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BIOLOGY A LEVEL > CHAPTER 18 - RESPIRATION > Flashcards

CHAPTER 18 - RESPIRATION Flashcards

1
Q

How many carbons does glucose contain

A

6 - Hexose sugar

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2
Q

How many stages are there in anaerobic respiration?

A

2 - Glycolysis then fermentation

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3
Q

How many stages are there in aerobic respiration

A

4 - Glycolysis, link reaction, Krebs cycle then electron transport chain (forming water)

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4
Q

Does Glycolysis require oxygen?

A

no it is an anaerobic process (but present in both aerobic and anaerobic pathways)

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5
Q

What are the products of Glycolysis

A

4 ATPs, 2 Reduced NADs and 2 Pyruvates

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6
Q

Describe the events that take place in Glycolysis

A

Phosphorylation -
2 phosphates from 2 ATP molecules attach to glucose molecule forming Hexose Bisphosphate

Lysis -
This destabilises the molecule causing it to split into two trios phosphate molecules

Phosphorylation 2 -
Another group is added to each triose phosphate to form 2 triode bisphosphate molecules, Phosphates are from free Pi in the cytoplasm

Dehydrogenation and formation of ATP -
The 2 triose bisphosphate molecules are then oxidised by removal of H atoms to form 2 pyruvate molecules - H atoms accepted by NAD forming reduced NAD and Phosphates form ATP (substrate-level phosphorylation)
(pg 481)

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7
Q

What is substrate-level phosphorylation

A

Formation of ATP without the involvement of an electron transport chain, from a short-lived highly reactive intermediate eg. creatine phosphate

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8
Q

Describe the processes of dehydration and phosphorylation in glycolysis

A

Dehydrogenation – removal of hydrogen from triose phosphate molecules to form pyruvate and reduction of NAD / formation of reduced NAD

phosphorylation – addition of phosphate group to a glucose molecule forming hexose bisphosphate

(both) catalysed by enzymes

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9
Q

Explain how NAD acts as a coenzyme in glycolysis

A

NAD accepts hydrogen (atom) and is reduced

during the formation of pyruvate

supplies hydrogen to enzyme involved in later stage of respiration

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10
Q

Explain the meaning of substrate-level phosphorylation

A

Addition of phosphate group

to ADP

or formation of ATP (using phosphate) from another molecule

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11
Q

Outline the importance of dehydrogenation and phosphorylation in glycolysis

A

Dehydrogenation –
hydrogen removed in breakdown of glucose

hydrogen required at a later stage

Phosphorylation –
addition of phosphate groups destabilises (large) molecules/glucose

leads to breakdown of glucose

synthesis of ATP

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12
Q

Where does the rest of aerobic respiration occur after glycolysis?

A

Mitochondria

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13
Q

What are the 5 parts of the mitochondria and what is their purpose

A

Outer Mitochondrial membrane - Separates the contents of the mitochondrion from the rest of the cell, creating a cellular compartment with ideal conditions for aerobic respiration

Inner Mitochondrial membrane - Contains electron transport chains and ATP synthase

Cristae - Projections of the inner membrane which increase Surface area available for Oxidative Phosphorylation

Matrix - Contains enzymes for the Krebs Cycle and Link Reaction, Also contains Mitochondrial DNA

Intermembrane space - Proteins are pumped into this space by the Electron Transport chain. The space is small so the concentration builds up quickly
(pg 482)

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14
Q

What is the Link reaction also called?

A

Oxidative Decarboxylation

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15
Q

Describe the events in The link reaction

A

Pyruvate (3-carbon) from Glycolysis loses a Carbon dioxide (diffuses away or gets removed from organism) - forming (2-Carbon) Acetyl group and a Hydrogen - which forms reduced NAD

Acetyl group binds to Coenzyme A to form Acetylcoenzyme A (acetyl CoA)

Coenzyme A delivers Acetyl group to next stage of respiration - Krebs cycle
(pg 482)

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16
Q

Explain why the removal of Carbon dioxide in the link reaction is called oxidative

A

Hydrogen is also removed

removal of hydrogen oxidises pyruvate

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17
Q

Name one organic compound and one inorganic compound produced in the link reaction

A

Acetyl group

carbon dioxide

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18
Q

Give the (simplified word) equation for the link reaction

A

Pyruvate + CoA + NAD —> Acetyl CoA + CO2 + NADH

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19
Q

Suggest why glycolysis occurs in the cytoplasm but not the mitochondrial matrix

A

Enzymes required are in cytoplasm

glucose molecule too large to move into mitochondrion

no transport proteins for pyruvate

mitochondria not originally present in (eukaryotic) cells

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20
Q

Describe the events in the Krebs Cycle

A

Acetyl CoA delivers Acetyl group to Krebs cycle. The two-carbon acetyl group combines with 4-carbon oxaloacetate to form 6 carbon citrate

The citrate molecule undergoes decarboxylation and dehydrogenation producing reduced NAD and CO2.
5 Carbon compound is formed.

The 5-carbon compound undergoes further decarboxylation and dehydrogenation reactions, producing in this order:
1: CO2, Reduced NAD
2: ATP
3: FADH2 (reduced FAD)
4: reduced NAD
5: Oxaloacetate (4 carbons)

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21
Q

What Is produced overall from the Krebs cycle

A

3 Reduced NADs
1 Reduced FAD
1 ATP
1 Oxaloacetate

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22
Q

What stages do NAD and FAD take part in

A

NAD - all stages of cellular respiration
FAD - Krebs cycle only

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23
Q

How many hydrogens does NAD and FAD accept?

A

NAD - 1 forming NADH
FAD - 2 forming FADH2

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24
Q

How many ATP molecules can FAD and NAD synthesise

A

NAD - 3
FAD - 2

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25
Compare the structures of ATP and NAD
ATP – three phosphate groups one ribose one nitrogenous base NAD – two phosphate groups two riboses two nitrogenous bases
26
ATP can be described as a coenzyme. Explain why
It is used to link reactions energy is released as a result of the activity of one enzyme and used by another enzyme
27
Calculate the number of ATP molecules produced by substrate-level phosphorylation after two rounds of the Krebs cycle
1 per turn 2 in total
28
The Krebs cycle doesn't use oxygen at any point. Suggest why the Krebs cycle is termed aerobic
Hydrogen needs to be removed for cycle to continue hydrogen removed using NAD/FAD and reduced then NAD/FAD are oxidised at electron transport chain oxygen required for electron transport
29
Suggest a reason for the involvement of FAD rather than NAD in only one specific step of the Krebs cycle
Enzymes are specific active site complementary to substrate different steps have different substrates different steps require different enzymes different enzymes (may) require different coenzymes only one step in cycle has enzyme which requires FAD coenzyme
30
Describe the events in oxidative phosphorylation
Hydrogen atoms that have been collected by the coenzymes NAD and FAD delivered to the electron transport chain present in the membranes of the Cristae of the mitochondria Hydrogen atoms dissociate into hydrogen ions and electrons. The high energy electrons are used in the synthesis of ATP by chemiosmosis (proton gradient) At the end of the transport chain, electrons combine with hydrogen ions and oxygen to form water. Oxygen is the final electron acceptor - cannot operate unless oxygen is present (pg 486)
31
What is oxidative phosphorylation
Coupling of the flow of protons down the electrochemical gadding through ATP synths to the phosphorylation of ADP to produce ATP
32
Explain why hydrogen ions have to be actively pumped across the membrane from the matrix and return to the matrix by diffusion through ATP synthase
Actively pumped to increase concentration gradient energy required as moving from low to high concentration membrane impermeable to ions so ions diffuse down concentration gradient ATP synthase provides hydrophilic channel
33
Explain why the electrons released from reduced FAD, lead to the synthesis of less ATP than electrons released from reduced NAD
Reduced NAD releases electrons to carriers at the start of the ETC reduced FAD releases electrons to carriers after the start of the ETC with FAD electrons transported a shorter distance so fewer protons are actively transported
34
Cyanide is a respiratory poison. It attaches to the iron in the haem group of cytochrome C oxidase in complex IV of the electron transport chain. Suggest an explanation for the toxicity of cyanide.
Stops flow of electrons stops active transport of protons proton gradient not formed (less) ATP synthesised; so less energy available for (vital) metabolic processes
35
Explain, with reasons, whether you agree with the following statements: 1) ATP Synthase is not actually part of the electron transport chain 2) oxygen is required for the transfer of electrons along the electron transport chain 3) Hydrogen ions return to the matrix by facilitated diffusion
1) agree not an electron carrier 2) agree oxygen is final electron acceptor, required for electron transport 3) agree diffuse through hydrophilic channels (of ATP synthase)
36
How many molecules of ATP does Aerobic respiration produce per glucose molecule
38
37
How many ATP molecules does Fermentation (form of anaerobic respiration) produce
(Net) 2
38
What are obligate anaerobes
Cannot survive in the presence of oxygen. Almost all obligate anaerobes are prokaryotes eg. Clostridium (bacteria that causes food poisoning), but some are fungi as well
39
What are facultative anaerobes
Synthesise ATP by aerobic respiration if oxygen is present, but can switch to anaerobic respiration in the absence of oxygen, eg. yeast
40
What are obligate aerobes
Can only synthesise ATP in the presence of oxygen, eg. mammals. The individual cells in some organisms, like muscle cells in mammals, can be described as facultative anaerobes because the supplement ATP supplies by employing anaerobic respiration in addition to aerobic respiration when O2 concentration is low; only for short periods and oxygen is eventually required. Anaerobic respiration produces compounds that have to be broken down when oxygen becomes available again, so the organism as a whole is an obligate aerobe
41
What is fermentation
A form of anaerobic process in which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of an electron transport chain. The organic compounds, such as glucose, are not fully broken down so fermentation produces much less ATP than aerobic respiration. The small quantity of ATP produced is synthesised by substrate-level phosphorylation alone. End products vary depending on organism
42
Describe the events in lactate fermentation (in mammals)
Pyruvate acts as Hydrogen Acceptor taking hydrogen from Reduced NAD, catalysed by enzyme lactate dehydrogenase Pyruvate is concerted to lactate (lactic acid) and NAD is regenerated Can be used to keep Glycolysis going so a small quantity of ATP is synthesised Reversible
43
What happens to the lactic acid after fermentation
Converted back to glucose in the liver (oxygen required to complete this process)
44
Why can't lactate fermentation occur indefinitely
Reduced quantity of ATP produced wouldn't be enough to maintain vital processes for along period of time Accumulation of lactic acid causes a fall in pH leading to proteins denaturing. Respiratory enzymes and muscle filaments are made from proteins and will cease to function at low pH
45
How is lactic acid removed from muscles and taken to the liver
Bloodstream
46
Why is one of the main aims when improving physical fitness to increase blood supply and flow through muscles
To increase rate of lactic acid removal, allowing the intensity and duration of exercise to be increased
47
Describe the events in Alcoholic fermentation (in yeast and many plant cells)
Pyruvate (3C) is converted into ethanal, catalysed by Pyruvate Decarboxylase, releasing CO2 Ethanal then accepts Hydrogen atom from Reduced NAD, becoming ethanol, regenerating NAD NAD can then continue to act as coenzyme and glycolysis can continue Non-reversible
48
Describe an investigation into respiration rates in yeast
Place brewers yeast in a conical flask with a glucose solution Seal flask ensure anaerobic conditions Releases carbon dioxide as a byproduct use gas syringe or stained water drop to see volume of carbon dioxide released
49
Explain why the student investigated respiration rates in yeast by doing: Carried out in Vacuum flask Covered solution containing the yeast with liquid paraffin
Vacuum flask to control the temperature paraffin prevents oxygen entering the solution ensures respiration is anaerobic
50
What mammalian adaptions are there for low oxygen environments
Biochemical adaptations - greater conc of Haemoglobin and myoglobin than land animals, helps maximise oxygen stores and delays onset of anaerobic metabolism High tolerance to CO2 levels, effective buffering systems Physiological - Modified circulatory system, peripheral vasoconstriction so blood is shunted to the brain, heart and muscles, heart rate slows by 80% Greater exchange of air in lungs (80-95% as opposed to 15% in humans) Physical adaptions - Streamlining to reduce drag, efficiency in propulsion
51
The lungs of whales are proportionally no larger than humans, but some whales can stay underwater for 2 hours. Suggest how the lungs might be adapted to enable these long dices and why larger lungs would be a disadvantage to a whale
Flexible rib cage; lungs can collapse under high pressure air compressed maintaining concentration gradients exhalation before inhalation increase proportion of air exchanged Larger lungs would increase buoyancy more energy would be used during dives
52
Summarise the adaptations of whales for making long underwater dives
Streamlined heart rate slowed reduced energy requirements blowhole on top of the head large breath (when surface) larger red blood cells more haemoglobin more blood faster oxygen transport more myoglobin increased oxygen storage
53
Explain why yeast cells are described as facultative anaerobes
Yeast cells normally respire aerobically can respire anaerobically when required
54
Describe why alcoholic fermentation can be described as having more in common with aerobic respiration than with fermentation
Electron transport chains present in some types of anaerobic respiration aerobic respiration always includes presence of electron transport chains no electron transport chains present in lactate fermentation
55
Explain why the build-up of lactic acid eventually stops muscle contraction which we experience as fatigue
Increase in lactic acid leads to decrease in pH muscle contraction depends on protein e.g., enzymes, contractile proteins decreasing pH denatures protein protein no longer functional
56
Glycolysis, the anaerobic stage of respiration, is the only source of ATP in red blood cells. Cardiac muscle is adapted to reduce the chances of anaerobic respiration ever being needed. Outline the benefits to red blood cells and cardiac muscle of different types of respiration they undertake
Red blood cells adapted to carry oxygen lack of mitochondria means more space for haemoglobin increased oxygen transport lactic acid not produced in cardiac muscle enzymes not denatured, no fatigue blood flow to rest of organism not interrupted
57
How are triglycerides converted to pyruvate ready to be respired?
Hydrolysed into fatty acids then enter Krebs cycle via Acetyl CoA and Glycerol,
58
How many molecules of ATP can the fatty acids in a triglyceride synthesise?
500 (forming 50 Acetyl CoA molecules)
59
How are proteins prepared to be respired
Hydrolysed into amino acids, then deaminated, before entering pathway, converting to ATP These steps require ATP therefore reducing net production
60
How is the Respiratory Quotient calculated
CO2 produced/O2 Consumed Calculated for a substrate
61
Biological molecules diagram of respiration
PAGE 493
62
What instrument is used to measure respiratory quotient
Respirometer
63
What are some key points about low carb diets to consider (maybe not needed but in textbook)
Read page 494
64
Describe an experiment into the factors affecting the rate of respiration using respirometers
Pea seeds, glass beads and varying water content in separate containers with mesh and KOH solution in Vary temperature and measure gas release using respirometer or gas syringe
65
Outline there respiration pathway of a triglyceride
Triglyceride is broken down into fatty acids and glycerol fatty acids undergo beta oxidation forming acetyl groups acetyl groups are taken into Krebs cycle by coenzyme A glycerol is converted to pyruvate, which undergoes oxidative phosphorylation
66
Describe the difference between a respirometer and a spirometer
Both measure oxygen uptake/carbon dioxide release so rate of respiration respirometer is modified spirometer/(usually) used for smaller organisms

BIOLOGY A LEVEL (24 decks)

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