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Biochem weeks 3-4 > Carbohydrate structure and glycolysis > Flashcards

Carbohydrate structure and glycolysis Flashcards

1
Q

which organs / tissues need a constant supply of glucose (need glucose at both high and low blood glucose levels)?

A

brain (neurons) & RBCs (erythrocytes)

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2
Q

stereoisomers have …

A

same chemical formula, different 3D structure

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3
Q

of isomers for a molecule =

A

2^ (# C atoms - 2)

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4
Q

enantiomers are …

A

mirror images of each other

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5
Q

anomers are specific to …

A

ring structures of monosaccharides

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6
Q

L-enantiomer has the OH group …

A

on the left

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7
Q

D-enantiomer has the OH group …

A

on the right

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8
Q

epimers have …

A

same chemical formula AND same 3D structure, BUT asymmetric around one carbon

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9
Q

the 4 most important disaccharides

A

lactose
sucrose
maltose
isomaltose

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10
Q

glycosidic bond is between …

A

OH group on anomeric carbon (on monosaccharide 1)

free OH group (on monosaccharide 2)

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11
Q

lactose

A

galactose beta(1 - 4) glucose

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12
Q

sucrose

A

glucose alpha(1 - 2) fructose

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13
Q

maltose

A

glucose alpha(1 - 4) glucose

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14
Q

isomaltose

A

glucose alpha(1 - 6) glucose

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15
Q

GLUT transporters are …

A

monosaccharide transporters

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16
Q

3 sources of glucose for glycolysis

A

glycogenolysis (during exercise in muscle)
dietary intake (during FED state)
glycogenolysis gluconeogenesis (during fasting / starvation)

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17
Q

what are 3 polysaccharides of glucose?

A

glycogen
starch
cellulose

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18
Q

glycogen structure

A

highly branched

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19
Q

starch structure (contains 2 components) and what does it supply humans?

A

amylose
amylopectin

dietary fuel from plants

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20
Q

cellulose (another name, origin, structure, behavior in humans)

A

aka fiber

from plants

UNbranched

not digestible, but has health benefits

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21
Q

draw GLUT transporter concept map out

A
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22
Q

draw glycolysis overview on whiteboard

A
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23
Q

what is the first irreversible step in glycolysis? what else is true about it?

A

glucose –(hexo-/glucokinase)–>
glucose-6P

committed, regulated step
NOT key step bc it’s not unique

24
Q

what kind of rxn is glucose-6P –> fructose-6P?

A

reversible,
not regulated

25
Q

what is the second irreversible step in glycolysis? what else is true about it?

A

fructose-6P –(PFK-1)–>
fructose-1,6-BP

  • 1 ATP

KEY and regulated step

26
Q

what is the last rxn in glycolysis?

A

PEP –(pyruvate kinase)–> pyruvate

+ 2 ATP / per glucose

regulated step

27
Q

irreversible rxn =

A

regulated

28
Q

reversible rxn =

A

NOT regulated

29
Q

what are the 3 phases of glycolysis?

A

investment
splitting
energy generation

30
Q

where does pyruvate go after glycolysis?

A

to mitochondria for TCA cycle

31
Q

where does 2 NADH produced go after glycolysis?

A

to mitochondria for ETC

32
Q

net production of glycolysis / per glucose

A

+ 2 pyruvate

  • 2 ATP
    + 2 NADH
    + 4 ATP
33
Q

what is the first step of glycolysis in fasting / starvation?
what tissue(s) does this occur?

A

glucose / fructose / galactose
|
{through GLUT 1 or GLUT 3}
|
(hexokinase)
|
V
glucose-6P

[- 1 ATP]

all tissues

34
Q

what is the first step of glycolysis in fed state?
what tissue(s) does this occur?

A

glucose
|
{through GLUT 2}
|
(glucokinase)
|
V
glucose-6P

[- 1 ATP]

only liver and pancreas

35
Q

draw hexokinase vs glucokinase comparison list

A
36
Q

what does Vmax mean for an enzyme?

A

capacity / amount of binding that the enzyme can handle

37
Q

what does Km mean for an enzyme?

A

the concentration of substrate required for enzyme to reach half of its Vmax

38
Q

what does a low Km indicate about binding affinity?

A

HIGH affinity for its substrate, bc it gets saturated quickly

39
Q

what does a high Km indicate about binding affinity?

A

LOW affinity for its substrate, bc it does not get saturated quickly

40
Q

what are the 3 stages of metabolism?

A
  1. digestion & absorption in GI tract
  2. glycolysis
  3. oxidation of Acetyl-CoA in TCA
41
Q

what are the products of anaerobic glycolysis? when does anaerobic glycolysis occur?

A

+ 2 lactate / per glucose

+2 ATP

absence of oxygen; in cells without mitochondria

42
Q

how does NADH get to the ETC in the liver / heart?

A

malate-aspartate shuttle takes e- from cyto. NADH, takes it into mito., converts it to NADH

recycles cyto. NAD+ into cytoplasmic pool

cyto. NADH -> mito. NADH

43
Q

how does NADH get to the ETC in the brain / muscle?

A

glycerol-3P shuttle takes e- from cyto. NADH, takes it into mito., converts it to FADH2

recycles cyto. NAD+ into cytoplasmic pool

cyto. NADH -> mito. FADH2

44
Q

arsenate can cause poisoning by inhibiting what rxn in glycolysis?

A

first rxn in energy production phase

glyceraldehyde-3P <–> 1,3-BP

45
Q

what can inhibit the rxn that produces PEP in glycolysis?

A

fluoride ions (ex. toothpaste)

46
Q

what 3 enzymes are alloesterically regulated in glycolysis?

A

hexokinase
PFK-1
pyruvate kinase

47
Q

what is hexokinase allosterically inhibited by?

A

glucose-6P

48
Q

what is PFK-1 allosterically stimulated by during FED state?

A

AMP
fructose-2,6-BP (only in liver)

49
Q

what is PFK-1 allosterically inhibited by during fasting / starvation state?

A

ATP
citrate
fructose-2,6-BPase (only in liver)

50
Q

what is pyruvate kinase allosterically stimulated by?

A

fructose-1,6-BP

51
Q

what is pyruvate kinase allosterically inhibited by?

A

ATP

52
Q

where does hormonal regulation of glycolysis occur?

A

only in the liver

53
Q

what is pyruvate kinase hormonally inactivated by? what does this prevent? where does PEP go now? in what state does this occur?

A

glucagon signaling

PK inhibition prevents PEP from being converted to pyruvate

PEP goes to gluconeogenesis instead

in fasting / starvation state

54
Q

why is glycolysis only on during fed state?

A

bc in fed state, liver is a glucose consumer
+
liver wants to store glucose

55
Q

why is glycolysis off during fasting / starvation states?

A

bc in fasting / starvation, liver is a glucose producer for all other cells in body via glycogenolysis / gluconeogenesis

if glycolysis is off then all glucose generated would just be wasted

56
Q

what is pyruvate kinase deficiency? what happens in glycolysis if it is severe?

A

mutation in enzyme encoding pyruvate kinase

0 PK activity = ATP produced during glycolysis is half of normal amount

57
Q

why can pyruvate kinase deficiency by catastrophic for RBCs?

A

RBCs only get ATP from glycolysis

RBCs use ATP to maintain membrane shape
without enough ATP -> become echinocytes (spikey cells)

echinocytes are digested by body = causes HEMOLYTIC ANEMIA

Biochem weeks 3-4 (5 decks)

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