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Respiration Flashcards

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Biology 101 flashcards
1
Q

What are autotrophs?

A

Eg. Plants
Have the ability to harness light energy from the sun and convert it into chemical energy which is stored in the form of carbohydrates and other organic compounds formed during photosynthesis

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2
Q

What are heterotrophs ?

A

Eg. Animals
Depend on autotrophs as the source of energy
They have digestive system to break down complex organic compounds into simple, soluble molecules for absorption into cell
They then obtain the energy stored in the absorbed molecules by further breaking them down via cellular respiration

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3
Q

What is cellular respiration ?

A

The sequence of enzyme-controlled steps in which chemical energy in an organic molecule, usually glucose, is released by oxidation
Energy released is trapped in the form of ATP

DIFFERENT from gaseous exchange - obtaining oxygen for respiration and removal of carbon dioxide as gaseous waste

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4
Q

What is the main respiratory substrate ?

A

Glucose

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5
Q

What are the two types of respiration ?

A

Aerobic respiration - occurs in presence of oxygen
Anaerobic respiration - occurs in absence of oxygen

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6
Q

What is ATP ?

A

Adenosine Triphosphate - the universal energy carrier functioning as instant readily available energy currency that cells use to carry out cellular processes in all living organisms

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7
Q

What are some roles of ATP

A
  • anabolic respiration
  • active transport
  • movement
  • maintenance of constant body temp
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8
Q

What is the structure of ATP ?

A

Ribose sugar
Nitrogenous base adenine
3 phosphate groups

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9
Q

How is ATP made ?

A

From AMP (adenosine monophosphate) by addition of 2 phosphate groups
From ADP (adenosine diphosphate) by addition of 1 phosphate group

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10
Q

What are the three characteristics of ATP ?

A
  1. Small and soluble - able to diffuse / transported to different parts of the cell where it is required
  2. Can be recycled - hydrolysis / de-phosphorylation of ATP to ADP releases energy for cell to do work, ADP can then be re-phosphorylated into ATP during cellular respiration
  3. Universal energy carrier
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11
Q

What is de-phosphorylation of ATP ?

A

Removal of phosphate groups from ATP - hydrolysis of ATP to release energy

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12
Q

What is phosphorylation of ATP?

A

ADP and inorganic phosphate converted back to ATP with addition of phosphate to ADP - condensation reaction

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13
Q

What does de-phosphorylation and phosphorylation link ?

A

Links the exergonic (reactions that release energy) and endergonic (reactions that require input of energy) reactions of cell

Exergonic - condensation
Endergonic - hydrolysis

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14
Q

What is the overall equation of aerobics respiration ?

A

C6H12O6 + 6O2 —> 6CO2 + 6H2O + ATP

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15
Q

What are the four stages of aerobic respiration and where it occurs in the cell?

A
  1. Glycolysis - cytoplasm
  2. Link reaction - matrix of mitochondria
  3. Krebs cycle - matrix of mitochondria
  4. Oxidative phosphorylation involving electron transport chain - inner membrane/cristae of mitochondria
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16
Q

What are the four main stages in glycolysis ?

A

I. Phosphorylation of sugar
II. Lysis
III. Oxidation via dehydrogenation
IV. Substrate-level phosphorylation

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17
Q

What happens during phosphorylation of sugar ?

A

Glucose (6C) enters cell via facilitated diffusion and is phosphorylated twice to form fructose-1,6 i phosphate (6C)
For each phosphorylation step, the phosphate group is donated by 1 ATP, thus 2 ATP used
Enz phosphofructokinase (PFK) catalyses addition of second phosphate group - rate determining step of glycolysis

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18
Q

Why phosphorylation glucose ?

A
  1. It activates glucose by increasing the energy level so that more energy can be extracted later on
  2. Phosphate group carry negative charge which cause the glucose molecules to be trapped within the cell as they cannot pass through the cell surface membrane
  3. Maintains steep concentration gradient for further uptake of glucose into cell as glucose concentration in cell is low as it is being converted to fructose-1,6 biphosphate
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19
Q

What is PFK inhibited by ?

A

High levels of ATP - allosteric inhibition or end-product inhibition

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20
Q

What occurs in Lysis ?

A

Fructose-1,6 biphosphate (6C) is lysed/split into 2 molecules of trios phosphates (TP) (3C)

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21
Q

What occurs in oxidation via dehydrogenation ?

A

TP oxidise via removal of 2 H atom per TP (dehydrogenation) by dehydrogenase enz
Co-enz NAD accepts protons and electrons from the H atoms (4 total from 2 TP) to form 2 reduced NAD
Inorganic phosphate is added to TP to form 1,3-bisphosphoglycerate

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22
Q

What occurs in substrate level phosphorylation ?

A

1,3-bisphosphoglycerate is dephosphorylated to form 3-phosphoglycerate (PGA) / glycerate-3-phosphate (GP) which is dephosphorylated to form pyruvate (3C)
The two phosphate groups removed are used to form 2 ATP from 2 ADP (total 4 ATP formed from 2 1,3-bisphosphoglycerate)
Enzyme is needed to transfer the phosphate from sugar substrate to ADP

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23
Q

What is the input/reactants of glycolysis per glucose molecule ?

A

1 glucose molecule (6C)
2 ATP
2 NAD

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24
Q

What is the output/products of glycolysis of one glucose molecule ?

A

2 molecules pyruvate (3C)
2 ATP
2 reduced NAD

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25
Q

How much ATP is produced from glycolysis of one glucose molecule ?

A

Net 2 ATP (4-2)

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26
Q

What kind of enzyme is PFK ?

A

Allosteric enzyme which is responsible for the second phosphorylation step in glycolysis

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27
Q

What are the substrates of PFK enz ?

A

Fructose-6-phosphate and ATP - in order to catalyse transfer of phosphate group from ATP to fructose-6-phosphate

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28
Q

What is the allosteric inhibitor of PFK?

A

ATP in high concentration - binds to allosteric site

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29
Q

What binds to the allosteric site and active site of PFK ?

A

Allosteric site : inhibitor - ATP
active site : substrate - ATP, fructose-6-phosphate

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30
Q

What happens at Low ATP concentrations for allosteric inhibition of PFK?

A
  • chances of ATP binding to allosteric site on PFK and acting as an allosteric inhibitor is low
  • 3D conformation of enz remains in active state and shape of active site is complementary
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31
Q

What happens at high ATP concentrations for allosteric inhibition of PFK?

A
  • as ATP level increases, chances of ATP binding to allosteric site increases
  • 3D conformation of enz will change to inactive, the active site is no longer complementary to substrate molecules
  • glycolysis is inhibited and respiration slows down
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32
Q

What are the other allosteric regulators of PFK ?

A
  • ADP and AMP act as allosteric activators : high levels of ADP and AMP = Low levels ATP
  • citrate from Krebs cycle act as allosteric inhibitors : high level citrate = high level respiration = high level ATP
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33
Q

What is the key reaction in link reaction ?

A

Oxidative decarboxylation

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34
Q

What happens during link reaction ?

A
  • pyruvate diffused through the outer membrane of mitochondria then is transported into the matrix of the mitochondria via a transport protein across the inner membrane
  • in the mitochondrial matrix pyruvate (3C) undergoes oxidative decarboxylation to form acetyl-coA (2C) :
    1. Pyruvate is decarboxylated via the removal of carbon dioxide to form a 2C fragment
    2. 2C molecule is then oxidised via dehydrogenation forming 1 reduced NAD
    3. coenzyme A added to oxidised 2C molecule to from acetyl-coA
35
Q

What are the products/outputs of link reaction per pyruvate molecule ?

A

1 CO2 (waste product)
1 reduced NAD
1 acetyl-coA

36
Q

What is the input/reactant of link reaction per pyruvate molecule ?

A

1 pyruvate molecule

37
Q

What is the products/outputs of link reaction per glucose molecule ?

A

2 CO2 (waste product)
2 reduced NAD
2 acetyl-coA

38
Q

What are the inputs/reactants of link reaction per glucose molecule ?

A

2 pyruvate

39
Q

What are the key reactions of Krebs cycle ?

A

Oxidative decarboxylation
Oxidation via dehydrogenation
Substrate-level phosphorylation

40
Q

Why is the Krebs cycle called a cycle?

A

The acetyl groups (in acetyl-coA) are not oxidised directly but are added to oxaloacetate (OAA) which acts as an acceptor
At the end of a series of reactions, the OAA is regenerated to allow more acetyl groups to be accepted

41
Q

What are the three main stages of the Krebs cycle ?

A
  1. Acetyl-coA (2C) is accepted by oxaloacetate (4C) to form citrate (6C)
  2. Citrate then undergoes oxidative decarboxylation twice to form 2 reduced NAD and 2 CO2 per acetyl-coA
  3. 1 ATP is formed via substrate-level phosphorylation. 2 additional oxidation reactions converts NAD and FAD into reduced NAD and reduced FAD and regenerates oxaloacetate (OAA)
42
Q

One Krebs cycle = ?

A

Complete oxidation of 1 acetyl-coA

43
Q

What are the outputs/products of Krebs cycle per molecule of acetyl-coA?

A

2 CO2
1 ATP
3 reduced NAD
1 reduced FAD

44
Q

What are the outputs/products of Krebs cycle per molecule of glucose ?

A

4 CO2
2 ATP
6 reduced NAD
2 reduced FAD

45
Q

What are the two key functions of oxidative phosphorylation?

A
  1. Produce ATP with the formation of water
  2. Regenerate NAD and FAD
46
Q

What is an electron transport chain ?

A

Electron carriers embedded in the inner mitochondrial membrane arranged in order of progressively lower energy levels

47
Q

What is the function of the ETC ?

A

transfer electrons while harnessing the energy from the electrons to pump protons (H+) from the matrix into intermembrane space

48
Q

What is an ATP synthase ?

A

Protein found in the inner mitochondrial membrane which allows the facilitated diffusion of protons (H+) from intermembrane space into matrix and the synthesis of ATP from ADP

49
Q

What is chemiosmosis ?

A

Mechanism which uses energy from proton gradient to synthesis ATP

50
Q

What are the three main components of chemiosmosis ?

A
  1. Electron transfer along ETC which releases energy to pump protons across the inner mitochondrial e membrane (active transport)
  2. Generation of proton gradient which allows protons to diffuse across ATP synthase (facilitated diffusion)
  3. ATP synthesis via ATP synthase which phosphorylates ADP into ATP
51
Q

Outline the process of oxidative phosphorylation (ETC)

A

Reduced NAD shuttle high energy electrons to the first electron carrier of the ETC, protons are released into the matrix

The electron carrier becomes reduced and passes the electrons to the next electron carrier, becoming oxidised to accept more electrons from another reduced NAD and the second carrier becomes reduced

As electron carriers are of progressively lower energy, at each transfer some energy is released which is used to pump protons from the matrix into intermembrane space

Since membrane is impermeable to protons, there is a build up of protons in the intermembrane space compared to matrix : energy stored in the form of a proton gradient / proton motive force

52
Q

Outline the process of oxidative phosphorylation (chemiosmosis)

A

Protons are allowed to flow back into matrix through ATP synthase via facilitated diffusion down its electrochemical gradient. Movement of protons provide energy for enz to synthesise ATP from ADP

Oxygen acts as final electron acceptor in ETC, it combines with protons and electrons to form water : reaction is catalysed by cytochrome oxidase

53
Q

How much ATP is produced from reduced NAD and reduced FAD ?

A

Reduced NAD : 2.5 ATP
Reduced FAD : 1.5 ATP

54
Q

Why is amount of ATP produced from reduced NAD and reduced FAD different ?

A

Reduced NAD passes electrons to the first electron carrier of the ETC while reduced FAD passes its electrons to an electron carrier further down

( the electron of reduced NAD a contributes to a greater extent of the proton gradient thus more ATP produced)

55
Q

What is the difference between oxidative phosphorylation and substrate-level phosphorylation ?

A

OP : energy in the form of proton gradient to form ATP
SLP : direct enzymatic transfer of phosphate from substrate to ADP to form ATP

56
Q

How much ATP is formed from OP per glucose ?

A

2 red NAD ( glycolysis ) = 5 ATP

2 red NAD ( linked reaction ) = 5 ATP

6 red NAD, 2 red FAD ( Krebs cycle ) = 18 ATP

Total : 28 ATP

57
Q

Total ATP formed from 1 glucose ?

A

32 ( 28 from OP, 2 net from glycolysis, 2 from Krebs cycle)

58
Q

Why is it important of a controlled release of energy for respiration ?

A
  • energy can be efficiently captured to form ATP
  • heat released can be controlled so that enz do not get denatured
  • cellular activities can be directed and regulated
59
Q

What is anaerobic respiration ?

A

Process in which energy in biological molecules are released then trapped in the form of ATP in the absence of oxygen

60
Q

What happens in the absence of oxygen ?

A
  • last electron carrier of ETC remains reduced as it cannot pass electron to oxygen
  • all other electron carriers cannot be re-oxidised as cannot pass on electron
  • ETC ceases thus OP cannot occur
  • reduced NAD and reduced FAD cannot be oxidised to regenerate NAD and FAD
  • Krebs cycle and linked reaction stops due to lack of NAD and FAD to accept H atoms
61
Q

What are the roles of anaerobic respiration for different organisms?

A

Aerobes : short term measure for energy to sustain vital cellular activities in anaerobic conditions
Facultative anaerobes (with or without oxygen) : allows exploitation of anaerobic environments
Obligate anaerobes (without oxygen) : survival

62
Q

Why is glycolysis still able to continue in anaerobic respiration ?

A

Presence of alternative hydrogen acceptor - allows NAD to be regenerated for glycolysis to continue and proceed 2 net ATP

63
Q

What is the alternative H acceptor for mammals and plants,fungi,yeast ?

A

Mammals : pyruvate
Yeast, plants, fungi : ethanal

64
Q

Where does anaerobic respiration occur ?

A

Cytoplasm

65
Q

What are the two types of anaerobic respiration ?

A

Alcoholic fermentation in yeast
Lactate fermentation in mammals

66
Q

What happens in alcoholic fermentation in yeast ?

A

Glucose converted to pyruvate with the formation of ATP
Pyruvate undergoes decarboxylation to form ethanal through enz pyruvate decarboxylase
Ethanal acts as alt H acceptor and accepts 2H from reduced NAD to form ethanol through alcohol dehydrogenase

67
Q

What happens in lactate fermentation in mammals ?

A

Glucose is converted into pyruvate with formation of ATP
Pyruvate acts as alt H acceptor and accepts 2H atoms from red NAD to form lactate through lactate dehydrogenase

68
Q

Compare the efficiency of anaerobic respiration to aerobic respiration

A

ATP produced per glucose : 32 ATP for aerobic VS 2 for anaerobic (16 times less efficient)

Incomplete oxidation of respiratory substrate in anaerobic:
Yeast - ethanol produced is excreted
Mammals - lactic acid will be metabolized to pyruvate in liver in presence of oxygen which then enters mitochondria for link reaction and Krebs cycle

69
Q

What are the five structural features of mitochondria ?

A

Small size
Outer membrane
Outer & inner membrane
Inner membrane
Matrix

70
Q

How is small size of mitochondria related to its function ?

A

Large SA:V, facilitating efficient diffusion of respiratory substrates between cytoplasm and mitochondria

Allows easier movement in cell to areas where energy demand is high

71
Q

How does outer membrane of mitochondria relate to its function ?

A

Allows compartmentalisation to separate contents of mitochondria form cytoplasm : allows for specialised metabolic pathways to occur inside mitochondria, regulates passage of substances in and out of mitochondria

Contains membrane proteins that function to shuttle hydrogen from reduced NAD in the cytoplasm to NAD in mitochondrial matrix

72
Q

What is the relation of outer & inner membrane of mitochondria to its function ?

A

Encloses intermembrane space and are impermeable to H+ allowing accumulation of H+ in the intermembrane space to generate proton gradient and proton motive force

73
Q

How is inner membrane of mitochondria related to its function?

A

Allows attachment of electron carriers onto membrane and their arrangement in specific order of progressively lower energy levels to form ETC

Allows attachment of ATP synthase which catalyses ATP synthesis

Infolding into cristae increases SA : allows more electron carriers to be attached to form more ETC and more ATP synthase to be attached, increases accessibility of NAD and FAD to ETC

Contains specific protein channels to facilitate movement of selective materials across thus is selectively permeable

74
Q

How is the matrix of the mitochondria related to its function ?

A

Contains enz that catalyse reactions in link reaction and Krebs cycle

Contains mitochondrial DNA RNA and ribosomes involved in synthesis of certain mitochondrial proteins

75
Q

What are the three factors affecting rate of respiration ?

A
  1. Substrate concentration
  2. Temperature
  3. Type of substrate
76
Q

How does substrate concentration affect respiration ?

A

Substrate concentration increase = increase in effective collision between respiratory substrate and enz = formation of enz-sub complex occurs at a faster rate = increase rate of respiration

At high substrate concentration : rate of respiration remains constant despite further increase in sub con as other factors have become limiting

77
Q

How does temperate affect rate of respiration ?

A

Rate of respiration increases as temp increases until optimum temp : increase in kinetic energy thus increased effective collision between respiratory enz and substrates

Beyond optimum temp rate of respiration decreases rapidly due to denaturation of respiratory enz

78
Q

How does type of substrate affect rate of respiration ?

A

Disaccharide or polysaccharide: need to be broken down into monosaccharides by hydrolysis with specific enz, if enz not found then substrate cannot be used

Other types of substrates (non carbohydrates) : lipids yield more energy due to higher H to C ratio but require more oxygen for complete oxidation than carbs, complete oxidation of proteins require more oxygen than carbs but less than fats

79
Q

What is the respiratory quotient (RQ) ?

A

Volume of carbon dioxide released over the volumen of oxygen absorbed during respiration

80
Q

How does RQ determine type of respiration and substrates ?

A

Type of respiration : RQ > 1 is anaerobic respiration since more CO2 produced than O2 used

Type of substrate : carbs RQ = 1 lipid RQ = 0.7 carbs RQ = 0.9

81
Q

What are the three ways respiration can be measured ?

A
  1. Measure rate of carbon dioxide produced
  2. Measure time taken for redox indicator to change colour
  3. Measure rate of oxygen taken up
82
Q

How is CO2 production measured ?

A
  • bubbling rate using weighted syringe
  • gas syringe
83
Q

How does time taken for redox indicator to change colour measure respiration rate ?

A

Change colour when reduced due to accepting H atoms produced from respiration

84
Q

How is oxygen taken up measured ?

A

Use a respirometer : movement of water level in U-tube = vol of oxygen taken in

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