Biochem Block 4 - Week 1C

Front 1

What enzyme begins the digestion of polysaccharides in your mouth? Where does it cleave?

Back 1

a-amylase

Cleaves non-reducing end

Front 2

What is the polysaccharide that is 2 consecutive glucose molecules?

3 consecutive?

What digests them?

Back 2

2: maltose

3: maltotriose

a-glucosidase

Front 3

What types of bond does a-glucosidase cleave?

Back 3

a-1,4 linkages

Front 4

What is sucrose made up of?

What enzyme digests it?

Back 4

Disaccharide: fructose and glucose

Sucrase

Front 5

What is lactose made up of?

What enzyme digests lactose?

Back 5

Glucose and galactose

Lactase

Front 6

What is the structure of trehalose?

What enzyme digests trehalose?

Where does it come from?

Back 6

2 glucoses linked a-1,1

Trehalase

Come from insects and some mushrooms

Front 7

What is the plant equivalent of glycogen?

Back 7

Amylopectin

Front 8

What digestive enzyme breaks down a-1,6 glycosidic linkages?

Back 8

a-dextrinase

Front 9

What are some examples of indigestible fibers?

Back 9

1. Cellulose (B-1,4 linkages)

2. Soluble fiber (B-1,3 and 1,4 linked glucose, galactose)

3. Inulin (fructose polymer)

4. Agar (glucose and galactose)

Front 10

Legume oligosaccharides contain what kind of linkage that can't be digested by our enzymes, but can be digested by our gut bacteria?

Back 10

a-1,4 galactose

Front 11

How does Splenda work?

Back 11

Sucrose but with: C4 on glucose and C1, C6 on fructose all replaced with -Cl

Cannot be digested anywhere

Front 12

What population of gut bacteria is seen more highly in obese people?

Back 12

Firmicutes

as opposed to Bacteroidetes

Front 13

What epithelial/immune receptor, when knocked out, produces fatter mice?

Back 13

TLR5

Front 14

What 3 membrane transporters are important for glucose absorption in the intestine?

Back 14

1. Na+/K+ exchanger (basolateral)

2. Na+/glucose symporter (apical)

3. GLUT2 (basolateral)

Front 15

How does fructose get absorbed in the intestine?

Back 15

In through GLUT5 (apical)

Out through GLUT2 (basolateral)

Front 16

In most tissues (not liver), how is fructose metabolized?

Back 16

Hexokinase phosphorylates it to fructose-6 phosphate -> glycolysis

BUT the Km is very high

Front 17

In liver, how is fructose metabolized?

Back 17

1. Fructokinase -> fructose 1-posphate

2. Fructose 1-phosphate aldolase -> cleaves to DHAP and glyceraldehyde

3. Triose kinase -> Glyceraldehyde to Glyceraldehyde 3-phosphate

Front 18

What is the deficiency in Fructosuria? Symptoms?

Back 18

Fructokinase deficiency

Fructose in urine but not many other problems

Front 19

What is the deficiency in Fructosemia?

Symptoms? Tx?

Back 19

Deficiency in fructose 1-phosphate aldolase

Liver damage

Tx: restrict fructose

Front 20

What is the pathway for making fructose from glucose?

Back 20

1. glucose -> sorbitol (enzyme: aldose reductase)

2. sorbitol -> fructose (enzyme: NAD-sorbitol 2-dehydrogenase)

Front 21

High activation of the sorbitol pathway can lead to what consequences in diabetics?

Back 21

Formation of cataracts in the lens, also some neurological damage

Front 22

How is galactose converted to glucose?

Back 22

1. Galactose -> galactose 1-P by galactokinase (req ATP)

2. Galactose 1P steals a UDP from a UDP-glucose to form UDP-galactose by Galactose 1-P uridyl transferase

(3.) Epimerized by UDP-galactose 4-epimerase to UDP-glucose

Front 23

What is the deficiency in galactosemia?

Symptoms?

Back 23

Galactokinase

Mild, but can get cataracts from galactitol

Front 24

What is the deficiency in Galactose intolerance/ Classic Galactosemia?

Symptoms?

Back 24

Galactose 1-phosphate uridyltransferase

Seen EARLY: failure to thrive, can lead to liver damage and mental retardation

Front 25

What enzyme present in teenagers/adults allows people with galactose 1P uridyltransferase deficiency to process galactose?

Back 25

UDP-galactose pyrophosphorylase

Front 26

What enzyme and accessory protein are required to produce lactose in the mammary glands?

Back 26

Enzyme: Galactosyltransferase

Protein: a-lactalbumin

Front 27

What compounds assist in the excretion of toxic substance, drugs, bilirubin, etc?

Back 27

Glucuronides

Front 28

What are the priorities, in order, of metabolism in the fasting state?

Back 28

1. Fuel/energy for brain and CNS

2. Maintain protein reserves

3. Replenish limited reserves of glycogen

Front 29

Insulin secretion stimulates entry of glucose into which tissues? Via which transporter?

Back 29

Muscle and adipose

GLUT4

Front 30

What effect does insulin have on glycolysis? Mainly through activation of ______?

At high levels, also through increased expression of ______?

Back 30

Increases glycolysis via PFK1

Increased expression of glucokinase

Front 31

What effect does insulin have on glycogen synthesis?

What protein does it activate and what protein does it inhibit?

Back 31

Increases glycogen synthesis

Activates glycogen synthase

Inhibits glycogen phosphorylase

Front 32

Glucagon stimulates glycogen breakdown via which pathway and eventual activation of which protein?

Back 32

Through PKA pathway,

activation of glycogen phosphorylase

Front 33

Glucagon stimulates gluconeogenesis by activating transcription of ....? (2)

Back 33

PEPCK and glucose 6-phosphate

Front 34

What protein does liver have that muscle lacks, allowing liver to release glucose into the circulation?

Back 34

Glucose 6-phosphatase

Front 35

What glycolysis enzyme is inhibited in liver but not in muscle during epinephrine/glucagon signaling?

How is it inhibited?

Back 35

Pyruvate kinase

Inhibited by phosphorylation

Front 36

In liver: what allosterically inhibits glycogen phosphorylase?

In muscle?

Back 36

ATP, glucose, glucose 6-P

ATP, glucose 6-P

Front 37

In muscle, what allosterically stimulates glycogen synthase?

Back 37

glucose 6-P

Front 38

What can activate glycogen phosphorylase in muscle by activating phosphorylase kinase?

Does this require phosphorylation of phosphorylase kinase?

Back 38

Ca++

NO phosphorylation

Front 39

Muscle hexokinase is inhibited by ________ while liver hexokinase (glucokinase) is not

Back 39

glucose 6-phosphate

Front 40

Liver hexokinase (glucokinase) is regulated by...

Back 40

Being sequestered in the nucleus

Front 41

What gluconeogenic enzymes do the opposite of pyruvate kinase?

Back 41

Pyruvate carboxylase and PEPCK

Front 42

Pyruvate kinase is inhibited by which 2 "high energy" things/substrates?

Back 42

ATP and alanine

Front 43

What is the enzyme of the commitment reaction of the oxidative phase of PPP?

What inhibits it?

Back 43

Glycose 6-phosphate dehydrogenase

Inhibited by product: NADPH

Front 44

What effect does Xyulose 5-phosphate have on glycolysis? Through modification of which protein?

Back 44

Activates glycolysis

through a protein phosphatase that dephosphorylates PFK-2/FBPase-2, activating PFK-2