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Biology > Photosynthesis > Flashcards

Photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is photosynthesis

A

Where organisms convert light energy into sugars

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2
Q

How are leaves adapted for photosynthesis

A

-has a large surface area so lots of sunlight can be absorbed
-lots of air spaces for efficient diffusion
-waxy cuticle preventing water loss
-has lots of veins (xylem and phloem)
-leaf is thin so short diffusion pathway for efficient diffusion
-has many chloroplast which contains chlorophyll to absorb sunlight for photosynthesis

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3
Q

What is autotroph and give an example

A

An organism that makes their own food from inorganic molecules using energy
E.g producers in an ecosystem

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4
Q

What is heterotroph and give an example

A

An organism that cannot make its own food so has to obtain organic compounds by consuming other organisms
E.g consumers or decomposers

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5
Q

What is a photoautotroph

A

An organism that photosynthesises
uses light to make food

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6
Q

What is a Chemoautotroph

A

Organism that does NOT photosynthesise
uses chemicals to make its food

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7
Q

What is the photosynthesis equation

A

Sunlight
Carbon dioxide + water > glucose + oxygen
Chlorophyll

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8
Q

What type of reaction is photosynthesis

A

-It is endothermic
-Glucose is the main product
~ transports as sucrose and stored as starch

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9
Q

What is the respiration equation and what type of reaction is it

A

Glucose + oxygen > carbon dioxide + water + energy
-it is an exothermic reaction

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10
Q

Define interrelationship

A

The products of one are the reactants of the other

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11
Q

What is compensation point

A

When photosynthesis and respiration proceed at the same rate, there is no net gain or loss of carbohydrate

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12
Q

Fill in the gap
Plants - - - - all day but can only - - - - in the day

A
  1. Respire
  2. Photosynthesise
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13
Q

What is the compensation point (on the graph) for rate of oxygen exchange and light intensity

A

Where the line crosses the x-axis

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14
Q

Where is the chloroplast found and how long is it

A

-found in plants and algae
-2-10 micrometres long

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15
Q

What internal structures are there in the chloroplast

A

-granum
-stroma
-thylakoid
-intergranal lamellae
-photosystems

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16
Q

what is the Granum

A

-Stack of thylakoids
-where light dependant stage of photosynthesis takes place

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17
Q

What does the grana do

A

-many grana in the chloroplast so there’s a huge surface area for:
~when the electron carriers and ATP synthase enzymes need to convert light energy into ATP
~distributions of the photosystems that contain the photosynthetic pigmented that trap sunlight energy

Large surface area for light absorption
Has electron carriers

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18
Q

What is the stroma

A

-fluid filled matrix surrounding the thylakoids

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19
Q

What does the stroma do

A

-contains enzymes to catalyse the reactions of the light dependent stage of photosynthesis
-it also contains
~starch grains
~oil droplets
~loop of DNA
~small ribosomes

20
Q

What is the thylakoid

A

-flattened disc like sacs that form stacks (grana)

21
Q

What is the intergranal lamellae

A

-Connects thylakoids in different grana, together

22
Q

What is a photosystem

A

-Funnel shaped structures found within the thylakoid membrane
-contains photosynthetic pigments
-each pigment absorbs sunlight of a particular wavelength whilst reflecting other wavelengths of light

~the light energy captured is tunnelled down to the primary pigment reaction centre consisting of a type of chlorophyll at the base of the photosystem

23
Q

What is chlorophyll’s

A

-mixture of pigments
-all have a similar molecular structure consisting of a porphyrin group which there is a magnesium atom and a long hydrocarbon chain

24
Q

What are the 2 chlorophylls

A

Chlorophyll A
Chlorophyll B

25
Q

Chlorophyll A

A

-2 forms
-Appear blue or green
-both absorb RED light but have different absorption peaks
P680 - found in photosystem 2 light of wavelength for absorption is 680nm
P700 - found in photosystem 1- light of wavelength absorption is 700nm

26
Q

Chlorophyll B

A

-absorbs light of wavelengths 400-500 nm and around 640

27
Q

What do accessory pigments do

A

-carotenoids absorb blue light of wavelengths 400-500 nm
-xanthophyll absorbs blue and green of 375 - 550nm
they reflect yellow

28
Q

Where does the light dependant stage of photosynthesis take place

A

-In the grana and involves the photosystems
-it uses direct light energy

29
Q

What are the 3 stages of light dependant stage of photosynthesis

A

-light harvesting at the photosystems
-photolysis of water
-phosphorylation (cyclic or non cyclic)

30
Q

What are the 2 photosystems (PS)

A

PS1 - chlorophyll a (p700)
PS2 - chlorophyll a (p680)

31
Q

What happens at the light harvesting at the photosystems stage

A

-light energy is funnelled down to the primary reaction centre
-has a type of chlorophyll depending on the base of the photosystem

32
Q

What happens at the photolysis of water stage

A

-occurs in PS2
-in the presence of light, water molecule is split into protons(H+), electrons and oxygen

(The oxygen can be used in respiration if production is high or it just diffuses out of the leaf)

33
Q

what happens at photo phosphorylation

A
  • the generation of ATP from ADP and inorganic phosphate in the presence of light
  • it can be cyclic or non cyclic
34
Q

Non cyclic stage of phosphorylation

A

-light is absorbed by PS2 and is passed to the PS2 primary pigment (P680)
-2 electrons are excited to a higher energy level and are emitted from the chlorophyll molecule
-excited electrons are passed down a chain of electron carriers (electron transport chain) before being passed on to PS1
-the energy released from the ETC allows H+ ions to pass from a low conc in stroma to a high conc in the thylakoid
-the H+ then diffuses back through ATP synthase to generate ATP
-in PS2 photolysis occurs
-these electrons replace the ones that are lost from PS2 to go to PS1
-The electrons leaving PSI combine with hydrogen ions giving reduced NADP
2H+ + 2e- + NADP → reduced NADP
-The reduced NADP (NADPH) then passes to the light-independent reactions to be used in the synthesis of carbohydrates

35
Q

What is electron carriers

A

-proteins embedded in the membrane with iron ions in it
-when the electrons bind to it, it becomes reduced
-it can then donate the electron to the next electron carrier becoming reoxidised

36
Q

What is Cyclic phosphorylation and give an example

A

Occurs only in PS1
- produces small amounts of ATP

  • e.g guard cells use this to generate ATP to actively bring potassium ions into the cells lowering the water potential so that water follows by osmosis
  • causes guard cells to swell and open the stomata
37
Q

What is the stages of cyclic phosphorylation

A

-light is absorbed and passed on through PS1 (P700)
-an electron is excited to a higher energy level and is emitted from the chlorophyll molecule
-excited electron is captured by an electron acceptor transported via electron transport chain before going back to PS1 (this process releases energy)
- energy is used to transport protons (H+) from stroma to thylakoid via proton pump
- a build up of protons in the thylakoid lumen means they diffuse back through the membrane via ATP synthase which generates ATP from ADP and P1

38
Q

What photosystems are involved in cyclic and non cyclic stages

A

Cyclic - PS1
non cyclic - BOTH

39
Q

does photolysis occur in cyclic or non cyclic

A

Non cyclic

40
Q

What are the products of cyclic and non cyclic

A

Cyclic- ATP
Non cyclic- ATP, oxygen and reduced NADP

41
Q

Factors affecting photosynthesis

A

Carbon dioxide
Light
Temperature
Water

42
Q

Light intensity

A

As light intensity increases rate of photosynthesis increases
However if it increases too much it levels out and plateaus because there is now another factor limiting it

43
Q

How light intensity affects the Calvin cycle

A

If it’s too LESS
GP cannot be reduced to TP
so if GP accumulates and TP levels fall RuBp cannot be regenerated

44
Q

Effect of carbon dioxide on Calvin cycle

A

If CO2 concentrations fall below 0.01%
Then RuBp cannot accept it so it accumulates and so GP cannot be made.
So TP cannot be made

45
Q

Effect of temperature on Calvin cycle

A

At high rates O2 competes with CO2 for RuBiSCOs active site
Lack of TP means growth rate reduced

46
Q

Uses of water

A

Keeps guard cell turgid so they can stay open
Used as reactant

47
Q

What is water stress and give examples

A

When water supply becomes limited for plant
E.g
Cells lose water and become plasmolysed
Rate of photosynthesis reduces greatly

Biology (5 decks)

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