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Respiration Flashcards

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AP® Biology flashcards Biology 101 flashcards
0
Q

There is one molecule of _________ produced in each turn of the Krebs Cycle

A

Reduced FAD

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1
Q

The link reaction produces…

A

Reduced NAD

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2
Q

Three molecules of ATP can be generated from…?

A

Reduced NAD

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3
Q

Electron transport chain occurs in the…?

A

Cristae

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4
Q

Two molecules of CO2 are produced in the…?

A

Krebs Cycle

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5
Q

In anaerobic respiration,__________ will produce ethanol and carbon dioxide

A

Yeast

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6
Q

In anaerobic respiration in animals, _________ is produced in addition to two molecules of ATP

A

Lactate

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7
Q

What does Coenzyme A do?

A

Transports Acetate from Link reaction to the Kreb’s cycle

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8
Q

What does NAD do?

A

It helps dehydrogenase enzymes by accepting two hydrogen ions when reduced.

Allows oxidative phosphorylation to occur.

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9
Q

What are the products of glycolysis?

A

2 ATP

2 Reduced NAD

2 Pyruvate

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10
Q

What are the products of the link reaction?

A

2 Acetate

2 CO2

2 Reduced NAD

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11
Q

What are the products of the Krebs Cycle?

A

2 ATP

4 CO2

6 Reduced NAD

2 Reduced FAD

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12
Q

What are the products of Oxidative Phospharylation?

A

(Theoretically) 26 ATP and 10 H2O

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13
Q

Why is the ATP yield in oxidative phosphorylation only theoretical?

A

Protons leak, reducing proton motive force.

ATP is used in the active transport of Pyruvate.

ATP is used to reoxidise NAD.

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14
Q

What is chemiosmosis?

A

Movement of protons to form an electrochemical gradient, which means potential energy builds up in inter membrane space.

Proton motive force drive ATP synthase.

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15
Q

What is the final electron acceptor in mammalian anaerobic respiration?

A

Pyruvate.

So NAD is reoxidised, so more ATP can be made.

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16
Q

What is the final electron acceptor in anaerobic respiration of yeast?

A

Ethanal

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17
Q

What is ATP?

A

Adenosine Triphosphate: the universal energy molecule

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18
Q

What is an anabolic reaction?

A

Large molecules are synthesised from smaller molecules in a condesation reaction

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19
Q

What is a catabolic reaction?

A

Large molecules are hydrolysed into smaller ones.

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20
Q

What is the metabolism?

A

All the chemical reactions that take place in an organism

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21
Q

What are redox reactions?

A

A coupling of oxidative and reduction reactions. Reduction means an addition of electrons, Oxidation is a loss of electrons

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22
Q

What is NAD?

A

Nicotinamide adeninde dinucleotide:

An organic non-protein molecule that helps dehydrogenase enzymes is oxidative reactions

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23
Q

What is glycolysis?

A

The first stage of respiration where a glucose molecule is broken down into two pyruvate molecules. It takes place in the cytoplasm and is common to all living things

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24
Q

What are the mitochondria?

A

Organelles found in eukaryote cells. It is the site of aerobic respiration

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25
Q

What is the endosymbiosis theory?

A

A theory that suggest that both mitachondria and chloroplasts evolved from independent prokaryotic organisms

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26
Q

What happen in the link reaction?

A

Converts pyruvate to acetate. NAD is reduced

27
Q

What happens during the Krebs cycle?

A

Oxidises acetate to carbon dioxide. NAD and FAD are reduced. ATP is made through substrate level phosphorylation.

28
Q

What happens during oxidative phosphorylation?

A

Formation of ATP by adding a phosphate group to ADP in the presence of oxygen

29
Q

What happens during chemiosmosis?

A

The diffusion of hydrogen ions across the membrane resulting in the production of ATP in respiration

30
Q

What is proton motive force?

A

Refers to the kinetic energy behind the protons causing them to diffuse down their concentration gradient through channels associated with ATP Synthase

31
Q

What is anaerobic respiration?

A

The release of energy from substrates in the absence of oxygen

32
Q

What happens during lactate fermentation?

A

Pyruvate acts as the hydrogen acceptor and is reduced to lactate

33
Q

What happens during alcoholic fermentation?

A

Pyruvate is decarboxylated to ethanal which acts as the hydrogen acceptor and is reduced to ethanol

34
Q

What is a respiratory substrate?

A

An organic substance that can be used in respiration

35
Q

What is a matrix?

A

The fluid filled centre of the mitachondria.

This contains all the enzymes required to carry out the link reaction and krebs cycle.

Also contains looped DNA.

36
Q

What is ATP synthase?

A

An enzyme that produces ATP because of the action of chemiosmosis. It protrudes from the inner membrane into the matrix. Also known as stalked particles.

37
Q

Outer mitochondrial membrane?

A

Similar to that of membrane bound organelles. It contains protein channels that allows the passage of pyruvate into the mitachondria.

38
Q

Describe the inner mitochondrial membrane

A

This membrane is impermeable to small ions and is heavily folded into cristae.

39
Q

What is cell metabolism?

A

The result of all the chemical reactions taking place in the cytoplasm

40
Q

What are hepatocytes?

A

Liver cells

They are specialised to perform a range of metabolic functions

41
Q

What are the Islets of Langerhans?

A

Small patches of tissue in the pancreas that have endocrine function

They consist of alpha and beta cells

42
Q

Outline why plants, animals and microorganisms need to respire, with reference to active transport and metabolic reactions

A
  • Active transport- much of an organism’s energy is used for this
  • Secretion- large molecules made in some cells are released by exocytosis
  • Endocytosis- bulk movement of larger molecules into the cell
  • Metabolic reactions- synthesis of large molecules from smaller ones- proteins from Amino Acids, steroids from cholesterol, cellulose from β-glucose. These are all anabolic
  • Replication of DNA and synthesis of organelles before a cell divides

• Movement
o Bacterial flagella
o Eukaryotic cilia and undulipodia
o Muscle contractions

• Activation of chemicals e.g. phosphorylation of glucose

43
Q

Describe the structure of ATP.

A

An Adenosine group attached to a Ribose sugar and three phosphate molecules

44
Q

ATP provides the…

A

Immediate source of energy for biological processes.

45
Q

Explain the importance of coenzymes in respiration, with reference to NAD and coenzyme A.

A

Coenzymes aid in the oxidation and reduction of reactions.

NAD combines with the Hydrogen atoms and takes them to the mitochondrial membrane where they can be later split into hydrogen ions and electrons for the election transport chain. It is used in glycolysis, the Krebs cycle and anaerobic respiration.

Coenzyme A carries acetate groups either from the link reaction, or that have been made from fatty acids or amino acids onto the Krebs cycle.

46
Q

Where does glycolysis take place?

A

In the cytoplasm

47
Q

Outline the process of glycolysis beginning with the phosphorylation of glucose to hexose bisphosphate, splitting of hexose bisphosphate into two triose phosphate molecules and further oxidation to pyruvate, producing a small yield of ATP and reduced NAD.

A
  1. An ATP molecule is hydrolysed and the phosphate attached to the glucose molecule at C-6
  2. Glucose 6 Phosphate is turned into fructose 6 phosphate
  3. Another ATP is hydrolysed, and the phosphate attached to C-1
  4. The hexose sugar is activated by the energy release from the hydrolysed ATP molecules. It now cannot leave the cell and is known as Hexose-1,6-biphosphate
  5. It is split into two molecules of Triose phosphate
  6. Two hydrogen atoms are removed from each Triose Phosphate, which involved dehydrogenase enzymes.
  7. NAD combines with the Hydrogen atoms to form reduce NAD
  8. Two molecules of ATP are formed- substrate level phosphorylation
  9. Four enzyme-catalysed reactions convert each triose phosphate molecule into a molecule of pyruvate.
  10. Two more molecules of ATP are formed, so there is a net gain of 2 ATP.
48
Q

During aerobic respiration in animals, pyruvate is actively transported into…

A

Mitochondria

49
Q

Explain how the structure of mitochondria enables them to carry out their functions.

A

The Matrix:

  1. Enzymes that catalyse the stages of aerobic respiration (highly-concentrated mixture of hundreds of enzymes).
  2. Molecules of coenzyme NAD.
  3. Oxaloacetate - the 4-carbon compound that accepts acetate from the link reaction.
  4. Mitochondrial DNA, some of which codes for mitochondrial enzymes and other proteins.
  5. Mitochondrial ribosomes where the proteins are assembled.

The Inner Membrane:

  1. Different lipid composition than the outer layer (Impermeable to most small ions, including protons (or else aerobic respiration would stop if damaged))
  2. Is folded into many cristae to give a large surface area.
  3. Has embedded on it many electron carriers and ATP synthase enzymes.
  4. High protein-to-phospholipid ratio.

The Outer Membrane:

  1. It contains proteins, some of which form channels or carriers, which allow the movement of molecules such as pyruvate.

Electron Transport Chain:

  1. Contain 100s of oxidoreductase enzymes - involved in oxidation and reduction reactions.
  2. Some of the electron carriers also have a coenzyme that pumps (using energy released from the passage of electrons) protons from the matrix to the intermembrane space.
50
Q

The link reaction takes place in the…

A

Mitochondrial matrix

51
Q

Outline the link reaction, with reference to decarboxylation of pyruvate to acetate and the reduction of NAD.

A

Pyruvate dehydrogenase removes hydrogen atoms from pyruvate

Pyruvate decarboxylase removes a carboxyl group, which eventually becomes CO2, from pyruvate NAD accepts the hydrogen atoms

CoA accepts the acetate to become Acetyl CoA, which then travels to the Krebs Cycle

52
Q

Acetate is combined with __________ to be carried to the next stage.

A

Coenzyme A

53
Q

The Krebs cycle takes place in the…

A

Mitochondrial matrix

54
Q

Outline the Krebs cycle; with reference to the formation of citrate from acetate and oxaloacetate and the reconversion of citrate to oxaloacetate.

A
  1. Acetate is offloaded from CoA and joins with Oxaloacetate to form citrate.
  2. Citrate is decarboxlyated and dehydrogenated to form a 5C compound.
    a. The hydrogen atoms are accepted by NAD, which take
    them to the Electron Transport Chain
    b. The Carboxyl groub becomes CO2.
  3. The 5C compound is decarboxylated and dehydrogenated to form a 4C compound.
  4. The 4C compound is changed into another 4C compound, and a molecule of ATP is phosphorylated.
  5. The second 4C compound is changed into a third 4C compound and a pair of hydrogen atoms are removed, reducing FAD.
  6. The third 4C compound is further dehydrogenated to regenerate oxaloacetate.
55
Q

During the Krebs cycle, __________ and dehydrogenation occur, NAD and _________ are reduced and substrate level__________ occurs.

A

Decarboxylation

FAD

Phosphorylation

56
Q

Outline the process of oxidative phosphorylation, with reference to the roles of electron carriers, oxygen and the mitochondrial cristae.

A
  • The final stage of respiration involved electron carriers embedded in the mitochondrial membrane
  • The membranes are folded into cristae, which increases the surface area for electron carriers and ATP synthase enzymes.
  • Oxidative phosphorylation is the formation of ATP by the addition of an inorganic phosphate to ADP in the presence of oxygen.
  • As protons flow through ATPsynthase, they drive the rotation part of the enzyme and join ADP to Pi to make ATP
  • The electrons are passed from the final electron carrier to molecular oxygen, which is the final electron acceptor.
  • Hydrogen ions also join, so oxygen is reduced to water
57
Q

Outline the process of chemiosmosis, with reference to the electron transport chain, proton gradients and ATP synthase.

A
  1. Reduced NAD and FAD donate hydrogens, which are split into protons and electrons, to the electron carriers.
  2. The protons are pumped across the inner mitochondrial membrane using energy released from the passing of electrons down the electron transport chain.
  3. This builds up a proton gradient, which is also a pH gradient, and an electrochemical gradient
  4. Thus, potential energy builds up
  5. The hydrogen ions cannot diffuse through the lipid part of the inner membrane, but can diffuse through ATP synthase- an ion channel in the membrane.

The flow of hydrogen ions is chemiosmosis.

58
Q

_________ is the final electron acceptor in aerobic respiration.

A

Oxygen

59
Q

Evaluate the experimental evidence for the theory of chemiosmosis.

A
  • Researchers isolated mitochondria and treated them by placing them in a solution with a very low water potential.
  • This meant that the outer membrane ruptured, releasing the contents of the intermembrane space.
  • If they further treated these mitoblasts with a strong detergent, they could release the contents of the matrix.

• This allowed them to identify the enzymes in the mitochondria, and to work out that the link reaction and Krebs cycle occurred in the matrix, whilst the enzymes for the electron transfer chain were
embedded in the mitochondrial membrane.

  • Electron transfer in mitoblasts did not produce ATP, so they concluded that the intermembrane space was also involved
  • ATP was also not made if the mushroom-shaped parts of the stalked particles were removed from the inner membrane of the intact mitochondria.
  • ATP was also not made in the presence of oligomycin, an antibiotic which is now known to block the flow of protons through the ion channel part of ATP synthase.

• In the intact mitochondria
o The potential difference across the membrane was
-200mV, being more negative on the matrix side than on
the intermembrane space side.
o The pH of the intermembrane space was lower than that of
the matrix.

60
Q

Explain why the theoretical maximum yield of ATP per molecule of glucose is rarely, if ever, achieved in aerobic respiration.

A

The maximum yield for ATP is rarely reached as:

• Some hydrogens leak across the mitochondrial membrane
o Less protons to generate the proton motive force

  • Some ATP is used to actively transport pyruvate into the mitochondria
  • Some ATP is used to bring Hydrogen from reduced NAD made during glycolysis, into the cytoplasm, into the mitochondria.
61
Q

Explain why anaerobic respiration produces a much lower yield of ATP than aerobic respiration.

A

Because only glycolysis occurs.

The electron transport chain cannot occur, as there is no oxygen to act as the final electron acceptor.

This means that the Krebs cycle stops, as there are no NAD- they are all reduced.

This prevents the link reaction from occurring.

Anaerobic respiration takes the pyruvate, and by reducing it, frees up the NAD, so glycolysis can continue, producing two molecules of ATP per glucose molecule respired.

62
Q

Compare and contrast anaerobic respiration in mammals and in yeast.

A

Mammals

Pyruvate combines with a hydrogen which is provided by reduced NAD, this forms lactate and oxidised NAD

It involves the enzyme lactate dehydrogenase and is refered to as the lactate pathway

Oxidised NAD can go back to accepting hydrogen from glucose, and so Glycolysis can continue

Yeast

Pyruvate is converted to ethanal which involves decarboxalation as CO2 is released.

Ethanal combines with hydrogen from reduced NAD to form ethanol, catalysed by alcohol dehydrogenase

Oxidised NAD can continue to go back and accept hydrogen from glucose, so glycolysis can continue

63
Q

Define the term respiratory substrate.

A

An organic substance that can be used for respiration

64
Q

Explain the difference in relative energy values of carbohydrate, lipid and protein respiratory substrates.

A

The higher the number of hydrogen atoms per mole, the higher the relative energy value, as more NAD molecules can be reduces & used in the Electron Transport Chain.

Lipids have the most, followed by proteins, and then carbohydrates.

Biology (13 decks)

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