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photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is autrophic nutrition?

A

synthesising large organic molecules from simple inorganic molecules like oxygen and carbon dioxide

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2
Q

What is an autotroph?

A

use light or chemical energy to synthesise food (organic molecules) from inorganic molecules

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3
Q

What are photoautotrophs?

A

Animals which photosynthesise

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4
Q

photoautotrophs use what as the energy source for autotrophic nutrition

A

light/photons

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5
Q

What are producers?

A

photoautotrophs; at first trophic level of food chain, provide energy and organic molecules to other organisms

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6
Q

Equation for photosynthesis

A

6CO2 + 6H2O => C6H12O6 + 6O2

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7
Q

Why is photosynthesis important?

A

How turn light energy to chemical energy for use in all organisms for all living processes

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8
Q

What is a photon?

A

a particle of light containing a quantum of energy

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9
Q

What is carbon fixation?

A

carbon dioxide is converted into sugars, providing carbon for all organic molecules

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10
Q

Carbon fixation needs what?

A

energy and addition of electrons (reduction)

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11
Q

Carbon fixation is endothermic or exothermic?

A

endothermic

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12
Q

What is an endothermic reaction?

A

A reaction which requires energy

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13
Q

What is an exothermic reaction?

A

A reaction which releases energy

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14
Q

What is a reduction reaction?

A

When electrons are added

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15
Q

How does carbon fixation help the environment?

A

Helps regulate levels of carbon dioxide in atmosphere and oceans

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16
Q

How do plants respire?

A

oxidise organic molecules produced in photosynthesis to release energy

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17
Q

What is a heterotroph?

A

A non-photosynthetic organism, obtain energy through intake/digestion of organic molecules, creating smaller molecules for respiration

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18
Q

Respiration is endothermic or exothermic?

A

exothermic

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19
Q

How are photosynthesis and aerobic respiration linked?

A

products of photosynthesis are raw materials for aerobic respiration

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20
Q

What is chlorophyll?

A

green pigment which absorbs light energy

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21
Q

What is a plants compensation point?

A

When photosynthesis and respiration occur at the same rate so there is no net loss or gain of carbohydrates, changes throughout day

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22
Q

Name for time taken for plant to reach compensation point?

A

compensation period

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23
Q

What is an oxidation reaction?

A

When electrons are lost/removed

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24
Q

What does OILRIG stand for?

A

oxidation is loss, reduction is gain (of electrons)

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25
Q

Respiration is oxidation or reduction?

A

oxidation

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26
Q

Photosynthesis is oxidation or reduction?

A

reduction

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27
Q

Describe structure of chloroplasts (3)

A

Double membrane, outer highly permeable, with intermembrane space;
fluid filled matrix called stroma;
grana - stacks flat sacs call thylakoids

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28
Q

What is stroma?

A

fluid filled matrix in chloroplasts

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29
Q

What are grana?

A

stacks of thylakoids in chloroplasts

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30
Q

Why does respiration rate increase slightly throughout the day?

A

warmer throughout the day, faster action of enzymes controlling reaction

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31
Q

Three membranes of chloroplasts?

A

outer, inner and thylakoid

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32
Q

Three compartments of chloroplasts?

A

intermembrane space, stroma, thylakoid space

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33
Q

How are thylakoids in different grana connected?

A

By intergranal lamellae/thylakoids

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34
Q

What is a photosystem?

A

Contains photosynthetic pigments which trap light energy

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35
Q

Why is it beneficial to have many thylakoids in a chloroplast?

A

Provides lots of membrane surface area

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36
Q

Why should chloroplasts have lots of surface area?

A

for photosystems to trap light energy, and for electron carriers and enzymes

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37
Q

What is chloroplast DNA used for?

A

Codes for enzymes and pigment molecules used in photosynthesis

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38
Q

What does the stroma contain? (5)

A

enzymes for photosynthesis;
small ribosomes;
starch grains;
lipid droplets;
one loop of DNA

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39
Q

What is needed to convert energy into ATP?

A

electron carriers and ATP synthase enzymes

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40
Q

What is found in thylakoid membrane?

A

What is found in thylakoid membrane?

41
Q

Describe the structure of photosystems?

A

funnel shape pointing into thylakoid, contain primary pigment at the end and accessory pigments

42
Q

What are accessory pigments for?

A

Absorb extra supplementary wavelengths of light, funnel energy down to primary pigment

43
Q

What happens to energy absorbed by accessory pigments?

A

funnelled down to primary pigment

44
Q

Name three accessory pigments

A

chlorophyll b, xanthophyll, carotene

45
Q

What is the primary pigment of photosystems?

A

chlorophyll A

46
Q

Two different types of chlorophyll A?

A

P700 or P680

47
Q

What does P700 or P680 means?

A

absorbs light at wavelengths of 700nm or 680nm

48
Q

What primary pigment is found in photosystem I?

A

contains chlorophyll A P700

48
Q

What primary pigment is found in photosystem II?

A

contains chlorophyll A P680

49
Q

What colour light does chlorophyll a absorb?

A

red and some blue

49
Q

What is the light dependent stage of photosynthesis?

A

stage which must occur when there is light

49
Q

The light dependent stage of photosynthesis includes…?

A

photolysis of water
photophosphorylation;
formation NADP
chemiosmosis

49
Q

Where does light harvesting occur?

A

photosystems

50
Q

Describe the photolysis of water in photosynthesis

A

water enters thylakoid space, light energy used to split into oxygen, two electron and two hydrogen ions.

50
Q

What is photophosphorylation?

A

production of ATP using light energy

51
Q

What is the equation for photolysis?

A

2H2O -> 4H+ + 4e- + O2

52
Q

What is the role of water in photosynthesis?

A

source of protons, donates electrons to photosystem II,

53
Q

What can oxygen from photolysis be used for?

A

aerobic respiration

54
Q

Describe fully cyclic photophosphorylation

A
  • electrons released by ps1 are not picked up by NADP
  • recycled back to photosystem 1
  • forms ATP
  • by electron releasing energy that pumps into thylakoid
  • causes hydrogen ions t pass through ATP synthase
54
Q

Two types of photophosphorylation?

A

cyclic and non-cyclic

54
Q

What is cyclic photophosphorylation

A

uses only PS I, produces only ATP in smaller quantities

55
Q

Describe movement of electrons in non-cyclic photophosphorylation

A

electrons from photolysis replace electrons excited from PS II,
passed down electron carrier, replace electrons excited in PS I,
which picked up by ferredoxin

55
Q

What is the calvin cycle?

A

process where carbon dioxide converted into organic molecules (glucose)

55
Q

How does carbon dioxide reach the stroma?

A

through the stomata, then spongy mesophyll, diffuses into palisade cells and into chloroplasts

55
Q

Describe fully non-cyclic photophosphorylation

A
  • photosystem 2 absorbs light
  • absorbed light excites and releases electrons
  • electrons move along electron transfer chain to photosystem 1
  • series of redox reactions:
  • electrons lose energy by chemiosmosis
  • converts ADP to ATP
  • electrons lost from photosystem 2 replaced by electrons from photolysis
  • causes H20 to disassociate to hydrogen ions and oxygen
  • electrons lost from ps1 are combined with hydrogen ions
  • accepted by NADP coenzyme
  • forms reduced NADP
  • catalysed by NADP reductase
55
Q

Describe movement of protons in non-cyclic photophosphorylation

A

protons pumped into thylakoid space using energy from electron carrier;
joined by protons from photolysis, creates conc. gradient;
pass through proton carrier, activating ATP synthase;
picked up by NADP for reduction

55
Q

Which enzyme catalyses the reduction of NADP?

A

NADP reductase

55
Q

How do guard cells use cyclic photophosphorylation

A

use it to produce ATP to draw potassium ions into the cells, water follows by osmosis to cause guard cells to swell and open the stomata.

55
Q

How does NADP become reduced?

A

addition of two electrons and two hydrogen ions by NADP reductase

55
Q

Describe the action of electron carriers

A

chain proteins with iron ion (3+),
electrons picked up by one, passed to next;
series of redox reactions;
releases energy

56
Q

Describe the Calvin Cycle

A
  • carbon dioxide diffuses into stroma
  • combines with RuBP to form 2 GPA molecules
  • catalysed by rubisco enzyme
  • GP reduced to TP using ATP and H from reduced NADP
  • some TP converted to organic substances
  • and used to regenerate RuBP
57
Q

How many carbon atoms in RUBP?

A

five

58
Q

How many carbon atoms in GP?

A

three

59
Q

how many carbon atoms in TP?

A

three

60
Q

How does the hydrogen pump benefit the Calvin cycle?

A

increases pH in stroma to 8, optimum for RUBISCO

61
Q

Why can the calvin cycle only occur in light?

A

concentration magnesium ions in stroma increases, cofactor to rubisco;
need continual supply ATP and NADPH;
ferredoxin reduced by electrons from PS I activates enzymes for calvin cycle

62
Q

How is TP used?

A

produce glucose, converted to sucrose, starch or cellulose;
used synthesise amino acids, fatty acids and glycerol;
used regenerate RUBP

63
Q

Four main limiting factors of photosynthesis

A

light intensity, carbon dioxide concentration, water availability and temperature

64
Q

What is a limiting factor?

A

the factor which determines the rate of a reaction,

65
Q

How do you know if something is a limiting factor?

A

when you increase it, rate increases

66
Q

Three other limiting factors of photosynthesis

A

chlorophyll, electron carriers and enzyme availability

67
Q

What are the products of the light dependent stage of photosynthesis?

A

ATP, NADP and waste oxygen

68
Q

What are the reactants of the light dependent stage of photosynthesis?

A

light and water

69
Q

Why does light intensity affect the rate of photosynthesis?

A

no ATP or NADPH to be used in the calvin cycle;
stomata open for gas exchange and transpiration

70
Q

What stages of calvin cycle cannot occur without light?

A

converting GP to TP - require ATP and NADPH;
TP cannot regenerate RUBP without ATP

71
Q

What is the result of the calvin cycle occurring in the dark?

A

build up of GP;
lower levels of RUBP

72
Q

Why does GP accumulate in the dark?

A

cannot be converted to TP as no ATP or NADPH

73
Q

Why do levels of RUBP drop in the dark?

A

TP cannot regenerate RUBP as there is no ATP

74
Q

What happens during the calvin cycle in low levels of carbon dioxide?

A

build up of RUBP;
less GP and TP

75
Q

Why is there a build up of RUBP when there is less carbon dioxide?

A

cannot bind with carbon dioxide, accumulates

76
Q

Why is there a drop in GP and TP when there is less carbon dioxide?

A

cannot be made as carbon dioxide doesnt bind with RUBP

77
Q

How does temperature affect the rate of photosynthesis?

A

more kinetic energy and collisions between enzyme and substrate catalysing photosynthesis, increases rate,
as enzymes begin to damage and denature rate decreases

78
Q

What happens to rate of photosynthesis above 30 degrees?

A

oxygen begins compete with carbon dioxide for RUBISCO active site - less GP and TP

79
Q

What is water stress?

A

Not enough water available to the plant

80
Q

What are the consequences of water stress?

A

roots cannot replace water lost through transpiration;
cells become plasmolysed;
roots produce abscisic acid which causes stomata to close;
tissues flaccid and leaves wilt;
photosynthesis rate reduces

81
Q

How does light intensity increase the rate of photosynthesis

A
  • rate of phtotsynthesis incteaes if light intesnity incfeases because
  • photosystmes/ pigments absorb more light
  • causing reduced levels of ADP and NADP
82
Q

what if theres low light intensity?

A
  • rate of phtotsyntessis reduced due to reduced ADP and NADP levels
83
Q

How does carbon dioxide affect rate of photosynthesis

A
  • low concentration
    rate of RubP to GP reduces so TP levels reduce
    -high concentration
  • increases rate of photosynthesis to a point but becomes toxic due to atmospheric level being 0.4%

Biology (18 decks)

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