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BSCI330 SPRING > final cellular energetics > Flashcards

final cellular energetics Flashcards

1
Q

why does cellular metabolism occur in a series of small enzyme-catalyzed steps

A

it allows energy to be stored/extracted in useful ways

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2
Q

how do catabolic reactions extract energy

A

through the breakdown of larger molecules into smaller ones

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3
Q

how is glucose catabolized

A

by glycolysis and the citric acid cycle

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4
Q

what glycolysis

A

metabolism of glucose; happens in cytosol

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5
Q

what does the citric acid cycle do

A

allows for further oxidation of glucose using respiration; happens in mitochondria

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6
Q

what are the electrons from glycolysis and the citric acid cycle used for

A

to generate ATP vis the electron transport chain and oxidative phosphorylation

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7
Q

what is catabolism

A

chemical breakdown

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8
Q

where does energy for cellular processes come from

A

catabolism of nutrients

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9
Q

how is energy harvested in useful quantities

A

sugar/other nutrients are oxidized in small, enzyme-catayzed steps

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10
Q

what happens with oxidation

A

electrons are removed

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11
Q

how do enzymes allow energetically favorable reactions to occur

A

by coupling them with energetically unfavorable reactions

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12
Q

what are the two phases of coupling of reactions by enzymes

A

metabolism of food molecule releases some energy and enzymes will couple this with formation of activated carrier molecule, then carrier will interact with other reactions

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13
Q

what is glycolysis at its core

A

take one molecule of glucose and convert it to two molecules of pyruvate with the net production of 2 ATP molecules and 2 NADH molecules

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14
Q

why is NADH referred to as a reducing power

A

because it has electrons available to reduce something else

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15
Q

what is the first phase of glycolysis

A

investment (2 ATP are spent to overcome activation energy barriers and activate glucose)

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16
Q

what is the second phase of glycolysis

A

cleavage (glucose is split into 2 3-carbon sugars)

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17
Q

what is the third phase of glycolysis

A

energy generation (4 ATP molecules are generated from final oxidation of the 3-carbon sugars)

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18
Q

what is reduction

A

addition of electrons - opposite of oxidation

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19
Q

what are the two types of coupling reactions

A

catabolism - energetically favorable
anabolism - energetically unfavorable

both reactions are coupled for ATP

20
Q

what happens in glycolysis

A

one molecule of glucose is converted to two molecules of pyruvate with the net production of 2 ATP and 2 NADH molecules (“reducing power”)

energetically unfavorable

21
Q

why must cells use fermentation

A

in the absence of O2, cells must use fermentation to oxidize NADH or they will run out of NAD+ and be unable to do glycolysis

22
Q

what are the details of glycolysis

A
  • enzyme makes a covalent linkage with substrate
    a high energy bond is then replaced with a phosphate, which is transferred to ADP to make ATP
  • the energy released by hydrolyzing this bond drives the reaction
23
Q

what is substrate-level phosphorylation

A

organic molecule (substrate) phosphorylates ADP to ATP

24
Q

what is oxidative phosphorylation

A

free phosphate is directly attached to ADP without organic compound intermediate

25
Q

what are the two modes of fermentation

A

first leads to excretion of alcohol and CO2, second leads to excretion of lactate

26
Q

how much ATP does glycolysis yield per glucose molecule

A

2 ATP. further pyruvate metabolism will generate more

27
Q

what does glycolysis yield in addition to ATP

A

2 NADH molecules. in the presence of O2, they can be oxidized back to NAD+, which can cycle back to be used for more glycolysis

28
Q

what is NAD+

A

electron acceptor and electron cofactor

29
Q

what happens in the absence of O2

A

cells use fermentation to oxidize NADH, or they’ll run out of NAD+

30
Q

what is fermentation

A

the mechanism cells use to regenerate NAD+ (two types)

31
Q

what is alcoholic fermentation

A

microbes use it to oxidize NADH back to NAD+ so they can continue glycolysis

32
Q

how does alcoholic fermentation occur

A
  • glucose goes through glycolysis to make pyruvate and 2 NADH
  • convert NADH to NAD+ by donating electrons back to pyruvate
  • pyruvate is decarboxylated (2 protons are added are CO2 is given off)
  • regenerate NAD by reducing aldehyde and taking electrons from NADH
  • generates ethanol
33
Q

what is lactic acid fermentation

A

generate pyruvate and 2 NADH and have to regenerate NAD+

34
Q

how does lactic acid fermentation occur

A
  • take electrons and put them directly back on pyruvate at carbonyl group to convert it into hydroxyl group
  • pyruvate is converted to lactate
  • lactate can be oxidized back to pyruvate, which can be reduced back to glucose by liver
35
Q

what is the purpose of lactic acid fermentation

A

allows maintenance of high level of glucose for muscles when only have enough oxygen to do glycolysis

36
Q

what are the two steps that aerobic organisms use to further oxidize pyruvate to CO2 and water

A

citric acid cycle (occurs in matrix) and electron transport chain (occurs in inner mitochondrial membrane)

37
Q

what happens in the citric acid cycle

A
  • 4-carbon molecule + 2-carbon molecule to get 6-carbon molecule
  • then oxidize this and release CO2 to get a 4-carbon molecule again
  • use energy from oxidation to generate NADH/FADH2 molecules and a GTP molecule
38
Q

what does glycolysis need for rearranging

A

glucose and enzymes

39
Q

what are the advantages of biochemical cycles

A
  • greater possibilities for regulation bc there are many steps
  • provides entry pointes for other molecules (in glycolysis, entry points only allow for things related to glucose)
  • lots of molecules are generated that are difficult to make from scratch
40
Q

what are the disadvantages of biochemical cycles (i.e. krebs cycle)

A

you need oxaloacetate for krebs cycle

41
Q

what does the citric acid cycle generate

A

6 NADH and 2 FADH2 per glucose molecule (add that to the 2 NADH from glycolysis + 2 NADH from pyruvate -> Acetyl CoA) = 10 NADH, 2 FADH2

42
Q

how can the energy used to reduce NAD+/FAD be used

A

it can be extracted to generate ATP, done by a proton pump that uses the energy of NADH/FADH2 oxidation to create a proton gradient across the inner mitochondrial matrix

43
Q

what reduction helps drive the formation of the proton gradient

A

the reduction of O2 to H2O provides another energetically favorable reaction

44
Q

what pumps protons out of the mitochondrial matrix

A

NADH and FADH2

45
Q

what is oxidative phosphorylation

A

ADP -> ATP generation by ETC in mitochondria

46
Q

putting it all together with catabolic metabolism

A
  • generate pyruvate in cytosol via glycolysis
  • pyruvate enters mitochondria and is converted to acetyl CoA, which passes thru citric acid cycle
  • generate CO2, NADH
  • electrons from NADH and FADH pass through electron transport chain
  • use oxygen to generate water
  • proton gradient makes ATP

BSCI330 SPRING (24 decks)

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