokinse mutation

A

give insulin

diabetes not actually caused by this!

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18
Q

See slide 9 for questions

A

see slide 9 for questions

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19
Q

is PFK1 stimulated or inhibited by a high energy charge (keep in mind that this is in the ATP using stage)

A

INHIBITED

if we have a lot of ATP around, we don’t need to make more ATP.
we do need enough ATP around to make the reaction happen, but we need to have a need to make ATP

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20
Q

T state

A

INACTIVE conformation

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21
Q

R state

A

ACTIVE conformation

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22
Q

Allosteric regulator of PFK-1

A

a tetramer

F-2,6-BP–> super activator of PFK-1 activity
AMP——–>activator
ADP——–> activaor

Citrate—-> inhibitor
ATP——–> inhibitor

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23
Q

citrate and PFK-1 activity

A

inhibits

because citrate is a metabolite of the citrate cycle, it builds up when energy levels are high

24
Q

F-2,6,BP and PFK-1 activity

A

super-duper activator (activating PFK-1 is its only job)

NOT a metabolite of glycolysis, just a regulatory molecule

25
Q

see slide 11 for questions

A

see slide 11 for questions

26
Q

review slide 12

A

review slide 12

27
Q

disaccharide sugars

A

maltose
sucrose
lactose

all of them can make glucose!!!!!

28
Q

maltose

A

from starch

enzyme is maltase to give 2glucose

29
Q

sucrose

A

table sugar

enzyme is sucrase to give glucose and fructose

30
Q

lactose

A

from milk

enzyme is lactase to give glucose and galactose

31
Q

glycerol

A

glycolytic intermediate derived from degradation of triglycerides (fats)

glycerol backbone is left once cleaved. it can enter glycolytic pathway

32
Q

why does decreased lactase enzyme cause stomach problems when eating dairy?

A

when lactase in small intestine can’t digest it, bacteria in the colon CAN digest it

by product of bacteria digestion is methane for ex

33
Q

cleaving maltose

A

makes to molecs of glucose

34
Q

lactose

A

cleaves into glucose and galactose

galactose undergoes a pathway using galactokinase and ATP and generating Glucose-1P

35
Q

Sucrose

A

splits into glucose and fructose

ATP used before each kinase

Fructose in liver:
fuctokinase phosphorylayes to make eventually 2 3-carbon molecs. ATP used on one to make GAP

Fructose in muscle:
hexokinase phosphorylates it to make fructose-6-P which continues into glycolysis

36
Q

review slide 15

A

review slide 15

37
Q

Fructose intolerance

A

due to deficiency in emzyme fructose-1-P aldolase (which splits in into 2 3-carbon molecs)

too much dietary fructose causes build up in fructose1-P, this depletes Pi in liver and inhibits ATP synthesis

38
Q

review slide 16

A

review slide 16

39
Q

what is the treatment for people with fructose intolerance?

A

limit fructose intake!

40
Q

why aren’t there people with a complete loss of PFK-1

A

they would die

41
Q

glycolytic metabolites of glycolysis can provide carbon skeletons for…

A

amino acid synthesis
pentose phosphate pathway
triacylglyceride synthesis

42
Q

aerobic conditions in mitochondria

Pyruvate converted to….

A

acetyl CoA

wich goes into citrate cylce or is converted to fatty acids

43
Q

ANaerobic conditions in cytoplasm

Pyruvate converted to….

A

Lactate

regenerates NAD+

44
Q

Anaerobic conditions in yeast

Pyruvate converted to….

A

ethanol

NAD+ regenerated

45
Q

Which glycolytic enzyme requires NAD+ as a substrate?

A

Glyceraaldehyde-3-P dehydrogenase

46
Q

NAD+ used to…

A

make NADH

47
Q

What would happen to metabolic flux through glycolysis if NAD+ not regenerated

A

it would stop!!!!

48
Q

Which glycolytic enzyme is responsible for decreased flux through the glycolytic pathway when NAD+ is not regenerated by LDH

A

Glyceraaldehyde-3-P dehydrogenase

49
Q

Lactase dehydrogenase (LDHA) defeciency

A

they can’t do much exercise because they can’t use glycolysis to make ATP needed

50
Q

when we talk about electron transport, where are they transported?

A

into the mitochondria (via shuttle systems)

the molecules itself is NOT transported into mitochondira

51
Q

Shuttle systems…

A

regenerate NAD+ when pyruvate is oxidized in mitochondria

responsible for oxitizing CYTOSOLic NADH (so the enzymes an continue to act)

52
Q

Review slide 22 for example questions

A

Review slide 22 for example questions

53
Q

lactose

A

sugar (carb)

54
Q

lactase

A

enzyme (protein)

55
Q

lactate

A

small metabolite

Biochem 385 Unit 1 (13 decks)

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