Glycolysis Flashcards
Glucose uptake occurs from?
Glucose recovery occurs from?
uptake–>GI tract/gut
recovery–> kidneys
glucose is transported ____ the concentration gradient by ____ in epithelial cells of the gut and kidneys.
against the concentration gradient
by SGLTs (sodium-glucose symport)
what do SGLTs utilize as the energy source for glucose transport?
the sodium gradient, this is active transport.
A sodium free diet might cause?
disruption to SGLTs, so glucose would remain in the gut, causing the osmotic gradient to increase and cause diarrhea.
There are __ types of Glucose transporters (GLUTs).
Which GLUT is regulated by insulin? Found in what tissues?
13 total GLUTs.
GLUT-4 is insulin dependent, found in skeletal MM, Cardiac MM, and Adipocytes
(All other GLUTs are NOT regulated by insulin, and are found in RBCs, Brain, kidney, liver, intestines….)
glucose transporters move glucose ____ (up/down?) its concentration gradient. Is this active or passive?
Down its concentration gradient, Passive.
move glucose into and out of all cells in the body
Insulin is a peptide hormone that is synthesize by ______?
What is also produced with insulin that can determine if someone has type 1 diabetes?
pancreatic B cells.
C peptide is also produced with insulin.
What is the optimal blood glucose level?
75-110 mg/dl
insulin causes a ___ in blood glucose levels, via uptake in gut, recovery in kidneys, and release in the liver.
decrease
Muscles can uptake glucose without insulin by?
By muscle contraction, which signals GLUT4 to increase glucose uptake.
Both insulin and muscle contractions can increase GLUT4 activity=increase glucose uptake in skeletal muscle.
Insulin also regulates glucose clearance, which is?
Which insulin dependent tissue would the most glucose go to?
how glucose gets OUT of the cell (in adipose, cardiac MM and skeletal MM)
-Whatever tissue has the most mass, Skeletal MM
Two types of insulin “highs”?
acutely & chronically
True or False:
Insulin goes into the cell.
False, insulin binds to receptors on the cell membrane, then degrades.
When is insulin acutely high? (3 times….)
- after a meal
- when anticipating a meal
- when you wake up (dawn phenomenon)
When would insulin levels be highest? (Breakfast, lunch, or dinner)
breakfast=highest insulin levels
The Dawn Phenomenon is associated a surge of which hormones?
Growth hormone and cortisol
Chronically high insulin is also called?
insulin resistance (pre-diabetes) or diabetes.
With chronically high insulin, if insulin is always high = diabetes.
The sympathetic nervous system and stress causes what to happen to insulin & glucagon ?
Sympathetic NS-
increases glucagon, decreases insulin.
(if you increase glucagon, you will have more glucose in your blood stream to be used as an energy source needed for fight-or-flight responses via sympathetic NS)
Parasympathetic nervous system and thinking about food/relaxation causes what to happen to insulin & glucagon ?
Para- Increases insulin, decreases glucagon.
Where would insulin and glucose go to first, second, and third?
(Liver ? Adipose? Skeletal MM? )
1st skeletal MM
2nd liver
3rd adipose
When insulin binds to muscles, what two events occur?
- glucose uptake
- anabolism
when insulin binds to liver, what 3 events occur?
- inhibition of ketogenesis
- activation of lipogenesis
- activation of glycogenesis
when insulin binds to adipose, what three events occur?
- glucose uptake
- activation of lipogenesis
- activation of adipogenesis
So overall, insulin reduces blood levels of what three things?
glucose
fats
ketones
^all reduced in blood by insulin because they are taken up into cells.
What is the only hormone that promotes fat storage and inhibits fat use?
insulin
cant gain fat without insulin
(need functional pancreas)
What counteracts insulin?
-Glucagon (mainly)
Also
- Epinephrine/Norepinephrine
- Catecholamines
- Cortisol
- Growth Hormone
^ these all do catabolism
What is the primary regulator of insulin and glucagon release?
plasma glucose concentration
Insulin effects muscles, liver, and adipose, while glucagon only effects?
liver and adipose
NOT muscles, because they lack receptors
In the liver, glucagon has what effects?
tells liver to make glucose
out of anything available!
activates keteogensis,
activates glycogenolysis
catabolism^
If you have a high blood glucose level, insulin will be ? Glucagon will be?
insulin- high
glucagon-low
with high blood glucose levels
In adipose cells, glucagon will cause ?
lipolysis,
fat to break down (catabolism).
Glucagon causes increase of blood levels of?
- glucose
- fat
- ketones
What are the end products of glycolysis?
2 ATP
2 NADH
2 Pyruvate
Once glucose is in the cell, what is the fate?
glycolysis
What are the three irreversible steps of glycolysis?
What are the starting and ending products of those three steps and the enzymes that catalyze them?
Step 1.
D-glucose –> glucose 6 P
via hexokinase (in Muscles) or glucokinase (in liver)
^^^ this step requires ATP, and commits glucose to metabolism within the cell, because g-6-p can’t escape cell
Step 3.
fructose 6 phosphate –> fructose 1-6 bisphosphate
via PFK-1
^^^ requires ATP
Step 9.
phosphoenolpyruvate –> pyruvate
via pyruvate kinase
^^ creates 2 ATP, second example of substrate level phosphorylation
Skeletal muscles use glycolysis primarily for production of?
ATP, but they can store a limited amount as glycogen
What are the two steps of glycolysis that include substrate level phosphorylation ?
What are the starting and ending products of those steps and the enzymes that catalyze them?
Step 6.
1,3 bisphosphoglyercate–>
3-phosphoglycerate
via phosphoglycercate kinase
Step 9.
phosphoenolpyruvate –> pyruvate
via pyruvate kinase
Both create two ATPs per 1 glucose
Which step of glycolysis produces 2 NADHs with the addition of two organic phosphates ?
What are the starting and ending products of that step and the enzymes that catalyze it?
Step 5.
glyceraldehyde 3 phosphate
1,3 bisphoglycerate
via glyceraldehyde-3-phosphate dehydrogenase
Where does glycolysis occur ?
Where does the pyruvate dehydrogenase reaction occur?
in cytosol
in mitochondria (inner matrix)
What are the starting and end products of pyruvate dehydrogenase reaction?
2 pryuvate –>
2 acetyl-coA
2 NADH
2 ATP
What inhibits the pyruvate dehydrogenase reaction?
-Acetyl-coA
-ATP
-NADH
^ which are the products
& the phosphorylation of pyruvate dehydrogenase kinase
all inhibit the pyruvate dehydrogenase reaction
Dephosphorylation of pyruvate dehydrogenase phosphatase ___ the pyruvate dehydrogenase reaction.
Activates it.
T or F:
The liver is capable of glucose catabolism and anabolism depending on hormonal and non-hormonal signals.
true
Liver uses glycolysis primarily to convert glucose into ___ and ___, but can use glucose for its own energy is glucose levels are high.
glycogen and fat
Non hormonal regulators of glycolysis in the liver?
ATP and AMP.
Also glucokinase because it has a high Km.
In the liver,
if ATP is low, and/or AMP is high,
is glycolysis activated or deactivated?
activated
What are the 2 hormonal regulators of glycolysis in the liver?
- fructose 2,6 bisphosphate, stimulates PFK-1, even if ATP levels are high
- pyruvate kinase phosphorylation/ dephosphorylation
(pyruvate kinase phosphorylation inhibits PK activity )
Insulin represses or induces synthesis of GK, PFK-1, and PK in the liver?
Glucagon represses or induces synthesis of GK, PFK-1, and PK in the liver??
Insulin induces,
Glucagon represses
insulin does what to PK?
dephosphorylates it!
PK must be dephosphorylated to be active
Insulin inhibits fructose 2,6 biphosphatase, causing an ____ of fructose 2,6 bisPhosphatate.
increase, which in turn increases fructose 2,6 bisPhosphate (which activates PFK-1)
(insulin activates products of glycolysis)
Glycolysis non hormonal regulators (3)
Glucokinase
phosphofructokinase-1
pyruvate kinase
(GK, PFK-1, PK)
PFK-1 is activated by? (2 things)
deactivated by?
activated - AMP (cAMP) & fructose 2,6 bisphosphate
deactivated by ATP
Pyruvate kinase activated by? (2)
deactivated by (3)?
activated by fructose 1,6 bisphosphate (the prod of step 3) and
dephosphorylation
deactivated by phosphorylation, ATP, Alaine
What is significant about Fructose 2,6 bisphosphate ?
regulates glycolysis by
stimulating PFK-1, even if ATP levels are high
What is the significance of fructose 1,6 bisphosphate (the product of step 3) in regards to pryuvate kinase?
it activates it pyruvate.
