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Exam 2 Flashcards

1
Q

CH6

Energy

A

The capacity to do work

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2
Q

CH6

Types of Energy (2)

A

Kinetic: the energy of motion
Potential: stored energy

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3
Q

CH6

What is the form of energy that most other forms can be converted to?

A

Heat energy

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4
Q

CH6

What is heat energy measured in?

A

Calories

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5
Q

CH6

Calories

A

One calorie = heat energy required to raise the temp of 1 g of water 1 degree C

1 kilocalorie (kcal) = 1000 calories = 1 food calorie

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6
Q

CH6

How is potential energy, stored in chemical bonds, transferred from one molecule to another?

A

They are transferred by way of electrons

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7
Q

CH6

Redox Reactions

A

First, remember that redox comes from reduction-oxidation (reduction-gaining an electron; oxidation-losing an electron)

This is both oxidation and reduction occurring at the same time

These reactions are always coupled to one another

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8
Q

CH6

First Law of Thermodynamics

A

Energy cannot be created or destroyed, it can only be converted from one form to another

Ex: sunlight energy –> chemical energy
(through photosynthesis)

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9
Q

CH6

Second Law of Thermodynamics

A

Without external energy input, all systems naturally become more disorderly over time

Ex: think of a room becoming messy over time-this seems to require zero energy, whereas cleaning it (making it orderly) requires work

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10
Q

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Entropy

A

Disorder

Written as “S”

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11
Q

CH6

Free Energy

A

The energy available to do work

Written as “G” (Gibb’s Free Energy)

Free energy = Enthalpy – (Temp X Entropy)
G = H - TS

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12
Q

CH6

Enthalpy

A

Energy contained in a molecule’s chemical bonds

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13
Q

CH6

What effect do chemical reactions have on free energy?

A

Chemical reactions create changes in free energy

ΔG = ΔH - T ΔS

(Δ is the symbol “delta,” it represents a change)

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14
Q

CH6

In a chemical reaction, what happens when the products have MORE free energy than the reactants?

A

ΔG is positive (the change in free energy is a positive change); energy is gained

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15
Q

CH6

In a chemical reaction, what happens when the products contain LESS free energy than the reactants?

A

ΔG is negative (the change in free energy is negative); energy is lost

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16
Q

CH6

Endergonic Reaction

A

Requires free energy (positive ΔG)
An “energy requiring” reaction

*ender/enter ~ energy enters

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17
Q

CH6

Exergonic Reaction

A

releases free energy (negative ΔG)
An “energy yielding” reaction

*exo/exit ~ energy leaves

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18
Q

CH6

Activation Energy

A

Energy needed to get a reaction started by destabilizing chemical bonds

*even exergonic reactions require some energy just to get started

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19
Q

CH6

Catalysts

A

Substances that lower the activation energy of a reaction

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20
Q

CH6

ATP

A

Adenosine triphosphate, the energy currency of the cells

Structure:
ribose (a 5-C sugar)
adenine (a nucleotide)
three phosphates

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21
Q

CH6

Where does ATP store energy?

A

In its phosphate bonds

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22
Q

CH6

Phosphates are highly _____

A

Phosphates are highly electronegative

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23
Q

CH6
What happens because of the electronegativity in phosphates? (What are some characteristics/properties they have due to their electronegativity?) (3)

A

They naturally repel each other
Much energy is required to keep them bound to each other
Much energy is released when the P bonds are broken

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24
Q

CH6

What happens when the bond between phosphates is broken by hydrolysis?

A

*First of all, hydrolysis is the chemical breakdown of a compound due to its reaction with water

When this occurs, energy is released
ATP = ADP + Pi

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25
Q

CH6

ATP = ADP + Pi

A

ATP: adenosine triphosphate
ADP: adenosine diphosphate
Pi: inorganic phosphate

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26
Q

CH6

When ATP is hydrolyzed, energy is released. What can this energy then do?

A

This energy can fuel endergonic reactions

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27
Q

CH6

Energy released from exergonic reactions can be used to produce ______

A

ATP from ADP + Pi

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28
Q

CH6

What do enzymes do?

A

Enzymes catalyse biological reactions

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29
Q

CH6

What are enzymes’ properties/characteristics? (4)

A

Nearly all are proteins (however, not all are proteins; certain reactions involving RNA molecules are catalyzed by the RNA itself)

Lower the activation energy required for a reaction

Are not permanently changed or consumed by the reaction

Temporary enzyme-substrate complexes are formed during reactions

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30
Q

CH6

Enzymes interact with _____

A

Enzymes interact with substrates

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31
Q

CH6

Substrate

A

A molecule that will undergo a reaction

Reactants

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32
Q

CH6

Active Site

A

Region of the enzyme that binds to the substrate

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33
Q

CH6

What does “induced fit” mean?

A

An “induced fit” is what occurs when the substrate forces the enzyme to change shape in order to bind together

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34
Q

CH6

Ribozymes

A

RNA with enzymatic abilities

Ex: the ribosome is a ribozyme

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35
Q

CH6

Enzyme function is affected by _______

A

its environment

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36
Q

CH6

Some changes in an enzyme’s environment that may affect its function include: (4)

A

pH
Temperature
Concentrations of reactants and products
Regulatory molecules (co-enzymes or co-factors)

*the effects of these changes may be positive or negative

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37
Q

CH6

What effect does temperature have on enzymes?

A

Up to the optimum temperature, enzyme activity increases with rising temperature. Beyond the optimum temperature, the enzymes will become denatured (their function is destroyed).

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38
Q

CH6

What pH do enzymes have their optimal shape and charge at?

A

The preferred pH is anywhere from 6 to 8

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39
Q

CH6

Inhibitors

A

Molecules that bind to enzymes and decrease their activity

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40
Q

CH6

Types of Inhibitors

A

Competitive inhibitors: compete with the substrate for binding to the active site
Noncompetitive inhibitors: bind to sites other than the enzyme’s active site. An example is an allosteric inhibitor

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41
Q

CH6

Allosteric Enzymes

A

Exist in either an active or inactive state and possess an allosteric site where molecules other than the substrate bind

Allosteric inhibitors bind to the allosteric site to inactivate the enzyme

Allosteric activators bind to the allosteric site to activate the enzyme

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42
Q

CH6

Metabolism

A

All the chemical reactions occurring inside an organism

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43
Q

CH6

Anabolism

A

Endergonic reactions use energy to make chemical bonds

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44
Q

CH6

Catabolism

A

Exergonic reactions break bonds and energy is released

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45
Q

CH6

What are examples of additional molecules that some enzymes may require for proper function?

A

Co-factors: usually metal ions found in the active site

Co-enzymes: organic molecules, often used to donate or accept electrons in a redox reaction

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46
Q

CH6

Biochemical Pathways

A

Are a series of reactions in which the product of one reaction becomes the substrate for the next reaction

*often regulated by feedback inhibition in which the end product of the pathway is an allosteric inhibitor of an earlier enzyme in the pathway

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47
Q

CH6

Multienzyme Complexes in Membranes:

A
  1. The product of one reaction is directly delivered to the next enzyme
  2. Unwanted side reactions are reduced
  3. Reactions can be regulated as a unit
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48
Q

CH7

How do autotrophs obtain their energy?

A

They capture energy and build organic (C-based) molecules through photosynthesis

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49
Q

CH7

How do heterotrophs obtain their energy?

A

They use preformed organic molecules for both energy and to build new organic molecules

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50
Q

CH7

How do ALL organisms (regardless of it being an auto/heterotroph) extract energy from organic molecules?

A

Through cellular respiration

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51
Q

CH7

What is cellular respiration?

A

A series of redox reactions (transfer of electrons) that are also dehydrogenations (H+ or proton transfers)

1 electron + 1 proton = 1 H atom
e- + H+ = H

Therefore, what is technically transferred is hydrogen atoms

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52
Q

CH7

During redox reactions, what are electrons transferring from molecule to molecule?

A

Electrons transfer energy from one molecule to another

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53
Q

CH7

Give an example of electrons transferring energy during redox reactions.

A

NAD+ is an electron carrier.-NAD+ accepts 2 electrons and 1 proton to become NADH (this reaction is reversible)

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54
Q

CH7

What is the goal of cellular respiration?

A

To generate lots of ATP

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55
Q

CH7

How are electrons moved during respiration?

A

Electrons are shuttled by electron carriers (e- transport chains) to a final electron acceptor

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56
Q

CH7

What is the final acceptor in aerobic respiration?

A

The final acceptor is O2 (oxygen)

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57
Q

CH7

What is the final acceptor is anaerobic respiration?

A

The final acceptor is an inorganic molecule (not O2)

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58
Q

CH7

What is the final acceptor in fermentation?

A

The final acceptor is an organic molecule

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59
Q

CH7

What is the formula for aerobic respiration?

A

C6H12O6 + 6O2 –> 6CO2 + 6H2O

Energy is released, this is an exergonic reaction (a large amount of energy is released in small steps)

The electrons use some energy at each level

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60
Q

CH7

What is the change in free energy (ΔG) during aerobic respiration?

A

ΔG = - 686 kcal per mole of glucose

This can be even higher in a cell

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61
Q

CH7

What is the main outcome in cellular respiration?

A

The capture of energy in ATP

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62
Q

CH7

Electron energy makes ATP from ___ + ___

A

ADP+Pi

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63
Q

CH7

What are two ways cells make ATP from ADP+Pi?

A

Substrate-level phosphorylation

Oxidative phosphorylation

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64
Q

CH7

What is the process of substrate-level phosphorylation?

A

Pi transferred directly from a molecule (substrate) to ADP

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65
Q

CH7

Describe the process of oxidative phosphorylation.

A

ATP synthase enzyme uses energy derived from a proton (H+) gradient to make ATP

also called chemiosmosis

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66
Q

CH7

What are the 4 stages of glucose oxidation and where do they occur?

A
  1. Glycolysis– in cytoplasm
  2. Pyruvate oxidation– in mitochondrial matrix
  3. Krebs cycle – in mitochondrial matrix
  4. Electron transport & chemiosmosis – across inner membrane of mitochondrion
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67
Q 
CH7 
Explain glycolysis (step 1 of glucose oxidation).
A

Converts glucose to 2 pyruvates

A 10-step biochemical pathway that occurs in the cytoplasm

Net production of 2 ATP molecules by substrate-level phosphorylation and 2 NADH by reduction of NAD+

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68
Q

CH7

What must occur for glycolysis to continue?

A

NADH must be oxidized back to NAD+ by either:

  1. aerobic respiration – NADH oxidized back to NAD+ during electron transport. Final e-/H+ acceptor is O2, producing H2O)
  2. fermentation – NADH donates e-/H+ to an organic molecule forming a reduced organic molecule (an alcohol or acid)
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69
Q

CH7

Pyruvate in relation to glycolysis

A

The fate of pyruvate also depends on O2availability

When O2 is present, each pyruvate is oxidized to acetyl-CoA which enters the Krebs cycle

Without O2, each pyruvate is reduced in order to oxidize NADH back to NAD+

70
Q

CH7

Explain pyruvate oxidation (step 2 of glucose oxidation).

A

When O2 is present, each pyruvate is oxidized in the mitochondria in eukaryotes

The enzyme pyruvate dehydrogenase
catalyzes the oxidation of pyruvate

71
Q

CH7

What are the products of pyruvate oxidation?

A

1 CO2

1 NADH

1 acetyl-CoA (2 Cs from pyruvate added to coenzyme A)

72
Q

CH7

Explain the Krebs cycle (step 3 of glucose oxidation)

A

Oxidizes the acetyl group (carried by acetyl CoA) in the mitochondrial matrix

This is a nine step biochemical pathway; step one is
acetyl group + oxaloacetate –> citrate
(2 carbons)+(4 carbons) –> (6 carbons)

After glycolysis, pyruvate oxidation, and the Krebs cycle, each glucose molecule has been completely oxidized to:
6 CO2
4 ATP
10 NADH
2 FADH2
*last two are carried on to electron transport chain

Also called TCA cycle

73
Q

CH7

What are the products of the remaining steps of the Krebs cycle?

A

2 CO2
3 NADH
1 FADH2
1 ATP from ADP + Pi via substrate-level phosphorylation

regenerates oxaloacetate so that cycle can continue

74
Q

CH7

Explain the connection/relationship between pyruvates, glucose, and acetyl-CoA

A

Two acetyl-CoAs enter the Krebs cycle for every glucose, and two pyruvates come from every glucose

75
Q

CH7

Explain electron transport (step 4 of glucose oxidation).

A

Electrons from NADH and FADH2 are transferred to the ETC carriers
Each carrier transfers electrons to the next carrier in the chain
Each level loses some energy

76
Q

CH7

What is the electron transport chain (ETC)?

A

A series of electron carriers embedded in the mitochondrial inner membrane

This energy is used to pump protons (H+) across the membrane from the matrix to the inner membrane space
A proton gradient is established

77
Q

CH7

Where do electron transport and oxidative phosphorylation (chemiosmosis) occur?

A

The inner membrane of the mitochondrion

78
Q

CH7

(In electron transport) what brings the protons back from the intermembrane space to the matrix?

A

The high negative charge within the matrix

79
Q

CH7

How does the accumulation of protons in the intermembrane space drive protons from that space into the matrix?

A

Diffusion (chemiosmosis)

80
Q

CH7

Some protons diffuse through the membrane, but how are MOST moved to the matrix?

A

Through the ATP synthase enzyme

81
Q

CH7

Where does ATP synthase get its energy and how does it function?

A

Uses the energy of the proton gradient to synthesize ATP from ADP + Pi

Functions similarly to the rotors of bacterial flagella. Whereas flagella rotors “use ATP to spin”, ATP synthase “uses spin to make ATP”

82
Q

CH7

What do ATP synthase and bacterial flagella rotors have in common?

A

They may have a common evolutionary origin

83
Q

CH7

What are the theoretical vs the actual energy yields?

A

Theoretical energy yields:
38 ATP per glucose for bacteria
36 ATP per glucose for eukaryotes

Actual energy yields:
30 ATP per glucose for eukaryotes
reduced yield is due to “leaky” inner membrane and use of the proton gradient for purposes other than ATP synthesis

84
Q

CH7

Respiration can occur without O2. How does glycolysis continue this way? (2 ways)

A

NADH must be oxidized back to NAD+ by either:

Anaerobic respiration - uses inorganic molecules (other than O2) as final electron/H+ acceptor

Fermentation - uses organic molecules as final electron/H+ acceptor

85
Q

CH7

Anaerobic methanogens use CO2 as the final e- acceptor, producing:

A

Methane instead of water

CO2 + 4H2 + NADH → CH4 + 2H2O + NAD+

86
Q

CH7

Anaerobic sulfur bacteria use:

A

SO4 as the final e- acceptor, regenerating both NAD+ and FAD

Produces H2S instead of H2O

This happens a lot in marshes and swamps

87
Q

CH7

What does fermentation do?

A

Reduces organic molecules in order to oxidize NADH to NAD+

88
Q

CH7

Two types of fermentation:

A

Ethanol fermentation occurs in yeast; CO2 is released from pyruvate forming acetaldehyde; NADH reduces acetaldehyde to ethanol + NAD+

Lactic acid fermentation occurs in animal cells (especially muscles); NADH reduces pyruvate to lactic acid + NAD+

89
Q

CH7

Explain the catabolism of proteins.

A 
Amino acids (AAs) are deaminated to remove amino group
remainder of the AA is converted to a molecule that can be directly used in glycolysis or the Krebs cycle

Ex: alanine is converted to pyruvate
aspartate is converted to oxaloacetate

90
Q

CH7

Explain the catabolism of fats.

A

Broken down to fatty acids and glycerol
Fatty acids are converted to acetyl groups by b-oxidation
Acetyl CoAs enter Krebs

A 6-carbon fatty acid yields 20% more energy than the 6-carbon glucose

91
Q

CH7

How does the regulation of aerobic respiration occur?

A

By feedback inhibition of key enzymes.
ATP and citrate both allosterically inhibit phosphofructokinase (glycolysis)
NADH inhibits pyruvate dehydrogenase (pyruvate oxidation)
ATP inhibits citrate synthetase enzyme (Krebs cycle)

92
Q

CH7

What can glucose be used for when feedback inhibition slows down respiration?

A

For storage or to build organic molecules

93
Q

CH7

What happens when the cell runs out of ATP and NADH?

A

ADP builds back up and respiration again begins to “burn” glucose

94
Q

CH8

Where does energy for nearly all life come from?

A

Photosynthesis

95
Q

CH8

What is the formula for photosynthesis?

A

6CO2 + 12H2O –> C6H12O6 + 6H2O + 6O2

96
Q

CH8

What carries out oxygenic photosynthesis?

A

Cyanobacteria, 7 groups of algae, and plants

97
Q

CH8

What carries out non-oxygenic photosynthesis?

A

Some bacteria

98
Q

CH8

In plants, where are chloroplasts abundant?

A

In the cells of parenchyma

or mesophyll tissues

99
Q

CH8

What two types of reactions does photosynthesis include?

A

Light-dependent and light-independent

100
Q

CH8

Explain light-dependent reactions.

A

Capture light energy to make ATP and NADPH

101
Q

CH8

Explain light-independent reactions.

A

Use energy from ATP and NADPH to synthesize glucose from CO2

102
Q

CH8

How are light-dependent and light-independent reactions linked?

A

Products of LD reactions in the thylakoid membrane “feed” the LI reactions in the stroma

103
Q

CH8

In chloroplasts, where do LD reactions take place?

A

In the thylakoid membranes

104
Q

CH8

Thylakoids contain: (2 things)

A

Chlorophyll a and accessory pigments

105
Q

CH8

What is grana?

A

Stacks of thylakoids

106
Q

CH8

What is stroma?

A

Semiliquid substance surrounding thylakoids (this is site of LI reactions)

107
Q

CH8

What is a photon?

A

A discrete packet of light energy

108
Q

CH8

How is energy related to the wavelengths?

A

Inversely: shorter wavelengths = higher energy

109
Q

CH8

What is the photoelectric effect?

A

Removal of an electron from a molecule by light energy

*Occurs when photons energize electrons in molecules

110
Q

CH8

The electromagnetic spectrum:

A

Shows the visible light range expanded

111
Q

CH8

What are pigments?

A

Molecules that absorb light energy

Pigments have characteristic absorption spectra (range and efficiency of photon absorbance)

112
Q

CH8

What is chlorophyll a?

A

The primary photosynthetic pigment in plants and cyanobacteria (absorbs violet-blue and red light, appears yellow-green)

113
Q

CH8

What is chlorophyll b?

A

Secondary or accessory pigment (absorbs wavelengths that chlorophyll a does not absorb well; appears blue-green)

114
Q

CH8

(chlorophyll pigments) Explain the porphyrin ring.

A

Ring with alternating double and single bonds, with Mg at the center

*Photons excite electrons in the ring, which are then shuttled away from the ring

115
Q

CH8

What are accessory pigments?

A

Secondary pigments (e.g., chlorophyll b, carotenoids, phycobilins); absorb wavelengths that are not absorbed well by chlorophyll a

increases the overall range of wavelengths absorbed (carotenoids also act as antioxidants)

116
Q

CH8

Photosystems (on the thylakoid membranes) consist of: (2 things)

A

An antenna complex of 100s of accessory pigment molecules

A reaction center of one or more chlorophyll a molecules

*Energy from light is transferred through the electrons of the antenna complex to the reaction center of a photosystem

117
Q

CH8

What are the two types of photosystems in plants?

A

Photosystem 2 and photosystem 1 (in that order”)

Electrons from PSII are passed to PSI where they are energized again

118
Q

CH8

Explain the general workings of a photosystem.

A

Energy from the antenna complex is transferred to the reaction center chlorophyll a, causing an e-to be boosted to a higher energy level and then transferring it to a nearby electron acceptor

119
Q

CH8

Explain photosystems in oxygenic photosynthesis.

A

Water donates an e-to replace the e-lost from chlorophyll a. This splits the water, releasing H+ and O2

120
Q

CH8

Explain photosystems in non-oxygenic photosynthesis.

A

The e- donor is a molecule other than H2O(e.g., H2S)

121
Q

CH8

What occurs in photosystems? (3 things)

A

1) Light energy boosts an e- within the reaction center to a high energy level
2) This e-is transferred to an e-acceptor in a redox reaction
3) The e-is replaced by an e-from H2O, which results in the production of H+ ions and O2. H2O is said to be “split”

122
Q

CH8

What are the four stages in light-dependent reactions?

A
  1. primary photoevent – absorption of a photon by a pigment molecule
  2. charge separation – transfer of energy to the reaction center, followed by the transfer of an excited electron to an acceptor molecule
  3. electron transport – transfer of electrons through carriers that pump H+ to the inside of the thylakoid and reduce NADP+ to NADPH
  4. chemiosmosis – production of ATP (similar to production of ATP in mitochondrion)
123
Q

CH8

In eukaryotic chloroplasts, two linked photosystems allow for what?

A

Noncyclic phosphorylation

124
Q

CH8

In light-dependent reactions, which photosystem works first? Explain its process.

A

Photosystem II acts first

accessory pigments shuttle energy to P680
excited electrons from P680 are transferred to b6-f complex (electron carriers)
electrons lost from P680 are replaced by electrons released by splitting water
H+ ions and O2 released; builds up in the thylakoid space

125
Q

CH8

What is the b6-f complex?

A

A short electron transport chain in the thylakoid membrane

As electrons are transferred through the complex, they lose energy. Energy released is used to by proton pumps to move H+ into the thylakoid space to establish a proton gradient

126
Q

CH8

Explain photosystem 1. (4 steps)

A

receives light energy from its antenna complex and shuttles it to P700
electrons from P700 are excited and transferred to an electron carrier
electrons are passed along transport chain and ultimately reduce NADP+ to NADPH
electrons lost from P700 are replaced by those in the b6-f complex (originally came from PS II)

so, PS2 “feeds” electrons to PS1

127
Q

CH8

In light-dependent reactions, ATP is produced via chemiosmosis. Explain what goes into this process. (4 things)

A

ATP synthase enzyme is embedded in the thylakoid membrane
protons (H+) have accumulated in the thylakoid space (establishing a proton gradient)
protons move into the stroma through ATP synthase
proton flow provides energy to produce ATP from ADP + Pi in the stroma (identical to chemiosmosis that occurs in the inner mitochondrial membrane during respiration)

128
Q

CH8

Cyclic photophosphorylation produces what?

A

ATP via PSI, but no NADPH

129
Q

CH8

Light-independent reactions are part of what cycle?

130
Q

CH8

What do cells need to build carbohydrates and where does this occur? (3 things)

A
  1. Energy from ATP (from LD reactions)
  2. Reducing power from NADPH (from LD reactions)
  3. Source of carbon (CO2 from air or water)

Done by Calvin Cycle in the stroma of chloroplast.

131
Q

CH8

What are the three phases of the calvin cycle?

A
  1. Carbon fixation (using Rubisco enzyme): RuBP + CO2 2 PGA
  2. Reduction: Each PGA is reduced to G3P
  3. Regeneration of RuBP: G3P is used to regenerate RuBP
132
Q

CH8

In the calvin cycle, what is needed for every 6 carbon glucose?

A

the following “raw materials” are needed:
18 ATP
12 NADPH
6 CO2

133
Q

CH8

Since glucose is not the immediate product of the Calvin cycle, what is?

A

3-carbon G3P

134
Q

CH8

Explain how 3-carbon G3P results in glucose.

A

For every 6 molecules of CO2 taken in, 2 G3P molecules “leave” the cycle (each contains 3 carbons = 6 carbons total)
Two G3Ps are bonded to produce one glucose in the cytoplasm.
2(G3P)–>glucose

135
Q

CH8

What is the energy cycle?

A

Photosynthesis uses the products of respiration as substrates
Respiration uses the products of photosynthesis as substrates

136
Q

CH8

Rubisco has two enzymatic activities. What are they?

A
  1. Carboxylation (good) – the addition of CO2 to RuBP (normal conditions)
  2. Photorespiration (bad) – the oxidation of RuBP by O2 (hot, dry conditions). Causes loss of CO2because it competes with O2for same active site on Rubisco
137
Q

CH9

What two things does communication between cells require?

A

Ligand: a signaling molecule
Receptor: a protein to which the ligand binds (may be on the plasma membrane or within the cell)

138
Q

CH9

There are four basic mechanisms for cellular communication between different cells, what are they?

A
  1. direct contact (e.g., via gap junctions)
  2. paracrine signaling
  3. endocrine signaling
  4. synaptic signaling
139
Q

CH9

What is direct contact in cell communication?

A

Ligand molecules on the surface of one cell are recognized by receptor molecules on an adjacent cell

Or they pass through gap junctions

140
Q

CH9

What is paracrine signaling?

A

Ligands released from a secretory cell bind to receptors on adjacent cells

141
Q

CH9

What is endocrine signaling?

A

Special ligands called hormones are released from secretory cells and bind to receptors on or within cells throughout the body

142
Q

CH9

What is synaptic signaling?

A

Nerve cells release the signal ligands (neurotransmitters) which binds to receptors on nearby nerve or muscle cells

143
Q

CH9

When a ligand binds to a receptor, the cell “responds” chemically. What is a name for this?

A

Signal transduction: a series of chemical reactions that occur following the binding of a ligand to a receptor.

144
Q

CH9

Do different types of cells all respond the same way to the same signalling liganing?

145
Q

CH9
Signal transduction often involves activating or inactivating proteins (e.g., by phosphorylating or dephosphorylating proteins). What activates/deactivates it?

A

Kinase – an enzyme that adds a phosphate to a protein, thus activating it.
Phosphatase – an enzyme that removes a phosphate from a protein, thus deactivating it.

146
Q

CH9

How do kinases activate the protein?

A

Kinases add a phosphate group (PO4-3 ) to the amino acids serine, threonine or tyrosine in proteins

147
Q

CH9

Where can cell receptors be located?

A

Cell surface or membrane receptor: on the plasma membrane

Intracellular receptor: located inside cell

148
Q

CH9

What are the three classes of membrane receptors?

A
  1. Channel linked or gated receptors – an ion channel that opens in response to ligand binding
  2. Enzymatic receptors – an enzyme that is activated by ligand binding
  3. G protein-coupled receptors – a G-protein (protein bound to GTP) that assists in transmitting the signal
149
Q

CH9

What is the receptor tyrosine kinase?

A

a special type of receptor that is a kinase enzyme

When the ligand binds, the receptor is dimerized and autophosphorylated
The activated receptor then adds a phosphate to tyrosine on a response protein

An example is the epidermal growth factor receptor

150
Q

CH9

What is kinase cascade?

A

a series of protein kinases that phosphorylate each other in succession, amplifying the signal.

So, a few signal ligand molecules can cause a large response.

Example: Mitogen-activated protein (MAP) kinases are activated by kinase cascades (a mitogen is a ligand that encourages cell division)

151
Q

CH9

What are g-proteins bound to?

152
Q

CH9

What are g-protein coupled receptors?

A

receptors bound to G proteins
G-protein is a switch turned on by the receptor
Signal ligand binds receptor, then G-protein activates an effector protein (usually an enzyme)
can activate effector proteins

153
Q

CH9

What happens when the effector protein is activated?

A

The effector protein produces a second messenger, which generates the cellular response

For example – one common effector protein is adenylyl cyclase which converts ATP to cAMP, which then acts as a second messenger (for example, activating protein kinase A).
Other second messengers include inositol phosphates, calcium ions (Ca2+)

154
Q

CH9

What does the formation of cyclic AMP (cAMP) do?

A

cAMP serves as a second messenger to activate or inactivate proteins

155
Q

CH9

Give an example of a G-protein coupled receptor/enzyme complex.

A

Adenylyl cyclase

156
Q

CH9

What are steroid hormones?

A

Nonpolar (lipid-soluble), so can cross the plasma membrane to a steroid receptor

Usually regulate gene expression: an inhibitor blocks the steroid receptor from binding to DNA until the hormone is present.

157
Q

CH9

What are the three functional domains of steroid receptors?

A
  1. Hormone-binding domain
  2. DNA binding domain
  3. Domain that interacts with coactivators to affect gene expression (activating or deactivating transcription)
158
Q

CH9

What are autoinducers?

A

Small molecules produced by bacteria that regulate gene expression.
Responsible for quorum sensing (Quorum sensing is the regulation of gene expression in response to fluctuations in cell-population density. Quorum sensing bacteria produce and release chemical signal molecules called autoinducers that increase in concentration as a function of cell density)

159
Q

CR

Overall equation for cellular respiration?

A

C6H12O6+6O2–>6CO2+6H2O

160
Q

CR
Glycolysis:
Where does it take place? (in eukaryotic cells)
What are the reactants? (Per glucose molecule in eukaryotes)
What are the products? (Per glucose molecule in eukaryotes)
What is the net ATP?
How is the ATP made?

A

Cytoplasm

Glucose, NAD (2), ATP(2), ADP(4), Pi(4)

Pyruvate(2),NADH(2),ATP(4)

2(2 used, 4 produced)

Substrate-level phosphorylation

161
Q

CR
Pyruvate oxidation:
Where does it take place? (in eukaryotic cells)
What are the reactants? (Per glucose molecule in eukaryotes)
What are the products? (Per glucose molecule in eukaryotes)
What is the net ATP?
How is the ATP made?

A

Mitochondrial matrix

Pyruvate(2),CoA(2),NAD+(2)

Acetyl CoA(2),NADH(2),CO2(2)

0

Not applicable

162
Q

CR
Krebs (TCA) Cycle:
Where does it take place? (in eukaryotic cells)
What are the reactants? (Per glucose molecule in eukaryotes)
What are the products? (Per glucose molecule in eukaryotes)
What is the net ATP?
How is the ATP made?

A

Mitochondrial matrix

Acetyl CoA(2), oxaloacetate(2),NAD+(6),FAD(2),ADP(2),Pi(2)

CO2(4),ATP(2),NADH(6),FADH2(2)

2

Substrate-level phosphorylation

163
Q

CR
Electron Transport:
Where does it take place? (in eukaryotic cells)
What are the reactants? (Per glucose molecule in eukaryotes)
What are the products? (Per glucose molecule in eukaryotes)
What is the net ATP?
How is the ATP made?

A

Inner membrane of the mitochondrion

NADH(10),FADH2(2),O2(6)

NAD+(10),FAD(2),H20(6),H+(34)into intermembrane space

0

Not applicable

164
Q

CR
Chemiosmosis:
Where does it take place? (in eukaryotic cells)
What are the reactants? (Per glucose molecule in eukaryotes)
What are the products? (Per glucose molecule in eukaryotes)
What is the net ATP?
How is the ATP made?

A

Inner membrane of the mitochondrion

H+(34),ADP(34),Pi(34)

ATP(34)

32(2 used to transport
pyruvates into mitochondrion)

Oxidative phophorylation (chemiosmosis of H+ ions driving ATP Synthase)

165
Q

CR

What is the net ATP in eukaryotes?

166
Q

CR

What is the net ATP in prokaryotes?

167
Q

P

What is the overall equation for photosynthesis?

A

6CO2+6H2O–>C6H12O6+6O2

168
Q

P

What’s combined in the cytoplasm to make one glucose molecule?

169
Q 
P
Light-Dependent(PSII):
Where does it take place?
What are the reactants?
What are the products?
How is the ATP made?
A

Photosystems on Thylakoid Membranes of Chloroplast

Photons, chlorophyll and accessory pigments, H2O, ADP, Pi

ATP, O2, H+

Chemiosmosis of H+ ions drives ATP synthase

170
Q 
P
Light-Dependent (PS1)
Where does it take place?
What are the reactants?
What are the products?
How is the ATP made?
A

Photosystems on thylakoid membranes of chloroplasts

Photons, electrons from PSII, chlorophyll and accessory pigments, NADP+

NADPH

Not applicable

171
Q 
P
Light-Independent (Calvin Cycle)
Where does it take place?
What are the reactants?
What are the products?
How is the ATP made?
A

Stroma of chloroplast

CO2 (6), ribulose biphosphate (RuBP), ATP (18), NADPH( 12)

Glyceraldehyde-3-Phosphates (G3P) (2)[2 combined for one glucose], ADP (18), Pi (18), NADP+(12), H+(12)

Not applicable

BIO 111 (2 decks)

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