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AP Biology > Chapter 6 > Flashcards

Chapter 6 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Where is energy stored?

A

chemical bonds of molecules

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2
Q

How is energy released and transformed?

A

by the metabolic pathways of living cells

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3
Q

How does a complex chemical transformation occur?

A

in a series of separate, intermediate reactions that form a metabolic pathway

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4
Q

How are reactions catalysed?

A

by specific enzymes

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5
Q

Are most metabolic pathways in all organisms similar or dissimilar?

A

similar

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6
Q

What does it mean for eukaryotes to have compartmentalised metabolic pathways?

A

certain reactions occur inside specific organelles

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7
Q

How is each metabolic pathway controlled?

A

by key enzymes that can be inhibited or activated, thereby determining how fast the reactions will go

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8
Q

free energy

A

chemical energy available to do work

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9
Q

What do the laws of thermodynamics say about energy?

A

a biochemical reaction may change the form of energy but not the net amount

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10
Q

exergonic

A

releases energy from the reactants

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11
Q

endergonic

A

energy must be added to the reactants

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12
Q

coupled reactions

A

an energy-releasing reaction is coupled in time and location to an energy-requiring reaction

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13
Q

What are two widely used coupling molecules?

A

coenzymes ATP and NADH

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14
Q

Where is the energy released in exergonic reactions captured?

A

in chemical reactions when ATP is formed from adenosine diphosphate and inorganic phosphate

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15
Q

What are some cellular activities that require free energy derived from the hydrolysis of ATP?

A

~active transport across a membrane
~condensation reactions that use enzymes to form polymers
~motor proteins that move vesicles along microtubules

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16
Q

What does an ATP molecule consist of?

A

nitrogen-containing base adenine bonded to ribose, which is attached to a sequence of three phosphate groups

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17
Q

What is the reaction for hydrolysis of ATP?

A

ATP + H2O –> ADP + Pi + free energy

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18
Q

Is ATP hydrolysis endergonic or exergonic?

A

endergonic

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19
Q

substrate-level phosphorylation

A

enzyme-mediated direct transfer of phosphate from another molecule to ADP

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20
Q

redox reaction

A

a reaction in which one substance transfers one or more electrons to another substance

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21
Q

reduction

A

the gain of one or more electrons by an atom, ion, or molecule

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22
Q

oxidation

A

the loss of one or more electrons

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23
Q

What is the relationship between how reduced a molecule is and the energy stored in its covalent bonds?

A

in general, the more reduced a molecule is, the more energy is stored in its covalent bonds

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24
Q

NAD

A

the coenzyme nicotinamide adenine dinucleotide, used by cells as an electron carrier in redox reactions

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25
Q

NAD+

A

oxidized form of NAD

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26
Q

NADH

A

reduced form of NAD

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27
Q

How does catabolism play a role in the flow of energy within cells?

A

catabolism releases energy by oxidation; this energy can be trapped by the reduction of coenzymes such as NAD+

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28
Q

How does ATP participate in the flow of energy within cells?

A

ATP supplies the energy for many energy-requiring processes, including anabolism

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29
Q

oxidative phosphorylation

A

the coupling of NADH oxidation to the production of ATP

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30
Q

cellular respiration

A

the set of metabolic reactions used by cells to harvest energy from food

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31
Q

What is the chemical equation that shows the complete oxidation of glucose to CO2?

A

Glucose + 6 O2 –> 6 CO2 + 6 H2O + energy

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32
Q

In the oxidation of glucose to CO2, how much energy is produced per mole of glucose?

A

686 kcal per mole of glucose

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33
Q

aerobic conditions

A

in the presence of O2

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34
Q

glycolysis

A

the six-carbon monosaccharide glucose is converted into two three-carbon molecules of pyruvate

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35
Q

pyruvate oxidation

A

two three-carbon molecules of pyruvate are oxidized to two two-carbon molecules of acetyl CoAand two molecules of CO2

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36
Q

citric acid cycle

A

two two-carbon molecules of acetyl CoA are oxidizes to four molecules of CO2

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37
Q

Where does glycolysis take place?

A

in the cytosol

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38
Q

What does glycolysis involve?

A

ten enzyme-catalysed reactions

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39
Q

What are the two stages of glycolysis?

A

~the initial energy-investing reactions that consume chemical energy stored in ATP
~the energy-harvesting reactions that produce ATP and NADH

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40
Q

coenzyme A

A

written as CoA, this is used in various biochemical reactions as a carrier of acetyl groups

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41
Q

What is the main role of acetyl CoA?

A

~donate its acetyl group to the four-carbon compound oxaloacetate, forming the six-carbon molecule citrate

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42
Q

acetyl CoA

A

starting point for the citric acid cycle

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43
Q

How many times does the citric acid cycle operate?

A

twice for each glucose molecule that enters glycolysis (once for each pyruvate that enters the mitochondrion)

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44
Q

What does the released energy from exergonic oxidation reactions in the citric acid cycle do?

A

Gets trapped by NAD+, forming NADH

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45
Q

How do cells fully use the energy harvested in catabolism?

A

transfer energy from NADH and FADH2 to the phosphoanydride bond of ATP

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46
Q

oxidative phosphorylation

A

NADH oxidation is used to actively transport protons across the inner mitochondrial membrane, creating a proton gradient

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47
Q

What happens when there is a proton gradient across the mitochondrial membrane?

A

the protons diffuse back across, driving the synthesis of ATP

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48
Q

respiratory chain

A

series of redox electron carrier proteins

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49
Q

electrons

A

when the electrons from the oxidation of NADH and FADH2 pass from one carrier protein to the next in the chain

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50
Q

Are the oxidation reactions endergonic or exergonic?

A

exergonic

51
Q

How do exergonic reactions help in the electron transport chain?

A

they release energy that is used to actively transport H+ ions across the membrane

52
Q

What is the reduction coupled with the oxidation of NADH into NAD+?

A

water formed from oxygen gas

53
Q

What is the key role of O2 in cells?

A

to act as an electron acceptor and then become reduced

54
Q

ATP synthase

A

an enzyme that uses the H+ gradient to drive the synthesis of ATP

55
Q

chemiosmosis

A

the movement of ions across a semipermeable barrier from a region of higher concentration to a region of lower concentration

56
Q

In which direction do substances diffuse in?

A

From regions of higher concentration to regions of lower concentration

57
Q

What happens if a membrane blocks diffusion?

A

the substance at the higher concentration has potential energy, which can be converted into other forms of energy

58
Q

How do protons cross the membrane, since they cannot readily diffuse across the non polar membrane?

A

through the ATP synthase

59
Q

What is the structure of the ATP synthase?

A

F0 unit and the F1 unit

60
Q

F0 unit of ATP synthase

A

transmembrane domain that functions as the H+ channel

61
Q

F1 unit of ATP synthase

A

contains the active sites for ATP synthesis

62
Q

Where does chemiosmosis occur in eukaryotes?

A

mitochondria and chloroplasts

63
Q

How is the H+ gradient in mitochondria set up?

A

using energy released by the oxidation of NADH and FADH2

64
Q

How many molecules of ATP are produced per fully oxidized glucose?

A

32

65
Q

How is most of the ATP produced in cellular respiration formed?

A

by oxidative phosphorylation

66
Q

anaerobic

A

absence of O2

67
Q

Why can the respiratory chain not operate in anaerobic conditions?

A

because the NADH produced by glycolysis would not be oxidised, so glycolysis would stop

68
Q

fermentation

A

a method that allows organisms to reoxidize NADH even in anaerobic conditions, thus allowing glycolysis to continue

69
Q

What is the overall yield of ATP from fermentation?

A

2 ATP per glucose

70
Q

Why is the overall yield of ATP from fermentation restricted to the ATP made in glycolysis?

A

the NADH made during glycolysis is not available for re0xidation from by the respiratory chain to form ATP

71
Q

lactic acid fermentation

A

pyruvate serves as the electron acceptor and lactate is the product

72
Q

alcohol fermentation

A

pyruvate is converted to ethanol; takes place in certain yeasts and some plant cells under anaerobic conditions

73
Q

carbon skeletons

A

molecules with covalently linked carbon atoms

74
Q

What do polysaccharides get hydrolysed into?

A

glucose

75
Q

How does the glucose that is hydrolysed from polysaccharides provide energy?

A

energy is captured in ATP

76
Q

What do lipids get hydrolysed into?

A

glycerol and fatty acids

77
Q

How does the glycerol that is hydrolysed from lipids provide energy?

A

converted into dihydroxyacetone phosphate

78
Q

How do the fatty acids that are hydrolysed from lipids provide energy?

A

become acetyl CoA, which can then be catabolised to CO2 in the citric acid cycle

79
Q

What do proteins get hydrolysed into?

A

amino acid building blocks

80
Q

How do the amino acids that are hydrolysed from lipids provide energy?

A

feed into glycolysis or the citric acid cycle at different points

81
Q

gluconeogenesis

A

when glycolytic and citric acid cycle intermediates are reduced and form glucose

82
Q

anabolic interconversions

A

many catabolic pathways can operate essentially in reverse, with some modifications

83
Q

Where does the energy released by catabolic pathways in almost all organisms ultimately come from?

A

the sun

84
Q

photosynthesis

A

an anabolic process by which the energy of sunlight is captured and used to convert carbon dioxide and water into glucose and oxygen

85
Q

light reactions

A

convert light energy into chemical energy in the form of ATP and the reduced electron carrier NADPH

86
Q

carbon-fixation reactions

A

use the ATP and NADPH made by the light reactions, along with CO2, to produce carbohydrates

87
Q

light

A

a form of electromagnetic radiation

88
Q

electromagnetic radiation

A

propagated in waves

89
Q

What is the relationship between energy in radiation and wavelength?

A

amount of energy in the radiation is inversely proportional to its wavelength

90
Q

photons

A

packets of light energy which have no mass

91
Q

What are the two behaviours of light?

A

travels in waves, also behaves as particles

92
Q

How do receptive molecules harvest energy for biological processes?

A

by absorbing only specific wavelengths of light – photons with specific amounts of energy

93
Q

What happens when a photon meets a molecule?

A

scattered/reflected, transmitted, or absorbed

94
Q

scattered/reflected

A

photon bounces off molecule

95
Q

transmitted

A

photon passes through the molecule

96
Q

absorbed

A

photon gets absorbed by the molecule, adding energy to the molecule

97
Q

What happens when a molecule acquires the energy of a photon?

A

raised from a ground state (lower energy) to an excited state (higher energy)

98
Q

pigments

A

molecules that absorb wavelengths in the visible spectrum

99
Q

What determines the colour of a pigment?

A

the scattered or transmitted wavelengths

100
Q

chlorophyll

A

absorbs both blue and red light, so it appears green

101
Q

absorption spectrum

A

plot light absorbed by a purified pigment against wavelength

102
Q

action spectrum

A

plot of biological activity of an organism against the wavelengths of light to which it is exposed

103
Q

light-harvesting complexes

A

energy-absorbed antenna systems of pigments

104
Q

photosystem

A

a large multiprotein complex where light energy is converted into chemical energy

105
Q

Where is the photosystem?

A

spans the thylakoid membrane

106
Q

What are the components of the photosystem?

A

multiple antenna systems with their associated pigment molecules

107
Q

reaction center

A

part of the photosystem; has antenna systems around it

108
Q

What does the reaction centre do?

A

converts the absorbed light energy into chemical energy

109
Q

What happens when the chlorophyll molecule in the reaction centre absorbs sufficient energy?

A

it gives up its excited electron to a chemical acceptor; in other words: chlorophyll gets oxidised while the acceptor molecule is reduced

110
Q

Photosystem I

A

absorbs light energy at 700nm and passes an excited electron to NADP+, reducing it to NADPH

111
Q

Photosystem II

A

absorbs light energy at 680nm, oxidises wter molecules, and initiates the electron transport chain that produces ATP

112
Q

What is the order of the photosystems in electron transport reactions?

A

Photosystem II, then Photosystem I

113
Q

cyclic electron transport

A

only uses photosystem I and produces ATP but not NADPH

114
Q

in what way is cyclic electron transport chain cyclic?

A

the electrons flow from the reaction centre of photosytem I, through the electron transport chain, and then back to photosystem I

115
Q

Calvin cycle

A

metabolic pathway occurring in the stroma of the chloroplast

116
Q

What are the 3 processes of the Calvin cycle?

A

Fixation of CO2, reduction of 3PG to form glyceraldehyde 3-phosphate, regeneration of the CO2 acceptor (RuBP)

117
Q

fixation of CO2

A

CO2 added to an acceptor molecule, the immediate six-carbon molecule product breaks down into two three-carbon molecules called 3PG

118
Q

What enzyme catalyses the fixation of CO2?

A

rubisco

119
Q

reduction of 3PG to form glyceraldehyde 3-phosophate

A

series of reactions that involves a phosphorylation and a reduction, producing glyceraldehyde 3-phosphate

120
Q

regeneration of the CO2 acceptor, RuBP

A

most of the G3P ends up as RuMP, and ATP converts it into RuBP

121
Q

What happens to the extra G3P?

A

~exported out of the cloroplast to the cytosol, where it is converted to hexoses
~glucose accumulates inside the chloroplast, and then link together to form starch, which allows sucrose to get exported to the rest of the plant even when photosynthesis is not taking place

122
Q

autotrophs

A

photosynthetic organisms

123
Q

heterotrophs

A

cannot photosynthesise

AP Biology (19 decks)

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