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Biology sem 1 > 1.8: Respiration > Flashcards

1.8: Respiration Flashcards

1
Q

What do all living organisms need?

A
  • All living organisms need a constant supply of energy to stay alive.
  • All living organisms also need a source of carbon.
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2
Q

What is an autotroph?

A
  • Organisms that can make organic molecules from inorganic molecule e.g. carbon dioxide
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3
Q

What is a heterotroph?

A

Organisms that need to feed on and digest complex organic molecules (e.g. carbohydrates, proteins) that have been made by another organism.

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4
Q

What metabolic processes need oxygen?

A
  • Active transport
  • secretion
  • endocytosis
  • anabolic reactions
  • DNA replications and cell organelles
  • Movement
  • activation of chemicals
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5
Q

Label this structure of ATP

A
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6
Q

Where is ATP found?

A

In the cells of all organisms (both pro and eukaryotic)

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7
Q

When is ATP produced?

A

when energy is released

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8
Q

How can ATP move around the cell?

A

Because its small and water soluble

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9
Q

What does ATP consist of?

A

Adenine (organic base) and Ribose (a pentose sugar) Which makes up adenosine (nucleoside)

When nucleoside combines with 3 phosphates it makes ATP

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10
Q

Why does ATP break down?

A

To release energy prn in small packets

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11
Q

What is the role of ATP

A
  • releases energy.
  • The first two phosphates groups can be removed by hydrolysis. This releases 30.6 kJ mol-1 energy.
    The energy released can used for metabolism.

ADP can attach a phosphate (forming ATP) during respiration and photosynthesis. The reaction is reversible.

Energy is released in small ‘packets’ to prevent cell damage

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12
Q

What is the equation for when two phosphates are removed by hydrolysis?

A

ATP –> ADP + P (i) by hydrolysis
or
ATP + H₂O –> ADP + P(I) must include water

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13
Q

What is the equation for respiration?

A

C6H12O6 + 6O2 —> 6CO2 + 6H20 + energy

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14
Q

What is substrate level phosphorylation?

A

Formation of ATP from ADP +pi during glycolysis and the Kreb’s cycle

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15
Q

What is oxidative phosphorylation?

A

Formation of ATP, in the presence of oxygen, the chemiosmosis

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16
Q

What is Chemiosmosis?

A

The flow of hydrogen ions (protons) through ATP synthase enzymes.

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17
Q

What are the 4 stages that respiration occurs in?

A
  • glycolysis
  • link reaction
  • krebs cycle
  • oxidative phosphorylation
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18
Q

Where does glycolysis occur?

A

The cytoplasm

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19
Q

Where does the link reaction occur?

A

Mitochondrial matrix

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20
Q

Where does the Krebs cycle occur?

A

The mitochondrial matrix

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21
Q

Where does Oxidative Phosphorylation occur?

A

stalked particles on cristae (inner mitochondria membrane)

22
Q

What is glycolysis?

A

Glucose - 6 carbon atoms –> pyruvate - 3 carbon atoms

23
Q

What is oxidation?

A
  • Loss of electrons
  • Loss of hydrogen atoms
  • Gain of oxygen atom
24
Q

what is reduction?

A
  • Gain of electrons
  • Gain of hydrogen atoms
  • Loss of oxygen atoms
25
Q

what is used instead of enzymes in oxidation reduction reactions

A

coenzymes (NAD) are used
to carry hydrogen atoms between the stages of respiration.

26
Q

What is the summary of the glycolysis process?

A
  1. One glucose (6C) is converted into 2 pyruvates (3C).
  2. Net yield of 2 ATP for use by cell (total 4).
  3. ATP produced by substrate - level phosphorylation
  4. Two NAD are converted into 2 reduced NAD.
27
Q

What is the summary of the link reactions?

A

Pyruvate (3C) —> Acetate (2C)

28
Q

What is the role of these enzymes in the link reactions?

A
  • Pyruvate dehydrogenase
    Removes hydrogen from pyruvate
  • Pyruvate decarboxylase
    Removes carboxyl group, which becomes CO2
29
Q

What enzymes catalyse the reactions in the link reactions?

A

Pyruvate dehydrogenase

Pyruvate decarboxylase

30
Q

What is the link reactions process?

A
  • Pyruvate (3C) is pumped (active transport) into the matrix of the mitochondria.
  • Carbon dioxide is removed (decarboxylation). Catalysed by pyruvate decarboxylase. Acetate formed.
  • The coenzyme NAD accepts hydrogen (2H) from pyruvate to form reduced NAD. Catalysed by pyruvate dehydrogenase.
  • Acetate (2C) combines with coenzyme A (CoA) to form acetyl coenzyme A.

NO ATP IS PRODUCED!!!

31
Q

what is the reaction of the link reactions?

A

2 pyruvate + 2NAD+ + 2CoA —> 2CO2 + 2 reduced NAD + 2 acetyl CoA

32
Q

What is the Krebs cycle?

A
  • Acetate (2C) is offloaded from acetyl CoA (CoA can return to link reactions to pick up more acetate).
  • Acetate (2C) combines with oxaloacetate (4C) to form citrate (6C).
  • Citrate (6C) is decarboxylated (one CO2 removed) and dehydrogenated (2H removed) to form a 5C intermediate.
  • NAD accepts the pair of hydrogen atoms and is reduced.
  • The 5C intermediate is decarboxylated and dehydrogenated to form a 4C intermediate and another molecule of reduced NAD.
  • The first 4C intermediate releases energy which is used to form ATP from ADP + Pi. This is substrate-level phosphorylation.
  • The second 4C intermediate is then dehydrogenated. The coenzyme FAD accepts the pair of hydrogen atoms and is reduced.
  • The third 4C intermediate is then dehydrogenated again and the hydrogen is accepted by NAD to produce another reduced NAD
  • Oxaloacetate is regenerated to combine with another acetate.
33
Q

What is a summary of the Krebs cycle?

A
  • 2 carbon dioxides
  • 1 reduced FAD
  • 3 reduced NAD – which pass to the electron transport chain
  • 1 ATP
34
Q

What is OXIDATIVE PHOSPHORYLATION?

A

the formation of ATP by the addition of an inorganic phosphate
to ADP in the presence of oxygen.

35
Q

What does Oxidative phosphorylation involve?

A

electron carriers embedded in the membrane

36
Q

What does the first stage of Oxidative phosphorylation involve?

A
  • This stage provides the energy for the phosphorylation of ADP to ATP by addition of Pi (inorganic phosphate).
  • Many hydrogen atoms have been generated from glycolysis and the Krebs cycle
  • These hydrogen atoms have been collected by carriers NAD and FAD.
  • The carriers are therefore reduced.
  • Reduced NAD and FAD pass hydrogen to the electron transport chain.
  • The coenzymes become reoxidised.
37
Q

What happens in the seconds stage of Oxidative phosphorylation?

A

Hydrogen atoms are removed from NAD and FAD and they split into H+ (protons) and e-.

The electron flow along a series of electron carriers (e.g. NADH coenzyme Q reductase) in a series of oxidation – reduction reactions until finally it is transferred to oxygen (final electron acceptor)

38
Q

What happens in the third stage of Oxidative phosphorylation?

A
  • Hydrogen ions (protons) will be drawn from the solution in the matrix to reduce oxygen to water. Oxygen is the final electron acceptor.
  • As the electrons pass along the series of carriers energy is released.
  • Some of this energy is lost as heat but at some points enough is released to pump protons (from reduced NAD, not reduced FAD) into the intermembrane space.
39
Q

What is the definition of chemiosmosis?

A

the flow of protons across the inner mitochondrial membrane, which is coupled to the generation of ATP during respiration

40
Q

What is the chemiosmotic theory?

A
  • Energy released from the electron transport chain is used to pump hydrogen ions from the matrix of the mitochondria into the intermembrane space.
  • The build-up of H+ ions in the intermembrane space forms an electrochemical and pH gradient. The inner mitochondrial membrane is therefore called an energy-transducing membrane.
  • A proton gradient has been set up. This gradient is a source of potential energy.
  • Hydrogen ions (protons) can only flow back into the matrix through a protein channel in the inner membrane. The protein channel is associated with an enzyme named ATP synthase.
  • The hydrogen ions (protons) flow through the ATP synthase protein channel across the inner mitochondrial membrane, down an electrochemical gradient.
41
Q

What is the second part of the chemiosmotic theory?

A
  • H+ ions drive the rotation of part of the enzyme and join ADP to and inorganic phosphate (Pi) to form ATP.
  • The kinetic energy, or force, of this flow is called the PROTON MOTIVE FORCE.
  • The more protons there are, the greater the proton motive force, and more ATP is produced.
42
Q

Oxidative phosphorylation and chemiosmosis?

A
43
Q

What should be the total yield of ATP molecules be per glucose respired in aerobic respiration assuming each reduced NAD can yield 2.5 ATP molecules and each reduced

A

32

44
Q

State the reasons why this is rarely achieved.


A
  • Some protons leak across the mitochondrial membrane, reducing the number of protons to generate the proton motive force.
  • Some ATP produced is used to actively transport pyruvate into the mitochondria.
  • Some ATP is used for the shuttle to bring hydrogen from reduced NAD made during glycolysis, in the cytoplasm, into the mitochondria
45
Q

What occurs in anaerobic respiration?

A
  • Oxygen acts as a final electron acceptor in aerobic respiration.
  • When oxygen is absent, the electron transport chain cannot function and so oxidative phosphorylation cannot take place. The Krebs Cycle and the Link reactions also stop.
  • Glycolysis does not require oxygen so can continue.
  • 2ATP are produced during glycolysis.
  • NAD is released from reduced NAD so that it can accept more hydrogen (reduced again) so glycolysis can continue.
  • NAD is therefore RECYCLED during glycolysis.
46
Q

What are the two pathways to deoxidise NAD?

A
  • Ethanol (alcohol) fermentation - fungi such as yeast.
  • Lactate fermentation – mammalian muscle cells
47
Q

What occurs in ethanol (alcohol) fermentation (anaerobic conditions)?

A
  • Pyruvate is decarboxylated to form ethanal. CO2 is removed.
  • Catalysed by the pyruvate decarboxylase (with coenzyme thiamine diphosphate).
  • Ethanal accepts hydrogen from reduced NAD and is reduced to ethanol.
  • Catalysed by ethanol dehydrogenase.
  • NAD can now be reused in glycolysis
48
Q

What occurs in the lactate fermentation (in mammalian muscle cells)?

A
  • Pyruvate is converted into lactate.
  • Pyruvate accepts hydrogen from reduced NAD.
  • Catalysed by lactate dehydrogenase.
  • NAD can now be reused in glycolysis.
49
Q

important facts about deoxidation of NAD

A

The ethanol pathway cannot be reversed.
 The lactate pathway can be reversed when O2 is available:
- Lactate is carried to the liver in the blood and oxidized back into pyruvate.
- Pyruvate can then enter the Krebs cycle via the link reactions to produce ATP.
OR it can be:
- Converted into glucose and then glycogen for storage.
 The oxygen needed for this is the OXYGEN DEBT.
 Muscle fatigue is not caused by the lactate itself but by the reduction in pH.

50
Q

Why is the anaerobic pathway not as efficient as the aerobic pathway?

A
  • Less ATP formed
  • No Krebs cycle or oxidative phosphorylation.
  • Energy remains in the lactate.
  • Incomplete oxidation.
51
Q

What occurs in a respirometer?

A

As the soda lime absorbs the CO2 the volume of air in the respiration chamber decreases as the O2 is used up
Reduced volume of air = reduced pressure
There is a higher pressure in the tube than the chamber so air is drawn in, the manometer fluid moves towards the tube
The rate the fluid moves can be measured

Any pressure changes in the compensation tube will be due to atmospheric pressure changes
Distance fluid moved in this tube can be taken away from distance in other tube for actual respiration rate

Biology sem 1 (9 decks)

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