blood glucose
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168 Terms
What is blood glucose homeostasis?
The regulation of glucose levels in the bloodstream to keep them relatively stable.
What is the fed state?
The state after eating when nutrients are being digested and absorbed.
What is the fasted state?
The state when food has not been consumed and the body relies more on stored energy.
What happens to blood glucose after eating?
Glucose enters the bloodstream and stimulates insulin secretion.
What happens to insulin during fasting?
Insulin secretion decreases.
What happens to glucagon during fasting?
Glucagon becomes more important for maintaining blood glucose.
What are the three major dietary energy sources?
Carbohydrates, fats, and proteins.
What is energy balance?
The relationship between energy intake, energy output, and energy storage.
What is mechanical work?
Energy used for muscle contraction and movement of cells and organelles.
What are synthetic reactions?
Processes that produce essential functional molecules.
What is membrane transport?
Movement of substances such as ions and amino acids across membranes.
What is signal generation and conduction?
Processes involving electrical, chemical, and mechanical signals.
What is heat production?
Energy released as heat that contributes to temperature regulation.
What is detoxification and degradation?
Processes including urea formation, conjugation, oxidation, and reduction.
Where are carbohydrates mainly digested and absorbed?
In the small intestine, especially the duodenum and jejunum.
What are the three parts of the small intestine?
Duodenum, jejunum, and ileum.
Where are most bile acids absorbed?
The ileum.
Where is vitamin B12 absorbed?
The ileum.
Where is iron mainly absorbed?
The duodenum.
Where is folate mainly absorbed?
The proximal small intestine.
What is the function of intestinal villi?
They increase the surface area for nutrient absorption.
What is the mucosa?
The innermost layer of the intestinal wall containing the epithelial lining.
What is the submucosa?
The layer of connective tissue containing blood vessels and other structures.
What is the muscularis externa?
The circular and longitudinal muscle layers of the intestinal wall.
What is the lamina propria?
Connective tissue underneath the intestinal epithelium.
What are goblet cells?
Cells that produce mucus.
What are enteric endocrine cells?
Cells that secrete hormones involved in digestive regulation.
What are intestinal stem cells?
Cells that produce new intestinal epithelial cells.
What are surface absorptive cells?
Epithelial cells specialized for absorbing nutrients.
What is SGLT1?
A sodium-dependent transporter that brings glucose or galactose into intestinal epithelial cells.
What does SGLT1 transport?
Sodium along with glucose or galactose.
What is GLUT5?
A transporter that allows fructose to enter intestinal epithelial cells.
What is GLUT2 in the intestine?
A transporter that moves glucose, galactose, and fructose from intestinal cells toward the bloodstream.
Which transporter absorbs glucose with sodium?
SGLT1.
Which transporter absorbs fructose?
GLUT5.
Which transporter allows sugars to exit intestinal epithelial cells?
GLUT2.
What maintains the sodium gradient used by SGLT1?
The sodium-potassium ATPase.
What does the sodium-potassium ATPase do?
Uses ATP to pump sodium out of cells and potassium into cells.
What is facilitated diffusion?
Movement of molecules down their concentration gradient through a membrane protein.
What are the islets of Langerhans?
Clusters of endocrine cells found in the pancreas.
Who discovered the pancreatic islets?
Paul Langerhans.
When were pancreatic islets discovered?
1869.
What do pancreatic alpha cells produce?
Glucagon.
What do pancreatic beta cells produce?
Insulin.
What do pancreatic delta cells produce?
Somatostatin.
What do pancreatic F cells produce?
Pancreatic polypeptide.
What are the two main hormones regulating blood glucose?
Insulin and glucagon.
What is the main function of insulin?
Promotes glucose uptake and storage, lowering blood glucose levels.
What is the main function of glucagon?
Promotes glucose production and release by the liver to maintain blood glucose.
Which pancreatic cells release insulin when glucose increases?
Beta cells.
Which pancreatic cells release glucagon?
Alpha cells.
What is preproinsulin?
The initial protein precursor used to make insulin.
What is proinsulin?
The insulin precursor containing the A chain, B chain, and C-peptide.
What is mature insulin composed of?
An A chain and B chain connected by disulfide bonds.
What is C-peptide?
The connecting peptide removed during the processing of proinsulin into insulin.
How many amino acids are in C-peptide?
31 amino acids.
What is released along with insulin?
C-peptide.
Where is insulin synthesized?
Pancreatic beta cells.
Where is insulin processed and packaged?
The endoplasmic reticulum, Golgi apparatus, and secretory granules.
What is the function of insulin secretory granules?
Store insulin and release it through exocytosis.
What happens to insulin levels after meals?
They increase.
What happens to insulin levels overnight?
They decrease.
What happens to C-peptide levels after meals?
They increase along with insulin.
What does postprandial mean?
After eating a meal.
What stimulates insulin release from pancreatic beta cells?
Increased circulating glucose.
Which transporter is shown bringing glucose into pancreatic beta cells?
GLUT2.
What is the first step of glucose-stimulated insulin secretion?
Glucose enters the pancreatic beta cell through GLUT2.
What happens after glucose enters the beta cell?
Glucose metabolism increases, producing more ATP.
What enzyme converts glucose into glucose-6-phosphate?
Glucokinase.
What does glycolysis do?
Breaks down glucose and contributes to energy production.
What is the role of mitochondria in insulin secretion?
They produce ATP during glucose metabolism.
What happens to the ATP-to-ADP ratio when glucose metabolism increases?
It increases.
What happens to ATP-sensitive potassium channels when ATP increases?
They close.
What is the ATP-sensitive potassium channel called?
KATP channel.
Which proteins are shown in the KATP channel?
Kir6.2 and SUR1.
What happens when KATP channels close?
The beta-cell membrane depolarizes.
What is membrane depolarization?
The membrane potential becomes more positive.
What happens after beta-cell depolarization?
Voltage-gated calcium channels open.
What enters the beta cell when calcium channels open?
Calcium ions.
What directly triggers insulin exocytosis?
Increased intracellular calcium.
What is exocytosis?
Secretory vesicles fuse with the cell membrane and release their contents.
What is the final step of glucose-stimulated insulin secretion?
Insulin-containing secretory granules release insulin into the blood.
What are the seven steps of glucose-stimulated insulin secretion?
Glucose enters through GLUT2, glucose metabolism increases, ATP rises, KATP channels close, the membrane depolarizes, calcium channels open, and calcium triggers insulin release.
What other sugars can stimulate insulin secretion?
Galactose and mannose.
What amino acids can stimulate insulin secretion?
Arginine and leucine.
What hormones can modulate insulin secretion?
Glucagon, somatostatin, and cholecystokinin.
What does CCK stand for?
Cholecystokinin.
What does ER stand for?
Endoplasmic reticulum.
What does PLC stand for?
Phospholipase C.
What does IP3 stand for?
Inositol 1,4,5-trisphosphate.
What does DAG stand for?
Diacylglycerol.
What does PKC stand for?
Protein kinase C.
What does PKA stand for?
Protein kinase A.
What is the role of calcium in insulin secretion?
Increased intracellular calcium triggers insulin-containing granules to release insulin.
What is the insulin receptor?
A cell-surface receptor that binds insulin and activates intracellular signaling.
What type of receptor is the insulin receptor?
A receptor tyrosine kinase.
What are the two types of insulin receptor subunits?
Alpha and beta.
Which insulin receptor subunit binds insulin?
The alpha subunit.
Which insulin receptor subunit contains the tyrosine kinase domain?
The beta subunit.
Which insulin receptor subunit undergoes autophosphorylation?
The beta subunit.