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Molucular Biology of Cell > Cellular Metabolism I > Flashcards

Cellular Metabolism I Flashcards

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1
Q

What are the bonds broken in food molecules?

A

Polysaccharides
Proteins
Fats

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2
Q

What are breakdown reactions called?

A

Catabolic reactions

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3
Q

What are the backbones of the molecules useful for?

A

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

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4
Q

What are anabolic reactions?

A

Synthesis

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5
Q

Three stages of Cellular Metabolism

A

Glycolysis
TCA Cycle
Oxidative Phosphorylation

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6
Q

First Stage of Cell Met

A

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

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7
Q

Second Stage of Cell Met

A

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

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8
Q

Third Stage of Cell Met

A 
Oxidative Phosphorylation 
Reduction of oxygen to water 
In mitochondria
Makes bulk of cellular ATP
Reduced cofactors from first two stages are re-oxidised
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9
Q

What are the wastes of cell metabolism reactions?

A

Water (reduction of oxygen)

Urea (breakdown of amino acids)

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10
Q

Delta G for combustion of oxygen

A

2872 kJ/mole

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11
Q

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

A

Overcome the activation energy barrier by applying heat to glucose.

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12
Q

How many ATPs does the complete oxidation of glucose make?

A

36-38

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13
Q

Delta G for hydrolysis of phosphoanhydride bond.

A

-31 kJ/mol

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14
Q

What are the 6 types of reactions that define metabolism?

A

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

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15
Q

Glycolysis

A 
Breaking of sugar 
Anaerobic
Occurs in cytoplasm
Start with glucose
End with two pyruvates and two ATP
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16
Q

How many reactions are in glycolysis?

A

10

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17
Q

Which two concepts is glycolysis split into?

A

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)

18
Q

Reaction One of Glycolysis

A 
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
19
Q

Reaction Two of Glycolysis

A

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

20
Q

Reaction Three of Glycolysis

A

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

21
Q

Reaction Four of Glycolysis

A

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

22
Q

Reaction Five of Glycolysis

A

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.

23
Q

What is achieved after the first half of glycolysis?

A

Two molecules of Glyceraldehyde-3-phosphate

24
Q

Reaction Six of Glycolysis

A

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.

25
Q

Reaction Seven of Glycolysis

A

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

26
Q

Reaction Eights of Glycolysis

A 
3-phosphoglycerate to 2-phosphoglycerate
Enzyme: phosphoglycerate mutase 
Group removal
Isomerisation
Moving the phosphoate group from position 3 to 2
27
Q

Reaction Nine of Glycolysis

A

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)

28
Q

Reaction Ten of Glycolysis

A

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

29
Q

Net Results of Glycolysis

A

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

30
Q

What are the three fates of pyruvate?

A

Alcoholic fermentation
Lactate production
Acetyl CoA production

31
Q

Alcoholic fermentation reaction

A

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

32
Q

Generation of lactate reaction

A

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

33
Q

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

A

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

34
Q

What does creatine kinase do?

A

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

35
Q

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

A

25 millimolar of CP

4 millimolar of ATP

36
Q

Acetyl CoA generation reaction

A

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

37
Q

What is a deficiency of thiamine?

A

Bert-Beri

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

38
Q

What is thiamine?

A

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.

39
Q

Why is the brain particularly vulnerable to Beri-Beri?

A

It relies heavily on glucose metabolism.

40
Q

How many steps are in the Krebs/TCA Cycle?

A

8

41
Q

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

A

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

Molucular Biology of Cell (1 decks)

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