Respiration Flashcards
What is respiration?
oxidation of organic matter (sugars, starch, fats, proteins) -> breakdown of bigger molecules -> CO2, H2O, ENERGY
True/False: respiration in produce is bad, it should be prevented
False: both good and bad effects
require some respiration to maintain quality
What are benefits of respiration?
produce energy
produce intermediate products
maintain tissue vigor
What are negative effects of respiration?
organic matter degraded -> loss of food value
aging
weight loss (lose $ value)
quality loss
The respiration level should be _____ to prevent the negative effects, but maintain _____.
minimized; maintain life of produce
The 2 types of respiration:
aerobic
anaerobic
Compare aerobic and anaerobic respiration in produce. Which is desirable?
aerobic: require oxygen, higher energy yield (GOOD)
anaerobic: no oxygen (fermentation), lower energy yield, produce off-flavors (BAD)
The energy currency of cells:
Produced through ____
Used for ____
ATP (adenosine tri-phosphate)
catabolism
synthesis
Simplified aerobic respiration equation:
glucose + 6 oxygen => 6 CO2 + 6 water + 673 kcal
180g glucose, 192g O2, 264g CO2, 108g water
respiration rate can be expressed as: (3)
oxygen consumed (mg or mL/kg/hr), CO2 produced (mg or mL/kg/h), heat produced (kcal or kJ/ton/day)
the steps of aerobic respiration require: (3)
oxygen
inorganic phosphate
enzymes, cofactors, metal ions, etc
substrates
2 major pathways of aerobic respiration:
- glycolysis (EMP pathway)
2. TCA cycle
In the glycolytic pathway, glucose is converted to ____.
This process is (aerobic/anaerobic).
Limiting enzyme is _____
It produces ___ ATP.
2 pyruvate
anaerobic
PFK (inhibit by high ATP)
8 ATP
In the TCA cycle, pyruvate is converted to ___.
It involves many ____, especially ______
and the transfer of electrons in the _____.
It uses nucleotides such as _____ to ______.
Throughout the cycle, various ____ are formed.
CO2, water enzymes/coenzymes, DEHYDROGENASE enzymes ETC NAD, NADP, FAD, GDP/GTP; to trap energy organic acids (citric, fumaric, succinic, oxalic)
How do fats, polysaccharides, proteins participate in respiration?
can be broken down to simple sugars
or enter cycle at different stages
What is another possible pathway for carb breakdown?What occurs, and what is produced?
Pentose Phosphate Pathway
6-carbon (glucose) enter -> convert to 5-carbon
-> important for nucleotide synth
(releases 1 C in cycle)
limiting enzyme for PPP:
G6P dehydrogenase
Which pathway produces the most ATP?
TCA (38 ATP)
PPP only has 30 ATP
What happens in the respiration pathway if oxygen is not present? What is produced?
glycolysis can still occur; followed by fermentation
pyruvate -> acetaldehyde + CO2 -> ethyl alcohol
OR pyruvate -> lactic acid
What controllable factors affect respiration?
temperature gas environment (CO2, O2) ethylene growth regulators stress
What uncontrollable factors affect respiration?
commodity type, variety
maturity
nature of substrates
climacteric behaviour
How does shelf life relate to respiration rate?
inversely proportional
most important factor affecting respiration:
Why?
temperature
respiration requires enzymes, which are influenced by temperature
What is the Q10 rule?
for every 10 degrees C increase, the reaction rate doubles
What is a climacteric fruit?
respiration rate will increase during ripening (peak)
True/False: all climacteric fruits show the same peak
False: all will show a peak, but occur at different times, different extent
How does nature of the substrate affect respiration?
substrates oxidized differently
glucose vs malic acid vs fatty acid
How does oxidation of malic acid or stearic acid compare to glucose?
organic acid: require less O2, produce less CO2 and heat
fatty acid: require more O2, produce more CO2 and heat
What it used to identify what substrate is being oxidized?
RQ (respiratory quotient)
How is RQ calculated?
RQ = CO2 produced/O2 consumed
If RQ > 1, then: _____
if RQ = 1, then: _____
if RQ < 1, then: _____
organic acids being oxidized
glucose being oxidized
fats being oxidized
What does a high RQ suggest?
What does a low RQ suggest?
high: anaerobic oxidation
low: incomplete oxidation
True/False: O2 levels above normal (21%) will increase respiration
False
Only lowering has effect (lower resp)
CO2 should be (increased/decreased) to lower respiration. What are other effects?
increased
fungicidal at higher concentrations
The lowest level of O2 needed to ______ is called the ______.
maintain aerobic respiration
extinction point
What effect does ethylene have?
climacteric: make ripen faster
nonclimacteric: increase respiration during ripening
What are some growth regulators and their effects?
Alar: change timing of ripening, improve color
GA: disease resistance, better yield
NAA: prevent detachment from tree, fruit thinning
MH: inhibit sprouting
Epthephon: fruit thinning
What types of injuries can occur to produce? How does this affect respiration and why?
physical/mechanical damage
freezing damage
chilling injury
damage membranes, flesh -> enzymes in contact with substrates
How can ethylene be removed from storage rooms?
K permanganate, activated charcoal
How is respiration monitored?
electronic sensors (measure CO2 or O2) pressure sensors (manometer, lime) chemical sensors (regulate airflow, NaOH)
