Lecture 12

Question 1

Gluconeogenesis def

Answer 1

new production of glucose. Important to maintain sugar levels (why we don’t wake up hypoglycemic) The source of excess sugar in blood in diabetes

Question 2

Gluconeogenesis done in

Answer 2

the liver and the kidney

Question 3

Gluconeogenesis Bypass steps 1/3

Answer 3

conversion of pyr to two different things

pyruvate → OAA → PEP

(3 c → 4 c → 3c)

1. pyruvate carboxylase
2. PEP Carboxylase
3. Pyruvate kinase

during last step, Glu-6P hydrolysed into glucose

Question 4

Gluconeogenesis vs. Glycolysios

Answer 4

Glycolysis: Carbon loss during Krebs. All tussies do glycolysis.

Gluconeogenesis: no loss of carbon, which means we can use. Happens in specific structures under specific conditions. Only in LIVER and KIDNEY

Regulated differently

Question 5

How does the liver decide between doing glycolysis or gluconeogenesis?

Answer 5

Levels of glucose!

Big impacts from: insulin and glucagon

Question 6

PEPCK

Answer 6

Phosphoenolpyruvate carboxykinase

often rate limiting step in gluconeogenesis

Question 7

Enzyme: bypass 1

Answer 7

Pyruvate carboxylase

Question 8

bypass second enzyme

Answer 8

first bypass, second step.

*important rate limiting step of gluconeogenesis

Question 9

bypass, third enzyme

Answer 9

first bypass,

Glu-6P is getting hydrolyzed into glucose

Question 10

Fructose 2,6-biphosphate as glucose indicator

Answer 10

acts as a regulator of glycolysis and gluconeogenesis

↑ glucose= ↑Fru 2,6bp

↓gluc = ↓ Fru 2,6bp

Question 11

Answer 11

Fructose 2,6 biphosphate

Question 12

↑ glucose triggers

Answer 12

relase on insulin (to absorb glucose and lower it in the blood)

Question 13

glucagon produced when

Answer 13

blood glucose is low (produced by α cells)

Question 14

glucagon activates ______ inhibits_____

Answer 14

activates gluconeogenesis

inhibits glycolysis

Question 15

insulin activates _____ inhibits _____

Answer 15

activates glycolysis

inhibits gluconeogenesis

Question 16

what controls the levels on Fru 2,6 bp??

Answer 16

separate distinct enzyme activities

Question 17

we want _____ active when glucose in abundant

Answer 17

PFK-2

Question 18

we want _____ active when glucose is low (gone)

Answer 18

FBPase-2

Question 19

_____(hormone) activates PFK-2

Answer 19

instulin

Question 20

_____ (hormone) activates

Answer 20

FBP-ase-2

Question 21

Carbon sources for gluconeogenesis

Answer 21

-Lactate: converted back to pyr & made into glu through the bypass steps

-Glycerol: phosphorylated then oxidized & enter gluconeogenic cycle

-Amino Acids: enters krebs at 4c levels , which produces intermediates (that are interchangable) that can produce glucose

Question 22

Glycoxilate cycle overview

Answer 22

is an anabolic pathway that converts Ac-CoA → succinate to synthesize carbohydrates

-a way around carbon loss from Krebs

*Cycle exclusive to plants, fungi and protists

Question 23

Can humans use Fatty acids for gluconeogenesis via glycoxilate cycle?

Answer 23

NO!

Humans don’t have glycoxilate cycle and can’t convert fat to sugar.

Every time you put in an acetate two CO₂ come out. Can’t get net profit. Spending as much as you put in.

Question 24

glycoxilate cycle: an end around carbon loss

Answer 24

very similar to krebs, fat converted separate organelles, succinate comes off then converted to OAA to make glucose

2Acetyl-CoA + NAD+ → succinate + NADH + H+

No carbon loss!!

Question 25

RUBISCO

Answer 25

most abundant enzyme on the planet

• takes ribulose bp + CO₂ → the breaks it into 2 identical molecules:

3-phosphoglycerate whic goes into coat hanger but backwards to make glucose