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5) Post-Harvest > Lecture 2: Respiration > Flashcards

Lecture 2: Respiration Flashcards

1
Q

What are 2 types of respiration?

which yields energy?

A

aerobic and anaerobic

both

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2
Q

what is anaerobic respiration? what does it lead to?

A
  • absence or limited O2

- leads to fermentation and off-flavours (undesirable)

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3
Q

which type of respiration is desirable and yields higher energy?

A

aerobic

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4
Q

respiration rate is expressed in terms of what?

A

O2 consumed, CO2 released or heat liberated per unit wt of the produce in a given time

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5
Q

how much heat energy is released for one glucose molecule?

A

673 kcal

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6
Q

what is the unit that O2 consumed is measured by?

A

mg or mL of O2 / kg (produce) / h

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7
Q

what is the unit that CO2 released is measured by?

A

mg or mL CO2 produced / kg (produce) / h

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8
Q

what is the unit that heat released is measured by?

A

kcal or kJ / ton (produce) / day

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9
Q

what is another name for glycolysis?

A

EMP (Embden-Meyerhof-Parnas) pathway

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10
Q

what is the key enzyme in glycolysis?

A

phospho-hexo-kinase (PFK)

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11
Q

what is PFK inhibited by?

A

excess of ATP

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12
Q

what does glycolysis yield?

A

8 ATPs and pyruvate

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13
Q

in TCA cycle, pyruvate is converted to what?

A

CO2 and H2O

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14
Q

what is the TCA cycle catalyzed by?

A

dehydrogenase enzymes

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15
Q

in TCA, what is used to initiate trapping of energy?

A

nucleotides (NAD, NADP, FAD, GDP, GTP)

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16
Q

what is the final end product of TCA?

A

carboxylic acids (all with 3 C atoms): citric, oxalic, fumaric, succinic

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17
Q

what does NAD stand for?

A

nicotinamide adenine dinucleotide

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18
Q

what does NADP stand for?

A

nicotiniamide adenine dinucleotide phosphate

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19
Q

what does FAD stand for?

A

flavin adenine dinucleotide

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20
Q

what does GDP stand for?

A

guanosine diphosphate

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21
Q

what is another route for glucose breakdown besides glycolysis-TCA?

A

PPP (pentose phosphate pathway)

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22
Q

describe the PPP

A

glucose (6C) enters the pathway and leaves as a pentose (5C), which is required for nucleotide synthesis

one C is released through each cycle

23
Q

how much ATP does the TCA and PPP yield?

which yields more?

A

TCA: 38ATP

PPP: 30 ATP

24
Q

differentiate the number of C of end products in TCA vs PPP.

what does each end product result in?

A

TCA: 3C; results in accumulation of organic acids

PPP: 5C which are needed for nucleotide synthesis

25
Q

what is the first step of anaerobic resp?

A

glycolysis

26
Q

in anaerobic resp, pyruvate is converted to ____ by _____ (enzyme)?

A

pyruvate –> acetaldehyde + CO2 (by decarboxylase)

27
Q

in anaerobic resp, acetaldehyde is converted to ____ by _____ (enzyme)?

A

ethyl alcohol

by alcohol dehydrogenase

28
Q

in anaerobic resp, pyruvate is converted to ____ by ___ (enzyme)?

A

lactic acid

by lactic decarboxylase

29
Q

what are factors influencing produce respiration?

A
  • temp
  • O2 availability
  • CO2 presence
  • ethylene
  • stresses
30
Q

shelf life is inversely proportional to ____

A

resp rate

31
Q

lower respiration rate = _____ (longer/shorter) shelf life

A

longer

32
Q

deterioration ____ (incr/decr) rapidly with resp rate

A

increases

33
Q

what is the most imp factor influencing resp rate? why?

A

temp

  • enzyme activity is influenced by temp
34
Q

what is the temperature quotient of respiration (Q10)?

what is it based on?

A
  • indicator of temp sensitivity

- based on vant Hoff’s law

35
Q

what is the Q10 relationship?

A

Q10 = [ R(T+10C) ] / R(t)

R(t) = resp at temp
R(T+10C) = resp at temp + 10C
36
Q

as fruit growth increases, how does this affect respiration?

A

respiration decreases

37
Q

how does the O2 required for oxidation change between the oxidation of glucose vs oxidation of stearic acid?

A

glucose is a simple sugar and uses 6 O2

stearic acid is a C18 FA and uses 26O2

38
Q

what is RQ? what is it used for?

A
  • respiratory quotient

- used to identify the nature of the respiring substrate

39
Q

what is the RQ equation?

how does RQ change depending on the nature of the substrate?

A

RQ = CO2 produced / O2 consumed

RQ = 1 for simple CHO
RQ > 1 for organic acids
RQ < 1 for FAs

40
Q

unusually high RQ indicates what?

unusually low RQ may indicate what?

A

onset of anaerobic resp

incomplete oxidation to CO2

41
Q

how does the availability of O2 affect the RR?

A

O2 level higher than 21%: no increase in RR

O2 level lower than 20%: decreases the RR

42
Q

what is EP?

A
  • extinction point

- the minimum O2 level to maintain aerobic respiration in storage

43
Q

excess of CO2 will ____ RR

A

suppress

44
Q

what is the result of higher concentration of CO2?

A

fungicidal effect

45
Q

what are the effects of using growth regulators?

A

influences product quality and RR

46
Q

what are examples of growth regulators? what are they used for?

A

Alar: delay or accelerate ripening; improvement of color

GA: higher yield or greater disease resistance

NAA prevention of abscission

MH: sprouting inhibition

47
Q

injuries to produce will result in what? why?

what type of injuries does this include?

A

slowing of RR; b/c injuries allows normally separated enzymes and substrates to come into contact, which triggers certain biochemical rxns

  • chilling injury
  • freezing injury
  • physical and mechanical damages
48
Q

what are ways to control resp activity?

A
  1. temp control
  2. harvesting at right maturity
  3. reducing the availability of O2
  4. adding Co2 to environment
  5. avoid ethylene
49
Q

what are ways to control temp to control resp activity?

A
  • harvest at cool times
  • cool and cold store as fast as possible
  • maintain lowest permissible temp
  • maintain cold storage properly
50
Q

how can you reduce the O2 availability to control resp activity?

A
  • use controlled atmosphere (CA) storage

- use appropriate coating or packaging (MAP)

51
Q

how can you add CO2 to environment to control resp activity?

A
  • use CA storage
  • use excess CO2 where permissible
  • remove excess CO2 where not beneficial
52
Q

what does a manometer measure?

A

pressure

53
Q

what are 3 ways to measure RR?

A
  1. electronic sensors: senses O2 or CO2
  2. pressure sensors: using a manometer
  3. chemical measurements: using sodium hydroxide
54
Q

how does potassium permanganate help to control resp activity?

A

it absorbs ethylene

5) Post-Harvest (17 decks)

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