Class: Name: Date: 21 Photosynthesis - Shared …bio662.dyndns.info/DSE/WS/ws_ch21_e.pdfClass: Name: ( ) Date: New Senior Secondary Mastering Biology Oxford University Press 2014 (Second

Class: Name: ( ) Date:

New Senior Secondary Mastering Biology Oxford University Press 2014 (Second Edition)

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21 Photosynthesis

21.1 The basic concepts of photosynthesis (Book 3, p. 21-3)

� Plants and algae are autotrophs. They make their own food by (1) _______________.

� Photosynthesis is the process by which (2) _______________ substances (such as

carbohydrates) are made from simple (3) _______________ substances (carbon dioxide and

(4) _______________) using (5) _______________ energy. During the process, light energy

is captured by (6) _______________ in plants and algae. Chlorophyll is found in

(7) _______________ in most plants.

� The light energy captured is converted to (8) _______________ energy that is stored in the

carbohydrates produced. (9) _______________ is released as a by-product.

� Photosynthesis is a / an (10) _______________ (catabolic / anabolic) process.

� (11) _______________ and (12) _______________ are made from intermediates of

photosynthetic reactions. Their production requires (13) _______________ absorbed from the

soil.

oxygen (released to the air)

carbon dioxide (from air)

water (from soil)

light

chlorophyll

photosynthesis

from

in

term

ed

iate

s

carbohydrates

lipids

proteins

plant materials, e.g. enzymes, chlorophyll, cell membrane and cell wall

▲ How plants make the materials they need

sun

�


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21.2 The site of photosynthesis (Book 3, p. 21-5)

� In plants, (1) _______________ are the main site of photosynthesis.

A What are the adaptive features of leaves for photosynthesis? (Book 3, p. 21-5)

Structure Feature Adaptation for photosynthesis

� Broad and flat � Provides a large (2) _______________

_____________ for absorbing sunlight Leaf blade

� Thin � Gases and light can reach the

photosynthetic cells easily

Palisade

mesophyll

� Consists of tightly packed cells that

contain many (3) _______________

� Located on the (4) ______________

(upper / lower) side of the leaf

� Allows effective absorption of sunlight

Spongy

mesophyll

� Consists of loosely packed cells with

many (5) _______________

_______________

� The cells contain chloroplasts (fewer

than palisade mesophyll)

� Allows gases to (6) _______________

freely

� Allows absorption of sunlight

� Covered by a thin layer of waxy

(7) _______________

� Reduce (8) _______________ loss

from the leaf, so that water is kept

inside for photosynthesis and keeping

the cells turgid Upper

epidermis

and lower

epidermis

� Contain numerous

(9) _____________ (more on lower

epidermis)

� Each stoma is surrounded by a pair

of (10) _______________

_______________

� Stomata open when the conditions are

favourable for photosynthesis. They

close when the conditions are less

favourable. This regulates the passage

of gases and water vapour into and out

of the leaf

Midrib and

veins

� Contain vascular bundles which are

made up of (11) _______________

and (12) _______________

� Allow efficient transport of materials

into and away from the leaf

� Support and spread the leaf blade


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B What are the adaptive features of chloroplasts for

photosynthesis? (Book 3, p. 21-7)

� A chloroplast is bounded by a (13) _______________ membrane and is filled with a

jelly-like fluid called (14) ______________ (基質). The stroma contains (15) ______________.

It also holds (16) _______________ grains.

� A network of disc-like membranous sacs called (17) _______________ (類囊體) is suspended

in the stroma. The thylakoids are arranged in stacks called (18) _______________ (基粒).

(19) _______________ is located on the thylakoid membranes.

� A chloroplast has about 50 grana, each consisting of about 50 thylakoids. This provides a large

(20) _______________ _______________ to pack more chlorophyll for absorbing light. The

grana are (21) _______________ by extensions from thylakoids. This allows efficient

(22) _______________ of photosynthetic products within the chloroplast.

21.3 The requirements for photosynthesis (Book 3, p. 21-9)

A How do we know if photosynthesis has occurred? (Book 3, p. 21-9)

1 Detecting the presence of starch

� We can carry out (1) _______________ test to test for the presence of starch in a plant.

2 Detecting the release of oxygen

� We can test for oxygen in the gas produced by a plant using a (2) _______________ splint.

� Go to

Practical 21.1 Detection of starch produced in photosynthesis (the iodine test)

(Book 3, p. 21-9; Practical Workbook for SBA 3 • 4, p. 21-1)

Practical 21.2 Detection of oxygen produced in photosynthesis


thylakoid

stroma

granum

outer membrane

inner membrane

▲ 3-D drawing of a chloroplast showing grana and thylakoids


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B Investigation of the requirements for photosynthesis(Book 3, p. 21-11)

� If we plan to use the presence of starch in leaves as the evidence that photosynthesis has

occurred, any starch that is present in the leaves originally must be removed before the

investigation.

� Plants used in such investigations must first be put in the (3) _______________ for at least

(4) _______________ hours to remove all the starch. This process of removing starch is called

(5) _______________ (脫澱粉).

1 Chlorophyll

� We can carry out the investigation on plants with (6) _______________

leaves (斑葉). Chlorophyll is (7) _______________ (present / absent) in

the non-green parts of the leaves.

� The part of a leaf with chlorophyll is the (8) _______________

(experimental / control) set-up.

� The part of a leaf without chlorophyll is the (9) _______________

(experimental / control) set-up.

▲ Variegated leaf of

Coleus

2 Carbon dioxide

� We can use (10) _______________ _______________ (氫氧化鉀) to remove carbon dioxide

from the air inside the control set-up.

� The leaf exposed to normal air is the (11) _______________ (experimental / control) set-up.

� The leaf exposed to air without carbon dioxide is the (12) _______________ (experimental /

control) set-up.

3 Light

� We can use a piece of black paper or aluminium foil to mask part of a leaf.

� The unmasked part of the leaf is the (13) _______________ (experimental / control) set-up.

� The masked part of the leaf is the (14) _______________ (experimental / control) set-up.

� Go to

Practical 21.3 Investigation of the need for chlorophyll in photosynthesis


Practical 21.4 Investigation of the need for carbon dioxide in photosynthesis


Practical 21.5 Investigation of the need for light in photosynthesis



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21.4 The process of photosynthesis (Book 3, p. 21-16)

� Photosynthesis involves many reactions, each of which is controlled by a different enzyme.

The reactions occur in two main stages: (1) _______________ _______________ (光反學反應)

and (2) _______________ _______________ (碳固定).

A Photochemical reactions (Book 3, p. 21-16)

� Photochemical reactions occur in the (3) _______________ of chloroplasts. The reactions

require (4) _______________. Therefore, they are also called (5) _______________

_______________ (光反應).

1 Light absorption

� When the chlorophyll molecule in the thylakoid captures (6) _______________ energy, some

(7) _______________ of the chlorophyll molecule are raised to a higher energy level and are

emitted from the chlorophyll molecule. These excited electrons then pass through a series of

electron carriers of (8) _______________ (increasing / decreasing) energy levels in the

thylakoid membrane. (9) _______________ is released in a step-wise manner. The series of

electron carriers is called the (10) _______________ _______________ _______________

(電子傳遞鏈).

▲ Absorption of light energy by a chlorophyll molecule

initial energy level

higher energy level

� Light energy is

absorbed by chlorophyll.

� An electron becomes ‘excited’.

� The ‘excited electron’

releases energy

when it passes

through an electron transport chain.

energy

chlorophyll molecule in thylakoid membrane

thylakoid

chloroplast

electron transport chain

sun


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2 Synthesis of ATP

� Some of the energy released by the electrons in the electron transport chain is used to form

(11) _______________ (adenosine triphosphate 腺苷三磷酸) by combining a phosphate with

(12) _______________ (adenosine diphosphate 腺苷二磷酸). This process is called

(13) _______________ (光磷酸化).

� In this way, (14) _______________ energy captured by the chlorophyll molecule is converted

to (15) _______________ energy stored in ATP. The ATP will provide energy to drive the

reactions in carbon fixation.

3 Photolysis of water

� The light energy captured by chlorophyll molecules is also used to split (16) ______________

molecules to form (17) _______________ and (18) _______________. This process is called

(19) _______________ (光解) of water.

- Hydrogen is accepted by (20) _______________ (nicotinamide adenine dinucleotide

phosphate 菸酰胺腺嘌呤二核苷酸磷酸) to form (21) _______________. NADPH is the

(22) _______________ (oxidized / reduced) form of NADP. It will act as a

(23) _______________ agent by donating (24) _______________ in carbon fixation.

- Oxygen is a (25) _______________ in the reaction. It is released as a

(26) _______________ to the atmosphere.

Light energy captured by chlorophyll

Synthesis of ATP

Photolysis of water

to carbon fixation

stroma thylakoid

space thylakoid

membrane

▲ Photochemical reactions

(photophosphorylation) sun

oxygen released to atmosphere


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B Carbon fixation: Calvin cycle (Book 3, p. 21-19)

� ATP and NADPH formed in the photochemical reactions are used to fix (27) ______________

into organic compounds. This stage is called (28) _______________ _______________. It

occurs in the (29) _______________ of chloroplasts.

� This stage is also called (30) ____________ _______________ (暗反應) because it does not

require (31) _______________.

� This stage is also known as the (32) _______________ _______________ (卡爾文循環). It

involves a cyclic series of reactions and occurs in three main steps.

1 Carbon dioxide fixation and formation of a 3-C compound

� Under the action of enzymes, a molecule of (33) _______________ _______________

combines with a molecule of a 5-C compound to form (34) _______________ molecules of a

3-C compound. The 5-C compound acts as a carbon dioxide (35) _______________ to ‘fix’

carbon dioxide into an organic compound which starts the reactions in the cycle.

2 Reduction of the 3-C compound and formation of glucose

� Using energy from (36) _______________ and hydrogen from (37) _______________

produced in photochemical reactions, the 3-C compound is (38) ______________ (oxidized /

reduced) to another 3-C compound called (39) ______________ _______________ (丙糖磷酸).

ADP and NADP are formed in the process. They will be reused in (40) _______________

reactions.

� Triose phosphate is a sugar. It is the primary product of the Calvin cycle. Two molecules of

triose phosphate combine to form one molecule of (41) _______________ (6-C).


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3 Regeneration of carbon dioxide acceptor

� Most triose phosphate molecules are used to (42) _______________ the original 5-C carbon

dioxide acceptor, so that the cycle can repeat itself to form more glucose. The regeneration of

carbon dioxide acceptor requires (43) _______________ from ATP.

Carbon dioxide fixation

Reduction of 3-C compound

Regeneration of carbon dioxide acceptor

3-C compound 5-C compound

triose phosphate (3-C)

glucose (6-C)

from photochemical reactions

from photochemical reactions

▲ The Calvin cycle

Calvin cycle


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C Overall process of photosynthesis (Book 3, p. 21-22)

� Photochemical reactions and the Calvin cycle are linked by (44) _______________ and

(45) _______________.

� The equation of the overall process of photosynthesis:

It shows that (46) _______________ molecules of carbon dioxide and (47) _______________

molecules of water are required to form one molecule of (48) _______________.

� The hydrogen and oxygen atoms in water molecules are found in the (49) _______________

and (50) _______________ _______________ produced respectively.

6 CO2 + 6 H2O

carbon dioxide water

C6H12O6 + 6 O2

glucose oxygen

light captured

by chlorophyll

ATP

NADPH

NADP

ADP + P

light

Photochemical reactions

thylakoid (with chlorophyll)

Calvin cycle

chloroplast

glucose

▲ Summary of the process of photosynthesis

stroma

sun


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21.5 Factors affecting the rate of photosynthesis (Book 3, p. 21-24)

A Effect of light intensity (Book 3, p. 21-24)

� Initially, the rate of photosynthesis

(1) _______________ proportionately with light

intensity as more (2) _______________ is

supplied to the photochemical reactions.

� As the light intensity increases, the rate levels off

when the light intensity reaches a

(3) _______________ ______________ (飽和點).

The rate is now (4) _______________ by other

factors. The light intensity at the saturation point

is called (5) _______________ light intensity.

B Effect of carbon dioxide concentration (Book 3, p. 21-25)

� Initially, the rate of photosynthesis (6) _______________

proportionately with carbon dioxide concentration

because more (7) _______________ are supplied to the

Calvin cycle.

� As the carbon dioxide concentration further increases, the

rate (8) _______________ _______________ because the

rate becomes limited by other factors.

� Go to

Practical 21.6 Investigation of the effect of light intensity on the rate of photosynthesis


Practical 21.7 Design an investigation of the effect of carbon dioxide concentration on the rate of

photosynthesis


rate limited by light intensity

rate limited by other factors

rate

of

pho

tosynth

esis

saturation point

optimum light intensity

light intensity

▲ Effect of light intensity on the rate of photosynthesis

CO2 concentration

rate

of

pho

tosynth

esis

▲ Effect of CO2 concentration on the rate of photosynthesis


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How can we know which factor is limiting?

� Without light, no photosynthesis takes place.

� At low light intensities, the rate (9) _______________ (increases / decreases) with increasing

light intensity. (10) _______________ _______________ is the limiting factor.

� At high light intensities, the rate in curve A (11) _______________ _______________. The

rate is limited by a factor other than light intensity.

� The rate (12) _______________ (increases / decreases) with higher CO2 concentration. This

shows that (13) _______________ _______________ _______________ is the limiting

factor when curve A levels off.

� The rate in curve B levels off again. It is limited by a factor other than

(14) _______________ _______________ _______________.

C Regulating the rate of photosynthesis (Book 3, p. 21-28)

� Farmers can build (15) _______________ (溫室) to monitor

environmental factors such as temperature, light intensity

and carbon dioxide concentration, so as to regulate the rate

of photosynthesis of their crops.

� In this way, the productivity (生產力) and the quality of the

crops can be (16) _______________.

▲ A greenhouse

rate

of

pho

tosynth

esis

light intensity

low CO2 concentration (curve A)

high CO2 concentration (curve B)


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21.6 The fate of photosynthetic products (Book 3, p. 21-31)

� (1) _______________ _______________ is the primary product of photosynthesis. This

molecule and other intermediates of photosynthesis are synthesized into biomolecules essential

for plant growth.

1 Carbohydrates

� Triose phosphate is quickly synthesized into (2) _______________. Some of the glucose is

used up in photosynthesizing cells as an (3) _______________ source.

� Most of the glucose formed is quickly built into (4) ______________ and is stored in cells. It

is a suitable form for storage because it is (5) _______________. It can be stored in leaves

without affecting the (6) _______________ _______________ of the cells.

� Starch can be broken down to form (7) _______________, which is transported by the

(8) _______________ to other parts of the plant. Sucrose is a suitable form for transport

because it is soluble but relatively (9) _______________.

� Some glucose molecules are built into (10) _______________, which is a major component of

(11) _______________ _______________.

2 Lipids

� The intermediates of photosynthesis can also be used to synthesize (12) _______________

and (13) ______________ ______________. Glycerol and fatty acids then combine to form

lipids.

� Lipids are used to form (14) _______________ _______________. They are also stored as

energy reserve in some plants.

3 Proteins

� The intermediates of photosynthesis can also combine with (15) _______________ to form

(16) _______________ _______________, which are the building blocks of proteins.

� Proteins are important for (17) _______________ and repair, and for the synthesis of

enzymes. They are also the components of (18) _______________ _______________.


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21.7 The significance of photosynthesis (Book 3, p. 21-33)

1 Providing the basic food source in ecosystems

� Most organisms depend on plants for food. Plants are (1) _______________ in ecosystems.

They serve as the basic food source for other organisms.

2 Maintaining energy flow in ecosystems

� During photosynthesis, light energy from the (2) _______________ is captured by plants. The

light energy is converted to (3) _______________ energy that is stored in plant bodies. The

chemical energy is transferred along (4) _______________ _______________ and is

eventually lost as (5) _______________ to the surroundings.

3 Maintaining oxygen and carbon dioxide balance

� (6) _______________ of organisms consumes oxygen and releases carbon dioxide. The

oxygen consumed is replaced by the oxygen released by plants during (7) _______________.

Therefore, photosynthesis is important in maintaining the oxygen balance in the atmosphere.

� Plants take in carbon dioxide from the environment for (8) _______________. This balances

the increase in carbon dioxide concentration in the atmosphere due to (9) _______________.

photosynthesis

respiration

carbon dioxide in atmosphere

oxygen in atmosphere

taken up by plants during

releases

releases consumed

during

▲ Balance of oxygen and carbon dioxide in the atmosphere

light energy from sun

producers (e.g. plants)

decomposers

heat heat

heat

consumers

▲ Energy flow in an ecosystem


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Answers

Ch 21 Photosynthesis

21.1 1 photosynthesis 2 organic 3 inorganic 4 water 5 light

6 chlorophyll 7 chloroplasts 8 chemical 9 Oxygen 10 anabolic

11 Proteins / Lipids 12 lipids / proteins 13 minerals

21.2 1 leaves 2 surface area 3 chloroplasts 4 upper 5 air spaces

6 diffuse 7 cuticle 8 water 9 stomata 10 guard cells

11 xylem / phloem 12 phloem / xylem 13 double 14 stroma 15 enzymes

16 starch 17 thylakoids 18 grana 19 Chlorophyll 20 surface area

21 interconnected 22 transport

21.3 1 iodine 2 glowing 3 dark 4 24 5 destarching

6 variegated 7 absent 8 experimental 9 control 10 Potassium hydroxide

11 experimental 12 control 13 experimental 14 control

21.4 1 photochemical reactions 2 carbon fixation 3 thylakoids 4 light

5 light reactions 6 light 7 electrons 8 decreasing 9 Energy

10 electron transport chain 11 ATP 12 ADP

13 photophosphorylation 14 light 15 chemical 16 water

17 hydrogen / oxygen 18 oxygen / hydrogen 19 photolysis 20 NADP 21 NADPH

22 reduced 23 reducing 24 hydrogen 25 by-product 26 gas

27 carbon 28 carbon fixation 29 stroma 30 dark reactions 31 light

32 Calvin cycle 33 carbon dioxide 34 two 35 acceptor 36 ATP

37 NADPH 38 reduced 39 triose phosphate 40 photochemical 41 glucose

42 regenerate 43 energy 44 ATP / NADPH 45 NADPH / ATP 46 six

47 six 48 glucose 49 glucose 50 oxygen gas


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21.5 1 increases 2 energy 3 saturation point 4 limited 5 optimum

6 increases 7 substrates 8 levels off 9 increases 10 Light intensity

11 levels off 12 increases 13 carbon dioxide concentration

14 carbon dioxide concentration 15 greenhouses 16 improved

21.6 1 Triose phosphate 2 glucose 3 energy 4 starch 5 insoluble

6 water potential 7 sucrose 8 phloem 9 inactive 10 cellulose

11 cell walls 12 glycerol 13 fatty acids 14 cell membranes 15 minerals

16 amino acids 17 growth 18 cell membranes

21.7 1 producers 2 sun 3 chemical 4 food chains 5 heat

6 Respiration 7 photosynthesis 8 photosynthesis 9 respiration

Documents

Class: Name: Date: 21 Photosynthesis - Shared …bio662.dyndns.info/DSE/WS/ws_ch21_e.pdfClass: Name: ( ) Date: New Senior Secondary Mastering Biology Oxford University Press 2014 (Second