photosynthesis Flashcards
1
Q
What is autrophic nutrition?
A
synthesising large organic molecules from simple inorganic molecules like oxygen and carbon dioxide
2
Q
What is an autotroph?
A
use light or chemical energy to synthesise food (organic molecules) from inorganic molecules
3
Q
What are photoautotrophs?
A
Animals which photosynthesise
4
Q
photoautotrophs use what as the energy source for autotrophic nutrition
A
light/photons
5
Q
What are producers?
A
photoautotrophs; at first trophic level of food chain, provide energy and organic molecules to other organisms
6
Q
Equation for photosynthesis
A
6CO2 + 6H2O => C6H12O6 + 6O2
7
Q
Why is photosynthesis important?
A
How turn light energy to chemical energy for use in all organisms for all living processes
8
Q
What is a photon?
A
a particle of light containing a quantum of energy
9
Q
What is carbon fixation?
A
carbon dioxide is converted into sugars, providing carbon for all organic molecules
10
Q
Carbon fixation needs what?
A
energy and addition of electrons (reduction)
11
Q
Carbon fixation is endothermic or exothermic?
A
endothermic
12
Q
What is an endothermic reaction?
A
A reaction which requires energy
13
Q
What is an exothermic reaction?
A
A reaction which releases energy
14
Q
What is a reduction reaction?
A
When electrons are added
15
Q
How does carbon fixation help the environment?
A
Helps regulate levels of carbon dioxide in atmosphere and oceans
16
Q
How do plants respire?
A
oxidise organic molecules produced in photosynthesis to release energy
17
Q
What is a heterotroph?
A
A non-photosynthetic organism, obtain energy through intake/digestion of organic molecules, creating smaller molecules for respiration
18
Q
Respiration is endothermic or exothermic?
A
exothermic
19
Q
How are photosynthesis and aerobic respiration linked?
A
products of photosynthesis are raw materials for aerobic respiration
20
Q
What is chlorophyll?
A
green pigment which absorbs light energy
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
22
Q
Name for time taken for plant to reach compensation point?
A
compensation period
23
Q
What is an oxidation reaction?
A
When electrons are lost/removed
24
Q
What does OILRIG stand for?
A
oxidation is loss, reduction is gain (of electrons)
25
Respiration is oxidation or reduction?
oxidation
26
Photosynthesis is oxidation or reduction?
reduction
27
Describe structure of chloroplasts (3)
Double membrane, outer highly permeable, with intermembrane space;
fluid filled matrix called stroma;
grana - stacks flat sacs call thylakoids
28
What is stroma?
fluid filled matrix in chloroplasts
29
What are grana?
stacks of thylakoids in chloroplasts
30
Why does respiration rate increase slightly throughout the day?
warmer throughout the day, faster action of enzymes controlling reaction
31
Three membranes of chloroplasts?
outer, inner and thylakoid
32
Three compartments of chloroplasts?
intermembrane space, stroma, thylakoid space
33
How are thylakoids in different grana connected?
By intergranal lamellae/thylakoids
34
What is a photosystem?
Contains photosynthetic pigments which trap light energy
35
Why is it beneficial to have many thylakoids in a chloroplast?
Provides lots of membrane surface area
36
Why should chloroplasts have lots of surface area?
for photosystems to trap light energy, and for electron carriers and enzymes
37
What is chloroplast DNA used for?
Codes for enzymes and pigment molecules used in photosynthesis
38
What does the stroma contain? (5)
enzymes for photosynthesis;
small ribosomes;
starch grains;
lipid droplets;
one loop of DNA
39
What is needed to convert energy into ATP?
electron carriers and ATP synthase enzymes
40
What is found in thylakoid membrane?
What is found in thylakoid membrane?
41
Describe the structure of photosystems?
funnel shape pointing into thylakoid, contain primary pigment at the end and accessory pigments
42
What are accessory pigments for?
Absorb extra supplementary wavelengths of light, funnel energy down to primary pigment
43
What happens to energy absorbed by accessory pigments?
funnelled down to primary pigment
44
Name three accessory pigments
chlorophyll b, xanthophyll, carotene
45
What is the primary pigment of photosystems?
chlorophyll A
46
Two different types of chlorophyll A?
P700 or P680
47
What does P700 or P680 means?
absorbs light at wavelengths of 700nm or 680nm
48
What primary pigment is found in photosystem I?
contains chlorophyll A P700
48
What primary pigment is found in photosystem II?
contains chlorophyll A P680
49
What colour light does chlorophyll a absorb?
red and some blue
49
What is the light dependent stage of photosynthesis?
stage which must occur when there is light
49
The light dependent stage of photosynthesis includes...?
photolysis of water
photophosphorylation;
formation NADP
chemiosmosis
49
Where does light harvesting occur?
photosystems
50
Describe the photolysis of water in photosynthesis
water enters thylakoid space, light energy used to split into oxygen, two electron and two hydrogen ions.
50
What is photophosphorylation?
production of ATP using light energy
51
What is the equation for photolysis?
2H2O -> 4H+ + 4e- + O2
52
What is the role of water in photosynthesis?
source of protons, donates electrons to photosystem II,
53
What can oxygen from photolysis be used for?
aerobic respiration
54
Describe fully cyclic photophosphorylation
- 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
Two types of photophosphorylation?
cyclic and non-cyclic
54
What is cyclic photophosphorylation
uses only PS I, produces only ATP in smaller quantities
55
Describe movement of electrons in non-cyclic photophosphorylation
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
What is the calvin cycle?
process where carbon dioxide converted into organic molecules (glucose)
55
How does carbon dioxide reach the stroma?
through the stomata, then spongy mesophyll, diffuses into palisade cells and into chloroplasts
55
Describe fully non-cyclic photophosphorylation
- 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
Describe movement of protons in non-cyclic photophosphorylation
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
Which enzyme catalyses the reduction of NADP?
NADP reductase
55
How do guard cells use cyclic photophosphorylation
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
How does NADP become reduced?
addition of two electrons and two hydrogen ions by NADP reductase
55
Describe the action of electron carriers
chain proteins with iron ion (3+),
electrons picked up by one, passed to next;
series of redox reactions;
releases energy
56
Describe the Calvin Cycle
- 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
How many carbon atoms in RUBP?
five
58
How many carbon atoms in GP?
three
59
how many carbon atoms in TP?
three
60
How does the hydrogen pump benefit the Calvin cycle?
increases pH in stroma to 8, optimum for RUBISCO
61
Why can the calvin cycle only occur in light?
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
How is TP used?
produce glucose, converted to sucrose, starch or cellulose;
used synthesise amino acids, fatty acids and glycerol;
used regenerate RUBP
63
Four main limiting factors of photosynthesis
light intensity, carbon dioxide concentration, water availability and temperature
64
What is a limiting factor?
the factor which determines the rate of a reaction,
65
How do you know if something is a limiting factor?
when you increase it, rate increases
66
Three other limiting factors of photosynthesis
chlorophyll, electron carriers and enzyme availability
67
What are the products of the light dependent stage of photosynthesis?
ATP, NADP and waste oxygen
68
What are the reactants of the light dependent stage of photosynthesis?
light and water
69
Why does light intensity affect the rate of photosynthesis?
no ATP or NADPH to be used in the calvin cycle;
stomata open for gas exchange and transpiration
70
What stages of calvin cycle cannot occur without light?
converting GP to TP - require ATP and NADPH;
TP cannot regenerate RUBP without ATP
71
What is the result of the calvin cycle occurring in the dark?
build up of GP;
lower levels of RUBP
72
Why does GP accumulate in the dark?
cannot be converted to TP as no ATP or NADPH
73
Why do levels of RUBP drop in the dark?
TP cannot regenerate RUBP as there is no ATP
74
What happens during the calvin cycle in low levels of carbon dioxide?
build up of RUBP;
less GP and TP
75
Why is there a build up of RUBP when there is less carbon dioxide?
cannot bind with carbon dioxide, accumulates
76
Why is there a drop in GP and TP when there is less carbon dioxide?
cannot be made as carbon dioxide doesnt bind with RUBP
77
How does temperature affect the rate of photosynthesis?
more kinetic energy and collisions between enzyme and substrate catalysing photosynthesis, increases rate,
as enzymes begin to damage and denature rate decreases
78
What happens to rate of photosynthesis above 30 degrees?
oxygen begins compete with carbon dioxide for RUBISCO active site - less GP and TP
79
What is water stress?
Not enough water available to the plant
80
What are the consequences of water stress?
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
How does light intensity increase the rate of photosynthesis
- rate of phtotsynthesis incteaes if light intesnity incfeases because
- photosystmes/ pigments absorb more light
- causing reduced levels of ADP and NADP
82
what if theres low light intensity?
- rate of phtotsyntessis reduced due to reduced ADP and NADP levels
83
How does carbon dioxide affect rate of photosynthesis
- 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%
