Metabolic Biochemistry - Glycolysis

Front 1

What are the two phases of Glycolysis?

Back 1

1) Energy Investment

2) Energy Generating

Front 2

How much ATP is hydrolysed in the energy investment phase of glycolysis?

Back 2

2ATP

Front 3

What is produced in the energy generating phase of glycolysis?

Back 3

4ATP (net 2) and 2NADH

Front 4

Which glucose transporters are used in glycolysis? What determines direction of transport?

Back 4

-GLUT 1, 2 or 4

-Concentration of glucose

Front 5

Why does glucose conversion and ATP hydrolysis need to be coupled?

Back 5

-Keeps the reaction delta G negative

-Otherwise rise in body temp would be seen

Front 6

Where is hexokinase found?

Back 6

In all cells capable of glycolysis

Front 7

Where is glucokinase found?

Back 7

Liver and Islets of Langerhans

Front 8

Properties of hexokinase?

Back 8

-Low Km and Vmax (allows function even at low bg)

-Prevents glucose trapping

-Allosterically inhibited by G6P

Front 9

Properties of glucokinase?

Back 9

-High Km and Vmax - acts as a glucose sensor

-Helps prevent hyper. - active at very high glucose concentrations

-Inhibited by F6P

Regulation via GKRP - -ve feedback loop

Front 10

Isomerisation of G6P to F6P is a conversion of what?

Back 10

An aldehyde to a ketone

Front 11

Which step is the commitment step in glycolysis?

Back 11

Conversion of F6P to F16BP via PFK-1.

Front 12

Why is magnesium needed in PEP formation?

Back 12

Mg dependent dehydration - needed to stabilise the anion formed when a proton is removed

Front 13

Roles of glycolysis?

Back 13

-Energy for cells without mitochondria

-Provides G6P for PPP

-Intermediate for AA synthesis

-Glycerol for TAG synthesis

Front 14

Role of glycolysis in the liver?

Back 14

Buffer blood glucose levels

Front 15

Role of glycolysis in the cornea and lens?

Back 15

Rely on AG - no bvs, transparent and no mitochondria

Obtain glucose from vitreous body and aqueous humour

Front 16

Importance of glycolysis in the kidney medulla?

Back 16

High ATP demand for active transport

Medulla has poor blood supply

Front 17

Importance of glycolysis in neonates?

Back 17

O2 deprived for approx 30 mins during birth

AG supplies all glucose during this time

Front 18

Importance of glycolysis in RBCs?

Back 18

No mitochondria - rely on AG

G6P needed for glutathione prod - dealing with oxidative stress

1,3BPG linked to 23BPG - adapting to high altitude

Front 19

Importance of glycolysis in tumour cells?

Back 19

Increasingly hypoxic towards the centre - reliance on AG

Front 20

How does trivalent arsenic inhibit glycolysis?

Back 20

-Binds to PDH

-Inhibits conversion of pyruvate to Acetyl CoA

-Causes decreased Ach production

-Leads to CNS pathologies

Front 21

How does pentavalent arsenic inhibit glycolysis?

Back 21

-Inhibits GAPDH - a homologue of phosphate so binds to block phosphate

-PGK reaction bypassed - 1ATP lost

Front 22

How does iodoacetate inhibit glycolysis?

Back 22

Binds to GAPDH, irreversibly inactivates the enzyme

Front 23

How do fluoride ions inhibit glycolysis?

Back 23

-Competitively inhibit enolases

-Binds to Mg ions

-Prevents PEP production, decreases ATP production

Front 24

Partial deficiencies in glycolysis result in?

Back 24

Haemolytic anaemia

Front 25

Why are mature RBCs effected in genetic defects in glycolysis?

Back 25

-ATP is needed to maintain biconcave shape

-ATP needed for Na/K transporters for blood pH

Front 26

What are the regulatory sites of glycolysis?

Back 26

-hexokinase reaction

-PFK-1 reaction

-PK reaction

Front 27

How is PFK-1 regulated?

Back 27

-ATP

-AMP

-Citrate

Front 28

How is PK regulated?

Back 28

-Inhibited by ATP

-Activated by F16BP

Front 29

Lactose can be broken down into which sugars?

Back 29

Galactose and Glucose

Front 30

Sucrose can be broken down into which sugars?

Back 30

Fructose and Glucose

Front 31

How can fructose enter pathways in muscle?

Back 31

Conversion to F6P to enter glycolysis

Front 32

How can fructose enter pathways in liver?

Back 32

-Conversion to F1P, then to Glyceraldehyde or DHAP to be converted to GAP

Front 33

Potential uses of pyruvate?

Back 33

-Conversion to lactate

-Formation of ethanol

-Formation of Acetyl CoA and entry to TCA

Front 34

How is pyruvate converted to ethanol?

Back 34

P>acetylaldehyde>ethanol

CO2 is released and NAD+ is regenerated

Front 35

How is pyruvate transported to the inner mito membrane?

Back 35

Via symport cotransporter with H+

Front 36

What is the prosthetic group for the E1 PDH subunit? What is the co factor?

Back 36

TPP

No cofactor

Front 37

What is the prosthetic group for the E2 subunit of PDH complex? What is the co factor?

Back 37

Lipoamide

CoA

Front 38

What is the prosthetic group for the E3 subunit of PDH complex? What is the cofactor?

Back 38

FAD

NAD+

Front 39

What are the subunits of the PDH complex?

Back 39

E1 - PDH

E2 - DH transacetylase

E3 - DHDH

Front 40

How is the PDH complex regulated?

Back 40

PDHK - inactivates

PDHP - activates

Ca2+ - from muscle, switches on PDHP

ATP, ACoA +NADH - switch on kinase

Front 41

Severe thiamine deficiency causes...

Back 41

inability of E1 to decarboxylate pyruvate

Beri Beri syndrome or WK