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PSIO 258: Elementary Physiology I > Cellular Metabolism > Flashcards

Cellular Metabolism Flashcards

1
Q

What is metabolism?

A

the sum of all chemical reactions occurring in a cell

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2
Q

What are chemical reactions?

A
  • reactants (or substrates) –> products

A + B –> C + D

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3
Q

Describe the directions of reaction.

A
  • forward (reactants transformed into products)
  • reverse (products transformed into reactants)
  • chemical reactions are bidirectional
    A + B C + D
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4
Q

What are metabolic reactions?

A

chemical reactions occurring in the body

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5
Q

What is catabolism?

A

breakdown of larger molecules into smaller molecules

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6
Q

What is anabolism?

A

synthesis of larger molecules from smaller reactants

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7
Q

Describe the metabolic pathway.

A

A–> B–> C–> D (intermediates along the way)

  • initial substrate
  • intermediates
  • end product
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8
Q

Metabolic reactions have ____ ______ and _____ ______ reactions.

A
  • energy releasing

- energy requiring

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9
Q

What is energy?

A

capacity to do work

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10
Q

Name the 2 forms of energy.

A
  • kinetic energy

- potential energy

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11
Q

Describe kinetic energy.

A
  • associated with motion

- thermal, radiant, electromagnetic, electrical

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12
Q

Describe potential energy.

A
  • stored energy
  • don’t have more than enough work for 2-3 seconds
  • chemical, mechanical, nuclear, gravitational
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13
Q

Energy releasing reactions are called ______ reactions.

A

exergonic reactions

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14
Q

Describe energy releasing reactions.

A
  • catabolic
  • proceeds spontaneously
  • released energy may power an energy requiring reaction (ex. breakdown of phosphocreatine, glycolysis, body cells transporting ions)
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15
Q

All reactions involve ____________________.

A

an exchange of energy

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16
Q

____ possess more energy than ______.

A

reactants, products

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17
Q

What is the equation for change of energy in a reaction?

A

Δ​E​​ ​=​ ​​E​products​​ ​–​ ​​E​reactants

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18
Q

Energy requiring reactions are called ______ reactions.

A

endergonic reaction

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19
Q

Describe energy requiring reactions.

A
  • anabolic
  • does not proceed spontaneously
  • energy input required
    Reactants​ ​+​ ​Energy​ ​→​ ​Products
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20
Q

What is the unit of energy?

A
  • ΔE​ ​expressed​ ​in​ ​calories​ ​(cal)​ ​or​ ​joules​ ​(J)
  • 1​ ​cal​ ​=​ ​4.18​ ​J
  • 1​ ​cal​ ​=​ ​energy​ ​required​ ​to​ ​raise​ ​the​ ​temperature​ ​of​ ​1​ ​mL​ ​of​ ​water​ ​by​ ​1​ ​degree​ ​C
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21
Q

Describe chemical equilibrium.

A

reactant product

  • rate of forward and reverse reactions are equal
  • no net charge in concentration of product or reactants
  • ΔE​ ​=​ ​zero
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22
Q

Increased reactant concentration pushes a reaction _____.

A

forward

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23
Q

Increased product concentration pushes a reaction in _____.

A

reverse

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24
Q

What reduces the activation energy barrier?

A

enzymes

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25
Q

energy of barrier = ______ ______

A

activation energy

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26
Q

What limits how fast a reaction goes?

A

activation energy barrier

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27
Q

What are the 6 factors that affect reaction rate?

A
  • reactant and product concentrations
  • temperature (hypothermia and hyperthermia)
  • height of activation energy barrier (decreased height = increased rate, increased height = decreased rate)
  • reactant and product concentrations (law of mass action)
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28
Q

What do catalysts do in chemical reactions?

A
  • proteins that are catalysts​ ​for​ ​reactions​ ​in​ ​biological​ ​systems
  • catalysts​ ​increase​ ​the​ ​rates​ ​of​ ​chemical​ ​reactions
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29
Q

What are the roles of enzymes in chemical reactions?

A
  • catalysts
  • decrease the activation energy
  • enzymes are specific for one set of substrates or a group of similar substrates
  • constant (not changed or consumed in the reaction)
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30
Q

Enzymes have the suffix …

A

…ase

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31
Q

What are the 2 models of substrate specificity?

A
  • lock and key model

- induced fit model

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32
Q

Describe the lock and key model.

A
  • perfect fit

- cannot explain the reversibility of most enzyme reactions

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33
Q

Describe the induced fit model.

A
  • Active​ ​site​ ​approximately​ ​fits​ ​substrates
  • As​ ​the​ ​substrate​ ​begins​ ​to​ ​bind,​ ​a​ ​conformational​ ​change​ ​in​ ​the​ ​enzyme​ ​allows​ ​it​ ​to​ ​fit
    better
34
Q

What are cofactors?

A
  • ions or molecules required by an enzyme for the enzyme to be active
  • trace metals: Mg, Cu, Zn, Fe
  • allow the substrate to bind to the active site
35
Q

What are coenzymes?

A
  • vitamins

- transfer small chemical groups

36
Q

What is used to synthesize adenosine triphosphate (ATP)?

A

energy from exergonic reactions

37
Q

Describe ATP synthesis.

A

ADP​ ​+​ ​Pi​ ​+​ ​Energy​ ​→​ ​ATP​ ​(+H20)

  • A​ ​condensation​ ​reaction​ ​(water​ ​is​ ​produced)
  • A​ ​phosphorylation​ ​reaction​ ​(phosphate​ ​is​ ​used)
  • Substrate-level​ ​phosphorylation
38
Q

What is the formula for substrate level phosphorylation?

A

X-P​ ​+​ ​ADP​ ​→​ ​X​ ​+​ ​ATP

39
Q

Oxidative phosphorylation requires:

A

electron transport chain

ADP​ ​+​ ​Pi​ ​→​ ​ATP

40
Q

Describe ATP breakdown.

A

ATP​ ​(+H20)​ ​→​ ​ADP​ ​+​ ​Pi​ ​+​ ​energy

  • temporary energy storage
  • hydrolysis reaction (water is used)
41
Q

What are the stages of glucose oxidation?

A
  • glycolysis
  • Krebs cycle
  • oxidative phosphorylation
  • electron transport chain
42
Q

In glycolysis, what does glucose/glycogen turn into?

A

2 pyruvate molecules

43
Q

Glucose comes from…

A

carbohydrates in blood, can move it into cell

44
Q

What is glycogen?

A
  • glucose molecules stuck together

- stored in muscle and liver

45
Q

How many ATP are produced from glycogen and how many from glucose?

A
  • glycogen: 3 ATP

- glucose: 2 ATP

46
Q

When is glycolysis needed?

A

when we need ATP quickly

47
Q

How many steps are in glycolysis? Where does it take place?

A
  • 10 steps

- cytosol

48
Q

What is the net gain of glycolysis?

A
  • 2 or 3 ATP
  • 2 NADH molecules
  • no O2 consumed/no CO2 produced
49
Q

Show the formula for glycolysis.

A

Glucose​ ​+​ ​2NAD++2ADP+2Pi​ ​→​ ​2​ ​pyruvate​ ​+​ ​2​ ​NADH​ ​+​ ​2H++​ ​2ATP

50
Q

How does glycolysis link to the Krebs cycle?

A
  • pyruvate turns into acetyl CoA
  • unidirectional
  • 1 NADH molecule produced (per pyruvate molecule)
  • 1 CO2 per pyruvate
  • acetyl group comes from CHO, fat, or protein breakdown
51
Q

Where is CoA synthesized?

A

in the body

52
Q

What is the initial substrate for the Kreb’s cycle?

A

acetyl CoA

53
Q

What is produced per each acetyl CoA?

A
  • 1​ ​GTP​ ​produced​ ​=​ ​1​ ​ATP

- 3​ ​NADH​ ​+​ ​3H+​ ​and​ ​1​ ​FADH2

54
Q

What waste is produced per each acetyl CoA?

A

2CO2

55
Q

Glucose generates ____ acetyl CoA molecules, thus the cycle turns ______.

A
  • 2 acetyl CoA

- twice

56
Q

What are the reducing equivalents in oxidative phosphorylation?

A

electron carriers (NADH and FADH2)

57
Q

Glycolysis and Krebs cycle = net gain of ____.

A

4 ATP

58
Q

Bulk of ATP is formed in _______.

A

ETC

59
Q

Movement of electrons down the ETC is used to…

A

synthesize ATP.

60
Q

Oxidative phosphorylation requires ______.

A

oxygen

61
Q

What is the electron transport system? Where is it located?

A
  • chain of molecules

- inner mitochondrial membrane

62
Q

What kind of reactions do molecules undergo in the ETC?

A
  • oxidation-reduction reactions

- from high to low energy

63
Q

Energy released from the ETC is used to…

A

synthesize ATP by oxidative phosphorylation

64
Q

What is the last electron accepter in the ETC?

A

O2

65
Q

Why does glucose catabolism occur in the absence of oxygen? What happens?

A
  • low oxygen availability
  • electron transport in chain backs up
  • Krebs cycle stops
  • Glycolysis​ ​can​ ​progress​ ​only​ ​if​ ​NADH​ ​is​ ​oxidized
  • lactate is synthesized
66
Q

Describe the conversion of pyruvate to lactate.

A
  • muscles can operate with low O2
  • ATP production inefficient
  • lactate accumulation
67
Q

What happens when O2 levels return?

A
  • lactate –> pyruvate

- oxidative phosphorylation continues

68
Q

What else converts lactate back into pyruvate?

A

Cori cycle in liver

69
Q

What is glycogen metabolism?

A

liver glycogen provides glucose for other cells/organs

70
Q

Glucose can leave the cell, with the exception of ____________.

A

glucose-6-phosphate

71
Q

What is glycogenolysis?

A

breakdown of glycogen to glucose-6-phosphate and glycogen

72
Q

The liver has ​glucose-6-phosphatase​ ​(enzyme), which does what.

A
  • converts​ ​G-6-P​ ​to​ ​glucose

- muscle​ ​does​ ​not​ ​contain​ ​this​ ​enzyme

73
Q

What is gluconeogenesis?

A
  • synthesis​ ​of​ ​new​ ​glucose
  • mainly in the liver
  • other enzymes are involved (not a reverse of glycolysis)
74
Q

What are the substrates involved with gluconeogenesis?

A
  • glycerol
  • lactate
  • amino acids
75
Q

Most energy is stored as…

A

triglycerides

76
Q

triglycerides = _______ + _______

A

3 fatty acids + glycerol

77
Q

lipids = _ kcal/g

carbohydrates or proteins = ~_ kcal/g

A
  • 9 kcal/g

- ~4 kcal/g

78
Q

Where are triglycerides stored?

A

adipocytes

79
Q

What happens in lipolysis?

A

Triglycerides​ ​+​ ​lipases​ ​→​ ​glycerol​ ​+​ ​3​ ​fatty​ ​acids
Glycerol​ ​→​ ​glycolysis (20 ATP)
Fatty​ ​acids​ ​→​ ​beta-oxidation

80
Q

Why does deamination of amino acids occur?

A

for energy

81
Q

What is proteolysis?

A

Proteins​ ​→​ ​amino​ ​acids

82
Q

What happens in deamination?

A

Amino​ ​group​ ​(–​ ​NH2)​ ​removed
→​ ​keto​ ​acid​ ​+​ ​ammonia​ ​(NH3)
Keto​ ​acid​ ​=​ ​pyruvate​ ​or​ ​acetyl​ ​CoA​ ​→​ ​Krebs​ ​cycle

PSIO 258: Elementary Physiology I (14 decks)

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