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MBC > Cellular Metabolism I > Flashcards

Cellular Metabolism I Flashcards

1
Q

Phosphoanhydride bond?

A

Convenient way for cell to harness energy liberated from breaking bonds w in food molecules: polysaccharides, proteins, fats

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2
Q

What are breakdown reactions?

A

= catabolic

most energy released - ATP

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3
Q

What are Anabolic reactions?

A

backbones of molecules imp for synthesis e.g. membranes, DNA, proteins.

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4
Q

Stages of cellular metabolism and where they occur?

A

Glycolysis - occurs in the cytosol. oxidation of glucose to generate ATP and NADH

tricarboxylic acid (TCA) cycle: occurs in mitochondria. Further oxidation of small molecules. Generates ATP, NADH, FADH2 and waste products.

Oxidative Phosphorylation: Mitochondria.
Reduced cofactors are reoxidised
bulk of ATP generated. oxygen reduced to water.

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5
Q

Waste products of cellular metabolism?

A

Urea from the breakdown of amino acids

Water from reduction of oxygen.

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6
Q

Where do the 3 major grouos of molecules enter cellular metabolism?

A

Polysac broken down into simple sugars = glucose: GLYCOLYSIS

Fats -> fatty acids and glycerol, enter TCA (Acetyl CoA)

Proteins -> AA = glycolysis, tca, op.
but produce NH4+ which is turned into urea

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7
Q

What is delta G for Glucose combustion / oxidation ?

A

-2872kJ/mol (minus

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8
Q

Complete oxidation of glucose produces how many ATP and how efficient does that make this process?

A

38 (36-38)

  • Delta G for hydrolysis for a phosphoanhydride bond is -31 kJmol

38 x -31 = -1178 kJ/mol

% efficiency = 1178/2872 = 41% efficient

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9
Q

What 6 types of metabolic reactions are present?

A 
Oxidation-reduction
Ligand requiring ATP cleavage
Isomerization
Group transfer
Hydrolytic
Addition or removal of functional groups
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10
Q

What are oxidation-reduction reactions?

A

Electron transfer

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11
Q

What are ligation reactions?

A

Formation of covalent bonds

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12
Q

What are isomerization reactions?

A

Rearrangement of atoms to form isomers

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13
Q

What are group transfer reactions?

A

Transfer of a functional group from one molecule to another

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14
Q

What are hydrolytic reactions?

A

Cleavage of a bond by the addition of water

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15
Q

What are the reduction reactions?

A

Addition of electrons or the addition of hydrogen

Removal of oxygen

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16
Q

What are oxidation reactions?

A

Addition of oxygen/removal of hydrogen

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17
Q

What is NAD?

A

Nicotinamide adenine dinucleotide. Coenzyme hydrogen acceptor.
Oxidised form is denoted as NAD+ /NADH

18
Q

What is FAD?

A

Flavin adenine dinucleotide

19
Q

Name the hydrogen acceptors present within the electron transport chain:

A

Flavoprotein, coenzyme Q, cytochrome b,c,a

20
Q

Is glycolysis anaerobic or aerobic?

A

Anaerobic.

Happens in cytoplasm of cells.

21
Q

Two main concepts of glycolysis?

A

1) formation of a high energy compound (involves investment of ATP)
2) Splitting of a high energy compound (produces ATP)

22
Q

What is the first step of glycolysis?

A

Glucose is phosphorylated into glucose-6-phosphate by hexokinase-4 (Phosphoryl transfer).
GROUP TRANSFER REACTION
ATP is hydrolysed into ADP

23
Q

Why is the first step of glycolysis irreversible?

A

After being phosphorylated, glucose becomes charged so it’s unable to leave cell by glucose transporters.

24
Q

Which enzyme catalyses the initial phosphorylation of glucose?

A

Hexokinase-4

25
Q

What is step 2 of glycolysis?

A

Glucose-6-phosphate undergoes isomerization reactions into fructose-6-phosphate, under the action of phosphoglucoisomerase (Aldose to ketose)

26
Q

What enzyme catalyses the isomerization of glucose-6-phosphate –> Fructose-6-phosphate?

A

Phosphoglucoisomerase

27
Q

Why does glucose-6-phosphate undergo an isomerisation reaction?

A

in an attempt to make the molecule more symmetrical so it can be split into equal halves when cleaved.

28
Q

What is step 3 of glycolysis?

A

Fructose-6-phosphate is phosphorylated by ATP into fructose-1,6-bisphosphate by phosphofructokinase (group transfer)

29
Q

What enzyme causes fructose-6-phosphate to be phosphorylated into fructose-1,6-bisphosphate?

A

Phosphofructokinase

30
Q

What is step 4 of glycolysis?

A

Fructose-1,6-bisphosphate is hydrolyzed into two molecules of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate (hydrolytic cleavage)

31
Q

Why do we need to regulate phosphofructokinase?

A

It is a key control step for the entry of sugars into the glycolysis pathway

32
Q

What enzyme hydrolyses fructose-1,6- bisphosphate? (Step 4)

A

Aldo lease

33
Q

Why are G-3-p and dihydroxy acetone phosphate high energy compounds ?

A
  • two high energy compounds bc of their phosphate groups
34
Q

What is Step 5 of glycolysis?

A

Dihydroxyacetone phosphate from step 4 produces glyceraldehyde 3-phosphate
Catalysed by Triose phosphate isomerase (TPI)

35
Q

What type of reaction is step 5 of glycolysis?

A

Isomerisation

36
Q

What happens if you’re deficient in TPI?

A

only glycolyyic enzymopathy that is fatal

Sufferers usually die within first 6 years of their lives

37
Q

What is step 6 of Glycolysis?

A

(2x )G3P forms 1,3 bisphosphoglycerate
At the same time NAD+ is reduced to NADH.
(Means bisphoglycerate is oxidised)
We are also phosphorylating using Pi

38
Q

What enzyme is used in step 6 of glycolysis?

A

Glyceraldehyde 3-phosphate dehydrogenase

39
Q

What type of reaction is step 6 of glycolysis

A

Redox and group transfer

40
Q

Why is NADH Production important in step 6

A

Can be used in oxidative phosphorylation to generate more ATP

41
Q

What is step 7 of glycolysis

A

…

MBC (9 decks)

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