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Biology > Chapter 12: Energy And Respiration > Flashcards

Chapter 12: Energy And Respiration Flashcards

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1
Q

What are autotrophs?

A

Organisms that can use an inorganic carbon source in the form of carbon dioxide are called autotrophs.

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2
Q

What are heterotrophs?

A

Those needing a ready made organic supply of carbon are heterotrophs.

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3
Q

What are some examples where work is done in living organisms? (6)

A
  1. The synthesis of complex substances from simpler ones(anabolic reactions). e.g. Polysaccharide from monosaccharides
  2. The active transport of substances against a diffusion gradient, such as the activity of the Na-K pump.
  3. Mechanical work such as muscle contraction and other cellular movements. e.g. movement of vesicles through the cytoplasm.
  4. In a few organisms, bioluminescence and electrical discharge.
  5. Homeostasis
  6. DNA replication
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4
Q

Write down the respiration equation?

A

glucose + oxygen= carbon dioxide + water

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5
Q

How is the activation energy of glucose overcome? (2)

A

It is overcome by lowering it using enzymes and also by raising the energy level of the glucose by phosphorylation.

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6
Q

What is the equation of the breakdown of ATP to ADP?

A

ATP+ H20 = ADP+H3PO4(Phosphoric acid)

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7
Q

Describe how ATP is broken down to adenosine.

A

ATP undergoes a hydrolysis reaction which removes one inorganic phosphate ion(Pi/phosphoric acid) from ATP(triphosphate) to form ADP(diphosphate). This releases 30.5kJ of energy.
The next reaction also produces an inorganic phosphate ion and breaks down to AMP. This reaction also releases 30.5kJ.
The last reaction where AMP is broken down to adenosine removes the last phosphate group, producing an inorganic phosphate ion and releasing 14.2kJ.
It doesn’t come from breaking bonds, but rather from changes in chemical potential energy.

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8
Q

Are the ATP reactions reversible?

A

Yes

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9
Q

What are some advantages of ATP in the body? (5)

A
  1. ATP is readily hydrolysed to release energy.
  2. It is an immediate source of energy.
  3. It is also small and water soluble allowing it to be transported around the cell.
  4. Due to the hydrolysis of ATP being a reversible reaction, ATP synthase can reattach the Pi to ADP to form ATP.
  5. It has a high turnover rate.
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10
Q

What happens to any excess energy produced when doing work?

A

Any excess energy produced due to the energy-requiring reactions using less energy than released by the hydrolysis of ATP is converted to thermal energy.

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11
Q

What is an energy currency molecule?

A

It acts as the immediate donor of energy to the cell’s energy requiring reactions.

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12
Q

What is an energy storage molecule? Give examples.

A

An energy storage molecule is a short term (glucose or sucrose) or long term (glycogen, starch or triglyceride) store of chemical potential energy.

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13
Q

What is active transport?

A

Active transport is the movement of ions and molecules across a partially permeable membrane against a concentration gradient requiring ATP.

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14
Q

How does the sodium-potassium pump work with respect to ATP?

A

The Na-K pump is a protein that spans the entire cell surface membrane. It has binding sites for sodium ions and for ATP on the inside, and for potassium ions on the outside. The protein acts as an ATPase and catalyses the hydrolysis of ATP to ADP and Pi, releasing energy to drive the pump. Changes in the shape of the protein move sodium and potassium ions across the membrane in opposite directions. For each ATP used, two potassium ions move into the cell and three sodium ions move out of the cell. As only two K ions are added to the cell contents for every three Na ions removed, a potential difference is created across the membrane that is negative on the inside with respect to the outside. Both K and NA ions leak back across the membrane, down their diffusion gradients. However, cell surface membranes are much less permeable to sodium ions that potassium ions, so this diffusion actually increases the potential difference across the membrane.

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15
Q

What are the four stages of glucose breakdown?

A

Glucose breakdown can be divided into four stages|:

  1. Glycolysis
  2. Link reaction
  3. Krebs cycle
  4. Oxidative phosphorylation
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16
Q

What is glycolysis?

A

It is the splitting/lysis of glucose to form 2 molecules of pyruvate (3C) which occurs in the cytoplasm of the cell.

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17
Q

Where does glycolysis take place?

A

In the cytoplasm of the cell.

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18
Q

Why is glucose phosphorylated during respiration?

A

It is phosphorylated using 2 ATP molecules to provide the activation energy for the reaction.

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19
Q

Draw the process of glycolysis

A

Up till pyruvate with ATP and NAD

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20
Q

What is the net gain of ATP and NAD at the end of glycolysis?

A

Net gain of 2ATP and 2NADH(reduced NAD)

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21
Q

What happens to the pyruvate in terms of location and how does it do it?

A

The pyruvate pass from the cytoplasm through the outer and inner membrane structure of the mitochondria into the mitochondrial matrix by means of active transport.

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22
Q

What happens in the link reaction?

A

It is decarboxylated (carbon dioxide is removed), dehydrogenated (hydrogen is removed) and combined with the coenzyme A(CoA) to give acetyl coenzyme A. This is known as the link reaction. The hydrogen removed from pyruvate is transferred to NAD.

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23
Q

What is coenzyme A and what is its function?

A

Coenzyme A is a complex molecule composed of nucleoside (adenine plus ribose) with vitamin (pantothenic acid). It acts as a carrier for acetyl groups (CH3-CO) to the Krebs cycle.

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24
Q

What else can also be used to produce acetyl CoA? *fat

A

Fatty acids from fat metabolism may also be used to produce acetyl CoA. Fatty acids are broken down in the mitochondrion in a cycle of reactions in which each turn of the cycle shortens the fatty acid chain by a two-carbon acetyl unit. Each of these can combine with CoA to produce acetyl CoA, which, like that produced from pyruvate, now enters the Krebs cycle.

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25
Q

What is the equation form of the reversible link reaction?

A

pyruvate + CoA + NAD = acetyl (2C) CoA + NADH + CO2

26
Q

What is the net gain after the link reaction?

A

There is a net gain of CO2 and NADH. Due to there being 2 pyruvate molecules formed during glycolysis, net gain is 2 times.

27
Q

Where does the Krebs cycle occur?

A

In the matrix of the mitochondrion

28
Q

What is the Krebs cycle and what is its main contribution in respiration?

A

The Krebs cycle is a closed pathway of enzyme controlled reactions. Its most important contribution is the release of hydrogens which is then used in oxidative phosphorylation to provide energy to make ATP.

29
Q

What are the three main stages of the Krebs cycle?

A
  • Acetyl (2C) CoA combines with Oxaloacetate (4C) to produce Citrate (6C).
  • Citrate is decarboxylated to produce CO2, and dehydrogenated to reduce NAD and FAD.
  • Oxaloacetate is regenerated to continue the cycle.
30
Q

What is the net gain at the end of the Krebs cycle? (4)

A
  1. 2 carbon dioxide molecules
  2. 1 FADH
  3. 3 NADH
  4. 1 ATP molecule

Remember there are 2 acetyl CoA molecules so net gain is 2 times.

31
Q

Does the Krebs cycle make use of oxygen?

A

Although a part of aerobic respiration, it makes no use of oxygen.

32
Q

Where does oxidative phosphorylation take place?

A

In the inner mitochondrial membrane

33
Q

What is a respiratory complex?

A

It is a functional unit that consists of one of four types of membrane protein carriers. These proteins are arranged in such a way that electrons can be passed from one to another down an energy gradient.

34
Q

What happens in oxidative phosphorylation and the electron transport chain (ETC)? *complete process

A

Reduced NAD and reduced FAD are passed to the electron transport chain. Here, the hydrogens are removed from the two hydrogen carriers (reduced NAD and FAD) and each is split into its constituent proton (H+) and electron (e−). Th e energetic electron is transferred to the first of a series of electron carriers.
the protein in a respiratory complex is arranged in such a way that electrons can be passed from one to another down an energy gradient. As an electron moves from one carrier at a higher energy level to another one at a lower level, energy is released. Some of this energy is used to move protons from the matrix of the mitochondrion into the space between the inner and outer membranes of the mitochondrial envelope. Th is produces a higher concentration of protons in the intermembrane space than in the matrix, setting up a concentration gradient. Now, protons pass back into the mitochondrial matrix through protein channels in the inner membrane, moving down their concentration gradient. Associated with each channel is the enzyme ATP synthase. As the protons pass through the channel, their electrical potential energy is used to synthesise ATP in the process called chemiosmosis.
Finally, oxygen has a role to play as the final electron acceptor. In the mitochondrial matrix, an electron and a proton are transferred to oxygen, reducing it to water. The process of aerobic respiration is complete.

35
Q

How does chemiosmosis work? Describe the steps.

A

Most ATP in cells is generated using electrical potential energy. This energy is from the transfer of electrons by electron carriers in mitochondria and chloroplasts. Protons are stored as a potential difference across the phospholipid membranes and are allowed to flow down their concentration gradient(by facilitated diffusion) through a protein channel that spans the phospholipid bilayer. Part of this protein acts as an enzyme that synthesises ATP and is called ATP synthase. The transfer of three protons allows the production of one ATP molecule, provided that ADP and an inorganic phosphate group (Pi) are available inside the organelle. This process occurs both in mitochondria and chloroplasts. ATP synthase has three binding sites and a part of a molecule (gamma) that rotates as hydrogen ions(H+) pass. This allows them to pass sequentially through three phases:

  1. binding ADP and Pi
  2. forming tightly bound ATP
  3. releasing ATP
36
Q

What happens to the carbon dioxide produced?

A

It leaves the mitochondrion.

37
Q

What happens to the water produced?

A

It leaves the mitochondrion and enters the cytoplasm

38
Q

What is the difference between the theoretical and realistic values of production of ATP from NAD and FAD and why?

A

Theoretical:
• Reduced NAD produces 3 molecules of ATP
• Reduced FAD produces 2 molecules of ATP

However, some energy is used to transport ADP into the mitochondrion and ATP into the cytoplasm. This takes up 25% of the total energy yield of electron transfer.

Realistically:
• Reduced NAD produces 2.5 molecules of ATP
• Reduced FAD produces 1.5 molecules of ATP

The number of ATP molecules actually produced varies in different tissues and different circumstances.

39
Q

What are the full forms of NAD and FAD?

A

NAD- nicotinamide adenine dinucleotide

FAD- flavin adenine dinucleotide

40
Q

What is the equation of oxygen in the final stage of respiration?

A

0.5O2 + 2H+ +2e= H2O

41
Q

Why does the intermembrane space of the mitochondria have a lower pH than the matrix?

A

This is as a result of the protons that are released into the intermembrane space by the activity of the electron transport chain.

42
Q

What is the role of the enzymes present in the mitochondrial matrix?

A

The matrix is the site of the link reaction and Krebs cycle and contains the enzymes needed for these reactions.

43
Q

What are the tiny spheres, about 9nm, present on the inner membrane?

A

ATP synthase

44
Q

What happens in alcoholic fermentation? Draw it

A

Glucose is converted to pyruvate producing an ATP molecule. This reaction gives off 2 hydrogen atoms which combine with NAD to produce 2 reduced NAD. The pyruvate is the decarboxylated to ethanal. This ethanal produced is then reduced with the hydrogen atoms from the reduced NAD(NAD gets recycled back to NAD). This reduction of ethanal(CH3CHO) to ethanol(C2H50H) is done by the enzyme alcohol dehydrogenase. This conversion of glucose to ethanol is called alcoholic fermentation.

45
Q

In which organisms does alcoholic fermentation take place?

A

Yeast and in some plant tissues.

46
Q

In which organisms does lactic fermentation take place?

A

In mammalian muscles and microorganisms excluding yeast.

47
Q

What happens in lactic fermentation?

A

Glucose is converted to pyruvate in the process of glycolysis. This reaction includes NAD becoming reduced and ATP being produced. The pyruvate formed is then reduced by the two hydrogen atoms that were released during glycolysis to lactate. This reduction conversion is done by the enzyme lactate dehydrogenase.

48
Q

Why is NAD released in both types of fermentation?

A

This is to allow glycolysis to occur in anaerobic conditions.

49
Q

What happens to the lactate produced?

A

It is carried by the blood to the liver and converted back to pyruvate(20%) and the remainder is converted to glycogen.

50
Q

What three things is oxygen needed for post-exercise?

A
  • Conversion of lactate to glycogen in the liver
  • Reoxygenation of haemoglobin in the blood
  • A high metabolic rate, as many organs are operating above resting level.
51
Q

What is oxygen debt?

A

Removing the lactic acid after exercise is the cause of the oxygen debt

52
Q

Can lipids be respired and how?

A

Lipids can be respired and when doing so, carbon atoms are removed in pairs, as acetyl coenzyme A, from the fatty acid chains and fed into the Krebs cycle.

53
Q

Can amino acids be respired and how?

A

Amino acids can be respired by converting the carbon-hydrogen skeletons of amino acids into pyruvate or into acetyl coenzyme A.

54
Q

Why do lipids have a higher energy density?

A

This is because most of the energy liberated in aerobic respiration comes from the oxidation of hydrogen to water when reduced NAD and reduced FAD are passed to the electron transport chain. Hence, the greater the number of hydrogens in the structure, the greater the energy value. Fatty acids have more hydrogens per molecule than carbohydrates and therefore, lipids have a greater energy density, than carbohydrates or proteins.

55
Q

What is the function of a calorimeter?

A

The energy value of a substrate is determined by burning a known mass of the substance in oxygen in a calorimeter

56
Q

What is the respiratory quotient and what is the equation?

A

The ratio of oxygen taken in to carbon dioxide given out. It is used to show what substrate is being used in respiration, and whether or not anaerobic respiration is occurring.
𝑅𝑄 = (𝑣𝑜𝑙𝑢𝑚𝑒/moles 𝑜𝑓 𝐶𝑂2 𝑔𝑖𝑣𝑒𝑛 𝑜𝑢𝑟 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑡𝑖𝑚𝑒)/
(𝑣𝑜𝑙𝑢𝑚𝑒/moles 𝑜𝑓 𝑂2 𝑡𝑎𝑘𝑒𝑛 𝑖𝑛 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑡𝑖𝑚e)

57
Q

What are the respiratory quotients for carbohydrates, lipids, proteins?

A

Carbohydrates- 1.0
Lipids- 0.7
Proteins- 0.9

58
Q

What values of the respiratory quotient determine whether it is anaerobic or aerobic?

A

When values are closer to infinity or higher than 1.0, anaerobic respiration is occurring
values below 1 shows aerobic respiration

59
Q

Why is there no RQ value for muscle cells?

A

No RQ value for muscle cells in anaerobic respiration as only lactate is produced with no CO2 being produced.

60
Q

What are the adaptations of rice for wet environments?

A
  1. Can respond to flooding by growing taller, ensuring top part of leaves and flowers are held above water, allowing oxygen and carbon dioxide to be exchanged via stomata.
  2. Contain loosely packed aerenchyma cells in the cortex of stems allowing oxygen to diffuse to deprived areas.
  3. Leaves have a hydrophobic surface that holds a thin layer of air in contact with the leaf surface.
  4. Can tolerate high levels of ethanol (toxic) by the
    production of alcohol dehydrogenase which breaks it
    down
  5. Ethanol stimulates gibberellin, which in turn stimulates cell division, hence increasing internodal length

Biology (19 decks)

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