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Biology Year 13 > Cellular Respiration > Flashcards

Cellular Respiration Flashcards

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1
Q

What do autotrophic organisms do?

A

Make their own food by photosynthesis

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2
Q

How does food provide energy?

A

The energy in the chemical bonds of the food is transferred to the bonds in ATP (adenosine triphosphate) during cellular respiration, providing the energy for all other metabolic reactions

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3
Q

What is cellular respiration?

A

The process by which food is broken down to yield ATP, which is used as a source of energy for metabolic reactions

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4
Q

What is the respiratory substrate?

A

The substance oxidised during cellular respiration

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5
Q

What is the main respiratory substance used by cells?

A

Glucose

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6
Q

What does the volume of oxygen used and carbon dioxide produced depend on in cellular respiration?

A

The level of activity of the organism, the type of food being respired and other external factors such as temperature

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7
Q

What is aerobic respiration?

A

The form of cellular respiration that takes place in the mitochondria in the presence of oxygen

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8
Q

What is the equation for respiration?

A

C6H12O6 + 6O2 -> 6O2 + 6H2O (+ATP) deltaH= 2880KJ

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9
Q

What happens when energy is needed by the body?

A

The third phosphate bond in ATP can be broken by a hydrolysis reaction, catalysed by the enzyme ATPase. The result is adenosine diphosphate (ADP) and a free inorganic phosphate group (Pi). About 30.5KJ energy is released for every mole of ATP hydrolysed. Some of this energy is transferred to the environment warming it up but the rest is available for any energy requiring biological activity.

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10
Q

What would you say happens when ADP is converted to ATP?

A

The ADP is phosphorylated. It is catalysed by ATPase and requires 30.5 KJ of energy

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11
Q

What would you say happens when ADP is converted to ATP?

A

The ADP is phosphorylated. It is catalysed by ATPase and requires 30.5 KJ of energy

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12
Q

What happens once the raw materials to make ATP are used up?

A

Cellular respiration cannot continue and no more ATP is made. Therefore metaboluc reactions stop and the body can no longer function

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13
Q

What are the two distinct phases of aerobic respiration and what happens in them?

A

1) glycosis. It doesn’t require oxygen. A little ATP is produced here, but more importantly the splitting of the respiratory substrate begins and the molecules are prepared for entry into the second stage of the process
2) Krebs cycle. Needs oxygen to proceed. A link reaction is needed to move the products of glycosis into the Krebs cycle and the electron transport chain

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14
Q

What is the rate of aerobic reaction controlled by?

A

Inhibition of the various enzymes usually by other chemicals in the chain

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15
Q

Where does glycosis take place?

A

It is not associated with any particular cell organelle. The enzymes controlling glycosis are found in the cytoplasm

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16
Q

Where do the stages other than glycosis in aerobic respiration take place?

A

The mitochondria

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17
Q

What are the features of the mitochondria?

A
  • large organelles
  • double membrane and the inner one is formed in many folds called the cristae
  • the matrix of the mitochondrion contains the enzymes of the Krebs cycle
  • the cristae carry the stalked particles associated with ATP synthesis
  • active cells such as the muscles and liver have large numbers of mitochondria
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18
Q

What are stalked particles?

A

Structures where ATP production takes place on the inner mitochondrial membrane

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19
Q

What is reduction?

A

The addition of electrons to a substance e.g. by the addition of hydrogen or removal of oxygen

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20
Q

What is oxidation?

A

The removal of electrons from a substance by the addition of oxygen or removal of hydrogen

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21
Q

What is a hydrogen acceptor?

A

A molecule which recieves hydrogen and becomes reduced in cell biochemistry when hydrogen is removed from compounds during cellular respiration

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22
Q

What happens in the electron transport chain?

A

The hydrogen that is removed from the compound is then passed from one hydrogen acceptor to the next hydrogen acceptor and along the electron transport chain. A series of linked oxidation and reduction (redox) reactions take place. Each redox reaction releases a small amount of energy which is used to drive the synthesis of a molecule of ATP

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23
Q

What is NAD?

A

The most common hydrogen acceptor in cellular respiration. It’s a coenzyme that acts as a hydrogen acceptor

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24
Q

What is a coenzyme?

A

A small molecule that assists in enzyme-catalysed reactions

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25
Q

What happens when NAD accepts hydrogen atoms from the metabolic pathway?

A

It becomes reduced to form reduced NAD

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26
Q

How is the oxidised form of NAD denotated?

A

NAD+

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27
Q

What is FAD?

A

A hydrogen carrier and coenzyme. In cellular respiration it accepts hydrogen to form reduced FAD (FADH2), driving the production of ATP

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28
Q

What has helped us study cellular respiration in cells?

A

The electron microscope

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29
Q

What is a respirometer?

A

A piece of apparatus used for measuring the rate of respiration in whole organisms or cultures of cells

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30
Q

How does a resiprometer work?

A

It measures the uptake of oxygen or the output of carbon dioxide by whole organisms. A chemical such as soda like or potassiuk hydroxide is used to absorb the carbon dioxide produced by respiration, therefore any changes in volume will be due to the uptake of oxygen by the organisms. As the organisms use oxygen the pressure reduces and so the fluid in the manometer moves towards the tube containing the organisms. The volume of gas needed to return the manometer to normal is measured using the syringe. This measurement can then be used to calculate rhe intake of oxygen per minute and give an approximate respiration rate for the organisms. By changing the external conditions (e.g. temperatures) it is possible to measure their effect on the rate of respiration by recording changes in the uptake of oxygena

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31
Q

What are ways of investigating respiration at the cellular level?

A
  • you can break open cells and centrifuge the contents to obtain a fraction just containing mitochondria. If these are kept supplied with glucose and oxygen they will produce ATP
  • The high resolving power of electron microscopes has shown us that the surface of the inner membrane of the mitochondrion is covered in closely packed stalked particles. These provide greatly increased surface area, which is an ideal site for enzymes to work
  • the stalked particles and the bits of membrane associated with them can be seperated feom the rest of the mitochondrial structure. Scientists have demonstated that ATP synthesis only occurs here. as a result the stalked particles have been accepted as vital for the formation of ATP
32
Q

What is glycosis?

A

The first stage of cellular respiration which is takes place in the cytoplasm and is common to both aerobic and anaerobic respiration

33
Q

What is pryuvate?

A

The end product of glycosis

34
Q

Where may the glucose for glycosis come from?

A

Directly from the blood or it may be produced by the breakdown of glycogen stores in muscle and liver cells

35
Q

What is the first step in glycosis?

A

It uses ATP to provide the energy to phosphorylate the 6C sugar glucose, adding two phosphate groups. This phosphorylatuon makes the sugar more reactive and also makes it unable to to pass through the cell membrane so it becomes trapped in the cell

36
Q

What is the second step of glycosis?

A

The phosphorylated sugar is then split to give two molecules of a 3-carbon sugar known as glycerate-3-phosphate (GP). GP is the converted by several steps into a molecule of pyruvic acid which is found in solution as pyruvate ions. During these reactions a small amount of ATP is produced

37
Q

What are the processes through which ATP is produced in glycolysis?

A
  • two hydrogen atoms are removed from the 3C sugars and taken up by NAD forming reduced NAD (NADH). This takes place in the cytoplasm of the cell. The reduced NAD then passes through the outer mitochondrial membrane into the electron transport chain
  • A small amount of ATP is also made directly from the energy transfer when the 3C sugar is converted to pyruvate. The phosphorylation of the sugar at the beginning of glycosis is reversed when the final intermediete compound is converted to pyrivate. The phosohate group released is used to convert ADP to ATP
  • if there is plenty of oxygen the pyruvate will enter the mitochondria and be used in the aerobic reactions of the Krebs cycle. If oxygen levels are low, the pyruvate remains in the cytoplasm and is converted into wither ethanol (in plants) or lactate (in mammals) with only a little ATP produced. This is anaerobic respiration in the cytoplasm
38
Q

What is ethanol?

A

An organic chemical with the formula C6H5OG produced as a result of anaerobic respiration (fermentation) in fungi and some plant cells

39
Q

What is lactate?

A

A 3-carbon compound which is the end product of anerobic respiration in mammals

40
Q

What is anaerobic respiration?

A

The form of cellular respiration that takes places only in the cytoplasm when there is no oxygen present

41
Q

What is glycerate 3- phosphate?

A

A phosporylated 3-carbon intermediete in the process of glycosis

42
Q

In aerobuc respiration in mammals what is the pyruvate from glycosis converted to?

A

Lactic acid which dissociates to form lactate and hydrogen ions

43
Q

How many molecules of ATP are produced per glucose molecule respired in anaerobic repiration compared to aerobic respiration?

A

2 in anaerobic respiration and 8 molecules are produced in aerobic respiration

44
Q

Why is the yield of ATP low during anaerobic respiration?

A

Because some of the reduced NAD is used to reduce pyruvate to lactic acid rather than entering the electron transport chain

45
Q

What is the equation for the conversion of glucose into lactic acid?

A

C6H12O6 -> 2C3H6O3 (+ATP) deltaH- 150 KJ

46
Q

Why does muscle contraction eventually stop when respiring anaerobically and how would this help your body?

A

The movement of lactate and hydrogen ions into the blood and muscles lowers the pH of the blood which in turn affects the central nervous system. The Reduced nervous stimulation from the CNS reduces and eventually stops muscle contraction.

Scientists think this is a protective adaptation to five muscles time to recover and return to aerobic respiration helping to raise the pH of the blood again

47
Q

Why were muscles originally thought to stop contracting in aerobic respiration?

A

It was thought that when lactate and hydrogen ions increase during aerobic respiration in the muscles the pH falls and the muscle tissue becomes acidic and this was thought to reduce the ability of the muscles, so the contractions lose their force and eventually stopped completely

48
Q

Why do you still breathe deeply when exercise stops?

A

The levels of lactate in the blood still remain raised. The lactate, which is toxic must be oxidised back to pyruvate to enter the Krebs cucle to be respired aerobically producing carbon dioxide, water and ATP. It takes oxygen to oxidise the lactate which is why we continue to breathe deeply

49
Q

What does training allow athletes to do?

A

Get more oxygen to their muscles faster as a better blood supply develops and to tolerate higher levels of lactate before the muscles fatigue. With repeated exposure to high lactacte levels, more lactate transporter molecules develop in the mitochondrial membranes, resulting in faster processing of lacrate to pyruvate when oxygen is available

50
Q

Which organisms when respiring anserobically produce ethanol?

A

Plants and yeast (fungi)

51
Q

When will plants need to respire anaerobically?

A

When their root cells are in waterlogged soil

52
Q

Why has yeast been the main experimental organism used in much of the worm on glycosis rather than plants?

A

It is easy to grow, reproduces rapidly, there are no ethical issues and yeast contains all the enzymes of glycosis

53
Q

What are three landmarks in the discovery of glycosis?

A
  • in 1897 Eduard Buchner discovered that an extract of yeast containing no cells could still convert glucose to ethanol, showing that the enzymes of fermentation and glycosis are mot associated closely with the structure of the cell
  • in the early 1900s the British bichemists Arthur Harden and W.J. Young showed that phosphate was needed for the pathway to process and also that there were two elements of the yeast extract needed before fermination could go ahead. One of thede ead inactivated by heat as it contained the enzymes. The other was not affected by heat in the same wat and contained NAD, ADP and ATP
  • work with inhibitors allowed some of the pathway intermediates to be studied and the german biochemists Gustab Embden and Otto Meyerhod worked out much of the rest of the sequence.
54
Q

What is the Krebs cycle?

A

A series of biochemical steps that lead to the complete oxidation of glucose, resulting in the production of carbon dioxide, water and relatively large amounts of ATP

55
Q

What is the link reaction?

A

The reaction needed to move the products of glycosis into the Krebs cycle

56
Q

What is fes through into the mitochondria where it enters the Krebs cycle at the end of glycosis?

A

Pyruvate

57
Q

Where do the reactions of the Krebs cycle take place?

A

In the matrix of the mitochondrion

58
Q

Where is ATP produced in aerobic respiration?

A

In the stalked particles on the inner mitochondrial membrane in the presence of oxygen

59
Q

What happens in the link reaction?

A

An atom of carbon is removed from pyruvate (decarboxylation) resulting in a CO2 molecule and a 2-C compound that joins with coenzyme A to form 2C acetyl coenzyme A (acetyl CoA). At the dame time pyruvate is oxidised, losing hydrogen ions to NAD (dehydrogenation), resulting in reduced NAD (NADH).

The NADH is used in the electron transport chain to produce ATP
the energy contained in the acetyl CoA is released in the Krebs cycle
Decarboxylases remove CO2
Dehydrogenase enzymes remove hydrogen

Pyruvate (3C) + CoA + NAD -> acetyl CoA (2C) + CO2 + NADH

60
Q

What are the key reactions of the Krebs cycle?

A
  • 2C acetly CoA combines with a 4C compound to form the 6C compound citric acid (citrate). At this point it has entered the Krebs cycle.
  • the 6C citric acid now goes through a series of cyclical reactions during which the compound is broken down in a number of stages to give the original 4C compound. Two further molecules of CO2 are removed in the process and are given off as a waste product.
  • the 4C compound combines with more 2C acetyl CoA and the cycle begins again
61
Q

For each of the molecules of pyruvate that enter the Krebs cycle how many molecules of reduced NADH, reduced FAD and ATP are produces and what happens to the the reduced NAD and FAD?

A
  • 3 molecules of reduced NAD
  • one molecule of reduced FAD
  • One molecule of reduced ATP

The reduced NAD and FAD enter the electron transport chain

62
Q

Why does the Krebs cycle turn twice for wach molecule of glucose that enters the glycolytic pathway?

A

Because the 6C molecule produced two 3C pyruvate molecules each of which passes through the Krebs cycle

63
Q

What is oxidative phosphorylation?

A

The oxygen-dependent process in the electron transport chain where ADP is phosphorylated

64
Q

What is the electron transport chain?

A

A series of electron carrying compounds along which electrons are transferred in a series of oxidation/reduction reactions, driving the production of ATP

65
Q

What is chemiosmosis?

A

The process that links the electrons that are passed down the electron chain and the production of ATP by the movement of hydrogen ions through the membrane along electrochemical, concentration and pH gradients

66
Q

Whaat happens in the final stage of respiration?

A

Reduced NAD or FAD feom glycosis and the Krebs cycle is used with oxygen to make ATP i a process called oxidative phosphorylation. It involves an electron transport chain in which the hydrogen ions left behind are used in chemiosmisus to supply the energy to synthesise ATP

67
Q

Why is the electron transport chain known as the electron transport chain?

A

Although it is hydrogen atoms that are removed from the compounds in glycosis and the Krebs cycle and hydrogen atoms that eventually join up with oxygen to form water, it is the electrons that are passed along the carrier system. The hydrogen ions remain in solution.

68
Q

What are the four main electron carriers involved in the electron transport chain?

A
  • the coenzymes NAD and FAD both act as hydrogen acceptors for hydrogen released in the Kreb cycle. One molecule of ATP is produced when the FAD is reduced and accepts hydrogen from the reduced NAD (NADH), which becomes oxidised in the process
  • cytochromes are protein pigments with an iron group like haemoglobin. They are involved in electron transport and are reduced by electrons from reduced FAD and reduced NAD which is oxidised again. A molecule of ATP is produced at this stage
  • cytochrome oxidase is an enzyme that recieves the electrons from the cytochromes and is reduced as the cytochromes are oxidised. A molecule of ATP is also produced at this stage
  • oxygen is the final hydrogen acceptor in the chain. When oxygen is reduced, water is formed and the chain is at an end
69
Q

How many molecules of ATP are produced when the hydrogen enters the chain from reduced NAD and reduced FAD?

A
  • 3 from reduced NAD

* 2 from reduced FAD

70
Q

Why does the electron transport chain and ATP production take place on the inner membrane of the mitochondria?

A

The inner membrane of the mitochondria is folded to form the cristae whoch are covered with closely packed stalked particles. These are the site of the enzyme ATPase which is needed in ATP production

71
Q

What is the chemiosmotic theory?

A

It was developed by Peter Mitchell to explain the production of ATP in mitochondria, chloroplasts and elsewhere in living cells

72
Q

What does the chemiosmotic theory propose?

A

That hydrogen ions are actively transported into the space between the inner and outer mitochondrial membranes using the energy provided as the electrons pass along the transport chain. The active transport of the hydrogen ions across the inner membrane results in a different hydrogen io concentration on each side of the inner membrane. The membrane space has a higher concentration of hydrogen ions than the matrix so there is a concentration gradient across the membrane. As a result of the different hydrogen ion concentrations there is also a pH gradient. And because positive hydrogen ions are concentrated in the membrane space there is an electrochemical gradient too. All of these factors mean that there is a tendency for the hydrogen ions to move back to the matrix. The only way they can move back to the matrix is through special pores. These pores are found on the stalked particled and have an ATPase enzyme associated with them. As the hydrogen ions move along, their electrical, concentration, and pH gradients through these pores, their energy is used to drive the synthesis of ATP

73
Q

What is the average amount of ATP produced by one molecule of glucose said to have been (for years)?

A

36 molecules. The actual total was taken as 38 molecules of ATP but it takes two molecules of ATP to transport the reduced NAD molecules produced in glycosis through the mitochondrial membrane leaving 36 available for body cells

74
Q

What do scientists now believe about the yield of ATP from one glucose molecule?

A

That it may not be in whole numbers and an overall yield for aerobic cellular respiration may be about 31 molecules

75
Q

Why is the amount of ATP from one glucose molecule in reality rarely going to be over 30 molecules?

A

Because the proton gradients in the mitochondria can be used to drive the active transport of several different molecules and ions through the inner membrane into the matrix and NADH can be used as a reducing agent for many different reactions

Biology Year 13 (16 decks)

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