Exam II-L7 (Glycolysis/Gluconeogenesis) Flashcards
What cell types does glycolysis primarily occur in? What organ does gluconeogenesis primarily occur in?
Glycolysis occurs in ALL cells
Gluconeogensis primarily occurs in LIVER cells
____: the process by which glucose is broken down to release usable energy (energy is released)
____: the process by which glucose is SYNTHESIZED, requires energy input (energy is consumed)
Glycolysis: the process by which glucose is broken down to release usable energy (energy is released)
Gluconeogenesis: the process by which glucose is SYNTHESIZED, requires energy input (energy is consumed)
True or False: A minimum level of glucose in the blood is required for survival
True
What is the central pathway for breakdown of sugar?
Glycolysis
Where does glycolysis occur within a cell?
Cytosol
One molecule of glucose is split into two molecules of ____
pyruvate
How many NADH molecules are produced during glycolysis?
2 NADH
How many ATP are invested in the early phase of glycolysis?
How many ATP are gained in the energy generation phase?
2 ATP are invested in early phase
4 ATP are generated in later phase
Glycolysis = net gain of 2 ATP
What are the two main purposes of glycolysis?
1) Energy production (NADH and ATP)
2) Cellular growth (biosynthesis)
Intermediates of glycolysis are used as building blocks of biosynthesis, which is important for processes such as ______
cell division and growth
True or False: Deficiencies in one or more glycolysis enzymes reduces energy output from glycolysis
True
When glycolytic activity is reduced, most cells can utilize other fuels (fatty acids, amino acids) to make ATP, but this requires ____
mitochondria
What cell types lack mitochondria and, therefore, are highly sensitive to decreases in glycolysis activity?
RBC’s!
Glycolysis is the only source of energy for what cell type?
RBC’s
When there is RBC’s loss, normal cellular functions are not maintained due to lack of ___
ATP
True or False: Disorders of glycolysis can reduce RBC lifespan from 120 days to a few days to weeks
True
Disorders of glycolysis can result in anemia. What are the clinical features of anemia?
1) Decreased RBC’s
2) SOB
3) Fatigue
Under anaerobic (!!!) conditions, glucose will be converted to ____, which will be converted to ___
pyruvate; lactate
Under aerobic (!!!) conditions, pyruvate is converted to ____ in the _____
acetyl-CoA in the mitochondria
Conversion of ___ to ___ reoxidizes NADH to ____, allowing the next round of glycolysis to occur
pyruvate to lactate; NAD+
What enzyme converts pyruvate to lactate?
Lactate dehydrogenase (LDH)
What molecule is required during lactate dehydrogenase reaction?
NADH
What cell types lack mitochondria?
RBC’s
____ muscle favors anaerobic metabolism, as well as the ____of the eye
skeletal muscle; lens/cornea
What two mechanisms are used by the liver to maintain blood glucose?
1) Glycogen
2) Gluconeogenesis
Glycogen ___ glucose
Gluconeogenesis ____ glucose
Glycogen stores glucose
Gluconeogenesis creates glucose
In gluconeogenesis, an equivalent of _ ATP are needed for each glucose made
6 ATP
True or False: The liver has the ability to manufacture glucose from other molecules (e.g pyruvate)
True
What process helps maintain and stabilize proper blood glucose levels in the absence of nutrients from the diet?
Gluconeogenesis
When blood glucose levels are low (glucose stores are depleted) which organ makes glucose from other intermediates and then secretes it into the body for use?
The liver
True or False: The brain does not requires a minimum level of glucose for proper function
False - The brain DOES requires a minimum level of glucose for proper function
The brain uses ~25% of glucose pool daily. It does not readily use other sources of fuel, such as ___
fatty acids
True or False: RBC’s lack mitochondria and cannot release energy from amino acids/fatty acids
True
What other molecules (besides pyruvate) can the liver use to make glucose via: gluconeogenesis?
1) Adipocytes = Glycerol
2) Skeletal muscle = Amino acids
3) Anaerobic Metabolism = Lactate
How does long-term activity of gluconeogenesis in the liver, due to starvation and malnutrition, affect muscle tissue?
Leads to muscle tissue breakdown
What does a baseline activity level of gluconeogenesis in the liver help prevent?
Lactate accumulation in the blood
Describe the Cori Cycle
In the Cori Cycle, the liver uses gluconeogenesis to convert lactate to ___
glucose
In the Cori Cycle, lactate travels in the blood to the ___
liver
True or False: Mutations in gluconeogenesis enzymes reduce body’s ability to maintain blood glucose levels
True
What are four clinical features of gluconeogenesis disorders?
1) Hypoglycemia
2) Fatigue
3) Lightheadedness
4) Fainiting
Patients with disorders of ____ can have difficulty maintaining minimum glucose levels, especially in between meals or overnight
gluconeogenesis
Defects in gluconeogenesis can lead to _______, a condition in which there is a build-up of acid
Lactic acidosis
True or False: Defects in gluconeogenesis can lead to reduced ability of liver to convert lactate to glucose, leading to lactate accumulation in the blood
True
True or False: Glycolysis and Gluconeogenesis are tightly controlled by a combination of mechanisms within the liver
True
Insulin is released from ___ cells in response to ___ blood glucose, which acts on many cells
Glucagon is release from ___cells in response to ___ blood glucose, which acts primarily in the ____
beta cells; high
alpha cells; low; liver
In a well fed state, the pancreas secretes ____, which promotes ____
insulin; glycolysis
In fasting/starvation conditions, pancreas secretes ___, which promotes ____
glucagon, gluconeogenesis
How many reversible and irreversible reactions does glycolysis contains?
7 reversible reactions
3 irreversible reactions
Gluconeogenesis must “bypass” irreversible reactions of glycolysis using different ___
enzymes
True or False: Both glycolysis and gluconeogenesis in a liver cell will be active at the same time
False - only glycolysis and gluconeogenesis in a liver cell will be active at the same time, to prevent futility
What enzyme mediates the first irreversible reaction of glycolysis
Hexokinase
- When blood glucose levels rise and glucose enters the cell, it is phosphorylated by hexokinase
-Higher glucose outside the cell causes an inward flow of glucose
In the first irreversible reaction of glycolysis, glucose is phosphorylated. What is the effect?
Glucose is trapped inside of the cell
What is the last step of gluconeogenesis?
G6P is converted to glucose via: G6P
- Blood glucose is low
- Higher glucose inside cell causes outward flow of glucose
True or False: G6Phosphatase is a gluconeogenesis bypass enzyme that is highly expressed in the liver
True
Low cellular levels (low ATP, high ADP and high AMP) activate ____ and inhibit _____
Activate glycolysis
Inhibit gluconeogenesis
What two glycolytic enzymes are activated under low cellular level energy conditions? (low ATP, high ADP, and high AMP)
PFK1 and Pyruvate kinase
High ATP inhibits ___ and activates ___
glycolysis; gluconeogenesis
Which glycolytic enzymes are inhibited when there is high cellular energy levels (high ATP)?
PFK1 and Pyruvate Kinase
True or False: Bypass enzymes are no longer inhibited under high cellular energy conditions, since gluconeogenesis requires sufficient ATP
True
Under high glucose conditions, the pancreas will secrete insulin, promoting ___ in the liver and activation of _____ (enzyme)
Covalent regulation !!!
Under high glucose conditions, the pancreas will secrete insulin, promoting glycolysis in the liver and activation of Protein Phosphatase-1 (enzyme)
Under low glucose conditions, the pancreas will secrete glucagon, promoting ___ in the liver and activation of _____ (enzyme)
Under low glucose conditions, the pancreas will secrete glucagon, promoting gluconeogenesis in the liver and activation of Protein Kinase A (enzyme)
What enzyme mediates the final step of glycolysis?
Pyruvate kinase
Insulin activates Protein Phosphatase 1, which removes phosphate from pyruvate kinase, activating it and promoting ___
glycolysis
Glucagon activates PKA, which adds a phosphate to pyruvate kinase, thereby inhibiting ____
glycolysis
How does F2,6BP exert its effects?
Allosteric Regulation
P2,6BP is a potent activator of ____ and inhibitor of ____
P2,6BP is a potent activator of glycolysis and inhibitor of gluconeogenesis
How does insulin activation of PP1 affect F2, 6BP?
Insulin activation of PP1 leads to an increase in F2,6BP
Does glucagon activation of PKA lead to an increase or decrease in F2,6BP levels?
Glucagon activation of PKA lead to a DECREASE in F2,6BP levels
Insulin increases G2,6BP, thereby activating which irreversible glycolysis enzyme?
PFK1
note: bypass enzyme is inactivated
High F2,6BP activates ___ and inhibits ____
Low F2,6B6 reduces activation of which enzyme? And removes inhibition of which enzymes?
High F2,6BP activates glycolysis and inhibits gluconeogenesis
Low F2,6BP reduces activation of PFK1 and removes inhibition of bypass enzymes
A person who has been in a well-fed state for a long time will have elevated ___ enzymes and decrease in ___ enzymes
increase glycolysis enzymes
decreases gluconeogenesis enzymes
How will epinephrine increase blood glucose?
Promoting gluconeogeneis in liver by activating PKA
Low blood glucose stimuli activates glucagon, which activates PKA and increases gluconeogenesis and blood glucose.
What stimuli activates this pathway, but with epinephrine?
Stress and fear
Insulin will increase glycolysis in liver and skeletal muscles.
However, glucagon will only increase gluconeogenesis in the liver and will have no effect in ____
skeletal muscles
How does epinephrine affect skeletal muscle and liver?
Epinephrine will INCREASE glycolysis in the skeletal muscle
Epinephrine will INCREASE gluconeogenesis in the liver
