Topic 3 - part 1 and a bit more Flashcards
Who should absolutely not be on a low CHO diet? Why?
Pregnant women, because glucose is crucial for the fetus
Name an exemple of pentose
Ribose, deoxyribose
What is a general recommendation concerning sugar consumption?
Reduce simple sugars consumption
True or false fructose is a hexose
TRue, but 5 membered ring
What disaccharide has a beta glycosidic bound?
Lactose
List in order of sweeteness (from high to low) mono (fructo and gluose) and disaccharides (3)
- Fructose
- Sucrose
- Glucose
- Maltose
- Lactose
What is the differences in glycosidic bounds in amylose and amylopectin?
Amylose : alpha (1-4) chains
Amylopectin : alpha (1-4) chains with alpha (1-6) branches
What is the recommendation for fibre?
25-35 g/day
What is the difference in soluble and insoluble fibre?
SOLUBLE:
- Pectin
- Forms a gel
- Glycemic control
- Delays intestinal emptying
- Binds to cholesterol and bile acids
- Fermented by colonic bacteria
INSOLUBLE :
- Hemicellulose, cellulose
- Bulk (retains water-> laxative effect)
- Delays intestinal emptying
- Some glycemic control
- Binds to cations
- Minor fermentation by bacteria
- Increased motility in GI tract, speeds up transit (even if slows digestion and absorption..)
What are enzymes involved in carbohydrate digestion in mouth, stomach, and small intestine?
Mouth:
- Salivary amylase
Stomahc:
- Salivary amylase denatured, inactive…
Small intestine:
- Pancreatic amylase
- Glucoamylase
Small intestine brush border
- Sucrase- isomaltase
- Lactase
How does glucose enter and exit enterocytes?
Enters through SGLT1 (using secondary active transport, no energy, but by symport with Na+ => Na+/K+ pomp…)
Exits: GLUT 2 (uniport, from high concentration in enterocytes, to lower concentration in blood)
True or false, GLUT is responsive to insulin?
false
true or false, galactose enters by using GLUT 5 and exits through GLUT 5 or GLUT 2
false, galactose uses SGLT1 (enter) and GLUT 2 to exit as glucose
It is fructose that uses GLUT 5
What does insulin do (to glucose) ?
- Increases glucose uptake by cell by GLUT 4
- Increases storage
- Increases conversion to fat
- Increases glucose oxidation
Inhibits glucose production
How do we call period after ingesting high GI CHO, when glucose goes under normal concentration? How does it happen?
Rebound hypoglecymia
- Increased insulin response to high GI food increase glucose uptake and can lead to low glucose concentration in the blood, can cause ENERGY CRASH
What are 2 enzymes involved in glycogen synthesis from glucose?
UDP- glucose pyrophosphorylase (converts glucose-Pi to UDP-glucose)
GLycogen synthase
What is the key enzyme involved in gycogen breakdown to form glucose? Where can we find this enzyme?
Glucose-6-phosphatASE
- In liver and kidney
- So only liver and kidney can export glucose… because G?P cannot cross cell membrane, only glucose can
What are the 3 glucose precursor?
Amino acid, pyruvate, glycerol
What are the 3 end-products (ketones) from ketogenesis?
Acetate
Acetoacetate
B-hydroxybutyrate
When are ketones made?
During (prolonged) fasting
When low or no glucose => so high b-oxidation of Fatty acids will produce high levels of acetyl-CoA=> build up of acetyl-coA, no anapleurosis of TCA cycle=> acetyl-Coa converted to ketones
Where does gluconeogenesis take place?
In the liver
What are the 3 main actions of glucagon?
- Glycogen released and converted to glucose by liver and muscles
- Adipose tissue release FA for FA oxydation
- Breakdown of muscle to provide glucogenic a.a. for gluconeogenesis
What does indirect calorimetry measure?
Measures CO2 and O2 concentration and flow of air
Measures RQ (respiratory quotient) : CO2 produced / O2 produced
What are the 4 components of total energy expenditure, and how much % do they represent (approx)?
Basal metabolic rate ( 67%)
Activity (23%)
Diet induced thermogenesis - Energy to digest nutrients from diet (10%)
Adaptive thermogenesis (…%)
