Control of Metabolism Flashcards
control of metabolism is directed primarly toward?
- mainting blood glucose sufficiently high for nervous tissue to function 2. insuring the other cells of the body have adequate substrate
what forms are energy stored in?
- glycogen 2. Protein 3. fat (triglycerides)
what are the forms of energy in blood?
- glucose 2. fatty acids 3. ketones
what is glucose derived from via gluconeogen
- amino acids 2. lactate 3. pyruvate 4. glycerol 5. keto acids
what is the difference between a ketone and keto acid?
ketones are derived from fatty acids and have 2 R groups (organic molecules) keto-acids are intermediates of the TCA (tricarboxylic acid cycle ak.a. krebs cycle), are metabolites of amino acids, and have a carboxyl group
examples of keto acids
pyruvic acid alpha ketogultaric acid oxaloacetic acid
examples of ketons
acetoacetate betahydroxybutyrate acetone acetoacetate and betahydroxybutyrate are functional ketons derived from acetone
which 2 metobolic intermediates play are large role in glycolosis and gluconeogenesis?
- glucose 6-phosphate 2. phosphenolpyruvate
what are 4 important body tissues that control body metabolism?
liver skeletal muscle adipose tissue brain
what protein acts as a primer at the core strucure of glycogen?
glycogenin
what is glycogen a polymer of?
D-glucose
what is synthesized in the ER of the hepatocyte?
apoprotein phosphatidylcholine triglycerol cholesterol esters
what role does the golgi play in the hepatocyte?
process particles synthesized in ER with additional phospholipids and perhaps cholesterol & cholesterol esters added
how are the particles released?
secretory vesicles moves the particles out of the hepatocyte as VLDL
what is the typical structure of a lipoprotein (VLDL)?
core of cholesterol and cholesterol esters surrounded by a phospolipid (monolayer) membrane in which apolipoproteins are embedded
what is the least dense lipoproteins?
chylomicrons
which organs capable of gluconeogenesis?
liver kidney
True or False. Skeletal muscle is capable of releasing glucose into the blood?
False. only the liver. skeletal muscle releases lactate & pyruvate
what is unique about the liver cells in regards to TG (triglycerides)?
can transport them into the blood
True or False. The liver is the ONLY organ that can synthesize and export ketones.
True
What metabolic capacity(s) does the liver share with skeletal muscle?
uptake of glucose and amino acides glycogenolysis and storage of glycogen
Which organ is capable of releasing glucose into the blood during the absorptive phase? .. during the postabsorptive phase?
absorptive - GI tract postabsoptive - liver
What metabolic capacity(s) does the liver share with adipose tissue?
can take up glucose can synthesize fatty acids and alpha-glycerol phospate from glucose to produce triglycerides
Which organ(s) can export triglyceride into the blood
GI track (as chylomicrons) Liver (as VLDL - Very low density lipoproteins)
Which organ(s) can catabolize triglyceride into glycerol and fatty acids?
adipose tissue
what is gluconeogenesis?
formation of new glucose from non-carbohydrate carbon substrates
which organs perform gluconeogenesis?
liver kidneys (in prolonged fast)
what are the substrates of gluconeogenesis?
pyruvate lactate glycerol glucogenic amino acids.
what are keto acids
carbohydrate like intermediate contains a keton and carboxylic acid group liver cells catablize for energy and formation of fatty acids
Which organ(s) can synthesize ketones?
liver
Which substrates of the blood may be used for energy by the cells of the body?
glucose (from substrates for gluconeogenesis) fatty acids ketones
__________________ is the energy depot of the body
fat (adipose tissue)
From where do fat cells get their triglyceride?
GI tract liver
Of the energy substrates in the blood which can the brain use for energy?
glucose
True or False. During the absorptive phase most cells of the body use glucose for energy.
true
True or False. During the postabsorptive phase most cells of the body use fat for energy
false - fatty acids, ketones, and glucose
Which hormone controls metabolic events during the absorptive phase?
insulin (decreased in post-absorptive)
What conditions cause insulin secretion from pancreatic beta cells?
- increase in plasma (blood) glucose 2. elevated amino acids 3. GIP (glucose-dependent insulinotropic peptide) from the pancrease 4. stimulation parasympathetic neurons (sight, smell, taste of food)
Explain the body’s response to an acute onset of hypoglycemia. In particular, why is the hypoglycemia potentially able to induce elevated heart rate, sweating, and other effects?
reflex response by the sympathetic nervous system. hypoglycemia causes increase in secretion of epinephrine secretion and sympathetic nervous system activity in order to stimulate glucagon secrection
what type of stimulation would inhibity the pancreatic beta cells from producing insulin?
sympathetic neurons and increased levels of epinephrine
which controls in production of insulin are “feedforward” mechanisms?
GIP parasympathetic neurons
5 mM of plasma glucose = ____ mg/ml
90 mg/100 mL
when is rate of insuline secretion at maximal level?
blood glucose about 25 mM (450 mg/ 100 ml)
what happens in muscle fibers and adipose tissue when insulin binds to the insulin receptor?
translocation of glucose transporters 1. upon binding signaling transduction pathway translocates GLUT 4 (glucose transporters) from endosome in cytoplasm to plasma membrane 2. glucose is transported via facilitated diffusion into the cell out of the plasma(extracellular fluid) 3. plasma glucose levels are reduced?
what is needed for the skeletal muscle fibers to take up glucose?
insulin (nearly absolutely dependent)
What is important about glucose transporters in liver cells in regards to substrate storage?
the transporters are insulin INdependent. (according to slide 47 of White’s lecture)
what type of feedback is associated with plasma glucose control over insulin secretion?
negative feedback
An increase in plasma insulin effects the liver, muscles, and adipose tissue in what way?
muscle and adipose tissue – increased glucose uptake liver - stops glucose output
summarize substrate storage
Summarize substrate release
what are the hypOglycemia counter-regulatory hormones ?
glucagon (first line of defense) catecholamines cortisol growth hormone
where is glucagon released from?
pancreatic A cells due to decreased glucose & increase in amino acids
When the plasma glucose levels fall below 70 mg/dL how does the central nervous system react in regards to epinephrine?
refex of glucose receptors in the CNS causes: 1. increase epinephrine secretion and increase stimulation to sympathetic nerves of adipose tissue and liver 2. increase epi causes increase glycogenolysis in skeletal and liver, increase lipolysis in adipose tissue, and increase gluconeogenesis in liver 3. epinephrine also stops beta cell insulin production 4. finally - increased plasma levels of glucose, fatty acids, and glycerol and decreased plasm insulin levels
When the plasma glucose levels fall below 70 mg/dL how does the central nervous system react in regards to growth hormone?
- hypothalmus releases GHRH 2. causes anterior pituitary to release growth hormone
what is the growth hormone responsible for ?
1.increases sensitivity of adipocytes to lipolytic stimuli 2.increases gluconeogenesis in liver hepatocyte 3. reduces effect of insulin to stimulate glucose uptake in muscle and adipose tissue.
When the plasma glucose levels fall below 60 mg/dL how does the central nervous system react in regards to cortisol
- hypothalmus releases CRH (cortisol releasing hormone) 2. causing anterior pituitary to release (ACTH) 3. causing adrenal gland to release cortisol
What are the effects of cortisol?
- increase GNG (in liver, like glucagon effect on liver)— increase glucose 2 increase TG breakdown (in adipose tissue)————–increase ffa (free fatty acid) 3 decrease glucose uptake by peripheral tissues (*)——increase glucose 4 increase protein catabolism (in muscle) ————-increase amino acids * decreased sensitivity to insulin
what is the difference between Type 1 DM and Type 2 DM?
Type 1 - low blood insulin levels Type 2 - low number of insulin receptors
Summary of Type 1 DM
