MCAT > Biochem Chapter 9 > Flashcards

Biochem Chapter 9 Flashcards

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1
Q

Glucose is too big to enter membrane, so what transporter do they use to cross

A

GLUT 1-4 transporters

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2
Q

Which one of the glucose transporters are more important for regulation

A

Glut 2 and 4

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3
Q

Normal glucose concentration in peripheral blood is

A

5.6 mM

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4
Q

Where is GLUT 2 found

A

Liver and pancreatic beta cells

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5
Q

How is the Km value of GLUT 2

What does that mean

A

High Km .

Means transporter has low affinity for glucose

So it only takes up glucose when blood glucose is high like after food or something

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6
Q

In beta cells how does GLUT 2 work
What does it work with and do what

A

Works with glucosekinase as a glucose sensor for insulin release

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7
Q

In summary what doles GLUT 2 do (2)

A

Detect changes in blood glucose
Plus take action

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8
Q

Where is glut 4 found

A

Muscles and adipose tissue

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9
Q

How is glut 4 Km like

A

Near normal blood glucose (5mM)
Highly responsive to daily fluctuations

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10
Q

Is glut 4 insulin dependant

A

Yes , if insulation increases, it triggers more glut 4 transporters to be inserted into cell membrane through exocystosis

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11
Q

When insulin levels fall what happens to glut 4 receptors

A

Transporters are pulled back into cells through endocytosis and stores it there

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12
Q

How does glut 2 and glut 4 work together lets say after a meal

A

You eat
High glucose levels
Enters pancreatic beta cells through glut 2
Insulin secretion is triggered
Circulate through blood stream
Signals muscles and adipose tissue to increase glucose uptake by move glut 4 transporters to cell surface

Rapid increase in glucose uptake
So then normal glucose levels

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13
Q

What does glut 4 do in summary

A

Insulin responsive transporter that takes up glucose when its high

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14
Q

Are glut 2 and 4 saturated at normal glucose levels

A

Glut 2 no

Glut 4 yes , saturated when glucose levels are slightly above 5mM

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15
Q

What is glycolysis process

A

Breaking glucose into 2 molecules of private

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16
Q

What is realeased in glycolysis

A

ATP and Nadh

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17
Q

Does glycolysis happen in aerobic or anaerobic conditions

What does pyruvate do in both conditions

A

Both

If aerobic, pyruvate can move into mitochondria and continue through rest of cellular respiration

If anaerobic , it can still run by pairing with fermentation pathways that generate nad+

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18
Q

In glycolysis , there are so many intermediates between glucose and lactate/ pyruvate, can you list the intermediates in between (10 starting from glucose to pyruvate)

A

Glucose
Glucose 6 phosphate
Fructose 6 phosphate
Fructose 1,6 bi phosphate
Glyceraldehyde 3 phosphate
1,3 biphosphoglycerate
3 phosphoglycerate
2 phosphoglycerate
Phosphenolpyruvate
Pyruvate

—> no oxygen : pyruvate will become lactate

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19
Q

For glycolysis, what is the rate limiting enzyme

What conversion does it do

A

phosphofruktokinase 1

Fructose 6 phosphate to fructose 1,6 bi phosphate

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20
Q

The first enzymes that convert glucose to glucose 6 phosphate are (2)

A

Hexokinase
Glucokinase

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21
Q

Where can hexokinase be found as opposed to glucokinase

A

Hexokinase is in most tissues

Glucokinase is found in liver and pancreatic beta cells

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22
Q

Does hexokinase have high or low Km, when does it reach maximum velocity then

A

Low Km, reaches maximum velocity at low glucose

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23
Q

Does glucokinase have low or high Km

What does that mean

A

High Km

Acts on glucose proportionately to its concentration

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24
Q

What inhibits Hexokinase

A

Glucose 6 phosphate

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25
What induces glucokinase
Insulin
26
What does phosphofructose kinase 1 phosphorylate from and to
Fructose 6 phosphate to fructose 1,6 biphosphate
27
What does phosphofructokinase use to operate
ATP
28
PFK-1 is inhibited by what
ATP and citrate
29
What is PFK-1 activated by
AMP
30
Why does PFK-1 turn off with ATP and turn on with AMP
When glycolysis has sufficient atp, that is when there is sufficient energy, so it’ll turn off PFK-1 When there isn’t enough energy, there is high AMP, so it’ll turn on PFK-1
31
If there is insulin present, instead of PFK-1, what gets activated
PFK-2
32
What does PFK-2 do
Converts fructose 6 phosphate to fructose 2,6 biphophate
33
What is the purpose of PFK-2 activating fructose 2,6 biphosphate Why does this need to happen
It in turn activates PFK-1 It bypasses the pathway of inhibition caused by ATP so that glycolysis continues without interruption
34
What stimulates and what inhibits PFK-2 in cells which indirectly affects PFK-1
Insulin stimulates Glucagon inhibits
35
Between glyceraldehyde 3 phosphate and 1,3 biphosphoglycerate , what intermediate is used
Glyceraldehyde 3 phosphate dehydrogenase
36
When there is glyceraldehyde 3 phosphate conversion to 1, 3 biphosphoglycerate What is oxidized and added What is reduced
There is an inorganic phosphate that gets oxidized and added to the Glyceraldehyde 3 phosphate NAD+ is reduced in NADH
37
How do you know NAD+ to NADH is reduction reaction
Because more bonding to H is reduction reaction More bonding to heteroatoms , not H and C , is oxidation reaction
38
To go from 1,3 biphosphoglycerate to 3 phosphoglycerate , what is used and what happens
3 phosphoglycerate kinase is used for the conversion The high energy phosphate in the bi form is transferred to ADP to make ATP
39
When ADP is added with a high energy phosphate from an intermediate to make ATP, what is this form of phosphorylation called
Substrate level phosphorylation
40
Is substrate level phosphorylation dependant on oxygen
No, they are not dependant on oxygen It is the only way ATP can generate in anaerobic tissue
41
To go from phosphophenolpyruvate to pyruvate , what enzyme is used
Pyruvate kinase
42
Pyruvate kinase is activated by what
Fructose 1,6 biphosphate from PFK-1 reaction
43
Pyruvate kinase is a type of what activation What does it mean
Feed forward activation Where a product of earlier traction of glycolysis activates an after product
44
When there is no oxygen ,how does glycolysis progress towards
Fermentation
45
Main fermentation enzyme in mammalian cells is
Lactate dehydrogenase
46
What are the two things lactate dehydrogenase do
Oxidizes NADH to NAD+ Replenishes the oxidised coenzyme of Glyceraldehyde 3 phosphate dehydrogenase
47
Is there a net loss of carbon in pyruvate or lactate
No , they are both 3 carbon molecules
48
Why does pyruvate reduce to lactate in anaerobic conditions
It prevents the problem of this : when all the NAD+ has been reduced to NADH , glycolysis stop. To stop this problem , fermentation occurs in the form of lactate, that is why it is reduced
49
In yeast cells, fermentation converts of pyruvate to what and what , and how many carbons are the two
Ethanol is 2 carbon, carbon dioxide is 1 carbon
50
The result of mammalian and yeast fermentation end product is the same what is it
NAD+ replenishment
51
What is DHAP intermediate in glycolysis for
It is for triacylglycerols synthesis
52
What is DHAP formed from
Fructose 1,6 biphosphate, , it can be isomerized to glycerol 3 phosphate and then converted to glycerol which is the backbone of triacylglycerols
53
Where is the only ATp gained in anaerobic respiration in glycolysis , which 2 high energy intermediates
1,3 biphosphoglycerate and phosphenolyruvate ( 1,3 BPG and PEP )
54
What are the 4 irreversible steps of glycolysis
Hexokinase Glucokinase PFK-1 Pyruvate kinase
55
In RBC, what form of glycolysis happens ( aerobic or anaerobic ) How many ATP are produced per glucose
Anaerobic 2 ATP
56
In red blood cells, what is the special enzyme it has What doles it convert from and to
Biphosphoglycerate mutate Produces 2,3 biphosphoglycerate from 1,3 biphosphoglycerate
57
What do mutases do as enzymes
They move functional group from one place to another , just rearrangement or shifting
58
Hexokinase purpose
Glucose to glucose 6 phosphate Trapping glucose in cell
59
Is Hexokinase reversible
No
60
Is Hexokinase inhibited by anything
Glucose 6 phospahate
61
Glucokinase does what
Phosproyaltes and traps glucose in liver and pancreatic cells Works with GLUT 2 as part of glucose sensor in B islet cells
62
Glucokinase induced by what
Insulin
63
Is glukonase reversible
No
64
What does PFK 1 do Using what
Phosphorylation fructose 6 phosphate Using atp
65
PFK 1 is inhibited by which 3 things
Amp Fructose 2,6 biphosphate insulin
66
Is PFK 1 reversible
No
67
Is Glyceraldehyde 3 phosphate dehydrogenase reversible
Yes
68
Is Glyceraldehyde 3 phosphate generate what
NADH
69
What does 3 phosphoglycerate kinase do
Substrate level phosptylation, transferring phosphate
70
Is 3 phosphoglycerate kinase reversible
Yes
71
What does pyruvate kinase do What it form
Substrate level phosphorylation, transfers phosphate to ADP from pep Forming atp and pyruvate
72
What is pyruvate kinase activated by
Fructose 1 6 bi phosphate
73
Is pyruvate kinase reversible
no
74
Fermentation regenerates what
NAD+
75
Does fermentation generate atp or energy carriers
No it just regenerates coenzymes
76
What does binding of 2,3-BPG do to its oxygen affinity in fetal hemoglobin Is it good or bad
Decreases hemoglobin’s affinity for oxygen Because baby needs oxygen in blood from mommy Disadvantageous to lower its affinity for oxygen
77
Galactose reaches liver through what
Hepatic portal vein
78
Galactose is phosphorylated by what what to trap in cell
Galactokinase
79
What do epimerases do
Catalyze the conversion of one sugar epimer to another
80
Two enzymes that are used in galactose metabolism
Galactokinase Galactose-1-phosphate urildyltransferase
81
Liver phosphorylates fructose using what auto trap it in the cell
Fructokinase
82
Why does fructose supply a quick source of energy in both aerobic and anaerobic cells Think about fructose metabolism What is downstream of what products of fructose metabolism
Because DHAP and Glyceraldehyde, which are both products of fructose metabolism are both downstream from the key regulatory and rate limiting enzyme of glycolysis which is PFK 1, that’s why
83
What does aldolase B make in fructose metabolism
CLeaves fructose 1 phosphate into Glyceraldehyde and DHAP
84
What is reactant of pyruvate dehydrogenase complex PDC 3
Pyruvate NAD+ CoA
85
What is 3 products of pyruvate dehydrogenase complex PDC
Acetyl coa NADH Co2
86
How does acetyl coA affect PDH activity
It inhibits it Because acetyl CoA is the product, signals that cell is energetically satisfied so the production of it should stop or slowed. Then pyruvate will be used to create other products
87
What are the 3 possible fates of pyruvate
Using PDH, convert to acetyl co A Conversion to lactate by lactate dehydrogenase Consverion to oxaloacetate using pyruvate carboxylase
88
What does glycogen in liver and skeletal muscles stored do differently
Liver glycogen is broken down to maintain a constant level of glucose in the blood Muscle glycogen is broken down to provide glucose to the muscle during intense exercise
89
Plants store glycogen in them ina form called
Starch
90
What is glycogenesis
Synthesis of glycogen granules
91
Which protein facilitates glycogenesis
Core protein called glycogenin
92
What other monosaccharides can contribute to atp production
Galactose and fructose
93
Why is fructose metabolized in liver
Because it bypasses the rate limiting of glycolysis
94
Wat is glycogenesis
Glycogen synthesis Production of glycogen using 2 main enzymes
95
Glycogenesis is with which 2 main enzymes
Glycogen synthase and branching enzyme
96
What is the rate limiting step for glycogenesis And what it from
Glycogen synthase to form 1,4 glycosidic bond
97
Branching enzyme introduces what types of branches
Alpha 1,6 glycosidic bonds
98
What is glycogenolysis
Process of breaking down glycogen when body needs glucose
99
What is opposite of glycogenolysis
Glycogenolysis - mobilizing glucose Glycogenesis: storing glucose
100
How does 2 main enzymes of glycogenolysis work and do
Glycogen phosphorylase breaks alpha 1,4 glycosidic bonds Debranching enzymes deconstructs branches
101
Debranching enzyme in glycogenolysis has 2 enzymes with different functions what they do
One moves terminal end of glycogen chain to branch point ( alpha 1,4 transferase) One removes glucose monomer actually present at branch point ( alpha 1,6 Glucosidase)
102
What are isoforms in terms of glycogen
Slightly different versions of the same protein
103
How do glycogen storage diseases occur
if glycogen can’t be broken down properlyy Glucose can’t be mobilized tissues that depedant on it will stop working
104
For glycogen to have branches what links are required
Alpha 1, 6 glycosidic links
105
Gluconeogenesis’ What is it
pathway body uses to amke new glucose when dietary glucose one isnt Availablle like when you’re fasting
106
Gluconeogenesis happens after what
Glycogenolysis
107
What hormones simulate glycogenolysis and Gluconeogenesis (3)
Glucagon Epinephrine Cortisol
108
Where do the carbons from Gluconeogenesis come from , the 3 substrates
Lactate Glycerol 3 phosphate Glucogenic amino acids
109
Which 2 amino acids are not glucogenic amino acids What are they called
Leucine and lysine Ketogenic amino acids
110
Can fattty acids be converted into glucose Any exceptions
No except odd chain fatty acids
111
What does pyruvate carboxlyase do in Gluconeogenesis
Converts pyruvate into oxaloacetate using CO2 and ATP
112
What are the 3 irreversible steps Gluconeogenesis has to surpass
Hexokinase PFK1 Pyruvate kinase
113
What does PEPCK do in Gluconeogenesis Using what energy source
Coverts oxaloacetate into PEP GTP
114
What activates pyruvate carbozylase in Gluconeogenesis
Acetyl co a
115
What activities PEPCK in Gluconeogenesis
Glucagon and cortisol
116
What does fructose 1 , 6 bi phophatase do in Gluconeogenesis
Bypasses pFK 1 Removes phosphate group back to fructose 6 phosphate
117
What is fructose 1 , 6 bi phophatase activated by in Gluconeogenesis Inhibited by what too
ATP activated Amp inhibited
118
What does glucose 6 phosphatase do in Gluconeogenesis
Bypass glucose 6 phosphate to become free glucose, which is then transported back to blood
119
How if glucose 6 phosphatase regulated in Gluconeogenesis
Not hormonal regulated
120
For each step of hormones regulating in Gluconeogenesis, where are they found
Pyruvate carboxlyase Found in mitochondria Then majority cytoplasm Then lastly glucose 6 phosphatase is in ER lumen
121
Why is Gluconeogenesis linked to fatty acid oxidation
Because Gluconeogenesis requires acetyl co A to happen. If source of acetyl co a was glycolysis, this would just burn the glucose that is being generated in Gluconeogenesis
122
What is the pentose phosphate pathway (PPP) for 2 things it makes
Production of NADPH Source of ribose 5 phosphate for nucleotide syntehsis
123
PPP pathway happens in which part of cells
Cytoplasm
124
PPP branches off which process at glucose 6 phosphate
Glycolysis
125
PPP can be divided into 2 phases Which one is reversible which isnt
Oxidative is irreversible Non oxidative is reversible
126
Oxidative phase of PPP, what is produced
NADPH
127
Rate limiting steep of PPP What is the enzyme used What is created
Glucose 6 phosphate oxidised by 2 dehydrogenase, NADP is reduced to NADPH
128
What is the product of oxidative irreversible part of PPP
2 NADPH Ribulose 5 phosphate
129
What is made in nonoxidative reserible section in PPP What else can it do for pivoting
Ribose 5 phosphate for nucleotide syntehsis It can become fructose 6 phosphate to enter glycolysis pathway again
130
What does NADH do
Produces ATP after being reduced from NAD+
131
nad+ and NADPH Didference in terms of which one is electron donor and acceptor
Nad+ IS HIGH ELECTRICTRON ENERGY ACCEPTOR NADPH IS ELECTRON DONOR
132
WHAT DOES NADPH do
Biosynthesis of cholesterol and fatty acids Used in immune ssystem Prevention oxidative damage from glutathione
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