Cellular Metabolism I

Question 1

What are the bonds broken in food molecules?

Answer 1

Polysaccharides
Proteins
Fats

Question 2

What are breakdown reactions called?

Answer 2

Catabolic reactions

Question 3

What are the backbones of the molecules useful for?

Answer 3

Starting points to synthesise components needed in the cell such as:
Membranes
DNA
Proteins

Question 4

What are anabolic reactions?

Answer 4

Synthesis

Question 5

Three stages of Cellular Metabolism

Answer 5

Glycolysis
TCA Cycle
Oxidative Phosphorylation

Question 6

First Stage of Cell Met

Answer 6

Glycolysis
Oxidation of glucose
In cytosol of individual cells
Makes ATP and (reduced cofactor) NADH

Question 7

Second Stage of Cell Met

Answer 7

Tricarboxylic Acids Cycle (TCA Cycle)
Further oxidation of smaller molecules from breakdown of sugars, fats, and proteins
In mitochondria of individual cells
Makes ATP, NADH, FADH2 and waste products

Question 8

Third Stage of Cell Met

Answer 8

Oxidative Phosphorylation 
Reduction of oxygen to water 
In mitochondria
Makes bulk of cellular ATP
Reduced cofactors from first two stages are re-oxidised

Question 9

What are the wastes of cell metabolism reactions?

Answer 9

Water (reduction of oxygen)

Urea (breakdown of amino acids)

Question 10

Delta G for combustion of oxygen

Answer 10

2872 kJ/mole

Question 11

What is needed to liberate the energy for combustion and cellular oxidation of glucose?

Answer 11

Overcome the activation energy barrier by applying heat to glucose.

Question 12

How many ATPs does the complete oxidation of glucose make?

Answer 12

36-38

Question 13

Delta G for hydrolysis of phosphoanhydride bond.

Answer 13

-31 kJ/mol

Question 14

What are the 6 types of reactions that define metabolism?

Answer 14

Oxidation-reduction - electron transfer

Ligation requiring ATP cleavage - formation of covalent bonds (i.e. C-C bonds)

Isomerisation - rearrangement of atoms to form isomers

Group transfer - transfer of a functional group from one molecule to another

Hydrolytic- Cleavage of bonds by the addition of water

Addition or removal of functional groups - addition to double bonds or removal to form double bonds

Question 15

Glycolysis

Answer 15

Breaking of sugar 
Anaerobic
Occurs in cytoplasm
Start with glucose
End with two pyruvates and two ATP

Question 16

How many reactions are in glycolysis?

Answer 16

10

Question 17

Which two concepts is glycolysis split into?

Answer 17

Formation of high energy compound - investment of energy in form of ATP

Splitting of high energy compound - production of useful energy in form of ATP

Split at half way point (between five and six)

Question 18

Reaction One of Glycolysis

Answer 18

Glucose to Glucose-6-phosphate
Enzyme: Hexokinase
Phosphorylation - Group Transfer
Also hydrolyses ATP to ADP
Irreversible, as glucose is charged and now can’t leave the cell by the glucose transporters
It is thus committed to the reaction

Question 19

Reaction Two of Glycolysis

Answer 19

Glucose-6-phosphate to Fructose-6-phosphate
Enzyme: Phosphoglucose isomerase
Isomerisation
Fructose can be split into equal halves when subsequently cleaved

Question 20

Reaction Three of Glycolysis

Answer 20

Fructose-6-phosphate to Fructose-1,6-biphosphate (symmetrical molecule)
Enzyme: Phosphofructokinase
Group transfer
Also turns ATP to ADP
Regulation of phosphofructokinase by negative feedback and other means is a key control step for the entry of sugars into the glycolysis pathway

Question 21

Reaction Four of Glycolysis

Answer 21

Fructose-1,6-biphosphate to Glyceraldehyde 3-phosphate and Dihydroxyacetone phosphate
Enzyme: Aldolase
Hydrolytic
Two high energy compounds generated

Question 22

Reaction Five of Glycolysis

Answer 22

Dihydroxyacetone phosphate to Glyceraldehyde-3-phosphate
Enzyme: Triose phosphate isomerase (TPI)
Isomerisation
Deficiency in TPI is the only glycolytic enzymopathy that is fatal, with most patients dying within the first 6 years of their lives.

Question 23

What is achieved after the first half of glycolysis?

Answer 23

Two molecules of Glyceraldehyde-3-phosphate

Question 24

Reaction Six of Glycolysis

Answer 24

Glyceraldehyde-3-phosphate to 1,3-biphosphoglycerate
Enzyme: glyceraldehyde-3-phosphate dehydrogenase
Also cofactor NAD+ (nicotinamide adenine dinucleotide) and Pi (inorganic phosphate) turns to NADH
Redox and group transfer
NADH generated can be used later to generate more ATP within the mitochondria in oxidative phosphorylation.

Question 25

Reaction Seven of Glycolysis

Answer 25

1,3-biphosphoglycerate to 3-phospgoglycerate Enzyme: phosphoglycerate kinase Also turns ADP to ATP Group transfer One phosphate group is transferred to ADP FROM THE 1,3-biphosphoglycerate

Question 26

Reaction Eights of Glycolysis

Answer 26

``` 3-phosphoglycerate to 2-phosphoglycerate Enzyme: phosphoglycerate mutase Group removal Isomerisation Moving the phosphoate group from position 3 to 2 ```

Question 27

Reaction Nine of Glycolysis

Answer 27

2-phosphoglycerate to Phosphoenolpyruvate and H2O Enzyme: Enolase Group removal Also known as dehydration as it is a removal of a hydroxyl group (HO) and a hydrogen (H)

Question 28

Reaction Ten of Glycolysis

Answer 28

Phosphoenolpyruvate to Pyruvate Enzyme: pyruvate kinase Group transfer Also ADP turns to ATP

Question 29

Net Results of Glycolysis

Answer 29

Net gain of 2 ATP (-2+4) Gain of 2 NADH Gain of 2 Pyruvate

Question 30

What are the three fates of pyruvate?

Answer 30

Alcoholic fermentation Lactate production Acetyl CoA production

Question 31

Alcoholic fermentation reaction

Answer 31

Pyruvate to Acetaldehyde (decarboxylation) Enzyme: pyruvate decarboxylase Also H+ turns to CO2 Acetaldehyde to Ethanol (reduction) Enzyme: alcohol dehydrogenase Also NADH and H+ turns to NAD+ Characteristic of yeast Occur under anaerobic conditions

Question 32

Generation of lactate reaction

Answer 32

Pyruvate to Lactate (reduction) Enzyme: lactate dehydrogenase Also NADH and H+ to NAD+ (oxidation) Characteristic of mammalian muscle during intense activity when oxygen is a limiting factor Anaerobic

Question 33

What is the common purpose of both alcoholic fermentation and generation of lactate?

Answer 33

Allow NAD+ to be regenerated and thus glycolysis to continue in oxygen deprivation I.e. conditions in which the rate of NADH formation by glycolysis is greater than its rate of oxidation by the respiratory chain

Question 34

What does creatine kinase do?

Answer 34

Acts as an enzyme for reaction that produces ATP Creatine phosphate to creatine and ATP (reversible) Also turns ADP and H+ to ATP Readily produce ATP Promotes phosphorylation of either ADP or creatine

Question 35

What is the cellular concentration of creatine phosphate and ATP in resting muscle?

Answer 35

25 millimolar of CP | 4 millimolar of ATP

Question 36

Acetyl CoA generation reaction

Answer 36

Pyruvate and HS-CoA to Acetyl CoA and CO2 Enzyme: pyruvate dehydrogenase complex Also turns NAD+ to NADH Occurs in mitochondria, thus acetylene CoA is committed to entry into TCA cycle

Question 37

What is a deficiency of thiamine?

Answer 37

Bert-Beri | Symptoms include damage to peripheral nervous system, weakness of the musculature and decreased cardiac output

Question 38

What is thiamine?

Answer 38

Thiamine pyrophosphate is a cofactor of the PDH complex (pyruvate dehydrogenase complex). It readily loses a proton and the resulting carbonion is very reactive and attacks the pyruvate, which kicks off catalysis.

Question 39

Why is the brain particularly vulnerable to Beri-Beri?

Answer 39

It relies heavily on glucose metabolism.

Question 40

How many steps are in the Krebs/TCA Cycle?

Answer 40

8

Question 41

What does one turn of the Krebs/TCA cycle produce?

Answer 41

Two molecules of CO2 (waste), three molecules of NADH , one molecule of GTP and one molecule of FADH2.