Cell Metabolism 1

Question 1

What is delta G for ATP —> ADP + Pi ?

Answer 1

-31 kJ/mol

Question 2

What are the three main stages of cellular metabolism?

Answer 2

Glycolysis TCA/Krebs cycle Oxidative phosphorylation

Question 3

Give a brief overview of Glycolysis

Answer 3

Oxidation of glucose in the cytosol of cells. Generates ATP and NADH

Question 4

Give a brief overview of the TCA cycle

Answer 4

Further oxidation of small molecules. Takes place in the mitochondria. Generates ATP, NADH and FADH2 and waste products (CO2)

Question 5

Give a brief overview of oxidative phosphorylation

Answer 5

Generation of ATP within the mitochondria by the reduction of oxygen to water

Question 6

What is the efficiency of the whole process?

Answer 6

41% DG of combustion of glucose = -2827 kJ/mol DG of ATP synthesis = -31 38 units of ATP 38 x -31 = -1178 (1178/2827) x 100 = 41%

Question 7

What are the six types of reaction that define metabolism and what do they do?

Answer 7

Redox- electron transfer Ligation requiring ATP cleavage- formation of covalent bonds Isomerisation- rearrangement of atoms to form isomers Group transfer- transfer of a functional group from one molecule to another Hydrolytic - cleavage using water Addition/removal of functional groups- across a double bond

Question 8

What would be the overall equation for glycolysis?

Answer 8

1 6C molecule —> 2 3C molecules Glucose —> 2 pyruvate (and net gain of 2 ATP)

Question 9

Where does glycolysis take place?

Answer 9

In the cytoplasm. It is an essentially anaerobic process

Question 10

How many steps are involved in glycolysis? And what is fundamentally involved in each part?

Answer 10

10 steps Part 1 - investment of ATP Part 2 - produces ATP

Question 11

What is the first step of glycolysis?

Answer 11

Glucose —> glucose-6-phosphate + H+ Using hexokinase and ATP—>ADP + Pi This traps glucose inside the cell because G6P has a negative charge Essentially irreversible

Question 12

Step 2 of glycolysis?

Answer 12

Glucose-6-phosphate —> fructose-6-phosphate Using phosphoglucose isomerase As fructose can be split into equal halves later

Question 13

Step 3 of glycolysis?

Answer 13

Fructose-6-phosphate —> fructose-1,6-bisphosphate Using phosphofructokinase and ATP—>ADP

Question 14

Step 4 of glycolysis?

Answer 14

Fructose-1,6-bisphosphate —> glyceraldehyde-3-phosphate + dihydroxyacetone phosphate Using aldolase Forms two high energy compounds as they both have a phosphate group attached

Question 15

Step 5 of glycolysis?

Answer 15

Dihydroxyacetone phosphate —> glyceraldehyde-3-phosphate Using triose phosphate isomerase TPI deficiency can be fatal in the first 6 years of life

Question 16

Step 6 of glycolysis?

Answer 16

2x glyceraldehyde-3-phosphate —> 2x 1,3-bisphosphoglycerate Using glyceraldehyde-3-phosphate dehydrogenase And Pi And 2 NAD+ —> 2 NADH The NADH produced is later used in oxidative phosphorylation

Question 17

Step 7 of glycolysis?

Answer 17

2x 1,3-bisphosphoglycerate —> 2x 3-phosphoglycerate Using phosphoglycerate kinase And 2 ADP —> 2 ATP

Question 18

Step 8 of glycolysis?

Answer 18

2x 3-phosphoglycerate —> 2x 2-phosphoclycerate Using phosphoglycerate mutase

Question 19

Step 9 of glycolysis?

Answer 19

2x 2-phosphoglycerate —> 2x Phosphoenolpyruvate + 2 H2O Using Enolase

Question 20

Step 10 of glycolysis?

Answer 20

2x phosphoenolpyruvate —> 2x pyruvate Using pyruvate And 2 ADP —> 2 ATP

Question 21

What is the net result of glycolysis?

Answer 21

2 ATP and 2 NADH Glucose + 2 ATP —> 2 pyruvate + 4 ATP + 2 NADH

Question 22

What are the three dates of pyruvate?

Answer 22

1) alcoholic fermentation 2)generation of lactate 3)Acetly CoA generation

Question 23

What are the two steps in alcoholic fermentation?

Answer 23

Pyruvate —> acetaldehyde + CO2 Using pyruvate decarboxylase And H+ Acetaldehyde —> ethanol Using alcohol dehydrogenase And NADH + H+ —> NAD+ Happens under anaerobic conditions in yeasts

Question 24

What are the steps in the generation of lactate?

Answer 24

Puruvate —> lactate Using lactate dehydrogenase And NADH + H+ —> NAD+ Reversible Anaerobic

Question 25

What step is involved in the generation of acetyl CoA?

Answer 25

Pyruvate + HS-CoA—\> acetyl CoA +CO2 Using pyruvate dehydrogenase complex And NAD+ —\> NADH Occurs in the mitochondria Therefore the acetyl CoA is committed to the TCA cycle

Question 26

What is the main purpose formation of lactate and alcoholic fermentation serve?

Answer 26

The regeneration of NAD+ so that glycolysis can continue in anaerobic conditions

Question 27

How is creative phosphate used as a buffer?

Answer 27

Creatine phosphate —\> creatine Buttttt ADP + H+ —\> ATP In muscle the amount of ATP can only sustain contraction for about 1 second But there is a large reservoir of crea to e phosphate to buffer demands for phosphate It may be used as a supplement in athletes diets

Question 28

Why is acetyl CoA useful?

Answer 28

There is a thioester bond (between soulful and carbon) thas is very high energy, so readily hydrolysed. This allows acetyl CoA to donate the acetate (2C) to other molecules

Question 29

Learn what the kerbs cycle /TCA cycle looks like

Answer 29

!!!

Question 30

What are the net products of the TCA cycle?

Answer 30

1 turn produces: 2 CO2 3 NADH 1 GTP (like ATP) 1 FADH2

Question 31

Why does the TCA cycle only take place in aerobic conditions?

Answer 31

Most ATP is generated when the reduced coenzymes are reoxidised with the help of oxygen in oxidative phosphorylation

Question 32

How do amino acids enter the TCA cycle

Answer 32

They are degraded to remove the amino group, which is eventually excreted as urea. And the carbon chain is inserted into the Krebs cycle Look at slide

Question 33

What does protein metabolism involve (in terms of so it can enter the Krebs cycle)

Answer 33

Transamination reactions Alanine + a-ketoglutarate —\> Pyruvate + glutamate See slide

Question 34

Why is NADH transportation a problem?

Answer 34

NADH produced in glycolysis must enter the mitochondria so it can be used in oxidative phosphorylation and regenerate NAD+ Finite NAD+, w/o it glycolysis stops

Question 35

How do the high energy electrons from NADH cross into the matrix?

Answer 35

The glycerol phosphate shuttle Skeletal muscle, brain The Malate-aspartate shuttle Liver, kidneys and heart

Question 36

How does the glycerol phosphate shuttle work?

Answer 36

Cytosolic glycerol-3-phosphate dehydrogenase transfers electrons from NADH to DHAP to generate glycerol-3-phosphate A membrane bound form of the same enzyme transfers the electrons to FAD, these then get passed to coenzyme Q, part of the electron transport chain

Question 37

How does the malate-aspartate shuttle work?

Answer 37

Honestly idk look at the slide

Question 38

How many molecules of ATP are formed from the re oxidation of NADH?

Answer 38

3

Question 39

How many molecules of ATP are formed from the re oxidation of FADH2?

Answer 39

2

Question 40

What is the difference between substrate level and oxidative phosphorylation?

Answer 40

Substrate level involves the direct transfer of a high energy phosphate group to ADP Eg 1,3-bisohosphoglycerate —\> 3-phosphoglycerate and ADP —\> ATP Oxidative phosphorylation occurs in the ETC