BIBC 120 Health Effects of Carbs
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What is normal blood glucose level after fasting (8 hours)?
3.9-5.6 mM (70-100 mg/dL)
What is normal blood glucose level after meal (30 min after eating)?
6.7 mM (120 mg/dL)
What is released when there is high blood glucose?
What is released when there is low blood glucose?
Where is GLUT 1 and what is its Km?
most cells and 2mM
Where is GLUT 2 and what is its Km?
enterocytes in β-cells in pancreas and 17mM
How does glucose trigger insulin release?
- 1. glucose moves into β-cells through GLUT 2
- 2. Glucokinase: glucose -> glucose 6-P
- 3. glycolysis, respiration -> ATP
- 4. ATP closes K+ channels
- 5. membrane depolarization opens Ca+ channels: Ca+ into cell
- 6. exocytosis of insulin vesicles
- 7. Insulin is released
How many amino acids make up insulin?
51 amino acids
Where are insulin receptors found?
insulin responsive tissues: liver, muscle, fat
What tissues perform exocytosis of GLUT 4 to the cell surface?
adipose and muscle tissue
What is the Km of GLUT4?
What is the fate of glucose in adipose and liver tissue?
glucose > glucose 6-P > glycolysis > pyruvate > PDH complex > acetyl CoA > fatty acid synthesis
What is the fate of glucose in liver and muscle tissue?
glucose > glucose 6-P > glycogen
What are considered to have limited storage capacities?
Glycogen and protein
What is considered to have unlimited storage capacity?
Where is glucagon released from and in response to what?
Glucagon is released from pancreatic alpha cells in response to low blood glucose
What is the breakdown of glycogen called and where does it happen?
What is the synthesis of glucose called, what is the carbon source, and where does it take place?
gluconeogenesis; pyruvate, amino acids; liver
What does glucagon stimulate in adipocytes?
release of fatty acids
What is diabetes mellitus?
Lack of insulin function leading to chronic high blood glucose levels
What is Type I diabetes?
autoimmune destruction of pancreatic beta cells
What is Type II diabetes?
- Loss of insulin response
- gradual loss of metabolic responses to insulin (insulin resistance)
- prolonged insulin secretion (hyperinsulinemia)
- eventual failure of insulin production by beta cells
- eventual damage to nerves and blood vessels from prolonged high blood glucose concentrations
- inability to utilize dietary carbs, elevated production of ketones
- increased cancer risk
What is glycation?
- unwanted reaction of glucose with proteins
- glycated hemoglobin is an early diagnosis
Risk factors of diabetes
- genetic factors
- diet and exercise (greatest determining factor)
How do you measure glycemic response?
- fast for 12 hours
- consume food/glucose that contains 50mg of digestible carbs
Factors of glycemic response
- type of carb
- fiber/protein/fat slow response
- amount and viscosity of GI tract contents
How do you measure glycemic index?
auc food at 120min/auc for glucose x 100
How do you measure glycemic load?
auc food/auc glucose x grams of carbs in one serving
What are the high cutoffs for GI and GL?
What is a food with high GI/GL?
What is a food with low GI/GL?
What are two caloric sweeteners?
- sucrose (table sugar)
- high fructose corn syrup
What is the GI of sucrose?
GI = 65
How is high fructose corn syrup made?
starch > amylase > glucose > xylose isomerase > glucose to fructose > final product: 45-55% fructose and 45-55% glucose
AMDR of carbs
45-65% of total Calories
What is the tolerable upper limit for carbs?
there is none
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