XI Chap 14 Respiration Plants Flashcards
The process of breathing is very much connected to the process of _____________
release of energy from food
Only _______ and _______ can prepare their own food
green plants, cyanobacteria
Only cells containing __________ located in __________ layers photosynthesize
chloroplasts, superficial layers
What is cellular respiration?
Mechanism of breakdown of food materials
within the cell
to release energy
and trapping of this energy for synthesis of ATP
In eukaryotes, photosynthesis takes place in __________, whereas breakdown of complex molecules to yield energy takes place in __________ and __________.
chloroplasts
cytoplasm, mitochondria
What is respiration?
Breaking of C-C bonds of complex compounds through oxidation within cells, release of considerable amount of energy
What are respiratory substrates?
Compounds that are oxidised during respiration
What are the possible respiratory substrates? Which are most common?
Carbohydrates (most common)
Proteins
Fats
Organic acids
During oxidation in a cell, all the energy contained in respiratory substrates is released free into the cell in a single step. T or F?
False, released is a series of slow step-wise reactions and trapped as chemical energy (ATP)
Energy released by oxidation in respiration can be used directly in dire circumstances whereby plant is unable to photosynthesize. T or F?
False, cannot be used directly
_______ acts as energy currency of the cell
ATP
Plants have no specialised organs for gaseous exchange but they have _____ and _______
stomata and lenticels
How can plants get along without respiratory organs?
- each part plant takes care of its own gas exchange needs
- plants do not have great demands for gas exchange
- distance that gases must diffuse even in large, bulky plants is not great
Each living cell in a plant is located quite close to the surface of the plant. T or F?
True
Why is O2 not a problem when cells photosynthesize?
Because O2 is released in within the cells
What are lenticels?
Openings in thick, woody parts of plant
Cells on interior of a stem or trunk are dead and only provide mechanical support. T or F?
True
Loose packing of _________ cells in leaves, stems and roots provide an interconnected network of _________
parenchyma, air spaces
What equation shows the complete combustion of glucose in plants?
C6H12O6 + 6O2 ———> 6CO2 + 6H2O + Energy
Most of the energy yielded during combustion of glucose is given out as heat. T or F?
True
Plant cell catabolises the glucose molecule such that not all liberated energy goes out as heat at once (several small steps). T or F?
True
The first cells on this planet lived in an atmosphere rich with oxygen. T or F?
False, that lacked oxygen
Facultative vs. obligate anaerobes?
Facultative - can choose to live in anaerobic conditions
Obligate - have to live in anaerobic conditions
What is glycolysis?
partially oxidise glucose without help of oxygen to pyruvic acid, all living organisms are capable of this
glycos means ?
lysis means ?
sugar, splitting
Scheme of glycolysis was given by ________ and is often referred to as the _______ pathway
Gustav Embden, Otto Meyerhof, and J. Parnas
EMP pathway
In anaerobic organisms, glycolysis is the only process in respiration. T or F?
True
Glycolysis occurs in the ______ of the cell
Cytoplasm
Glucose undergoes _________ oxidation to form ____ molecules of pyruvic acid in glycolysis.
partial, 2 molecules
In plants glucose is derived from _______, the end product of photosynthesis or from storage ___________
sucrose, carbohydrates
During glycolysis,
Sucrose is converted into ______ and _______ by the enzyme ________
glucose, fructose, invertase
Glucose and fructose are polysaccharides. T or F?
False
In glycolysis, Glucose and fructose are __________ to give rise to glucose-6-phosphate by the enzyme ___________
phosphorylated, hexokinase
Glucose-6-phosphate _________ to form fructose-6-phosphate
isomerises
In glycolysis a chain of ____ (how many?) reactions take place under the control of ______ (same or different) enzyme(s).
10, different
During glycolysis,
Fructose-6-phosphate is converted to ___________
Fructose1,6-biphosphate
During glycolysis,
Fructose1,6-biphosphate is split into ______ and _________
dihydroxyacetone phosphate (triose phosphate) and 3-phosphoglyceraldehyde (PGAL)
During glycolysis,
PGAL is oxidised with inorganic phosphate to get converted into _________
1,3 biphosphoglyceric acid (BPGA)
During glycolysis,
BPGA is converted to ____________
3-phosphoglyceric acid (PGA)
During glycolysis,
PGA is converted into _________
2-phosphoglycerate
During glycolysis,
2-phosphoglycerate is converted into ________
phosphoenolpyruvate (PEP)
During glycolysis,
PEP is converted to _________
pyruvic acid
Which are the energy utilising steps of glycolysis?
Glucose to glucose 6-phosphate
fructose 6-phosphate to fructose 1, 6-biphosphate
What are the energy yielding steps of glycolysis?
BPGA -> PGA
PEP to pyruvic acid (final step)
energy is trapped in the form of ATPs
Where is NADH + H+ formed during glycolysis?
When PGAL -> BPGA
During glycolysis, two ________ are removed in the form of 2 hydrogen atoms from PGAL and transferred to a molecule of _______
redox-equivalents, NAD+
Metabolic fate of pyruvate depends on availability of oxygen, organism and cellular need. T or F?
True
What are the 3 major ways different cells handle pyruvic acid?
- lactic acid fermentation
- alcoholic fermentation
- aerobic respiration
Fermentation takes place under anaerobic conditions in ________
many prokaryotes, unicellular eukaryotes and germinating seeds
For complete oxidation of glucose to CO2 + H2O, organisms adopt the ________ cycle aka __________
Kreb’s, aerobic respiration
The enzymes _______ and _________ catalyse conversion of pyruvic acid to CO2 and ethanol in yeast.
pyruvic acid decarboxylase,
alcohol dehydrogenase
Some bacteria produce ________ from pyruvic acid.
Lactic acid
In animal muscles when oxygen is inadequate for cellular respiration during exercise, pyruvic acid is reduced to __________ by enzyme ___________
lactic acid, lactate dehydrogenase
In formation of lactic acid or ethanol from pyruvic acid, the reducing agent is ________ which is _________ to NAD+
NADH + H+
reoxidised
In both lactic acid and alcohol fermentation, significant energy is released. T or F?
False, less than 7% of energy in glucose, and not all trapped as ATP
The process of producing lactic acid or alcohol from glucose is hazardous. T or F?
True
Yeasts poison themselves to death when the concentration of alcohol reaches about _____%
13%
__________ is the process that leads to complete oxidation of organic substances.
Aerobic respiration
In eukaryotes, aerobic respiration takes place within the ____________
mitochondria
Aerobic respiration releases _____, _____ and ________
CO2, water, and large amounts of energy
________ type of respiration is more common in higher organisms
Aerobic
For aerobic respiration to take place, the final product of glycolysis, ________, is transported from the _________ to the _________
pyruvate, cytoplasm, mitochondria
What are the crucial events in aerobic respiration?
- Link reaction + Kreb’s cycle: complete oxidation of pyruvate by stepwise removal of all hydrogen atoms, leaving 3 molecules of CO2
- Electron transport system + Oxidative phosphorylation: Passing on of electrons removed as part of hydrogen atoms to molecular O2 with simultaneous synthesis of ATP
Complete oxidation of pyruvate including stepwise removal of all hydrogen atoms takes place in the ______ of the mitochondria.
matrix
Passing on of electrons to O2 and synthesis of ATP takes place in the ________ of the mitochondria
inner membrane
Pyruvate is formed by the glycolytic catabolism of carbohydrates in the cytosol. T or F?
True
After pyruvate enters mitochondrial matrix it undergoes ____________ catalysed by _____________
oxidative decarboxylation, pyruvic dehydrogenase
Oxidation of pyruvate requires participation of several coenzymes such as ?
NAD+ and Coenzyme A
mg2+?
Chemical reaction for link reaction of aerobic respiration?
Pyruvic acid + CoA + NAD+
—-Mg2+, Pyruvate dehydrogenase—->
Acetyle CoA + CO2 + NADH + H+
During linked reaction of aerobic respiration ___ molecules of NADH are produced from the metabolism of 1 molecule of glucose (i.e. _____ molecules of pyruvic acid)
2, 2
What happens to acetyl CoA after aerobic respiration?
enters kreb’s cycle
Kreb’s cycle is named after _________ and is aka _________ (2)
Hans Krebs,
tricarboxylic acid cycle (TCA cycle) OR citric acid cycle
TCA cycle starts with condensation of _______ with ______ and _______ to yield _______
acetyl group, oxaloacetic acid, water, citric acid
The condensation of acetyl group in TCA is catalysed by the enzyme _______ and _______ is released
citrate synthase, CoA
In TCA cycle,
Citrate is isomerised to __________
isocitrate
In TCA cycle,
formation of isocitrate is followed by ________ leading to the formation of __________ and then _______
2 successive steps of decarboxylation, alpha-ketoglutaric acid,
succinyl CoA
In TCA cycle,
succinyl-CoA is oxidised to ______ allowing the cycle to continue
OAA
In TCA cycle,
conversion of ______ to __________ involves a molecule of GTP being released.
succinyl CoA, succinic acid
When succinyl-CoA is converted to succinic acid, it is aka ____________
substrate level phosphorylation
In TCA cycle,
in a coupled reaction, GTP is converted to _____ with simultaneous synthesis of _______
GDP, ATP from ADP
There are _______ (how many?) point(s) in the Kreb’s cycle where NAD+ is reduced to NADH + H+
3
There are _______ (how many?) point(s) in the Kreb’s cycle where FAD+ is reduced to FADH2
1
Continued oxidation of _________ in the Kreb’s cycle requires the continuous replenishment of _______
acetyl CoA, oxaloacetic acid (OAA)
_________ is the first member of the Kreb’s cycle
OAA
Continuation of TCA cycle requires replenishment of not just OAA but also NADH + H+ and FADH2. T or F?
False, requires replenishment of NAD+ and FAD+
Summary equation of Kreb’s cycle?
Pyruvic acid + 4NAD+ FAD+ 2H2O + ADP + Pi ——Mitochondrial matrix—–> 3CO2 + 4NADH + 4H+ + FADH2 + ATP
Glucose breaks down to release how many molecules of ATP in TCA cycle (directly)?
2 molecules of ATP (since 1 glucose => 2 pyruvate and 1 pyruvate => 1 molecule of ATP)
Glucose breaks down to release how many molecules of CO2 in TCA cycle?
NADH + H+?
FADH2?
6, 8, 2
ETS and Oxidative phophorylation serve to release and utilize energy stored in _____ and _____
NADH + H+
FADH2
___________________ are oxidised through the electron transport system and the electrons are passed on to _________ resulting in the formation of ______
NADH+H+ AND FADH2,
O2,
H2O
What is electron transport system?
Metabolic pathway through which electron passes from one carrier to another
ETS is present in ___________
inner mitochondrial membrane
Electrons from NADH produced in the mitochondrial matrix during citric acid cycle are __________ by __________ and electrons are then transferred to __________ located within the _________
oxidised, NADH dehydrogenase (complex I),
ubiquinone, inner membrane
Ubiquinone also receives reducing equivalents via _________ generated during oxidation of ______ in the citric acid cycle
FADH2 (complex II), succinate
The reduced ubiquinone (aka _________) is then _________ with the transfer of electrons to ________ via _____________
ubiquinol, oxidised, cytochrome c (compkex IV) via cytochrome bc1 complex (complex III)
Cytochrome c is a small _____ attached to the ________ surface of the inner membrane and acts as a mobile carrier for transfer of electrons between complex ______ and complex ____
protein, outer, complex III and IV
Complex IV refers to ______________ containing cytochromes ____ and _____ and two copper centres
cytochrome c oxidase complex, a, a3
When electrons pass from one carrier to another from complex I to IV, they are coupled to _________ for production of ATP from ______ and ______
ATP synthase (complex V), ADP and inorganic phosphate
Number of ATP molecules synthesized in ETS depends on _________
nature of the electron donor
Oxidation of 1 molecule of NADH gives rise to ______ molecules of ATP,
1 molecule of FADH2 produces _____ molecules of ATP
3, 2
Role of oxygen in aerobic process is limited to ______ stage
terminal
Why is presence of oxygen in aerobic respiration vital?
Removes hydrogen from the system i.e. acts as the final hydrogen acceptor
In photophosphorylation, _____ is used for production of proton gradient
light energy
In respiration, _____ is used for production of proton gradient
energy of oxidation-reduction
Why is aerobic respiration aka oxidative phosphorylation?
since energy of redox (not light) results in creation of proton gradient
ATP synthase consists of 2 components:
F1 (headpiece) and F0 (channel)
F1 headpiece of ATP synthase is a _________ complex and contains the site for _________
peripheral membrane protein complex,
synthesis of ATP from ADP and inorganic phosphate
F0 is a ________ complex that forms the channel through which _________ cross the inner membrane
integral membrane protein complex,
protons
For each ATP produced, ______ H+ ions pass through F0 from ________ to _______
4, intermembrane space, matrix
We know the exact actual net gain of ATP for every glucose molecule oxidised. It is 38 ATP molecules. T or F?
False, number of ATP is correct but calculations are a theoretical exercise
What are the assumptions underlying the respiratory balance sheet?
- Sequential, orderly pathway functioning - one substrate forms the next - glycolysis, TCA cycle and ETS pathway follow in that order
- NADH synthesized in glycolysis is transferred into mitochondria and undergoes oxidative phosphorylation
- None of the intermediates in pathway are utilized to synthesize any other compound
- Only glucose is being respired, no other alternative substrates entering pathway at any stage
The assumptions underlying our calculation of number of ATP synthesized per molecule of glucose are not really valid in a living system. T or F?
True, pathways work simultaneously, substrates enter and withdraw, etc.
How many ATP molecules are gained during aerobic respiration of 1 glucose molecule?
38
Fermentation vs. aerobic respiration?
Fermentation - partial breakdown of glucose, produces pyruvic acid, net gain of only 2 ATP, NADH oxidized to NAD+ very slowly
Aerobic - complete breakdown of glucose, produces CO2 and H2O, many ATP (~38), vigorous oxidation of NADH
____________ is the favored substrate for respiration
Glucose
- All carbohydrates are first converted into glucose before respiration.
- No other substrates can be respired.
T or F?
1 - True
2 - False, glucose is preferred but others can be respired
If fats are respired, they would need to be broken down into _______ and _______ first.
fatty acids and glycerol
Fatty acids are first degraded to ______ to enter the pathway.
acetyl CoA
Glycerol is first degraded to ______ to enter the pathway.
PGAL
If respired, proteins would be degraded by _____ and the individual amino acids depending on ______________ would enter the pathway at _______ stage within Kreb’s cycle
proteases, their structure, some
Proteins would enter the respiratory pathway as _____ or ______
pyruvate or acetyl CoA
Respiration has traditionally been considered a ________ pathway
(anabolic, catabolic, amphibolic)
catabolic (traditionally!!!)
Breaking down processes within the living organisms is _________ and synthesis is _________
catabolism, anabolism
Respiratory pathway is a _______ pathway
amphibolic (both anabolism and catabolism)
What is respiratory quotient? aka?
ratio of volume of CO2 evolved to volume of O2 consumed
aka respiratory ratio
Respiratory quotient depends on ________
type of respiratory substrate
When carbohydrates are substrate, RQ is ?
1
When fats are substrate, RQ is ?
less than 1
e.g. 0.7 (tripalmitin - fatty acid)
When proteins are substrate, RQ is ?
~ 0.9
Pure proteins or fats are never used as respiratory substrates. T or F?
True
The fate of pyruvate depends on _______ and ______
availability of oxygen, organism
