Topic 3 - part 1 and a bit more

Question 1

Who should absolutely not be on a low CHO diet? Why?

Answer 1

Pregnant women, because glucose is crucial for the fetus

Question 2

Name an exemple of pentose

Answer 2

Ribose, deoxyribose

Question 3

What is a general recommendation concerning sugar consumption?

Answer 3

Reduce simple sugars consumption

Question 4

True or false fructose is a hexose

Answer 4

TRue, but 5 membered ring

Question 5

What disaccharide has a beta glycosidic bound?

Answer 5

Lactose

Question 6

List in order of sweeteness (from high to low) mono (fructo and gluose) and disaccharides (3)

Answer 6

• Fructose
• Sucrose
• Glucose
• Maltose
• Lactose

Question 7

What is the differences in glycosidic bounds in amylose and amylopectin?

Answer 7

Amylose : alpha (1-4) chains

Amylopectin : alpha (1-4) chains with alpha (1-6) branches

Question 8

What is the recommendation for fibre?

Answer 8

25-35 g/day

Question 9

What is the difference in soluble and insoluble fibre?

Answer 9

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..)

Question 10

What are enzymes involved in carbohydrate digestion in mouth, stomach, and small intestine?

Answer 10

Mouth:
- Salivary amylase

Stomahc:
- Salivary amylase denatured, inactive…

Small intestine:

• Pancreatic amylase
• Glucoamylase

Small intestine brush border

• Sucrase- isomaltase
• Lactase

Question 11

How does glucose enter and exit enterocytes?

Answer 11

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)

Question 12

True or false, GLUT is responsive to insulin?

Answer 12

false

Question 13

true or false, galactose enters by using GLUT 5 and exits through GLUT 5 or GLUT 2

Answer 13

false, galactose uses SGLT1 (enter) and GLUT 2 to exit as glucose

It is fructose that uses GLUT 5

Question 14

What does insulin do (to glucose) ?

Answer 14

• Increases glucose uptake by cell by GLUT 4
• Increases storage
• Increases conversion to fat
• Increases glucose oxidation

Inhibits glucose production

Question 15

How do we call period after ingesting high GI CHO, when glucose goes under normal concentration? How does it happen?

Answer 15

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

Question 16

What are 2 enzymes involved in glycogen synthesis from glucose?

Answer 16

UDP- glucose pyrophosphorylase (converts glucose-Pi to UDP-glucose)

GLycogen synthase

Question 17

What is the key enzyme involved in gycogen breakdown to form glucose? Where can we find this enzyme?

Answer 17

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

Question 18

What are the 3 glucose precursor?

Answer 18

Amino acid, pyruvate, glycerol

Question 19

What are the 3 end-products (ketones) from ketogenesis?

Answer 19

Acetate
Acetoacetate
B-hydroxybutyrate

Question 20

When are ketones made?

Answer 20

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

Question 21

Where does gluconeogenesis take place?

Answer 21

In the liver

Question 22

What are the 3 main actions of glucagon?

Answer 22

• 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

Question 23

What does indirect calorimetry measure?

Answer 23

Measures CO2 and O2 concentration and flow of air

Measures RQ (respiratory quotient) : CO2 produced / O2 produced

Question 24

What are the 4 components of total energy expenditure, and how much % do they represent (approx)?

Answer 24

Basal metabolic rate ( 67%)
Activity (23%)
Diet induced thermogenesis - Energy to digest nutrients from diet (10%)
Adaptive thermogenesis (…%)

Question 25

Where do you find GLUT 1? When is it efficient?

Answer 25

RBCs, blood brain barrier (bbb), fetus

- it increases at low glucose concentration

Question 26

Where do you find GLUT 2? when is it effiencient?

Answer 26

Small intestine, Liver, Beta-cell, kidney

• High capacity transporter
• High efflux and efflux of glucose

Question 27

Where do you find GLUT 3? When is it efficient?

Answer 27

Placenta, Brain, (neurons)

- High affinity, even if low concentration

Question 28

Where do you find GLUT 4? When is it efficient?

Answer 28

Heart, muscle, adipose tissue

- insulin mediated

Question 29

What is GLUT 5 used for? Where?

Answer 29

Found in small intestine

- Fructose transporter

Question 30

Insulin is a _________ hormone

Answer 30

anabolic, protein hormone