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4U BIO > 4.1/4.2 > Flashcards

4.1/4.2 Flashcards

1
Q

Overall Reaction for Photosynthesis

A

6 CO2 + 6 H20 + energy —> C6H12O6 + 6 O2

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2
Q

What organelle does photosynthesis require?

A

Chloroplasts

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3
Q

What organisms carry out photosynthesis?

A

A) Some Bacteria
B) Protists (algae provide 67% of Earth’s oxygen)
C) plants

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4
Q

What are the two sets of reactions in photosynthesis?

A
  • Light-Dependent (photo)

- Light-Independent (synthesis)

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5
Q

Light-Dependent Reactions

A

In photosynthesis, the reaction that traps solar energy and uses it to generate ATP and NADPH.

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6
Q

Light-Independent Reaction

A

In photosynthesis, the reaction that assimilates carbon dioxide to produce an organic molecule that can be used to produce biologically important molecules such as carbohydrates.

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7
Q

Stages that Make Up The Light Dependent Reaction

A

1) photoexcitation

2) electron transport and chemiosmosis

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8
Q

Photoexcitation

A

Absorption of a photon to “excite” an electron in chlorophyll

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9
Q

Electron Transport Chain and Chemiosmosis

A

Series of membrane bound electron carriers pumping H+ through the membrane creating an H+ gradient and NADPH; chemiosmosis: production of ATP

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10
Q

Grana

A

Stack of Thylakoids (approx. 60 chloroplasts)

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11
Q

Lamellae

A

Unstacked thylakoids between grana.

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12
Q

Thylakoids Membrane

A

A photosynthetic membrane within a chloroplast that contains light-gathering pigment molecules and electron transport chains.

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13
Q

Thylakoid Lumen

A

The fluid filled space inside a thylakoid.

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14
Q

Thylakoid

A

One of many interconnected sac-like membranous disks within the chloroplast, containing the molecules that absorb energy from the Sun.

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15
Q

Photon

A

Package of light.

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16
Q

Longer-wavelength photons have _________ amounts of energy and shorter wavelength photons have ________ amounts of energy.

A

Smaller; Larger

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17
Q

Pigment

A

A compound that absorbs certain wavelengths of visible light while reflecting others.

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18
Q

Photosynthetic Pigment

A

A compound that traps light energy and passes it on to other compounds.

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19
Q

Chlorophyll b and carotenoids

A

Act as accessory pigments.

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20
Q

Chlorophyll a

A

Only pigment that can transfer the light energy.

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21
Q

What two types of chlorophyll are contained in chloroplasts?

A

Chlorophyll a

Chlorophyll b

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22
Q

What happens during photoexcitation?

A
  • Chlorophylls a and b absorb photons with energies in blue-violet and red regions of spectrum and reflect the green light.
  • The photon of light striking the chlorophyll a molecule gives an electron energy and raises it to a higher potential energy level.
  • Excited Electron is captured by primary electron acceptor (a compound embedded in the thylakoid membrane)
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23
Q

Absorbance Spectrum

A

A graph that shows the relative amounts of light of different wavelengths that a compound absorbs.

24
Q

Photosystem

A

One of two protein-based complexes composed of cluster of pigments that absorb light energy.

25
What do the chloroplasts of algae and plants have?
Photosystems I and II
26
Reaction Centre Pigment of Photosystem I
Chlorophyll P700
27
Reaction Centre Pigment of Photosystem II
Chlorophyll P680
28
Step 1 of the Light-Dependent Reactions
- P680 molecule in the reaction centre absorbs light photon, exciting an electron which travels to an electron acceptor - transferred to ETC - happens twice
29
Step 2 of the Light-Dependent Reactions
- water is split by the 'z' protein (oxygen leaves as byproduct) - H+ is in thylakoid space
30
B6-f complex
Pumps hydrogen ions from the stroma across the thylakoid membrane and into the thylakoid space
31
Step 3 of the Light-Dependent Reactions
- Electrons leave PS II - H+ gradient is formed - Electrons move through ETC
32
Step 4 of the Light-Dependent Reactions
- light energy is absorbed by PS I - energy is transferred to reaction centre P700 where electrons become excited - electrons are transferred to electron acceptor
33
Step 5 of the Light-Dependent Reactions
-electrons from PS I pass through another ETC with ferrodoxin (Fd) and move to enzyme NADP reductase to reduce NADP+ to NADPH (with H+)
34
Step 6 of the Light-Dependent Reactions
-H+ protons move through ATPase complex from lumen to stroma forming ATP (chemiosmosis)
35
How are the lost electrons in PS I replaced?
Replaced by electrons that have reached the end of the electron transport system from PS II.
36
Photophosphorylation
The use of photons of light to drive the phosphorylation of ADP to produce ATP via chemiosmosis.
37
Non-Cyclic Photophosphorylation
- the production of ATP by the passing of electrons through the Z scheme * flow of electrons is unidirectional (electrons are transferred from photosystem II to NADP+ to form NADPH*
38
Cyclic Photophosphorylation
-excited electrons leave PS I and are passed to an electron acceptor, then to the b6-f complex and back to PS I
39
CO2 Assimilation
Conversion of carbon dioxide into organic compounds.
40
Calvin Cycle
In photosynthesis, the reactions that convert carbon dioxide to the three-carbon organic molecule glyceraldehyde-3-phosphate (G3P); can occur in the absence or presence of light; also called the dark reactions and the Calvin-Benson cycle
41
Where do the light independent reactions take place?
Stroma
42
Three Phases of Calvin Cycle
1) Carbon Fixation 2) Reduction 3) Regeneration of RuBP
43
For every ___ molecules of G3P made in the Calvin Cycle, ___ are used to make glucose and other high-energy compounds.
12;2
44
Carbon Dioxide Fixation
The reaction of carbon dioxide with RuBP to produce two identical three carbon molecules, 3-phosphoglycerate
45
Process of CO2 Fixation
- the carbon in CO2 bonds to RuBP resulting in an unstable 6 carbon molecule - immediately breaks down into 2 identical molecules (PGA) * catalyzed by rubisco*
46
C3 Photosynthesis
A process of converting carbon dioxide to G3P using only the Calvin cycle; involves production of a three-carbon intermediate (PGA)
47
Reaction for Carbon Dioxide Fixation
CO2 + RuBP ---> unstable C6 ---> 2 PGA
48
C3 Plants
- regular everyday plants - open stomata during the day to breathe in CO2 and release O2 - go through light and dark reactions
49
Reduction (Second Phase of Calvin Cycle)
- PGA is in low-energy state so to get to higher energy state it is activated by ATP and reduced by NADPH - results in two G3P [in reduced state (higher energy), some G3P leaves the cycle and can be used to form glucose or other molecules] - remaining G3P move to the third phase of Calvin cycle
50
Regenerating RuBP (Third Phase of Calvin Cycle)
- most G3P molecules are used to make more RuBP | - requires ATP to break and reform bonds
51
How many times must the Calvin Cycle be completed to form a glucose molecule?
6
52
What is regenerated by the 12 G3P from 6 cycles?
- 10 are used to regenerate RuBP | - 2 are used to make glucose
53
Net Equation of Calvin Cycle
6 CO2 + 18 ATP + 12 NADPH + water ---> 2 G3P + 16 Pi + 18 ADP + 12 NADP+
54
Photorespiration
-the reaction of O2 with RuBP in a process that reverses carbon fixation and reduces the efficiency of photosynthesis
55
Efficiency of photosynthesis in C3 plants
If each photosystem absorbs the maximum amount of light, the efficiency is 30%.
56
C4 Plants
- have structures that separates the initial uptake of carbon dioxide from the Calvin Cycle into different types of cells - concentrates CO2 in bundle sheath cells - different metabolic pathway brings the limited CO2 the bundle sheath cells where it is then used in the Calvin Cycle
57
CAM
- water-storing plants - use biochemical pathway in the same cell - CO2 fixation is separated from the Calvin cycle by time of day rather then types of cells - at night stoma open and CO2 enters the leaf, stoma is closed during the day and no CO2 enter

4U BIO (11 decks)

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