Cellular Metabolism Flashcards
Glycogenolysis occurs _________ after your last meal
4-12 hours
*along with Gluconeogenesis
Gluconeogenesis occurs ________ after your last meal
1-2 days
Glycolysis occurs in the…
cytosol
(Glucokinase/Hexokinase) is a regulatory enzyme for the Liver
Glucokinase
(Glucokinase/Hexokinase) is a regulatory enzyme for Muscle
Hexokinase
_______________________ ___________________ in the Muscle dictates whether pyruvate turns into Acetyl CoA (in mitochondria) or Lactate (cytosol)
Pyruvate Dehydrogenase
Major regulatory enzymes for Glycolysis in the LIVER (3 total)
Glucokinase
PFK-1
Pyruvate Kinase (mitochondria)
Enzyme that converts glucose to glucose-6-P (either in the Liver or Muscle)
Glucokinase (liver)
Hexokinase (muscle)
Purpose of Glucokinase and Hexokinase
Phosphorylate glucose to keep it in the cell
Hexokinase (is/isn’t) inhibited by Glucose-6-P and has a (low/high) capacity for glucose storage
Is inhibited; low capacity for storage*
*muscle not meant to store
Glucokinase (is/isn’t) inhibited by Glucose-6-P and has a (low/high) capacity for glucose storage
Is not inhibited; high capacity for storage*
*liver is meant for storage
Rate-limiting step for Glycolysis
PFK-1
Product of PFK-1
Fructose-1-6-biphosphate
The rate-limiting step for Glycolysis, PFK-1, is further regulated by…
PFK-2
*can further stimulate glycolysis and storage, even in energy-satisfied states
Which enzyme reverses the effects of PFK-2
Fructose biphosphatase-2 (seen gluconeogenesis)
Phosphoenolpyruvate (PEP) is unstable and donates its phosphate group to…
ATP
The conversion of PEP to pyruvate is (reversible/irreversible)
Irreversible (so takes a conversion to oxaloacetate to malate and a shuttle to get back)
Enzyme that converts PEP to Pyruvate
Pyruvate Kinase (irreversible)
Pyruvate Kinase is stimulated by _____________________________ and inhibited by _______
Stimulated: Fructose-1-6-Biphosphate
Inhibited: ATP
Regulatory enzyme that links Glycolysis and TCA cycle
Pyruvate Dehydrogenase
________ is ESSENTIAL for glycolysis
NAD+
(Fed/Fasting) state is when ingested nutrients enter the GI tract
Fed (or Absorptive) state
(Fed/Fasting) state is when the GI tract is empty and body stores must supply energy
Fasting (or Postabsorptive)
Where can Glucose/energy be stored in the body
Skeletal muscle (glycogen)
Adipose (triglycerides)
Liver (glycogen and triglycerides)
What are the ONLY fuel sources for the brain
Glucose
Ketones*
*only during prolonged starvation
Where are the LARGEST glycogen stores in the body
Muscle
The largest TOTAL energy stores in the body is where?
Adipose
*largest GLYCOGEN is muscle
The Liver removes roughly ________ of glucose from the blood
2/3
The liver makes NADPH for fatty acid syntheses via what process?
Pentose P Shunt
The absence of mitochondria in RBCs means that they can ONLY use ___________ for energy
Glucose (convert to lactate)
During the Fed state, what is produced?
CO2, H2O and energy (Glycolysis)
Glycogen (liver and muscle)
Triglycerides (liver and adipose)
Metabolic processes during the Fasting State
Glycogenolysis (breakdown of glycogen)
Gluconeogenesis (from protein and fat)
During lipolysis, hydrolysis produces what two products? (2 total)
Glycerol
Free Fatty acids
Normal range of blood glucose
70-100 mg/dL
What hormones increase during Hyperglycemia (4 total)
Insulin
Amylin
GLP-1
GIP
What hormones increase during Hypoglycemia (5 total)
Glucagon Epi GH Cortisol Thyroxine
Peptide that is co-released with Insulin; Dec. gastric emptying, glucagon release and appetite
Amylin
Incretins that enhance Insulin release in response to inc. blood glucose levels
GLP-1 & GIP
GLP-1 and GIP function to (enhance/inhibit) Insulin release in response to (increased/decreased) glucose levels
Enhance Insulin release; increased blood sugar
Functions of Insulin
Inc. glucose uptake into Liver, Muscles and Adipocytes (storage as glycogen or fatty acids)
Cessation of Glycogenolysis
Which hormones oppose the action of Insulin (4 total)
Which hormones oppose the action of Insulin (4 total)
Which organ is the main target of glucagon
Liver (breakdown of glycogen and create ketones)
Glucokinase has a (higher/lower) affinity for glucose
Lower affinity (doesn’t hog glucose, allows rest of body to have some; only stores glucose at really high levels)
Why is Glucokinase having a LOW affinity for glucose beneficial
Doesn’t hog glucose, allowing the rest of the body to have some; ONLY stores glucose at really high levels
Glycogen (synthase/phosphorylase) increases glycogen synthesis
Synthase
Glycogen (synthase/phosphorylase) increases glycogen breakdown
Phosphorylase
Glucokinase is found only in the Liver (True or False)
False; also in Beta cells (let pancreas know when glucose levels are really high)
How do Epi and Thyroxine act synergistically during the Fasting State?
Individually, only a little release of FAs from adipose
Together, a LARGE amount released
Describe the roles of Cortisol in metabolism
Inc. gluconeogenesis, lipolysis and proteinolysis
Describe the roles of GH in metabolism
Mobilize glucose (inc. lipolysis and gluconeogenesis while dec. uptake)
Example of Secondary active glucose transporter in Nephrons and Intestines
Sodium-Glucose Linked Transporters (SGLTs)
Glucose transporter present in ALL tissues; HIGH affinity (so rapid uptake)
GLUT-1
Glucose transporter present only in Liver, Beta cells and Intestine; LOW affinity; BIDIRECTIONAL flow
GLUT-2
Glucose transporter; main transporter in the CNS
GLUT-3
Glucose transporter in Muscle and Adipocytes; INSULIN responsive
GLUT-4
Exercise stimulates the insertion of what glucose transporter into skeletal muscle
GLUT-4 (insulin responsive)
What STIMULATES Pancreatic Beta-cells (and thus Insulin release)
Inc. glucose or amino acids
Beta-adrenergic agonists
Inc. Parasympathetic activity
Inc. GIP and GLP-1
What INHIBITS Pancreatic Beta-cells (and thus Insulin release)
Glucagon
Somatostatin
NorEpi
Alpha-adrenergic agonists
