Carbohydrates

Question 1

How are disaccharides joined?

Answer 1

Aceytly (glycosidic) bond

Question 2

Monosaccharides: What does an aldehyde and ketone make?

Answer 2

Aldehyde = aldose = hemiacetal
Ketone = ketose = hemiketal

Question 3

Monosaccharides: how do you know if the sugar is D or L?

Answer 3

D = highest chiral C - OH is on right
L = OH is on left

Question 4

Polysaccharides: What are the polysacharides in plants and animals and give a characteristic?

Answer 4

Plants = starch (amylose - no branching, amylopectin - branching at a–6)
Animal tissue = glycogen (branching)
More branching = better for energy.

Question 5

What is dietary fiber?

Answer 5

Structural part of plants.

Question 6

Soluble vs insoluble fiber

Answer 6

Insoluble - remain intact through intestinal tract and doesn’t dissolve in water which decreases constipation
Soluble - forms a gel that does dissolve in water which increases satiety and decreases cardiovascular disease risk by lowering blood cholesterol and type 2 diabetes.

Question 7

Carb digestion: the mouth

Answer 7

a amylase breaks down a-1,4 glycosidic bonds (cellulose and lactose are resistant)

Question 8

Carb digestion: stomach

Answer 8

a amylase is deactivated by low pH

Question 9

Carb digestion: SI

Answer 9

a amylase (pancreas) are active at a neutral pH

Question 10

Carb digestion: SI - BBE, list the 4 and what they do.

Answer 10

1. a dextrinase: isomaltose –> 2 glucose
2. maltase: maltose –> 2 glucose
3. Invertase: sucrose –> glucose + fructose
4. Lactase: lactose –> glucose + galactose

Question 11

What is lactose intolerance?

Answer 11

lactose –> bacteria fermentation

Question 12

How are monosaccharides absorbed?

Answer 12

Through enterocytes.

Question 13

How is glucose absorbed?

Answer 13

Small amounts leak back out into the lumen from the enterocyte, small amounts diffuse into blood through basal membrane, but majority is trasnported into blood bly GLUT2. This is dependent on NA-K ATPase activity (glucose and galactose). To get sodium required for NaK ATPase, SGLT1 cotransports glucose and 2Na+. Fructose is brought into apical by facilitated transport and therefore, glucose, galactose and fructose all enter the blood via basolateral GLUT2.

Question 14

What is the primary source of energy in the body and prevents ketosis?

Answer 14

Glucose

Question 15

What are the three fates of glucose?

Answer 15

Glycogenesis for energy storage (forming glycogen)
Glycolysis for energy production
Hexose monophosphate shunt to generate precursors for biogenesis.

Question 16

Glycogenesis - what does insulin do?

Answer 16

Insulin activates glycogen synthase, hexokinase in the muscle and glucokinase in the liver.

Question 17

Glycolysis - what is the committed step and what are the 3 cycles glucose can go?

Answer 17

Phosphofructokinase is the first irreversible committed step which and then the glucose can either go to krebs (aerobic), lactic acid (anaerobic - 2 ATP produced), or Cori cycle (anaerobic - 2 molecule of lactate formed = 6 ATP consumed).

Question 18

Glycolysis - pyruvate dehydrogenase
what is it? how many nadh produced?

Answer 18

gatekeeper to the krebs cycle
2NADH produced because must cycle twice for 1 molecule of glucose = 6ATP

Question 19

Glycolysis - krebs cycle
how many Atp produced here?

Answer 19

3NADH + 1FADH2 + 1 GTP = 9 + 2 + 1 = 12 ATP x 2 cycles per one molecule = 24ATP

Question 20

What are the conversion rates for nadh, fadh2 and gtp?

Answer 20

1NADH = 3 ATP
1FADH2 = 2 ATP
1 GTP = 1 ATP

Question 21

therefore how many aTP formed from one glucose?

Answer 21

glycolysis = 8 ATP
pyruvate dehydrogenase = 6 ATP
Krebs cycle = 24ATP
Total = 38 ATP

Question 22

What does the hexose monophosphate shunt produce?

Answer 22

NADPH

Question 23

What is gluconeogenesis?

Answer 23

for when glucose is needed by the body (starvation), happens in the liver because muscle and adipose tissue lack the enzyme needed = glucose 6 monophosphatase, fructose 1-6 bisphosphatase, pyruvate carboxylase, phosphoenol pyruvate carboxykinase.