MB+B metabolism

Question 1

how is glycolysis stopped when there are high concentrations of ATP are produced

Answer 1

enzymes are released that prevent the formation of fructose-1,6-biphosphate formation allowing for glucose storage
in liver and muscle cells phosphorylase enzymes can be activated using phosphorylase kinase to make them more reactive

Question 2

how do fructose and galactose enter glycolysis

Answer 2

they are phosphorylated to form intermediate steps in the pathway such a fructose- 6 phosphate

Question 3

how is glucose formed from glycogen

Answer 3

the enzyme glycogen phosphorylase hydrolyses the gycosidic bond between a chain of glycogen and phosphorylates one of the residues

Question 4

how is glucose produced through gluconeogenesis

Answer 4

pyruvate is carboxylated using pyruvate carboxylase into oxyaloacetate. this reacts with guanosine to produce phosphoenolpyruvate. ATP reliant reactions are replaced by phosphatase reactions The phosphoryl groups areremoved by hydrolysis

Question 5

what does metabolism comprise of

Answer 5

anabolism - rections that require energy
catabolism - reactions that release energy

Question 6

why does ATP have such high phosphoryl potential

Answer 6

resonance stabilisation
hydration and electrostatic repulsion

Question 7

what are the steps of gylcolysis

Answer 7

phosphorylation of glucose to make glucose -6- phosphate using hexokinase

conversion to fructose-6-phosphate using phosphoglucose isomerase

further phosphorylation using phosphofructokinase to form fructose-1,6-biphosphate

formation of 2 triose sugars by aldolase to form DHAP and GAP

DHAP is converted to GAP using triose phosphospate isomerase

oxidation of GAP with NAD+ using glyceraldehyde 3 phosphate dehydrogenase to form 1,3-bisphosphateglycerate

ATP production using phosphoglycerate kinase to form 3-phosphate glycerate and ATP

mutated using phosphoglycerate mutase to form 2-phosphate glycerate

dehydration using enolase to form phosphenol pyruvate

pyruvate kinase create an ATP and forms pyruvate

Question 8

what can form Acetyl CoA

Answer 8

pyruvate, fatty acids and amino acids

Question 9

what is required to convert pyruvate into Acetyl CoA

Answer 9

pyruvate dehydrogenase
NAD+
FAD
lipoate
TTP

Question 10

how is pyruvate converted to acetyl coA

Answer 10

release of CO2 triggered by pyruvate dehydrogenase
transfer of acetyl group to CoA through the reduction of lipoate
Oxidation of NAD+ to regenerate lipoate

Question 11

each cylce of the citric cycle generates what

Answer 11

3 NADH
1 FADH2
2CO2
1 GTP

Question 12

steps of the citric cycle

Answer 12

the formation of a more reactive carbon for oxidation: citrate through citryl CoA intermediate using citrate synthase

2-5 oxidations
isocitrate using aconitase
alpha ketoglutarate using isocitrate dehydrogenase and forming NADH + CO2
succinyl CoA using alpha ketoglutarate dehydrogenase complex and forming NADH + CO2
succinate using succinyl CoA synthetase anf forming GTP (ATP)

fumarate formed using succinate dehydrogenase create FADH2

hydrate in the presence of fumarase to form malate

oxidised to form oxaloacetate to complete the cycle using malate dehydrogenase and forming NADH

Question 13

how is the citric acid cycle regulated

Answer 13

pyruvate dehydrogenase, citrate synthese, isocytrate dehydrogenase and alpha- ketoglutarate dehydrogenase are are inhibited by products of the pritate cycle preventing further formation of products

Question 14

what is the pentose phosphate pathway most typically used in

Answer 14

rapidly dividing cells

Question 15

what does the pentose phosphate pathway create

Answer 15

pentoses and NADPH

Question 16

what is the pentose phosphate pathway

Answer 16

glucose-6-phosphate to 6-phosphogluconate forming NADPH from NADP+ and 2GSH from GSSG
ribulose-5-phosphate through the release of CO2 and the formation of NADPH (transkelolase can be used to regenerate this to glucose-6-phosphate)
ribose-5-phosphate

Question 17

in what context would the regeneration of ribulose-5-phosphate to glucose-6-phosphate be necessary

Answer 17

if needed for glycolysis
or in cells that dont require pentoses

Question 18

how else can ribose-5-phosphate be aquired when NADPH isnt needed by a cell

Answer 18

fructose-6-phosphate and GAP can be converted in a reverse of the pentose phosphate pathway

Question 19

what are the types of carriers in the electron transport chain

Answer 19

ubiquinone, cytochrome and iron sulfur centres

Question 20

what happens in complex 1 of the ETC

Answer 20

NADH donates 2 electrons through Fe-S centres to reduce ubiquinone to ubiquinol allowing it to diffuse into the membrane

4H+ ions are pumped out of the mitochondria into the intermembrane space

Question 21

what happens in complex 2 of the ETC

Answer 21

succinate is oxidised allowing another molecule of ubiquinone to be reduced and FADH2 donates 2 e- becoming FAD- once again

Question 22

what happens in complex 3 of the ETC

Answer 22

the ubiquinol formedin complexes 1 + 2 are passed into the complex and the e- and protons pass to cytochrome C. this is soluble and moves throiugh intermembrane space to complex 4

4 protons are pumped into the intermembrane space

Question 23

what happens in complex 4

Answer 23

4 molecules of cytochrome C bind to the complex and donate and electron each to O2 to produce H2O

2 H+ pumped into the intermembrane space for every 2e- donated to O2

this formsa proton gradient in the intermembrane space

Question 24

what does the difference in concentration of protons and electrical potential energy cause

Answer 24

proton motive force

Question 25

how is ATP formed in ETC

Answer 25

the proton motive force cause protons to defuse back through to the matrix through ATP synthase forming ATP

Question 26

how does poison inhibit the ETC

Answer 26

rotenone inhibits complex 1
antimycin a blocks the process of complex 3
complex 4 blocked by cyanide, azide and CO

Question 27

alternative uses of mitochondria

Answer 27

newborn mammels have brown adipose tissue that contains lots of mitochondria whose job is to produce heat

Question 28

how many ATP do NADH andFADH create in the ETC

Answer 28

NADH = 2.5
FADH2 = 1.5