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BIO 101 EXAM 2 > CHAPTER 9 > Flashcards

CHAPTER 9 Flashcards

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1
Q

how do cells get energy

A

cells get energy from glucose in a series of metabolic pathways

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2
Q

what are the five principles of metabolic pathways

A

-Complex transformations occur in a series of separate reactions.
-Each reaction is catalyzed by a specific enzyme.
-Many metabolic pathways are similar in all organisms.
-In eukaryotes, metabolic pathways are compartmentalized in specific organelles.
-Key enzymes can be inhibited or activated to alter the rate of the pathway.

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3
Q

burning/metabolism of glucose

A

C6H12O6 + 6O2 –> 6CO2 + 6H2O + free energy
ΔG = - 686 kcal/mol
-this is highly exergonic (releasing energy); which drives endergonic formation of many ATP molecules

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4
Q

what are the three catabolic processes that harvest energy from glucose?

A

-glycolysis (anaerobic)
-cellular respiration (aerobic)
-fermentation (anaerobic)

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5
Q

oxidation-reduction (redox) reactions

A

-one substance transfers electrons to another substance
-reduction: gain of electrons (oxidizing agent)
-oxidation: loss of electrons (reducing agent)
-always occur together
-partial transfer also happens

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6
Q

what is oxidized/reduced in glucose metabolism

A

-glucose is the reducing agent meaning it gains and electron
-O2 is the oxidizing agent meaning it losses and electron
-the more reduced a molecule is the more energy it has

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7
Q

transfer of electrons is often associated with what?

A

-with transfer of hydrogen ions: H = H+ + e-
-when a molecules loses H atom it becomes oxidized

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8
Q

what happens to coenzyme NAD+ in redox reactions

A

-it is reduced if it is changing from NAD+ to NADH
-it is oxidized if it is changing from NADH to NAD+

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9
Q

In aerobic conditions, _______?

A

-O2 is available as the final electron acceptor

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10
Q

in anaerobic conditions,_______?

A

-the pyruvate produced by glycolysis is metabolized by fermentation

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11
Q

glycolysis and cellular respiration

A

-glycolysis –> pyruvate oxidation –> citric acid cycle –> electron transport/ ATP synthesis –> products are CO2 and H2O

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12
Q

glycolysis and fermentation

A

-glycolysis –> fermentation –> products are lactate or alcohol

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13
Q

Glycolysis

A

-takes place in the cytoplasm
-converts glucose into 2 molecules of pyruvate
-produces 2 ATP and 2 NADH
-occurs in 10 steps

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14
Q

what happens in steps 1-5 and steps 6-10 of glycolysis

A

-steps 1-5 require ATP
-steps 6-10 produces NADH and ATP

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15
Q

two types of reactions occur repeatedly in many metabolic pathways:

A

-oxidation-reduction: energy released by glucose oxidation is trapped via the reduction of NAD+ to NADH
-substrate-level phosphorylation: energy released transfers a phosphate from the substrate to ADP, forming ATP

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16
Q

pyruvate oxidation

A

-occurs in the mitochondrial matrix
-pyruvate is oxidized to acetate and CO2
-acetate binds to coenzyme A to form acetyl CoA
-exergonic; one NAD+ is reduced to NADH

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17
Q

what does Acetyl CoA do?

A

-acetyl CoA donates its acetyl group to oxaloacetate, forming citrate. this initiates the critic acid cycle

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18
Q

citric acid cycle

A

-acetyl CoA is the starting point
-eight reactions completely oxidizes the acetyl group to 2 molecules of CO2
-energy released is captured by GDP, NAD+, and FAD
-oxaloacetate is regenerated in the last step

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19
Q

citric acid cycle steps (important step 8)

A
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20
Q

what can GTP do?

A

-it can transfer its high-energy phosphate to form ATP

21
Q

overall, the oxidation of one glucose molecules produces what?

A

-6 CO2
-10 NADH
-2 FADH2
-4 ATP

22
Q

for the citric acid cycle to continue what must happen?

A

-the starting molecules (acetyl CoA and oxidized electron carriers) must be replenished

23
Q

oxidative phosphorylation

A

-ATP is synthesized by deoxidation of electron carriers in the presence of O2

24
Q

what are the two components of oxidation phosphorylation?

A

-electron transport
-chemiosmosis

25
Q

electron transport

A

-electrons from NADH and FADH2 pass through the respiratory chain of membrane-associated carriers
-electron flow results in a proton concentration gradient across the inner mitochondrial membrane
-the respiratory chain is located in the folded inner mitochondrial membrane
-energy is released as electrons are passed between carriers

26
Q

chemiosmosis

A

-electrons flow back across the membrane through a channel protein, ATP synthase, which couples the diffusion with ATP synthesis

27
Q

why does the electron transport chain have so many steps?

A

-a single reaction would release too much free energy all at once which would be damaging to organelles and cells
-in a series of reactions, each releases a small amount of energy that can be captured by an endergonic reaction

28
Q

what happens to protons during electron transport? what does this create?

A

-protons (H+) are actively transported into the inter membrane space during electron transport
-this creates a concentration gradient and charge different

29
Q

proton-motion force

A

-this is potential energy
-diffusion of protons back across the membrane is coupled to ATP synthesis (chemiosmosis)

30
Q

what can ATP synthase act as?

A

-it can also act as ATPase, hydrolyzing ATP to ADP and P

31
Q

why is ATP synthesis important?

A

-ATP leaves the metric as soon as it is made, keeping ATP concentration in the matrix low
-H+ gradient is maintained by active transport

32
Q

what was the first experimental evidence of chemiosmosis?

A

-it came from studies on isolated chloroplast thylakoid membranes

33
Q

brown fat cells

A

-in them, a protein called UPC1 inserts into the mitochondrial membrane and makes it permeable to protons.
-This uncouples electron transport and chemiosmosis, and energy is released as heat rather than being trapped in ATP.
-EX: babies have more brown fat cells so they can regulate their temperature

34
Q

ATP synthase in all living organisms

A

-its all the same in all living organisms

35
Q

what organism use anaerobic respiration? what electron acceptors do they use?

A

-many bacteria and archaea
-they use alternate electron acceptors such as SO4 -2, Fe3 +, and CO2
-this allows them to exist where O2 is scarce or absent

36
Q

without O2 how is ATP made?

A

-made by glycolysis and fermentation

37
Q

glycolysis and fermentation

A

-occurs in the cytoplasm
-glucose is only partially oxidized
-2 ATP: 1 glucose are produced by substrate-level phosphorylation
-NAD+ is regenerated to keep glycolysis going

38
Q

lactic acid fermentation

A

-pyruvate is the electron acceptor; lactate is the product
-microorganisms and some complex organisms
-lactate dehydrogenase catalyzes fermentation; in presence of O2, it catalyzes oxidation of lactate to pyruvate

39
Q

other than organisms what also uses lactic acid fermentation?

A

-muscle cells break down glycogen and cary out lactic acid fermentation if O2 cannot be delivered fast enough for aerobic respiration
-causes muscle pain and lowers pH

40
Q

alcoholic fermentation

A

-yeasts and some plant cells
-requires two enzymes to metabolize pyruvate to ethanol
-reactions are reversible
-used to produce alcoholic beverages

41
Q

energy produced difference between cellular respiration and fermentation

A

-glycolysis and fermentation: 2ATP; glucose is only partially oxidized in fermentation which means more energy remains in the products than in CO2
-glycolysis plus cellular respiration: 32 ATP

42
Q

how do metabolic pathways operate?

A

-there is an interchange of molecules in and out of the pathways all the time

43
Q

catabolic interconversions

A

-polysaccharides are hydrolyzed to glucose –> enters glycolysis
-lipids are broken down to
1. glycerol -> DHAP -> glycolysis
2. fatty acids -> acetyl CoA -> citric acid cycle
-proteins are hydrolyzed to amino acids, –> glycolysis or citric acid cycle

44
Q

anabolic interconversions

A

-most catabolic reactions are reversible
-gluconeogenesis: citric acid cycle and glycolysis intermediates are reduced to form glucose “going backward”
-acetyl CoA can be used to form fatty acids

45
Q

what can the critic acid cycle intermediates be used for

A

-can be used to synthesize nucleic acid components

46
Q

how do cells “decide” which pathway to use?

A

-the levels of substances in the metabolic pool are quite constant “balanced”
-organisms regulate enzymes to maintain balance between catabolism and anabolism

47
Q

mechanisms that regulate rates of each steps in a metabolic pathways:

A

-regulating gene expression
-phosphorylation
-feedback inhibition by allosteric enzymes
-substrate availability

48
Q

how is glycolysis and the citric acid cycle regulated?

A

-allosteric regulation of key enzymes
-a high concentration of the final product an inhibit an enzyme making it slow down to stop
-an excess of product of one pathway can activate an enzyme in another pathway

BIO 101 EXAM 2 (4 decks)

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