Carbohydrate Metabolism

Question 1

what hormones lead the anabolic state

Answer 1

insulin

Question 2

what hormones lead the catabolic state

Answer 2

epinephrine and glucagon

Question 3

what happens during the catabolic state

Answer 3

glucagon and epinephrine signal for the breakdown of glycogen leading to ATP production or release of glucose from the liver

Question 4

what is glycolysis

Answer 4

this is the conversion of glucose to pyruvate used to generate ATP.

it is a catabolic pathway

Question 5

what is stage 1 of glycolysis

Answer 5

2 ATP are used to prepare glucose for its breakdown of glucose and conversion into two GAPs (glyceraldehyde phosphate- 3 carbon molecule)

Question 6

what is stage 2 of glycolysis

Answer 6

production of 2 pyruvates, 2 NADH and a net of 2 ATP molecules

Question 7

After the production of pyruvate in glycolysis what can it be further used for?

Answer 7

it can be oxidized in the mitochondria to generate more NADH

Question 8

is the glycolytic pathway ender or exergonic

Answer 8

exergonic because it releases energy

Question 9

in the glycolytic pathway what is fructose converted into

Answer 9

GAP and DHAP

Question 10

what is galactose converted into

Answer 10

glucose 6 phosphate

Question 11

what does a negative delta G symbolize

Answer 11

an irreversible reaction

Question 12

what are the three regulatory steps of glycolysis?
what is about these specific steps make them highly regulated?

Answer 12

steps 1, 3 and 10 are highly regulated steps in glycolysis and this is because they have very negative delta Gs indicating irreversibility

Question 13

describe the three regulatory steps in glycolysis

Answer 13

step 1: glucose to glucose 6 phosphate by hexokinase. hexokinase can be inhibited by a build up of glucose 6 phosphate

Step 3: fructose 6 phosphate to fructose 16 bisphosphate by phosphofructokinase 1 (PFK-1) can be inhibited by high ATP and citrate present or activated by AMP/ADP or fructose 2-6 bisphosphate

Step 10: pyruvate kinase generating pyruvate can be inhibited by phosphorylation (PTM) and allosteric regulators

Question 14

what is glucose 6 phosphate used for in the cell

Answer 14

generate energy

stored as glycogen for later

used to make new molecules

Question 15

what inhibits phosphofructokinase 1 (PFK 1)? What activates it

Answer 15

inhibited allosterically by ATP or citrate

activated by AMP/ADP and fructose 26 bisphosphate

Question 16

describe the structure of phosphofructokinase and how does this contribute to its allosteric regulation

Answer 16

PFK1 has 2 binding sites, an active site and an allosteric site

ATP binds to its allosteric site inhibiting PFK1 and AMP/ADP binding stimulates PFK1

Question 17

when pyruvate kinase is phosphorylated, is it more or less activated?

Answer 17

less active.

Question 18

what amino acid can we derive pyruvate from?

Answer 18

alanine

Question 19

what enzyme converts alanine to pyruvate

Answer 19

alanine aminotransferase

Question 20

Fill in the blank.

Allosteric Regulation is dependent on _____

Answer 20

structural changes

Question 21

what happens to the excess glucose when glycolysis is inhibited?

Answer 21

it can be stored as glycogen in the liver and muscle cells

Question 22

what converts glucose to glycogen in glycogen synthesis (glycogenesis)

Answer 22

glycogen synthase

Question 23

in the anabolic pathway, when glucose is high what exactly happens to it as it gets converted to glycogen

Answer 23

glucose is still phosphorylated however it is quickly isomerized by phosphoglucomutase to form glucose 1 phosphate

glucose 1 phosphate is transformed into UDP glucose by UDP glucose phosphorylase

glucose synthase requires the active form of glucose (UDP glucose) to frm new alpha 1,4 glycosidic bonds on the non reducing end of the glycogen

Question 24

how does insulin activate glycogen synthase

Answer 24

via dephosphorylation

Question 25

in glycogenolysis (glycogen breakdown) how does epinephrine and glucagon lead to in the inactivation of glycogen synthase

Answer 25

via phosphorylation of glycogen phosphorylase and inactivation of glycogen synthase

Question 26

what is happening in the liver cells as glucose levels drop and glucagon rises

Answer 26

it will release glucose to help stabilize the glucose levels

Question 27

Fill in the blank.

Glycogenolysis is a __________ reaction

Answer 27

phosphorolysis using P to release glucose 1 phosphate from non reducing end

Question 28

what inhibits glycogen phosphorylase? what activates it?

Answer 28

inhibited by ATP and glucose 6 phosphate

activated by AMP

Question 29

why can’t glucose leave muscle cells like they do in liver cells

Answer 29

because they are missing the phosphatase enzyme