Respiration

Question 1

What is respiration?

Answer 1

oxidation of organic matter (sugars, starch, fats, proteins) -> breakdown of bigger molecules -> CO2, H2O, ENERGY

Question 2

True/False: respiration in produce is bad, it should be prevented

Answer 2

False: both good and bad effects

require some respiration to maintain quality

Question 3

What are benefits of respiration?

Answer 3

produce energy
produce intermediate products
maintain tissue vigor

Question 4

What are negative effects of respiration?

Answer 4

organic matter degraded -> loss of food value
aging
weight loss (lose $ value)
quality loss

Question 5

The respiration level should be _____ to prevent the negative effects, but maintain _____.

Answer 5

minimized; maintain life of produce

Question 6

The 2 types of respiration:

Answer 6

aerobic

anaerobic

Question 7

Compare aerobic and anaerobic respiration in produce. Which is desirable?

Answer 7

aerobic: require oxygen, higher energy yield (GOOD)
anaerobic: no oxygen (fermentation), lower energy yield, produce off-flavors (BAD)

Question 8

The energy currency of cells:
Produced through ____
Used for ____

Answer 8

ATP (adenosine tri-phosphate)
catabolism
synthesis

Question 9

Simplified aerobic respiration equation:

Answer 9

glucose + 6 oxygen => 6 CO2 + 6 water + 673 kcal

180g glucose, 192g O2, 264g CO2, 108g water

Question 10

respiration rate can be expressed as: (3)

Answer 10

oxygen consumed (mg or mL/kg/hr), CO2 produced (mg or mL/kg/h), heat produced (kcal or kJ/ton/day)

Question 11

the steps of aerobic respiration require: (3)

Answer 11

oxygen
inorganic phosphate
enzymes, cofactors, metal ions, etc
substrates

Question 12

2 major pathways of aerobic respiration:

Answer 12

1. glycolysis (EMP pathway)

2. TCA cycle

Question 13

In the glycolytic pathway, glucose is converted to ____.
This process is (aerobic/anaerobic).
Limiting enzyme is _____
It produces ___ ATP.

Answer 13

2 pyruvate
anaerobic
PFK (inhibit by high ATP)
8 ATP

Question 14

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.

Answer 14

CO2, water
enzymes/coenzymes, DEHYDROGENASE enzymes
ETC
NAD, NADP, FAD, GDP/GTP; to trap energy
organic acids (citric, fumaric, succinic, oxalic)

Question 15

How do fats, polysaccharides, proteins participate in respiration?

Answer 15

can be broken down to simple sugars

or enter cycle at different stages

Question 16

What is another possible pathway for carb breakdown?What occurs, and what is produced?

Answer 16

Pentose Phosphate Pathway
6-carbon (glucose) enter -> convert to 5-carbon
-> important for nucleotide synth
(releases 1 C in cycle)

Question 17

limiting enzyme for PPP:

Answer 17

G6P dehydrogenase

Question 18

Which pathway produces the most ATP?

Answer 18

TCA (38 ATP)

PPP only has 30 ATP

Question 19

What happens in the respiration pathway if oxygen is not present? What is produced?

Answer 19

glycolysis can still occur; followed by fermentation

pyruvate -> acetaldehyde + CO2 -> ethyl alcohol
OR pyruvate -> lactic acid

Question 20

What controllable factors affect respiration?

Answer 20

temperature
gas environment (CO2, O2)
ethylene
growth regulators
stress

Question 21

What uncontrollable factors affect respiration?

Answer 21

commodity type, variety
maturity
nature of substrates
climacteric behaviour

Question 22

How does shelf life relate to respiration rate?

Answer 22

inversely proportional

Question 23

most important factor affecting respiration:

Why?

Answer 23

temperature

respiration requires enzymes, which are influenced by temperature

Question 24

What is the Q10 rule?

Answer 24

for every 10 degrees C increase, the reaction rate doubles

Question 25

What is a climacteric fruit?

Answer 25

respiration rate will increase during ripening (peak)

Question 26

True/False: all climacteric fruits show the same peak

Answer 26

False: all will show a peak, but occur at different times, different extent

Question 27

How does nature of the substrate affect respiration?

Answer 27

substrates oxidized differently

glucose vs malic acid vs fatty acid

Question 28

How does oxidation of malic acid or stearic acid compare to glucose?

Answer 28

organic acid: require less O2, produce less CO2 and heat

fatty acid: require more O2, produce more CO2 and heat

Question 29

What it used to identify what substrate is being oxidized?

Answer 29

RQ (respiratory quotient)

Question 30

How is RQ calculated?

Answer 30

RQ = CO2 produced/O2 consumed

Question 31

If RQ > 1, then: _____
if RQ = 1, then: _____
if RQ < 1, then: _____

Answer 31

organic acids being oxidized
glucose being oxidized
fats being oxidized

Question 32

What does a high RQ suggest?

What does a low RQ suggest?

Answer 32

high: anaerobic oxidation
low: incomplete oxidation

Question 33

True/False: O2 levels above normal (21%) will increase respiration

Answer 33

False

Only lowering has effect (lower resp)

Question 34

CO2 should be (increased/decreased) to lower respiration. What are other effects?

Answer 34

increased

fungicidal at higher concentrations

Question 35

The lowest level of O2 needed to ______ is called the ______.

Answer 35

maintain aerobic respiration

extinction point

Question 36

What effect does ethylene have?

Answer 36

climacteric: make ripen faster
nonclimacteric: increase respiration during ripening

Question 37

What are some growth regulators and their effects?

Answer 37

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

Question 38

What types of injuries can occur to produce? How does this affect respiration and why?

Answer 38

physical/mechanical damage
freezing damage
chilling injury

damage membranes, flesh -> enzymes in contact with substrates

Question 39

How can ethylene be removed from storage rooms?

Answer 39

K permanganate, activated charcoal

Question 40

How is respiration monitored?

Answer 40

electronic sensors (measure CO2 or O2)
pressure sensors (manometer, lime)
chemical sensors (regulate airflow, NaOH)