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Biology HL > Respiration (CQC) > Flashcards

Respiration (CQC) Flashcards

1
Q

What is energy?

A

The ability to work

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2
Q

What can you do with ATP?

A
  • Muscle contraction
  • Active transport
  • Mitosis
  • Glycolysis (in respiration)
  • Endocytosis and exocytosis
  • Phosphorylates other molecules to make them more reactive
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3
Q

How does ATP release energy?

A

When ATP is hydrolysed energy is released. To synthesise more ATP, energy is needed.

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4
Q

Why is ATP useful in biological processes?

A
  • Releases energy in small amounts
  • Adds a phosphate group to other phosphate molecules, lowering the activation energy of a reaction
  • It is easily reformed
  • Can not pass out of cells
  • Broken down in a one-step reaction so acts as a rapid energy source
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5
Q

what is the word equation for respiration?

A

Glucose + Oxygen → Carbon Dioxide + Water + 32 ATP

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6
Q

what is respiration?

A

It is the controlled release of energy from organic compounds to produce ATP. This ATP is then immediately available as a source of energy in the cell.

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7
Q

what are the two forms of respiration?

A
  • Aerobic→ requires oxygen → larger yield of ATP from glucose
  • Anaerobic→ does not require oxygen→ small yield of ATP from glucose
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8
Q

why is soda lime used in respirometers?

A

Soda lime (or an alkali) is used to absorb the carbon dioxide, this is used to indicate how much respiration is going on, as the volume of the respirometer will reduce when oxygen is used in respiration

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9
Q

why does temperature need to be kept constant in respirometers?

A

Temperature needs to be kept constant as it can affect the activity of the enzymes in respiration

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10
Q

why is oxygen consumption used as a measure of metabolic rate?

A
  • Oxygen is required for aerobic respiration
  • Respiration produces ATP to release energy and produces heat
  • Oxygen consumption is proportional to energy released and metabolic rate
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11
Q

what is the structure of a mitochondrion?

A
  • outer mitochondrial membrane
  • inner mitochondrial membrane
  • cristae
  • matrix
  • inter-membrane space
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12
Q

what is the outer mitochondrial membrane?

A

Separates the contents of the mitochondria from the rest of the cell, creating ideal conditions for respiration

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13
Q

what is the inner mitochondrial membrane?

A

Contains the electron transport chains and ATP synthase. The energy lost by electrons as they move down the ETC provides energy to transport H+ ions into the inter-membrane space. H+ moving through ATP synthase provides the energy to convert ADP+ Pi → ATP

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14
Q

What are the cristae?

A

Projections of the inner membrane which increase the surface area for oxidative phosphorylation so more ATP can be produced

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15
Q

what is the matrix?

A

Converts enzymes for the Krebs Cycle and link reaction

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16
Q

what is the intermembrane space?

A

Energy lost by electron carriers is used to pump protons into this space. The concentration builds up quickly creating a proton gradient for chemiosmosis

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17
Q

where does glycolysis take place?

A

Cytoplasm

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18
Q

where does the link reaction take place?

A

the mitochondrial matrix

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19
Q

where does the krebs cycle take place?

A

The mitochondrial matrix

20
Q

where does oxidative phosphorylation take place/

A

The cristae in the inner mitochondrial membrane

21
Q

what is a coenzyme?

A

A coenzyme is a molecule that aids the function of an enzyme by transferring a chemical group from one molecule to another.

NAD, FAD and coenzyme A, are coenzymes used in respiration.

22
Q

what is phosphorylation?

A

The addition of an inorganic phosphate group (Pi) to a molecule like ADP is called phosphorylation. ADP is phosphorylated during respiration.

23
Q

what are the two types of phosphorylation that occur during respiration?

A
  • substrate-level phosphorylation
  • oxidative phosphorylation
24
Q

what is substrate level phosphorylation?

A
  1. glycolysis and Krebs cycle

A single reaction involving the direct transfer of a phosphate group from a donor molecule to ADP.

25
Q

what is oxidative phosphorylation?

A
  1. electron transport chain

A series of oxidation reactions that produce sufficient energy to form ATP from ADP and phosphate

26
Q

what is dehydrogenation?

A

The removal of hydrogen from a molecule (oxidation)

27
Q

what is decarboxylation?

A

The removal of a carbon molecule

28
Q

Outline the stage of glycolysis (AEROBIC)

A

Glycolysis is the first stage of respiration. It is unique in that it does not require oxygen so it is utilised in both aerobic and anaerobic respiration. Glycolysis takes place in the cytoplasm

  1. Glucose is activated during the process of phosphorylation to make it more reactive by the addition of phosphate groups from two molecules of ATP. Hexose Biphosphate is formed
  2. Hexose Biphosphate is split (lysis) into two molecules of Triose Phosphate (TP) which is a three carbon compound
  3. Each molecule of Triose phosphate is dehydrogenated by NAD+ to form pyruvate. This process synthesises 4 molecules of ATP (substrate level phosphorylation) and 2 molecules of reduced NAD (NADH) per triose phosphate. This creates a net gain of 2 ATP.
29
Q

What is produced from glycolysis (aerobic)

A
  • 2 pyruvate (3C)
  • 2 reduced NAD (NADH)
  • 4ATP (net gain of 2 ATP)
30
Q

what happens in the link reaction (aerobic respiration)

A

The link reaction occurs in the matrix of the mitochondria

  1. Pyruvate is dehydrogenated using NAD to form NADH. Pyruvate is decarboxylated by removing one carbon as CO2. This forms Acetate (2C)
  2. Acetate combines with Coenzyme A forming Acetyl Co-A
31
Q

what is produced from the link reaction?

A

2 Acetyl Co-A
2 Carbon Dioxide (released as a waste product)
2 reduced NAD (NADH) (For oxidative phosphorylation)

32
Q

What happens in the krebs cycle?

A
  1. Acetate from the acetyl Co-A binds with a four-carbon compound called Oxaloacetate. This releases coenzyme A to return to the Link reaction. The acetate and oxaloacetate form a six-carbon compound called citrate.
  2. Oxidative decarboxylation: a molecule of carbon dioxide is removed and a molecule of NAD+ is reduced to NADH, while oxidising and dehydrodgenating the citrate. This changes the 6- carbon citrate into a 5 carbon compound.
  3. Another oxidative decarboxylation reaction takes place, reducing another NAD+ and releasing another carbon dioxide molecule. There is also one ATP molecule generated in this step through substrate-level phosphorylation. The remaining carbon compound now has four carbons left. All six of the carbons from the original glucose molecule have now been released as six molecules of carbon dioxide
  4. To continue the cycle oxaloacetate must be regenerated, which requires further modification of the 4-carbon compound. This modification involves oxidation, reducing another molecule of NAD to reduced NAD (NADH) and also reducing a new molecule (FAD) to reduced FAD (FADH2). FAD functions similarly to NAD, as a hydrogen carrier. FAD is able to carry one more H+ than NAD when it is reduced. Oxaloacetate is now available to bind with another acetate, continuing the cycle.
33
Q

what is produced in the Krebs cycle?

A
  • oxaloacetate (recycled in Krebs cycle)
  • Co-A (recycled in links reaction)
  • 2 CO2 (released as a waste product)
  • 3 Reduced NAD (used later in oxidative phosphorylation)
  • 1 Reduced FAD (used later in oxidative phosphorylation)
  • 1ATP
34
Q

what is oxidative phosphorylation and what does it require?

A

The final stage of aerobic respiration is known as oxidative phosphorylation (in the presence of oxygen, energy is released to allow phosphorylation of ADP). In the cristae (inner mitochondrial matrix)

This occurs in the electron transport chain. This process requires:

  • Oxygen (to act as the final electron acceptor)
  • Reduced NAD and FAD which carry hydrogen
  • Electron carriers (cytochromes
35
Q

what occurs in stage 1 of oxidative phosphorylation? (the electron transport chain)

A

Reduced NAD delivers two electrons it has carried from glycolysis, the link reaction or the Krebs cycle, to the first protein complex in the ETC. These electrons power the pumping of hydrogen ions (H+) or protons across the membrane from the matrix to the inter-membrane space. The H+ must be pumped across as the membrane is impermeable to them and they are moving against their concentration gradient. The electrons are transported along the ETC, pumping more H+ as they go. Reduced FAD also delivers its two electrons to the ETC but does so at the second protein complex and therefore leads to fewer protons being pumped

36
Q

what occurs in stage 2 of oxidative phosphorylation? (generation of a proton gradient along the ETC)

A

The electrons from all ten reduced NAD and two reduced FAD will pump many H+ ions across the inner membrane into the intermembrane space. As the space between the inner and outer membranes is small and narrow, and because the protons do not diffuse across membranes on their own, a high concentration of protons is established in the intermembrane space. This forms a proton gradient across the inner membrane with a high concentration on the intermembrane side and a low concentration on the matrix side of the membrane.

37
Q

what happens in stage 3 of oxidative phosphorylation? (chemiosmosis and the synthesis of ATP in the mitochondrion)

A

The H+ have one path to follow to move back across the inner membrane and down their concentration gradient. This is through a specialised protein channel called ATP synthase.

The flow of protons (proton motive force) generates the energy required to phosphorylate ADP using inorganic phosphate to form ATP. This method of generating ATP is called oxidative phosphorylation. The ATP synthase has a structure that rotates like a turbine. As the H+ flow through, it rotates and generates the ATP. This flow of protons down their electrochemical gradient is called chemiosmosis. It is thought that three H+ are used to phosphorylate each ADP to ATP but estimates range from two to four in most cases.

38
Q

what happens in stage 4 of oxidative phosphorylation? (role of oxygen as the terminal electron acceptor in aerobic cell respiration?

A

Once the electrons have passed along the ETC, they need somewhere to go. Each molecule of oxygen splits and accepts four electrons and four protons becoming two molecules of H2O in the matrix of the mitochondrion. This allows all of the other processes of aerobic respiration to continue. When oxygen is not present to accept these electrons, more cannot join the ETC, which means NAD and FAD cannot be regenerated by oxidation and therefore there is no longer a supply of NAD and FAD to continue the link reaction and the Krebs cycle.

39
Q

outline the process of oxidative phosphorylation (full process)

A

Reduced NAD delivers two electrons it has carried from glycolysis, the link reaction or the Krebs cycle, to the first protein complex in the ETC. These electrons power the pumping of hydrogen ions (H+) or protons across the membrane from the matrix to the inter-membrane space. The H+ must be pumped across as the membrane is impermeable to them and they are moving against their concentration gradient. The electrons are transported along the ETC, pumping more H+ as they go. Reduced FAD also delivers its two electrons to the ETC but does so at the second protein complex and therefore leads to fewer protons being pumped
The electrons from all ten reduced NAD and two reduced FAD will pump many H+ ions across the inner membrane into the intermembrane space. As the space between the inner and outer membranes is small and narrow, and because the protons do not diffuse across membranes on their own, a high concentration of protons is established in the intermembrane space. This forms a proton gradient across the inner membrane with a high concentration on the intermembrane side and a low concentration on the matrix side of the membrane.
The H+ have one path to follow to move back across the inner membrane and down their concentration gradient. This is through a specialised protein channel called ATP synthase.

The flow of protons (proton motive force) generates the energy required to phosphorylate ADP using inorganic phosphate to form ATP. This method of generating ATP is called oxidative phosphorylation. The ATP synthase has a structure that rotates like a turbine. As the H+ flow through, it rotates and generates the ATP. This flow of protons down their electrochemical gradient is called chemiosmosis. It is thought that three H+ are used to phosphorylate each ADP to ATP but estimates range from two to four in most cases.
Once the electrons have passed along the ETC, they need somewhere to go. Each molecule of oxygen splits and accepts four electrons and four protons becoming two molecules of H2O in the matrix of the mitochondrion. This allows all of the other processes of aerobic respiration to continue. When oxygen is not present to accept these electrons, more cannot join the ETC, which means NAD and FAD cannot be regenerated by oxidation and therefore there is no longer a supply of NAD and FAD to continue the link reaction and the Krebs cycle.

40
Q

why does the lack of oxygen lead to anaerobic cell respiration?

A

Most energy in aerobic respiration comes from oxidative phosphorylation. Anaerobic respiration only produces ATP in glycolysis, because if there is no oxygen present it cannot act as the final electron acceptor. This stops the electron transport chain and Krebs cycle as NAD and FAD cannot be oxidised. Less ATP is produced in anaerobic respiration as it can only be synthesised in glycolysis.

41
Q

what are the two anaerobic pathways?

A
  • Alcoholic fermentation (Plants and yeast)
  • Lactic fermentation (animals and some bacteria/fungi)
42
Q

what happens in alcoholic fermentation (plants and yeast)

A

When there is insufficient oxygen, the reduced NAD (NADH) must be oxidised back to NAD+ so that the energy-yielding phase of glycolysis can continue
In yeast, pyruvate is decarboxylated to ethanal (2C), releasing CO2. The enzyme alcohol dehydrogenase then reduces ethanal to ethanol, and at the same time oxidises NAD back to NAD+
CH3CHO + NADH → C2H5OH + NAD+
This process is irreversible and a high concentration of ethanol will kill the cell

43
Q

what happens in lactic fermentation (Animals and some bacteria/ fungi)

A

The main aim of lactic fermentation is to:
→ Re-oxidise NAD so that it can be reused in glycolysis
→ Prevent build-up of pyruvate so glycolysis can continue
Pyruvate is reduced by NADH to form lactate also known as lactic acid. As this is a redox reaction, NADH is oxidised back to NAD since an H atoms is donated to the pyruvate.
This reaction is catalysed by lactate dehydrogenase
1 molecule of NADH is oxidised per pyruvate molecule
1 molecule of glucose will produce two molecules of ATP in using this form of anaerobic respiration. This process is reversible as the lactate can react with oxygen to reform pyruvate.

44
Q

why is lactate harmful to animals?

A

Why is lactate harmful to animals?

Lactate lowers the pH as it forms lactic acid. This inhibits enzyme activity, leading to muscle fatigue.

Therefore, lactate can be converted back into pyruvate or be transported to the liver where it is stored as glycogen.

45
Q

what are the key differences between aerobic and anaerobic respiration?

A

Aerobic:
Requires Oxygen
Involves glycolysis, the link reaction, Krebs cycle and oxidative phosphorylation (ETC)
Generates large amounts of ATP slowly
Takes place in the cytoplasm and mitochondria
Requires activation energy provided by two molecules of ATP
Net production of 32-34 ATP
Generates reduced NAD
Regenerates NAD in the Krebs cycle

Anaerobic:
Does not require oxygen
Involves glycolysis only
Generates small amounts of ATP rapidly
Takes place in the cytoplasm
Requires activation energy provided by two molecules of ATP
Net production of 2 ATP
Generates reduced NAD
Regenerates NAD by alcoholic fermentation or lactate fermentation

46
Q

Oxidative Phosphorylation (condensed)

A
  1. The carriers reduced NAD and reduced FAD carry hydrogen. When it is released and it seperates to H+ and electrons
  2. Electrons are passed down the electron transport chain in a series of oxidation- reduction reactions. The electrons lose energy as they move down the ETC
  3. This energy is used to pump protons into the inter-membrane space
    - this creates an electrochemical gradient where the concentration of protons is higher in the inter-membrane space than that of the matrix
  4. H+ diffuse down their electrochemical gradient
    - H+ through the stalked particle which has the enzyme ATP synthase as the head peice
    - this causes a conformational change which releases energy to convert ADP +Pi –> ATP
  5. Oxygen acts as the final electron acceptor
    - oxygen combines with electrons from the ETC and protons from reduced NAD and reduced FAD
    4H+4e- +O2 –> H2O
    - This enables more electrons to move down the electron transport chain and ATP synthesis to continue

Biology HL (8 decks)

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