3.5.2 - Respiration Flashcards
Topic 5
1
Q
Why is respiration important?
A
● Respiration produces ATP (to release energy)
● For active transport, protein synthesis etc.
2
Q
Summarise the stages of aerobic & anaerobic respiration
A
- Aerobic respiration:
1. Glycolysis - cytoplasm (anaerobic)
2. Link reaction - mitochondrial matrix
3. Krebs cycle - mitochondrial matrix
4. Oxidative phosphorylation - inner
mitochondrial membrane - Anaerobic respiration
1. Glycolysis - cytoplasm
2. NAD regeneration - cytoplasm
3
Q
Describe the process of glycolysis
A
- Glucose phosphorylated to glucose phosphate
○ Using inorganic phosphates from the hydrolysis of 2 ATP molecules - Phosphorylated glucose is Hydrolysed to 2 x triose phosphate molecules
- The triose phosphate molecules are then Oxidised to 2 pyruvate molecules (hydrogen is removed)
○ 2 NAD are reduced into NADH (from addition of the hydrogen)
○ 4 ATP regenerated (net gain of 2)
4
Q
Why is the phosphorylation of glucose necessary in glycolysis?
A
- before it can be split in two, glucose must first be made more reactive by the addition of two phosphate molecules
- the addition of a phosphate group to glucose effectively traps it in the cell, as phosphorylated glucose cannot diffuse across the lipid bilayer.
- the reaction decreases the concentration of free glucose inside the cell, favouring additional diffusion of the molecule (as it maintains concentration gradient)
5
Q
Explain what happens after glycolysis if respiration is anaerobic
A
- Pyruvate converted to lactate (animals &
some bacteria) or ethanol and CO2 (plants & yeast) - Oxidising reduced NAD → NAD regenerated
- So glycolysis can continue (which needs
NAD) allowing continued production of ATP
6
Q
Suggest why anaerobic respiration produces less ATP per molecule of
glucose than aerobic respiration
A
● Only glycolysis involved which produces little ATP (net gain of 2 molecules)
● No oxidative phosphorylation which forms majority of ATP (around 34 molecules)
7
Q
Where does pyruvate go after glycolysis if respiration is aerobic?
A
- Pyruvate is actively transported into the mitochondrial matrix
8
Q
Describe the link reaction
A
- Pyruvate oxidised (and decarboxylated) to acetate
> losing a carbon dioxide molecule and hydrogens
○ CO2 produced
○ Reduced NAD produced (accepts hydrogen) - which is later used to produce ATP - The 2-carbon Acetate combines with coenzyme A, forming Acetyl
Coenzyme A
9
Q
Overall equation for link reaction
A
Pyruvate + NAD + Conezyme A > Acetyl coenzyme a + Reduced NAD + CO2
10
Q
- Products per glucose molecule from link reaction
A
2 x Acetyl Coenzyme A,
2 X CO2 and 2 X reduced NAD
11
Q
Describe the Krebs cycle
A
- Acetyl coenzyme A (2C) reacts with a
4C molecule
○ Releasing coenzyme A
○ Producing a 6C molecule that enters the Krebs cycle - In a series of oxidation-reduction
reactions, the 4C molecule is regenerated and:
○ 2 x CO2 is lost
○ Coenzymes NAD & FAD are reduced
○ ATP is produced by Substrate level phosphorylation
(direct transfer of Pi from
intermediate compound to ADP)
12
Q
Products per glucose molecule of Kreb’s cycle
A
6 x reduced NAD,
2 x reduced FAD, 2 x ATP and 4 x CO2
13
Q
Describe the process of oxidative phosphorylation
A
- Reduced NAD/FAD oxidised to release H atoms → split into protons (H+) and electrons (e-)
- Electrons are transferred down electron transfer chain (chain of carriers at decreasing energy levels)
○ By redox reactions - Energy released by electrons used in the production of ATP from ADP + Pi (chemiosmotic theory):
○ Energy used by electron carriers to actively transport (pump) protons from matrix → intermembrane space
○ Protons move by facillitated diffusion into matrix down an electrochemical gradient, via ATP synthase (embedded)
○ Releasing energy to synthesise ATP from ADP + Pi - In matrix at end of ETC, oxygen is final electron acceptor (electrons can’t pass along otherwise)
○ So protons, electrons and oxygen combine to form water
14
Q
Give examples of other respiratory substrates
> Breakdown products of lipids and amino acids, which enter the Krebs cycle. For example:
A
● Fatty acids from hydrolysis of lipids → converted to Acetyl Coenzyme A
● Amino acids from hydrolysis of proteins → converted to intermediates in Krebs cycle
15
Q
Structure of mitochondria
A
- Outer mitochondrial membrane
> Intermembrane space - Inner mitochondrial membrane
- Christae
- Matrix - contains:
> ribosomes
> mitochondrial DNA
16
Q
Significance of kreb’s cycle
A
- breaks down macromolecules into smaller ones
> pyruvate broken down into CO2 - produces hydrogen atoms that are carried by NAD to the electron transfer chain and provide energy for oxidative phosphorylation
> leads to production of ATP that provides metabolic energy for the cell. - Regenerates the 4-carbon molecule that combines with acetyl coenzyme A, which would otherwise accumulate
- Source of intermediate compounds used by cells in the manufacture of other important substances such as fatty acids, amino acids and chlorophyll.
17
Q
Site of glycolysis
A
cytoplasm
18
Q
Site of link reaction and krebs cycle
A
mitochondrial matrix
19
Q
Site of oxidative phosphorylation
A
inner mitochondrial membrane
20
Q
Where do both stages of anaerobic respiration take place?
A
Both glycolysis and NAD regeneration take place in the cytoplasm
21
Q
Adaptations of mitochondria
A
- cristae contain enzymes + other proteins involved in oxidative phosphorylation - ATP synthesis
- mitochondria numbers are greater in metabolically active cells (needed for respiration)
- mitochondria in more metabolically active cells have more densley packed cristae
> which provide greater surface area of membrane incorporating enzymes (+ other proteins in oxidative phosphorylation
22
Q
Why are electrons passed along an electron transfer chain?
A
- The greater the energy released in a single step, the more of it released as heat and so the less available for more useful purposes
- By having electrons be passed along a series of electron transfer carrier molecules, each of which at slightly lower energy levels, electrons move down an energy gradient.
> transfer of electrons down this gradient allows their energy to be released gradually and more usefully.
23
Q
Anaerobic respiration in plants and yeast
A
- pyruvate molecule formed at the end of glycolysis loses a molecule of carbon dioxide and accepts hydrogen from reduce NAD to produce ethanol.
Pyruvate + reduced NAD > ethanol + CO2 + NAD
24
Q
How can anaerobic respiration of yeast be exploited in industry?
A
- ethanol production can be exploited in brewing industry
> yeast is grown in anaerobic conditions and ferments carbohydrates in plant products (eg: grapes, barley seeds) - CO2 produced from yeast used to make bread rise
25
Anaerobic respiration in animals...
- leads to the production of lactate as a temporary means of overcoming a temporary shortage of oxygen
> often occurs in muscles as a result of strenuous exercise
> whereby oxygen is used up at a faster rate than it can be supplied - oxygen debt occurs.
- lactate is produced because muscles need to keep contracting even in shortage of O2
> when O2 is in short supply, NADH from glycolysis can accumulate and must be removed
> each pyruvate molecule produced takes up the two hydrogen atoms from the NADH produced in glycolysis to form lactate
Pyruvate + NADH > lactate + oxidised NAD
26
At some point, lactate produced in the anaerobic respiration of animals is oxidised back into pyruvate which can...
- either be further oxidised to release energy or converted into glycogen
> happens when O2 is once again available
27
Issue with an accumulation of lactate in muscles
- causes muscle fatigue + cramps
- lactate is an acid so causes PH changes which can cause enzymes to denature
28
lactate is removed by the blood and...
taken to liver to be converted into glycogen
29
How many ATP molecules produced in oxidative phosphorylation?
34
30
The Respiratory Quotient (RQ) can provide information on the type of respiration taking place in an organism. The following equation is used to calculate the RQ.
RQ = volume of CO2 produced in respiration/Volume of O2 used in respiration
> What would be the RQ for aerobic respiration of glucose?
1
31
A student calculated that the RQ of germinating seeds was 1.8.
RQ = volume of CO2 produced in respiration/Volume of O2 used in respiration
Use the information provided to explain this result.
1. Aerobic and anaerobic respiration occurring
2. More carbon dioxide produced than oxygen uptake;
32
Aerobic respiration produces more ATP per molecule of glucose than anaerobic respiration.
Explain why.
1. Oxygen is final/terminal (electron) acceptor / oxygen combines with electrons and protons;
2. (Aerobic respiration) includes oxidative phosphorylation
3. In Anaerobic (respiration) only glycolysis occurs / no Krebs / no link reaction;
33
Oxygen concentration falls during aerobic respiration because
1. Aerobic respiration (uses oxygen) because
2. Oxygen is a terminal / final electron acceptor
3. (oxygen combines with) protons / H+ and electrons / e- to form water / H2O;
34
Malonate inhibits a reaction in the Krebs cycle.
Explain why malonate would decrease the uptake of oxygen in a respiring cell.
- Less/no reduced NAD/coenzymes
- so no oxidative phosphorylation
- Oxygen is the final/terminal (electron) acceptor in oxidative phosphorylation
35
CREB is a protein synthesised in the cytoplasm of neurones. Transport of CREB from the cytoplasm into the matrix of a mitochondrion requires two carrier proteins.
Use your knowledge of the structure of a mitochondrion to explain why transport of CREB requires two carrier proteins.
- Mitochondrion has two membranes / inner and outer membranes;
- For each (different) membrane a (different) carrier required;
36
Large areas of tropical forest are still found on some Caribbean islands. The concentration of carbon dioxide in the air of these forests changes over a period of 24 hours and at different heights above ground.
Use your knowledge of photosynthesis and respiration to describe and explain how the concentration of carbon dioxide in the air changes:
* over a period of 24 hours
* at different heights above ground.
1. High concentration of / increase in carbon dioxide linked with respiration at night / in darkness;
2. No photosynthesis in dark / night / photosynthesis only in light / day;
3. In light net uptake of carbon dioxide / use more carbon dioxide than produced / (rate of) photosynthesis greater than rate of respiration;
4. Decrease in carbon dioxide concentration with height;
More carbon dioxide absorbed higher up
5. (At ground level)
less photosynthesis / less photosynthesising tissue / more respiration / more micro-organisms / micro-organisms produce carbon dioxide.
37
a) Explain how microorganisms contributed to the increase in temperature during processing of organic waste.
b) Explain the advantage of showing the data using standard deviations rather than ranges.
a) 1. Respiration/metabolism/ammonification;
2. (Releases/produces) heat;
b) - SD is spread of data around the mean
- reduces effect of anomalies/ outliers;
- can be used to determine if (difference in results is) significant/not significant/due to chance /not due to chance
38
In muscles, pyruvate is converted to lactate during anaerobic respiration.
(i) Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration.
1. pyruvate is reduced into lactate - gains hydrogen from NADH which oxidises it forming NAD which can be reused in glycolysis
- allowing Oxidation of / hydrogen removed from pyruvate and carbon dioxide released;
- and Addition of coenzyme A.
39
Explain how pyruvate being reduced into lactate/ethanol enables glycolysis to continue
1. Regenerates/produces NAD / oxidises reduced NAD;
2. NAD reduced in stage 1/glycolysis / NAD accepts hydrogen in stage 1/glycolysis;
