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Biology Mock AS 2 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

what is the light energy in photosynthesis used for

A

to split strong bonds in water molecules (H2O), releasing hydrogen and oxygen

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2
Q

what is the waste product when splitting water molecules

A

Oxygen is released into the atmosphere as a waste product

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3
Q

state some reasons why organisms may need a constant supply of energy

A

To move substances across cell membranes in active transport or to move substances within cells

For muscle contraction

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4
Q

structure of ATP

A

type of nucleic acid

It is a phosphorylated nucleotide
consists of a nitrogenous base, a sugar, and three phosphate group hence triphosphate

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5
Q

what does the breakdown of glucose in respiration release

A

energy needed to phosphorylate ADP

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6
Q

what does the hydrolysis of ATP release

A

inorganic phosphate as well as a small amount of energy which can be used by the cell

ATP –> ADP + Pi

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7
Q

what is the removal of a phosphate group called and what is it catalysed by

A

dephosphorylation
catalysed by the enzyme ATPase

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8
Q

what 2 processes can ATP go through

A

is formed during respiration and can be hydrolysed to release energy for processes such as active transport, muscle contraction, and building new molecules

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9
Q

what is each chloroplast surrounded by

A

double-membrane known as the chloroplast envelope

Each of the envelope membranes is a phospholipid bilayer

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10
Q

what are chloroplast filled with

A

cytoplasm-like fluid known as the stroma

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11
Q

what does the stroma contain

A

enzymes and sugars, as well as ribosomes and chloroplast DNA

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12
Q

describe membrane system in the stroma

A

flattened fluid-filled sacs known as thylakoids, each surrounded by a thylakoid membrane

Thylakoids stack up to form structures known as grana

Grana are connected by membranous channels called lamellae which ensure the stacks of sacs are connected but distanced from each other

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13
Q

state the structures of a chloroplast

A

Chloroplast envelopes
Stroma
DNA
Ribosomes
Thylakoid membrane
Grana
Photosystems

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14
Q

function chloroplast envelope

A

double membrane encloses the chloroplast, keeping all of the components needed for photosynthesis close to each other
The transport proteins present in the inner membrane control the flow of molecules between the stroma and cytoplasm

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15
Q

function of stroma

A

The gel-like fluid contains enzymes that catalyse the reactions of photosynthesis

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16
Q

function of DNA in chloroplast

A

genes that code for some of the proteins used in photosynthesis

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17
Q

function of ribosomes in chloroplast

A

enable the translation of proteins coded by the chloroplast DNA

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18
Q

function of grana

A

large surface area, maximising the number of photosystems and allowing maximum light absorption

(granum) is formed from many layers of thylakoid membranes to increase surface area (for absorbing light)
thylakoid membranes contain chlorophyll to absorb light
electron carrier molecules in thylakoid membrane involved in ATP production

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19
Q

what does a photosystem do

A

absorbs light of a different wavelength, maximising light absorption

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20
Q

where does the light dependent reaction take place

A

across the thylakoid membrane

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21
Q

where does the light independent reaction take place

A

in the stroma

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22
Q

what enables the splitting of water molecules

A

Light energy in the light-dependent reactions in a reaction known as photolysis

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23
Q

what does photolysis produces

A

The hydrogen ions and electrons are used during the light-dependent reactions while the oxygen is given off as a waste product

2 hydrogen ions (2H+), also known as protons
2 electrons (2e-)
One atom of oxygen (O)

24
Q

what process occurs in the light dependent reaction

A

light energy is converted into chemical energy in the form of ATP and reduced NADP

25
Q

what is NADP

A

coenzyme; its role is to transfer hydrogen from one molecule to another
When NADP gains hydrogen, it is reduced and can be known as either reduced NADP or NADPH

26
Q

how can NADPH reduce other molecules

A

by giving away hydrogen

27
Q

what are the useful products of the light dependent reaction

A

ATP and NADPH transferred to the light-independent reactions within the chloroplast

28
Q

what is photophosphorylation

A

photo = light
the addition of phosphate; in this case to ADP to form ATP

utilizing light energy from photosynthesis to convert ADP to ATP

29
Q

what does non cyclic photophosphorylation produce

A

This produces both ATP and NADPH

30
Q

what does Cyclic photophosphorylation produce only

A

This produces ATP only

31
Q

describe electron transport chain

A

Electrons pass from one protein to another along the electron transport chain, releasing energy as they do so

32
Q

what is chemiosmosis

A

The energy released as electrons pass down the electron transport chain is used to produce ATP

33
Q

explain non cyclic photophosphorylation

also explain what happens to the H+ ions as electrons passed down

A

Light energy hits photosystem II in the thylakoid membrane

Two electrons gain energy and are said to be excited to a higher energy level

The excited electrons leave the photosystem and pass to the first protein in the electron transport chain

the electrons pass down the electron transport chain

Energy is released as the electrons pass down the electron transport chain which enables chemiosmosis to occur

H­­+ ions are actively pumped from a low concentration in the stroma to a high concentration in the thylakoid space

H­­+ ions diffuse back across the thylakoid membrane into the stroma via ATP synthase enzymes embedded in the membrane

The movement of H­­+ ions causes the ATP synthase enzyme to catalyse the production of ATP

At the end of the electron transport chain the electrons from photosystem II are passed to photosystem I

Light energy also hits photosystem I, exciting another pair of electrons which leave the photosystem

The excited electrons from photosystem I also pass along an electron transport chain

electrons combine with hydrogen ions from the photolysis of water and the coenzyme NADP to form NADPH

The reduced NADP and the ATP pass to the light-independent reactions

34
Q

Explain cyclic photophosphorylation

A

same as non cyclic

Light hits only photosystem I

At the end of the electron transport chain the electrons rejoin photosystem I in a complete cycle; hence the term cyclic photophosphorylation
The ATP produced enters the light-independent reaction

35
Q

what does the light independent reaction produce

A

Starch for storage
Sucrose for transport
Cellulose for making cell walls

36
Q

what does light independent reaction require

A

ATP and reduced NADP from the light-dependent reactions

37
Q

3 steps of light independent reaction

A

1) Carbon dioxide is combined with RuBP a 5-carbon (5C) compound; this yields two molecules of GP a 3-carbon (3C) compound

2) GP is reduced to (GALP), another 3C compound, in a reaction involving reduced NADP and ATP

3) RuBP is regenerated from GALP in reactions that use ATP

38
Q

explain step 1 : Carbon dioxide and RuBP are combined

A

Carbon dioxide combines with a 5C sugar known as RuBP in a reaction catalysed by the enzyme rubisco

The resulting 6-carbon (6C) compound is unstable and splits in two

This results in two molecules of a 3C GP

39
Q

explain step 2 : Reduction of GP

A

Energy from ATP and hydrogen from reduced NADP, both produced during the light-dependent reactions, are used to reduce the two molecules of GP to two 3C molecule known as GALP

production of useful organic molecules such as glucose, while the rest remain in the Calvin cycle to allow the regeneration of RuBP

40
Q

explain step 3 : Regeneration of ribulose bisphosphate

A

Five sixths of the GALP molecules are used to regenerate RuBP
This process requires ATP

41
Q

what does GP produce

A

Amino acids which can be used in protein synthesis for building polypeptides

Fatty acids which form the tails of lipid molecules such as triglycerides and phospholipids

42
Q

What does GALP produce

A

Hexose sugars e.g. glucose

Glucose can be used by the plant in respiration while other biological molecules are used to build new plant biomass

43
Q

how is NADPH formed

A

electrons are picked up by the coenzyme NADP along with hydrogen ions from photolysis, forming NADPH

44
Q

why do indicators change colour

A

indicators accept the electrons instead of NADP

45
Q

what colour does DCPIP and methylene blue go

A

blue to colourless

46
Q

why may the colour of reduced solution appear green

A

due to the presence of chlorophyll

47
Q

Method for the Hill reaction

A

Grind up the leaves with 20 cm3 isolation solution and blend them in a food blender for 10 seconds

Filter the resulting liquid into a clean beaker using a funnel and some filter paper

Transfer the filtered liquid into a centrifuge tube and centrifuge for 10 minutes

Discard the liquid in the centrifuge tube and keep the pellet of chloroplasts

Place 2 cm3 fresh isolation medium and the chloroplast pellet into a clean test tube, stirring with a glass rod to re-suspend the chloroplasts in the liquid; this is now the chloroplast extract

transfer the chloroplast extract to an ice-cold water bath

Place a test tube containing 0.5 cm3 chloroplast extract into a test tube rack set up at a set distance from a lamp

Add 5 cm3 DCPIP solution to the chloroplast extract and mix together using a clean glass rod

Use a pipette to immediately remove a sample of the DCPIP-chloroplast mixture and place the sample into a clean cuvette

Place the cuvette into a colorimeter and take a reading for absorbance

Repeat steps

48
Q

why do we grind up leaves and blend them in food blender and put isolation solution

A

breaks apart the tissues of the leaf

isolation medium will prevent cell damage due to osmosis or extreme pH

49
Q

why transfer filtered liquid in centrifuge tube and centrifuge

A

result in a pellet of chloroplasts forming at the bottom of the tube

50
Q

what is liquid in centrifuge known as

A

supernatant

51
Q

why ice cold water

A

The cold temperature of the water bath slows down the activity of the chloroplasts

52
Q

what should happen to absorbance reading of colorimeter

A

The absorbance reading of the colorimeter should decrease over the 10 minute test period as the DCPIP indicator is reduced by electrons in the chloroplasts

53
Q

what does the removal of one phosphate from ATP form and two phosphates

A

Removal of one phosphate creates ADP, and removal of two phosphates creates AMP.

54
Q

describe the role of rubisco in the production of GALP in the light independent reaction

A

reference to RUBISCO as an {enzyme / catalyst};

in the Calvin cycle;

involved in {carbon fixation / bonding of CO2 to RuBP / reaction between COz and RuBP / eq} ;
to form GP / eg;

GP converted to GALP / eg;
using ATP and {reduced NADP / NADPH} (COz to
GALP / GP to GALP);

55
Q

describe how membranes inside the chloroplast are involved in photosynthesis

A

site of light-dependent reaction;
credit named molecules {within / on / eq} membrane;
idea of {ATPase / eq } in (thylakoid) membranes ;
idea that (thylakoid) membranes provide a space for accumulation of H*;
reference to photophosphorylation;

56
Q

suggest how GALP can be used to synthesise the cellulose in plant cell walls

A

reference to conversion (of GALP) to glucose / eg;

(which is) B glucose;
reference to formation of glycosidic bonds;

between C1 and Ca / these bonds are 1-4 (glycosidic bonds) ;

by condensation;
reference to {straight / unbranched} (chains of glucose) ;

reference to cellulose as a {polysaccharide / polymer of glucose / eq}

57
Q

describe the roles of the products of the light dependant reactions in the calvin cycle

A

(the products) ATP and reduced NADP
(1)

ATP is used (by the enzyme) converting
(GP to GALP / GALP to RuBP} (1)
reduced NADP used to convert GP to
GALP (1)

Biology Mock AS 2 (23 decks)

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