Exam 3: Cheng & Chaney

Question 0

Structure of amylopectin

Answer 0

Homo-polymer of glucose, alpha 1-4 and alpha 1-6 linkages

Highly branched, highly soluble, less dense, quickly degraded

Question 1

Structure of amylose

Answer 1

Homo-polymer of glucose, alpha 1-4 linkages

Mostly linear, high density, degraded slowly, insoluble

Question 2

Structure of lactose

Answer 2

Galactose + Glucose, beta 1-4 linkage
Milk sugar
Has an exposed reducing end, will spoil

Question 3

Structure of sucrose

Answer 3

Glucose + fructose, alpha 1-2 linkage
Table sugar
Reducing end blocked, so stable at room temperature

Question 4

Structure of maltose

Answer 4

Glucose + glucose, alpha 1-4 linkage

Produced when starch is broken down

Question 5

Structure of trehalose

Answer 5

Glucose + glucose, alpha 1-1 linkage

Question 6

List the 2 monosaccharides

Answer 6

Glucose, fructose

Question 7

List the 5 categories of indigestible carbohydrates (dietary fiber)

Answer 7

Cellulose, hemicellulose, lignins, pectins, and mucilages and gums.

Question 8

Describe role of sucrase-isomaltase complex.

Answer 8

Activity highest in jejunum
Sucrase digests sucrose to fructose and glucose.
Isomaltase digests isomaltose to form glucose.
Maltase activity also is present in the sucrase-isomaltase complex and accounts for 80% of maltase activity. Maltase digests maltose to glucose.

Question 9

Describe the role of Beta-Glycosidase Complex (Lactase-glucosylceramidase)

Answer 9

Activity highest in jejunum
Lactase digests lactose into gluctose and galactose.
Relatively low activity, but very sensitive to injury

Question 10

Describe the role of trehalase.

Answer 10

Digests trehalose into 2 glucose units.

Question 11

Describe the role of glucoamylase

Answer 11

Activity highest in the ileum

Hydrolyzes non-reducing terminal alpha 1-4 glucoside in starch, glycogen, alpha-dextrins, maltose.

Question 12

Describe the function of GLUT-1

Answer 12

Found in human RBC, blood-barrier locations

High affinity glucose transport system

Question 13

Describe the function of GLUT-2

Answer 13

Found in the liver, kidney, pancreas
High-capacity, low-affinity transporter.
Because this is a low-affinity transporter, it has a high Km.
Important function: blood glucose concentration sensor for the pancreas
Found on the serosal side

Question 14

Describe the function of GLUT-3.

Answer 14

Found in brain (neurons)

High affinity transporter

Question 15

Describe the function of GLUT-4

Answer 15

Found in adipose tissue, skeletal muscle
Insulin sensitive system (increased insulin, increased number of GLUT-4 transporters on the cell surface)
High affinity transporter

Question 16

Describe the function of GLUT-5.

Answer 16

Found in sperm
Fructose transporter
Found on the serosal and mucosal sides.

Question 17

How is creatine formed?

Answer 17

Creatine is synthesized by the transamidination of glycine using arginine as a nitrogen donor.
Marker of tissue damage.

Question 18

How is carnitine formed?

Answer 18

Carnitine is synthesized from protein-bound lysine.

Question 19

How is acetylcholine formed?

Answer 19

Acetylcholine is synthesized from choline, which is formed from serine and methionine.

Question 20

How is serotonin formed?

Answer 20

Serotonin is a product of tryptophan.

SSRIs and MAOIs are designed to increase serotonin levels in patients.

Question 21

How is Gamma-aminobutyric acid (GABA) formed?

Answer 21

GABA is an inhibitory neurotransmitter synthesized from glutamate, and is degraded to succinate, which enters the TCA cycle.

Question 22

How are catecholamines formed?

Answer 22

Catecholamines are formed from phenylalanine and tyrosine.

Question 23

How is nitric oxide (NO) formed?

Answer 23

NO is synthesized from arginine.

Question 24

How is histamine formed?

Answer 24

Histamine (a vasodilator in response to allergic reactions or trauma) is synthesized from histidine.

Question 25

How are polyamines formed?

Answer 25

Polyamines are formed from ornithine and methionine. They are present in all cells and inhibition of their synthesis blocks cell growth.

Question 26

What is the role of ferroportin?

Answer 26

Ferroportin is a carrier that allows for iron release into the blood. It is a transporter on the basolateral side, allowing for iron to move from the inside of the cell into the bloodstream. It can be inhibited by hepcidin when the body no longer needs more iron to be released.

Question 27

What is the role of hepcidin?

Answer 27

Hepcidin is a hormone that can inhibit ferroportin release of iron into the blood stream. It is up-regulated by increased iron in the blood, and it is inhibited by active erythropoiesis.

Question 28

What is the role of transferrin?

Answer 28

Transferrin delivers iron to cells that need it for heme biosynthesis. Also can deliver iron for storage as ferritin. Each transferrin molecule can bind to Fe+ molecules, however normally only transferrin is 30% saturated (important, allows leeway for jump in erythropoeisis).

Question 29

What is the role of ferritin?

Answer 29

Molecule designed to store excess iron. Each ferritin molecule can contain over 4,000 iron atoms.