BIOCHEM - ATP & Blood Glucose Control Flashcards
Define ‘glucose homeostasis’.
The process by which blood glucose levels are maintained by the body within a narrow range.
Normal range: 4-6 mmol/L
Define ‘glycaemic response’.
Post prandial blood glucose concentration curve.
What are the normal, pre diabetic and diabetic BG ranges:
- fasted
- post prandial
Fasting:
normal - < 100 mg/100ml
prediabetic - 100 - 125 mg/100ml
diabetic - > 126 mg/100ml
Post prandial:
normal - < 140 mg/100ml
prediabetic - 140 - 199 mg/100ml
diabetic - > 200 mg/100ml
Describe how HbA1c levels can show long term blood sugar control.
What is a good HbA1c score?
What is a poor HbA1c score?
Chronically high blood glucose levels = formation of HbA1c.
HbA1c molecules are glycosylated Hb molecules. These molecules form non-enzymatically.
Lifespan of RBS is approx 120 days, therefore HbA1c concentration in blood shows overall blood glucose control over past few weeks.
Good HbA1c - 4-8
Poor HbA1c - 8-14
Describe what are Advanced Glycation End products (AGEs) and how are they formed?
- Chemically diverse group of compounds.
- Formed non-enzymatically.
- Carbonyl groups of sugars join to amine groups of proteins/lipids in blood
- Go through series of rearrangements (early glycation end products e.g., Schiff bases, Amadori products)
- Eventually yield stable, irreversible end products.
Why are AGE’s harmful?
Evidenced to contribute to the pathophysiology of several non-communicative diseases e.g.,
- diabetes
- cancer
- cardiovascular
- neurodegenerative diseases
AGEs form on a variety of different molecules (lipids, collagen, laminin, elastin) and alter the function and constitution of these molecules e.g., increase stiffness.
AGE’s bind to receptors (RAGE’s) on epithelial cell membranes - triggers cascade of signalling that leads to inflammatory response.
What are some of the consequences of high blood sugar?
(large blood vessels & small blood vessels)
Large vessels:
- increased risk of stroke
- hypertension
- increased risk of heart attack
- reduced blood flow & high BG results in slow healing wounds prone to infection
Small vessels:
- neuropathy
- retinopathy
- renal issues e.g., recurrent UTI’s and kidney failure
What are the processes that increase and decrease blood glucose concentrations?
Increase:
- digestions/absorption of food
- glycogenolysis (release of glucose from liver glycogen stores)
- gluconeogenesis (formation of new glucose molecules)
Decrease:
- oxidation (used to generate ATP)
- glycogenesis (stored as glycogen)
- lipogenesis (storage of excess glucose as fat)
How is an increase in blood glucose concentration managed?
1) beta-cells in pancreas sense increased blood glucose
2) pancreatic beta-cells release insulin
3) insulin binds to insulin receptor on cell membrane
4) signal transduction cascade
5) exocytosis of GLUT4 channel protein to cell membrane and opening of channel to allow entry of glucose into cell
How is a decrease in blood glucose concentration managed?
1) pancreatic alpha-cells detect drop in blood glucose concentration
2) release of glucagon from pancreatic alpha-cells
3) glucagon stimulates:
- hepatic glycogenolysis (release of glucose from liver glycogen stores
- gluconeogenesis (synthesis of new glucose molecules)
Define the term ‘glycaemic index’
- how is GI calculated/determined?
Scientific term describing the effect of foods on blood glucose after intake of that food containing 50g carbohydrate (score between 1-100).
GI = AUC (food) / AUC (glucose) X 100
- 50 grams carbohydrate in test food.
- Blood samples taken periodically over 3 hours:
1st hour: every 15 minutes
2nd hour: every 30 minutes
3rd hour: every 30 minutes (in diabetics) - Values plotted; AUC calculated.
- Test food response compared to reference food response.
- Average GI of 8-10 volunteers = GI of test food.
What are some factors that can impact individual glycaemic response to food?
- Speed of stomach emptying
- Speed of CHO digestion
- Speed of glucose absorption
What are the scores given to
- Low GI foods
- Mid GI foods
- High GI foods
Give examples of foods for each category.
Low GI = 0-55
- lentils
- rolled oats
- baked beans
Mid GI foods = 56-69
- wholemeal bread
- raisins
- corn
High GI foods = 70-100
- glucose
- white bread
- sweet potato
Describe the term glycaemic load
How is GL calculated?
Value describing the expected change in blood glucose concentration after intake of a specific portion of food.
Value describing the expected change in blood glucose concentration after intake of a specific portion of food.
Reflects both the quality and quantity of dietary carbohydrates.
GL = (GI x CHO per serving (g)) / 100
The GL of carrots is: (47 × 5) / 100 = 2.4
What are the individual and whole day ranges for GL?
Low GL
- individual 10 or less
- whole day < 80
Mid GL
- individual 11-19
- whole day 80 - 120
High GL
- individual > 20
- whole day > 120
