13.34: Respiration - Biology

Where does oxygen get into blood?

Red blood cells are like trucks that transport cargo on a highway system. Their cargo is oxygen, and the highways are blood vessels. Where do red blood cells pick up their cargo of oxygen? The answer is the lungs. The lungs are organs of the respiratory system. The respiratory system is the body system that brings air containing oxygen into the body and releases carbon dioxide into the atmosphere.


The job of the respiratory system is the exchange of gases between the body and the outside air. This process, called respiration, actually consists of two parts. In the first part, oxygen in the air is drawn into the body and carbon dioxide is released from the body through the respiratory tract. In the second part, the circulatory system delivers the oxygen to body cells and picks up carbon dioxide from the cells in return. The lungs are organs of the respiratory system. It is in the lungs where oxygen is transferred from the respiratory system to the circulatory system.

The use of the word “respiration” in relation to gas exchange is different from its use in the term cellular respiration. Recall that cellular respiration is the metabolic process by which cells obtain energy by “burning” glucose. Cellular respiration uses oxygen and releases carbon dioxide. Respiration by the respiratory system supplies the oxygen and takes away the carbon dioxide.

  • Respiration is the process in which gases are exchanged between the body and the outside air.
  • The lungs and other organs of the respiratory system bring oxygen into the body and release carbon dioxide into the atmosphere.


  1. What is respiration?
  2. Describe the two parts of respiration.
  3. How is respiration different from cellular respiration?

1) The energy releasing process in which the substrate is oxidised without an external electron acceptor is called?
a) Aerobic respiration b) Glycolysis
c) Fermentation d) Photorespiration

2) How many net ATP molecules are obtained from fermentation of 1 molecule of glucose?
a) 2 b) 4
c) 3 d) 5

3) In anaerobic respiration, from one glucose molecule how many total ATP molecules are formed?
a) 2 b) 8
c) 6 d) 4

4) The incomplete breakdown of sugars in anaerobic respiration results in the formation of?
a) Fructose and water
b) Glucose and CO2
c) Alcohol and CO2
d) Water and CO2

5) When a molecule of pyruvic acid is subjected to anaerobic oxidation and forms lactic acid, there is?
a) Loss of 3 ATP molecules
b) Loss of 6 ATP molecules
c) Gain of 2 ATP molecules
d) Gain of 4 ATP molecules

6) During cellulose fermentation by anaerobic bacteria in rumen and reticulum, cellulose is majorly converted into?
a) Lactic acid b) Ethyl alcohol
c) Volatile acids d) CO2

7) Fermentation is?
a) Anaerobic respiration after glycolysis outside cell
b) Incomplete oxidation of carbohydrate inside matrix
c) Complete oxidation of carbohydrates
d) None of the above

8) Which of the following minerals activate the enzymes involved in respiration?
a) Nitrogen and phosphorus
b) Magnesium and manganese
c) Potassium and calcium
d) Sulphur and iron

9) During anaerobic respiration in yeast?
a) Water and CO2 are end products
b) CO2, C2H5OH and energy are end products
c) H2S, C6H12O6 and energy the end products
d) H2O, CO2 and energy are the only end products

10) During anaerobic respiration the conversion of pyruvate into acetaldehyde, along with co-enzyme TPP, the cofactor required is?
a) Na+
b) Mn++
c) Fe++
d) Zn++

11) During lactic acid fermentation, ………….
a) O2 is used, CO2 is liberated
b) Neither O2 is used, nor CO2 is liberated
c) O2 is used, CO2 is not liberated
d) O2 is not used, CO2 is liberated

12) When protein is aerobically oxidized the RQ (Respiration Quotient) value will be?
a) One b) Zero
c) More than one d) Less than one

13) There is no direct transfer of electron from cyt b to cyt c as?
a) Energy is not available
b) The two are not nearby
c) Electrons are transported in pairs
d) Electrons have no affinity for cytochromes.

14) Number of oxygen atoms required for complete oxidation of pyruvic acid is?
a) 6 b) 12
c) 3 d) 0

15) Which of the following biomolecules is common to respiration-mediated breakdown of fats, carbohydrates and proteins?
a) Pyruvic acid
b) Acetyl CoA
c) Glucose-6-phosphate
d) Fructose 1,6-bisphosphate

16) Which of the following metabolites enter the TCA cycle during glucose oxidation?
a) Oxaloacetic acid
b) Pyruvic acid
c) Acetyl CoA
d) Malic acid

17) Electrons from NADH produced in the mitochondrial matrix during citric acid cycle are oxidized by?
a) Complex II b) Complex III
c) Complex I d) Complex IV

18) There are various types of ATPase pump found in different types of cells of these, F-type,ATPase, also are found in all of the following except?
a) Inner membrane of mitochondria
b) Thylakoid membrane of chloroplasts
c) Plasma membrane of fungi
d) All are correct

19) Which statement is wrong for Kreb’s cycle?
a) There is one point in the cycle where FAD+ is reduced to FADH2
b) During conversion of succinyl CoA to succinic acid, a molecule of GTP is synthesised
c) The cycle starts with condensation of acetyl group(acetyl CoA) with pyruvic acid to yield cirtic acid
d) There are three points in the cycle where NAD+ is reduced to NADH + H+

20) A glucose fed yeast cell is moved an aerobic environment to an anaerobic one. For the cell continue generating ATP at the same rate, of glucose consumption should increase?
a) 2 times b) 4 times
c) 19 times d) 38 times

21) Which of the following enzymes involved in Kreb’s cycle is not present in the mitochondrial matrix?
a) Aconitase b) Malate dehydrogenase
c) Fumarase d) Succinate dehydrogenase

22) HMP shunt is a set of reactions?
a) Cyanide resistant pathway
b) Which bypasses EMP route of glucose oxidation
c) Both of the above
d) Which converts glucose to phosphoglycerate

23) Pentose phosphate pathway, an alternative pathway of respiration was elucidated by?
a) Horecker b) Warburg and Dickens
c) Blackman d) Kelvin

24) In hexose monophosphate shunt, the number of CO2 moelcules evolved is?
a) Same as in glycolysis
b) Less than glycolysis
c) More than glycolysis
d) Much lesser than glycolysis

25) Which of the following is produced in oxidative pentose phosphate pathway?
a) Pyruvic acid b) Acetyl CoA
c) NADH2 d) NAD(P)H

26) Which of the following respiratory material may show the unit value of R. Q.?
a) Stem of wheat b) Leaf of barley
c) Leaf of oat d) All the above

27) Substance whose RQ is less than one is?
a) Carbohydrate b) Protein
c) Organic acid d) All the above

28) The energy content in Kcal/g of carbohydrates : protein : Triglycerol respectively is approximately in the ratio of?
a) 1 : 2 : 2 b) 1 : 1 : 2
c) 2 : 1 : 1 d) 2 : 2 : 1

29) The respiratory quotient during cellular respiration would depend on?
a) The nature of enzymes involved
b) The nature of the susbtrate
c) The amount of carbon dioxide released d) The amount of oxygen utilized

30) R. Q. in anaerobic respiration is?
a) 0
b) ∞
c) 1
d) > 1

31) The R. Q. of a plant organ depends upon the nature of the substrate which is?
a) Reduced b) Oxidized
c) Catabolized d) Metabolized

32) In Opuntia, in night the R. Q. will be?
a) One b) Less than one
c) More than one d) Zero

33) The R. Q. value of oxalic acid is?
a) 1.0 b) 0.7
c) 4 d) 1.5

34) In germinating castor seeds, the R. Q. is?
a) One b) More than one
c) Less than one d) Zero

35) R. Q. of malic acid is?
a) 0.7 b) 1
c) More than one d) 4

36) The correct relationship of value of Respiratory Quotient is?
a) Glucose > Fats > Organic acid
b) Glucose < Fats < Organic acid c) Fats > Glucose > Organic acid
d) Fats < Glucose < Organic acid

37) R.Q. is more than one in case of?
a) Fat b) Fructose
c) Glucose d) Organic acid

38) R. Q. of sprouting potato tubers will be?
a) 1 b) < 1 c) > 1 d) 0

39) The potato growing in hilly areas is bigger in size due to?
a) High rate of photosynthesis at high altitude
b) Low rate of respiration at high altitude
c) Due to formation of more fat
d) None of the above

40) When an unripe banana is sealed in a polythene bag, it remains green for many days. But if an apple is also sealed in the same bag, the banana ripens and turns yellow within a few days. The reason is that apple?
a) Removes O2 released by the banana and thus promotes ripening
b) Produces CO2 which promotes ripening
c) Removes CO2 which inhibits ripening
d) Release ethylene which promotes ripening

Biology - R. Currey

Instructions: Clicking on the section name will show / hide the section.

Biology Introduction

Biology Concepts and Themes

Monday, August 24 - Tuesday, August 25

Wednesday August 26 - Thursday August 27

Finish Prokaryotic Cells and start Eukaryotic Cells

Friday August 28 and Tuesday September 1

Plant Cells and Cell Theory

Monday August 31 and Thursday September 3


Standards to be covered:

(4) Science concepts. The student knows that cells are the basic structures of all living things with specialized parts that perform specific functions and that viruses are different from cells. The student is expected to:

Objective(s) for the Week:

(C) compare the structures of viruses to cells, describe viral reproduction, and describe the role of viruses in causing diseases such as human immunodeficiency virus (HIV) and influenza

Cyanide Resistant Respiration and its Significance

The flow of electrons in the usual mitochondrial electron transport chain (in both animals and plants) during aerobic respiration is blocked by the presence of cyanides which inhibit the activity of cytochrome oxidase. This type of respiration is there­fore, known as cyanide sensitive respiration.

Plant mitochondria, however, differ from the ani­mal mitochondria in having an alternate oxidase system pathway through which terminal oxi­dation of reduced coenzyme continues even in the presence of cyanides. This type of respira­tion is known as cyanide resistant (or cyanide insensitive) respiration.

In cyanide resistant respiration, the flow of electrons from reduced coenzymes to Ubiquinone is the same as in usual mitochondrial electron transport chain. But after this point (branch point) the electrons pass from UQ to a flavoprotein FPma (with a mid-range E’0 (= + 0.02 V) and a large absorbance change on redox change), and from there to a cyanide resistant or alternate oxidase (designated as X) and finally to O2 (Fig. 16.17). Usually the reduction of O2 should result in the formation of H2O but present evidences indicate the possibility of H2O2 being formed instead of H2O. The H2O2 can easily be converted into water arid oxygen then by the enzyme catalase.

(The exact nature of alternate terminal oxidase X is not clearly understood. It is probably an iron- containing protein which is neither a hemoprotein nor an iron-sulphur (Fe-S) protein. The activity of alternate oxidase is inhibited by m-CLAM (= m-chlorobenzhydroxamic acid).

P/O ratio (i.e. no. of ADP molecules converted into ATP molecules per O atom) in cya­nide resistant respiration is one. As in conventional electron transport chain, the first phosphorylation site is coupled with electron transport chain in cyanide resistant respiration also.

Physiological Significance of Cyanide Resistant Respiration:

The physiological significance of cyanide resistant respiration is not very clear. Following roles are usually attributed to it.

1. Cyanide resistant respiration is believed to be responsible for the climacteric in fruits (i.e., remarkable increase in respiration during and just before ripening). The climacteric is induced by ethylene and the latter may act to implement the cyanide resistant respiration in ripening fruit, (production of H2O2 and superoxide increases the oxidation and breakdown of membrane which are necessary activities in the ripening process).

2. Cyanide resistant respiration is known to generate heat in thermogenic tissues. Thermogenecity is observed in the flowers or inflorescences of some plants such as water lily (Victoria), arum lilies, Arum maculatum, Symplocarpus foetidus (skunk cabbage) etc. The ex­cessive heat produced in the inflorescence of Arum etc. is used to volatilize the odiferous compounds such as amines & indoles which are produced in them and which serve to attract pollinating insects. The amount of heat produced in thermogenic tissues may be as high as 51°C with an atm. temp, of 15°C (e.g., in appendix of Arum italicum).

(In cyanide resistant respiration, most of the energy liberated in the oxidation of respiratory sub­strate is lost as heat and only little of it is consumed in the production of ATPs. For instance the P/O ratio for 1 NADH molecule is only one in cyanide resistant respiration while in cyanide sensitive or usual respiration it is 3).

3. If ATPs generated in usual respiration in mitochondria are not sufficiently drained off, they may inhibit the Krebs’ cycle (TCA cycle) via the stoppage of electron flow in electron trans­port chain. Therefore, cyanide resistant respiration may provide continued oxidation of NADH and operation of TCA cycle though the energy demand is lesser. The operation of TCA cycle is impor­tant because TCA cycle intermediates are precursors for cellular components.


This study evaluated the metabolic responses of newly released brooded coral larvae to temperature, and used the results to gain insight into the consequences of their synchronous release (Harrison and Wallace, 1990 Fan et al., 2006). The results demonstrate that the respiration of three sympatric pocilloporids, P. damicornis, S. hystrix and S. pistillata, responded in rapid and distinctive ways to temperature with thresholds at ∼28°C. Analysis of the seawater temperature into which larvae of P. damicornis and S. hystrix were released in Nanwan Bay (Fan et al., 2002) revealed modal temperatures that were close to the thermal threshold for larval respiration. Together with the negative skewing and leptokurtosis of these temperatures, we interpret the concordance of this modal temperature with the thermal threshold for respiration as having beneficial consequences for the larvae. Given the selective pressure for rapid growth in small life stages of corals (Jackson, 1977 Vermeij and Sandin, 2008), the enhanced supply of ATP through temperature-stimulated respiration is probably advantageous, whereas the reduction in ATP supply at temperatures above the threshold is probably detrimental.

Measurement of respiration has long been recognized as an important objective for understanding the biology of pelagic larvae (Zeuthen, 1947 Crisp, 1976), but this task has been hindered by the difficulty of accurately recording the slow rate of larval O2 consumption (Hoegh-Guldberg and Manahan, 1995). In the present study, larval O2 consumption was measured using optical sensor technology, which avoided the traditional problems of the leading alternative technology, polarographic oxygen sensors. These problems include flow-dependency of the sensor, and O2 consumption by the sensor itself (Klimant et al., 1995). The efficacy of the optical technology was assessed by titrating O2 consumption against the number of larvae, and using the results to predict the O2 consumption in the absence of larvae. The outcome created a linear relationship whose intercept on the ordinate was not statistically discernible from zero, thereby confirming that only larvae were consuming O2 at a measurable rate (Marsh and Manahan, 1999). This interpretation is consistent with the similarity of the present respiration rates with those previously recorded for coral larvae (Table 1).

Aerobic respiration of planulae (mean ± s.e.m.) as a function of temperature (upper panels), and the number of planulae released as a function of mean daily seawater temperature (lower panels). (A) Respiration of Pocillopora damicornis planulae (N=5–6 for each temperature), with the line displaying the best-fit second-order polynomial (y=–11.11+0.80x–0.01x 2 , r 2 =0.89). (B) Respiration of Seriatopora hystrix planulae, with the line displaying the best-fit second-order polynomial (y=–7.46+0.54x–0.01x 2 , r 2 =0.76). Aerobic dark respiration is also displayed for planulae from Stylophora pistillata, although these results are not considered in detail because of incomplete sampling across temperatures and small sample sizes (N=1–4). (C) Cumulative release of P. damicornis planulae over 2003, 2005, 2007 and 2008 by mean daily seawater temperature (in 0.5°C bins) on the day of release. (D) Cumulative release of S. hystrix planulae over 2003, 2004, 2005, 2007 and 2008 by mean daily seawater temperature (in 0.5°C bins) on the day of release. Refer to Results for further details.

Aerobic respiration of planulae (mean ± s.e.m.) as a function of temperature (upper panels), and the number of planulae released as a function of mean daily seawater temperature (lower panels). (A) Respiration of Pocillopora damicornis planulae (N=5–6 for each temperature), with the line displaying the best-fit second-order polynomial (y=–11.11+0.80x–0.01x 2 , r 2 =0.89). (B) Respiration of Seriatopora hystrix planulae, with the line displaying the best-fit second-order polynomial (y=–7.46+0.54x–0.01x 2 , r 2 =0.76). Aerobic dark respiration is also displayed for planulae from Stylophora pistillata, although these results are not considered in detail because of incomplete sampling across temperatures and small sample sizes (N=1–4). (C) Cumulative release of P. damicornis planulae over 2003, 2005, 2007 and 2008 by mean daily seawater temperature (in 0.5°C bins) on the day of release. (D) Cumulative release of S. hystrix planulae over 2003, 2004, 2005, 2007 and 2008 by mean daily seawater temperature (in 0.5°C bins) on the day of release. Refer to Results for further details.

Positive temperature dependency of respiration in poikilotherms is a consequence of kinetic principles (Hochachka and Somero, 2002), at least until harmful temperatures are reached, and the consequences reflect a greater availability of ATP. Rates of enzyme-catalyzed reactions typically double for each 10°C increase in temperature (Hochachka and Somero, 2002), with greater increases possible when enzyme kinetics are augmented by changes in the fundamental biochemical systems (Hochachka and Somero, 2002) and behavioral mechanisms. Thermal stimulation of respiration necessitates an immediate response because ATP supply is usually balanced with ATP use (Hochachka and Somero, 2002), and typically the ATP is used to fuel chemical synthesis and mechanical work. However, the production of ATP through respiration consumes food reserves, and thermal stimulation of this process can have deleterious effects when the reserves cannot be replaced. When severely depleted, diminished food reserves are a leading cause of metabolic depression (Hand and Hardewig, 1996). Therefore, the extent to which thermal stimulation of respiration is beneficial depends on the demands for cellular energy and the speed with which reserves can be replaced, but regardless of the benefits, the effects reverse when temperature declines. Beyond the threshold, however, further increases in temperature result in metabolic depression, and these effects are less readily reversed because they reflect the effects of damage (Hochachka and Somero, 2002).

Against this backdrop, the present analysis of larval respiration – with a distinctive threshold at 28°C – represents a predictable example of a general response. Remarkably, there are so few empirical analyses of larval respiration in scleractinians that it has not previously been possible to describe the shape of this relationship, or to pinpoint with accuracy the threshold temperature. This is unfortunate, because the high thermal sensitivity of adult corals (Jokiel and Coles, 1990) provides good reason to study similar effects in the life stage (i.e. larvae) that is critical to reef recovery following damage (Richmond and Hunter, 1990). Further, studies of the effects of temperature on a variety of pelagic larvae underscore the profound impacts of high temperature in shortening PLD and dispersal distances (O'Connor et al., 2007). The proximal cause of the effect of temperature on PLD is the acceleration of metabolism (O'Connor et al., 2007), yet to our knowledge, this critical example of biophysical coupling has been studied in only two species. For Porites astreoides, larval respiration increased 1.4-fold between 26 and 28°C (Q10≈6.1), but did not change further between 28 and 33°C (Q10≈1.9 between 26 and 33°C (Edmunds et al., 2001) for Acropora millepora, larval respiration increased 1.6-fold between 24 and 31°C (Q10=1.9) (Rodriguez-Lanetty et al., 2009). The results from the small number of other studies of larval respiration in corals are difficult to compare with those of the present study owing to incongruent methodology and the use of a single temperature in virtually all studies. Nevertheless, together they are consistent with the notion of parabolic thermal effects with a threshold at ∼27–28°C, although the statistical fit to this functional relationship is weak and more data are required to characterize the general temperature–respiration response (Fig. 3).

Respiration rates of larvae from tropical scleractinians

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Speaker Bio

Victor de Lorenzo

Although trained as a chemist, Víctor de Lorenzo is now a Professor of Molecular Environmental Microbiology at the Centro Nacional de Biotecnología-CSIC. His lab uses Pseudomonas putida to recreate and build circuits for the sake of new-to-nature biological activities that will have an environmental impact by interacting with chemical waste. Dr. de Lorenzo is a… Continue Reading

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