Lecture 2: Respiration Flashcards
What are 2 types of respiration?
which yields energy?
aerobic and anaerobic
both
what is anaerobic respiration? what does it lead to?
- absence or limited O2
- leads to fermentation and off-flavours (undesirable)
which type of respiration is desirable and yields higher energy?
aerobic
respiration rate is expressed in terms of what?
O2 consumed, CO2 released or heat liberated per unit wt of the produce in a given time
how much heat energy is released for one glucose molecule?
673 kcal
what is the unit that O2 consumed is measured by?
mg or mL of O2 / kg (produce) / h
what is the unit that CO2 released is measured by?
mg or mL CO2 produced / kg (produce) / h
what is the unit that heat released is measured by?
kcal or kJ / ton (produce) / day
what is another name for glycolysis?
EMP (Embden-Meyerhof-Parnas) pathway
what is the key enzyme in glycolysis?
phospho-hexo-kinase (PFK)
what is PFK inhibited by?
excess of ATP
what does glycolysis yield?
8 ATPs and pyruvate
in TCA cycle, pyruvate is converted to what?
CO2 and H2O
what is the TCA cycle catalyzed by?
dehydrogenase enzymes
in TCA, what is used to initiate trapping of energy?
nucleotides (NAD, NADP, FAD, GDP, GTP)
what is the final end product of TCA?
carboxylic acids (all with 3 C atoms): citric, oxalic, fumaric, succinic
what does NAD stand for?
nicotinamide adenine dinucleotide
what does NADP stand for?
nicotiniamide adenine dinucleotide phosphate
what does FAD stand for?
flavin adenine dinucleotide
what does GDP stand for?
guanosine diphosphate
what is another route for glucose breakdown besides glycolysis-TCA?
PPP (pentose phosphate pathway)
describe the PPP
glucose (6C) enters the pathway and leaves as a pentose (5C), which is required for nucleotide synthesis
one C is released through each cycle
how much ATP does the TCA and PPP yield?
which yields more?
TCA: 38ATP
PPP: 30 ATP
differentiate the number of C of end products in TCA vs PPP.
what does each end product result in?
TCA: 3C; results in accumulation of organic acids
PPP: 5C which are needed for nucleotide synthesis
what is the first step of anaerobic resp?
glycolysis
in anaerobic resp, pyruvate is converted to ____ by _____ (enzyme)?
pyruvate –> acetaldehyde + CO2 (by decarboxylase)
in anaerobic resp, acetaldehyde is converted to ____ by _____ (enzyme)?
ethyl alcohol
by alcohol dehydrogenase
in anaerobic resp, pyruvate is converted to ____ by ___ (enzyme)?
lactic acid
by lactic decarboxylase
what are factors influencing produce respiration?
- temp
- O2 availability
- CO2 presence
- ethylene
- stresses
shelf life is inversely proportional to ____
resp rate
lower respiration rate = _____ (longer/shorter) shelf life
longer
deterioration ____ (incr/decr) rapidly with resp rate
increases
what is the most imp factor influencing resp rate? why?
temp
- enzyme activity is influenced by temp
what is the temperature quotient of respiration (Q10)?
what is it based on?
- indicator of temp sensitivity
- based on vant Hoff’s law
what is the Q10 relationship?
Q10 = [ R(T+10C) ] / R(t)
R(t) = resp at temp R(T+10C) = resp at temp + 10C
as fruit growth increases, how does this affect respiration?
respiration decreases
how does the O2 required for oxidation change between the oxidation of glucose vs oxidation of stearic acid?
glucose is a simple sugar and uses 6 O2
stearic acid is a C18 FA and uses 26O2
what is RQ? what is it used for?
- respiratory quotient
- used to identify the nature of the respiring substrate
what is the RQ equation?
how does RQ change depending on the nature of the substrate?
RQ = CO2 produced / O2 consumed
RQ = 1 for simple CHO
RQ > 1 for organic acids
RQ < 1 for FAs
unusually high RQ indicates what?
unusually low RQ may indicate what?
onset of anaerobic resp
incomplete oxidation to CO2
how does the availability of O2 affect the RR?
O2 level higher than 21%: no increase in RR
O2 level lower than 20%: decreases the RR
what is EP?
- extinction point
- the minimum O2 level to maintain aerobic respiration in storage
excess of CO2 will ____ RR
suppress
what is the result of higher concentration of CO2?
fungicidal effect
what are the effects of using growth regulators?
influences product quality and RR
what are examples of growth regulators? what are they used for?
Alar: delay or accelerate ripening; improvement of color
GA: higher yield or greater disease resistance
NAA prevention of abscission
MH: sprouting inhibition
injuries to produce will result in what? why?
what type of injuries does this include?
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
what are ways to control resp activity?
- temp control
- harvesting at right maturity
- reducing the availability of O2
- adding Co2 to environment
- avoid ethylene
what are ways to control temp to control resp activity?
- harvest at cool times
- cool and cold store as fast as possible
- maintain lowest permissible temp
- maintain cold storage properly
how can you reduce the O2 availability to control resp activity?
- use controlled atmosphere (CA) storage
- use appropriate coating or packaging (MAP)
how can you add CO2 to environment to control resp activity?
- use CA storage
- use excess CO2 where permissible
- remove excess CO2 where not beneficial
what does a manometer measure?
pressure
what are 3 ways to measure RR?
- electronic sensors: senses O2 or CO2
- pressure sensors: using a manometer
- chemical measurements: using sodium hydroxide
how does potassium permanganate help to control resp activity?
it absorbs ethylene
