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Biology 1610 > Chapter 10 - Photosynthesis > Flashcards

Chapter 10 - Photosynthesis Flashcards

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1
Q

Autotrophs

A

Self-feeders

Sustain themselves without eating anything derived from other living beings

Produce organic molecules from CO2 and other inorganic raw materials from the environment (producers)

Photoautotrophs - use light to make food

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2
Q

How does an organism acquire the organic compounds it uses for energy?

A

Either by creating its own food (being an autotroph), or consuming it (heterotroph)

Photosynthesis is the foundation of this process

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3
Q

Heterotrophs

A

Biosphere’s consumers because they consume compounds produced by other organisms

Decomposers (bacteria) that feed on carcasses and waste, are also heterotrophs

Depend on Photoautotrophs for both food and oxygen

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4
Q

Where does most photosynthesis occur?

A

The leaves of a plant , more specifically he Mesophyll - which occurs mainly in the chloroplasts

30-40 chloroplasts per Mesophyll cell

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5
Q

Mesophyll

A

The tissue in the interior of the leaf where most chloroplasts are found

30–40 chloroplasts per Mesophyll cell

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6
Q

Stomata

A

Pores that allows carbon dioxide in and oxygen out.

Also allows water to come out

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7
Q

Stroma

A

An envelope with two membranes surrounding a dense fluid of the chloroplasts

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8
Q

Thylakoids

A

Third membrane system that includes sacs which segregates the Stroma from the thylakoid space inside the sacs

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9
Q

Granum

A

Stacked thylakoid stacks in columns

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10
Q

Chlorophyll

A

Green pigment that gives leaves their color inside thylakoid membrane of the chloroplast

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11
Q

What happens when a plant is exposed to light?

A

The green parts of the plant produce organic compounds and oxygen from carbon dioxide and water

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12
Q

Photosynthesis chemical equation

A

6CO2 + 12 H2O + light energy —-> C6H12O6 + 6 O2 + 6H2O

The reverse equation of cellular respiration

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13
Q

Where does O2 come from in photosynthesis?

A

H2O; not carbon dioxide like most people think

The chloroplast splits water into hydrogen and oxygen

They incorporate the electrons of hydrogen into sugar molecules and then release oxygen as a byproduct

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14
Q

Photosynthesis

A

Chloroplasts capture light energy and converts it to chemical energy that is stored in sugar and other molecules

It’s a redox reaction in which H2O is oxidized (loses an electron) to become 6O2 and CO2 is reduced (gains an electron) to become C6H12O6

It’s endergonic because it uses light to aid the process.

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15
Q

Explain van niel’s discovery about photosynthesis

A

He studied photosynthesis in bacteria. They make their carbohydrate from CO2, but don’t release O2.

Concluded that co2 isn’t split to make carbon and oxygen; it split its hydrogen sulfide instead. He reasoned that plants are more likely to split their h2o and use the hydrogen electrons releasing O2 as a byproduct

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16
Q

Photosynthesis is reverse of cellular respiration

A

It reverses the electron flow.

Water is split and electrons are transferred along with hydrogen ions from water to co2, reducing it to sugar.

It’s endergonic because the electrons increase in potential energy as they move from water to sugar

Light provides this energy boost.

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17
Q

What are the two cycles of photosynthesis

A

Light reactions (photo part)

Calvin cycle (synthesis part)

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18
Q

Light reactions

A

Covert solar energy to chemical energy

Water is split providing a source of electrons and protons (H+) ions giving off O2 as a byproduct

Light absorbed by chlorophyll drives a transfer of electrons and hydrogen ions from water to NADP+ where they’re temporarily stored

Light uses solar energy to NADP+ to NADPH by adding a pair of electrons along with H+

The light reactions also generate ATP using chemiosmosis to power the additional phosphate group to ADP using phosphophorylation

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19
Q

Phosphorylation

A

Using chemiosmosis to add a phosphate to ADP

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20
Q

Which two compounds are converted to chemical energy in the first stage of photosynthesis?

A

NADPH and ATP

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21
Q

NADPH

A

A source of electrons that reduce power that can be passed along to an electron acceptor

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22
Q

Calvin cycle

A

Carbon fixation

Then reduces the fixed carbon to carbohydrate by the addition of electrons (done via NADPH)

Uses ATP convert CO2 to carbohydrate which is generated by light reactions

Referred to as dark reactions, or light independent reactions because they don’t require light directly.

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23
Q

How is light used to covert solar energy into chemical energy?

A

Because chloroplasts are solar powered chemical factories…

Use thylakoids to transform lights energy into chemical energy of ATP and NADPH

24
Q

Light

A

A form of electromagnetic energy/radiation

Occurs in rhythmic waves

25
Q

Wavelength

A

Involves the distance between crests of the waves

It determines the type of electromagnetic energy

26
Q

Electromagnetic spectrum

A

The entire range of electromagnetic energy or radiation

27
Q

Visible light

A

Involves all the wavelengths we can physically see

Includes light waves for photosynthesis

This is how we see color

380 nm - 750 nm

28
Q

Photons

A

Lights ability to function as particles as well.

Particles of light

29
Q

Photosynthetic pigments

A

Pigments that Absorb light

Different pigments absorb different wavelengths

Wavelengths that are not absorbed are transmitted or reflected

Leaves appear green because chlorophyll reflects/transmits green light

30
Q

Spectrophotometer

A

Measures a pigment’s ability to absorb various wavelengths

It sends light through the pigments and measures the fraction of light transmitted at each wavelength

31
Q

Absorption spectrum

A

A graph that documents pigment’s light absorption versus wavelength

Chlorophyll a which is violet-blue and red work best for photosynthesis

400-500 nm?

32
Q

Engelmann experiments

A

Used aerobic algae to test which wavelengths were the most suitable for photosynthesis

The wavelengths that were suitable to photosynthesis caused the algae to expel excess O2 and then the aerobic bacteria would congregate around it.

33
Q

What is the main pigment of photosynthesis?

A

Chlorophyll a

34
Q

What are accessory pigments?

A

Chlorophyll b and carotenoids

35
Q

Carotenoids

A

They are responsible for photoprotection.

They absorb excess light that would damage chlorophyll

36
Q

What happens when light hits chlorophyll?

A

When a pigment absorbs light, its electrons get excited and jump from one shell to one that’s unstable.

When the electrons fall back to their ground state, they release photons called fluorescence

It gives off light and heat.

37
Q

Photosystem

A

Consists of a reaction center complex (a type of protein complex) surrounded by light harvesting complexes

38
Q

Light harvesting complex

A

Pigment molecules bound to proteins

Transfer the energy of photons to the reaction center

39
Q

Primary electron acceptor

A

Exists in the reaction center and accepts excited electrons and is reduced as a result

40
Q

What are the two types of photosystems in the thylakoid membrane?

A

Photosystems 2 is the first and its chlorophyll best absorbs wavelengths that are 680 nm long

Its reaction center is called P680

Photosystems 1 is best at absorbing wavelengths that are 700 nm long and its reaction center is called P700

41
Q

What are the two possible pathways during the light systems reaction?

A

Cyclical and linear

Linear electron flow is the primary pathway and it involves both photosystems creates both ATP and NADPH using light energy

42
Q

What are the 8 steps in linear electron flow?

A
  1. Photon hits the pigment and the energy is passed from pigment molecules until it excites P680
  2. An excited electron from P680 is transferred via the primary electron transport (P680+)
  3. H2O is split by enzymes and the electrons are transferred from the hydrogen atoms to P680+ thus reducing it to P680 (O2 is released as a byproduct)
  4. Each electron “falls” down an electron transport chain to from the primary electron acceptor of PS 2 to PS 1
  5. Energy released by the fall drives the creation of a proton gradient across the thylakoid membrane (diffusion of H+ across the membrane drives ATP synthesis)
  6. In PS 1 transferred light energy excites P700 which loses an electron (P700+ accepts an electron passed down from PS 2 through the transport chain)
  7. Each electron falls down the chain from the primary electron acceptor in PS1 to ferredoxin (fd)
  8. The electrons are then transferred to NADP+ and reduced to NADPH

NADPH is then available for the Calvin cycle

This also removed H+ from the Stroma

43
Q

Cyclic electron flow

A

Electrons cycle back from Fd to PS1 reaction center

Uses only PS 1 and produces ATP, but no NADPH

Don’t release O2

Ie purple bacteria which have PS1 but not PS2

Evolved before linear flow and may protect the plant from light damage

44
Q

Chemiosmosis in chloroplasts vs mitochondria

A

Both generate ATP via chemiosmosis

Mitochondria use food, chloroplasts use light

Mitochondria pump protons into the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix

In chloroplasts protons are pumped into the thylakoid space and they generate ATP as they diffuse back into the Stroma

45
Q

Calvin cycle

A

Similar to the citric acid cycle because it regenerates its starting material after molecules enter and leave the molecule

It builds sugar from smaller molecules using ATP and reducing the power of electrons via NADPH

Carbon enters as CO2 and releases as glyceralhyde three phosphate G3P (has to go through Calvin cycle three times for this to occur

46
Q

Three Phases of the Calvin Cycle

A
  1. Carbon fixation (catalyze do by the protein rubisco)
  2. Reduction
  3. Regeneration of CO2 acceptor by RuBP
47
Q

Photosynthesis in hot climates

A

Plants close stomatas on hot days, which keeps H20 in, but also limits photosynthesis

Closed stomatas reduces access to CO2 and causes a buildup of O2

48
Q

Photorespiration

A

rubisco adds O2 instead of
CO2 in the Calvin cycle, producing a two-carbon
compound

consumes O2 and organic fuel
and releases CO2 without producing ATP or sugar

In many plants, photorespiration is a problem
because on a hot, dry day it can drain as much
as 50% of the carbon fixed by the Calvin cycle

49
Q

C3 plants

A

most plants

initial fixation of CO2,
via rubisco, forms a three-carbon compound
3-phosphoglycerate

50
Q

C4 plants

A

minimize the cost of photorespiration by
incorporating CO2 into four-carbon compounds

two distinct types of cells in the leaves
of C4 plants:
Bundle-sheath cells
mesophyll cells

51
Q

Bundle-sheath cells

A

arranged in tightly packed

sheaths around the veins of the leaf

52
Q

mesophyll cells

A

loosely packed between the

bundle sheath and the leaf surface

53
Q

Three steps for Sugar production in C4 plants

A
  1. The production of the four carbon precursors is
    catalyzed by the enzyme PEP carboxylase in
    the mesophyll cells
    PEP carboxylase has a higher affinity for CO2
    than rubisco does; it can fix CO2 even when CO2
    concentrations are low
  2. These four-carbon compounds are exported to
    bundle-sheath cells
  3. Within the bundle-sheath cells, they release CO2
    that is then used in the Calvin cycle
54
Q

crassulacean acid metabolism (CAM)

A

what succulent plants use to fix carbon

open their stomata at night,
incorporating CO2 into organic acids

Stomata close during the day, and CO2 is released
from organic acids and used in the Calvin cycle

55
Q

LIGHT REACTIONS

A 
• Are carried out by molecules
in the thylakoid membranes
• Convert light energy to the
chemical energy of ATP
and NADPH
• Split H2O and release O2
to the atmosphere
56
Q

Calvin cycle

A 
Take place in the stroma
• Use ATP and NADPH to convert
CO2 to the sugar G3P
• Return ADP, inorganic phosphate,
and NADP+ to the light reactions

Biology 1610 (14 decks)

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