Photosynthesis

Question 1

Prior Knowledge…..
During photosynthesis, light is absorbed by _____________and used to convert carbon dioxide and water to _________and __________.
The rate of photosynthesis may be limited by shortage of ______, ________ _________or low/high ________________.
Graphs can be interpreted showing how factors affect the rate of photosynthesis.
There are benefits to artificially manipulating the environment in which plants are grown but these must be evaluated.

Answer 1

During photosynthesis, light is absorbed by chlorophyll and used to convert carbon dioxide and water to glucose and oxygen.
The rate of photosynthesis may be limited by shortage of light, carbon dioxide or low/high temperature.
Graphs can be interpreted showing how factors affect the rate of photosynthesis.
There are benefits to artificially manipulating the environment in which plants are grown but these must be evaluated.

Question 2

Energy is needed for…plants vs animals

Answer 2

plants
For photosynthesis
Active transport – energy to change the shape of carrier proteins
Activation of molecules
Cell division
Metabolic processes eg: polypeptide synthesis & DNA replication

animals
Muscle contraction
Maintenance of body temperature (mammals and birds)
Active transport – energy to change the shape of carrier proteins
Activation of molecules eg: Glucose -> Glucose P
Cell division
Metabolic processes eg: polypeptide synthesis & DNA replication

Question 3

How is the palisade cell adapted to its function? Complete the sentences

Many chloroplasts so ….

Chloroplasts are able to move within the cytoplasm so …

Palisade cells are long and narrow so ….

Many leucoplasts to store starch – the insoluble polymer produced in photosynthesis

Many mitochondria and RER to …. such as…

Large permanent vacuole to …

Answer 3

Many chloroplasts so they can absorb as much light as possible for photosynthesis

Chloroplasts are able to move within the cytoplasm so they can absorb as much light as possible for photosynthesis

Palisade cells are long and narrow so many cells can be packed into the surface layers of the leaf

Many leucoplasts to store starch – the insoluble polymer produced in photosynthesis

Many mitochondria and RER to provide energy for the synthesis of the proteins such as enzymes and carrier proteins required in photosynthesis

Large permanent vacuole to store cell sap – a sugary solution that maintains cell turgor and help support the plant cells holding them upright to absorb as much light as possible

Question 4

How are chloroplasts adapted to their function?
Contain ________ pigments - these absorb _______ ________ for photosynthesis.
T__________ m___________ give a large surface area for the attachment of pigments.
The pigments are attached to proteins. The protein and pigment is a ______________
Photosystem 1 (PS1) absorbs light best at 700nm
Photosystem 11 (PS11) absorbs light best at 680nm
G_______membranes have _________on them for ATP synthesis
Stroma contains ______droplets , _______and organic _____as well as DNA and ribosomes

Answer 4

Contain photosynthetic pigments - these absorb light energy for photosynthesis.
Thylakoid membranes give a large surface area for the attachment of pigments.
The pigments are attached to proteins. The protein and pigment is a photosystem
Photosystem 1 (PS1) absorbs light best at 700nm
Photosystem 11 (PS11) absorbs light best at 680nm
Granal membranes have enzymes on them for ATP synthesis
Stroma contains lipid droplets , sugars and organic acids as well as DNA and ribosomes

Question 5

ATP is useful in many biological processes. Explain why.
(4 marks)

Answer 5

1.Releases energy in small / manageable amounts;
1. Accept less than glucose
2.(Broken down) in a one step / single bond broken immediate energy compound / makes energy available rapidly;
2. Accept easily broken down
3.Phosphorylates / adds phosphate makes (phosphorylated substances) more reactive / lowers activation energy;
3. Do not accept phosphorus or P on its own
4.Reformed / made again;
4. Must relate to regeneration

Question 6

ai). Name the factors that limited the rate of photosynthesis between X and Y. (1 mark)
aii). Use information from the graph to explain your answer. (2 marks)
b). Use information from the graph to find the gross rate of photosynthesis at 20°C and medium light intensity (1 mark)
c. Creeping azalea is a plant which grows on mountains. Scientists predict that in the area where this plant grows the mean summer temperature is likely to rise from 20 °C to 23 °C. It is also likely to become much cloudier. Describe and explain how these changes are likely to affect the growth of creeping azalea. (3 marks)

Answer 6

Question 7

Photosynthetic pigments – this links with RP7 Chromatography
__________and other pigments absorb light of a __________wavelength.
You can plot a graph of the ____________of light against absorption and produce an absorption spectrum for the different pigments.
The action spectrum of the pigments shows how effectively wavelengths of light are used in photosynthesis – by measuring the _________given off.

Answer 7

Chlorophyll and other pigments absorb light of a specific wavelength.
You can plot a graph of the wavelength of light against absorption and produce an absorption spectrum for the different pigments.
The action spectrum of the pigments shows how effectively wavelengths of light are used in photosynthesis – by measuring the oxygen given off.

Question 8

What are the stages of photosynthesis?

Answer 8

1. Light dependent reaction
2. Calvin cycle ( light independent reaction)

Capturing the light energy- involves chlorophyll in photosystems
The Light- Dependent Reaction- produces reduced NADP, ATP and oxygen
The Light Independent Reaction- Reduces CO2 to produce sugars etc

Question 9

The Light Dependent Reaction
The _______ _________ is ____________by the ______________. Electrons become __________and are __________from the chlorophyll- photoionisation.
The energy from this is used to
- make ___from ____and __(=Photophosphorylation)
- Make reduced ______from ______
- _____________ of water into protons (H+ ions), electrons and oxygen

Answer 9

The light energy is absorbed by the chlorophyll. Electrons become excited and are released from the chlorophyll- photoionisation.
The energy from this is used to make ATP from ADP and Pi (=Photophosphorylation)
Make reduced NADP from NADP
Photolysis of water into protons (H+ ions), electrons and oxygen

Question 10

Co-enzymes eg NADP
A molecule that aids the function of an _________
They work by transferring a _________ group from one molecule to another
______is a coenzyme used in photosynthesis
______transfers ______________from 1 molecule to another. It can _______(give hydrogen to) or _______(take hydrogen from) a molecule

Answer 10

A molecule that aids the function of an enzyme
They work by transferring a chemical group from one molecule to another
NADP is a coenzyme used in photosynthesis
NADP transfers hydrogen from 1 molecule to another. It can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule.

Question 11

Photophosphorylation – making ATP using light energy
Non-Cyclic VS Cyclic

Non-Cyclic
- Produces ___, _________ ______and ________
- Photosystems in the ___________ membranes are linked by ________carriers
- The photosystem and electron carriers are called the __________ __________ _______
- The _________electrons pass along the _____of carriers

Cyclic
- Produces ____
- Only uses ____
- Electrons from ___________are not passed onto _____
- They are passed back to PS1 via electron __________
- Only produces a _______amount of ATP

Answer 11

Non-Cyclic
Produces ATP, reduced NADP and oxygen
Photosystems in the thylakoid membranes are linked by electron carriers
The photosystem and electron carriers are called the electron transport chain
The excited electrons pass along the chain of carriers

Cyclic
Produces ATP
Only uses PS1
Electrons from chlorophyll are not passed onto NADP
They are passed back to PS1 via electron carriers
Only produces a small amount of ATP

Question 12

Non cyclic photophosphorylation
Light energy is ____________by chlorophyll in _____
The light energy ______ ______in the chlorophyll
The electrons move to a __________energy level- they have more _______. They are ___________from the chlorophyll – this is called _____________________.
__________electrons move down the _________ _____________ ________to PS1

Answer 12

Light energy is absorbed by chlorophyll in PS11
The light energy excites electrons in the chlorophyll
The electrons move to a higher energy level- they have more energy. They are released from the chlorophyll – this is called photoionisation.
Excited electrons move down the electron transport chain to PS1

Question 13

Photolysis

Answer 13

The excited electrons that have left the chlorophyll have to be replaced. Light energy splits water into protons, electrons and oxygen

Question 14

As the electrons move down the electron transport chain the energy they lose is used to transport protons into the thylakoid. This means …
the ____________has a higher concentration of __________than the stroma. There is a ________gradient across the membrane (A store of energy). Protons move ______the gradient via a _________pump - ATP ___________back into the stroma. This energy is used to make ATP.

Answer 14

This means the thylakoid has a higher concentration of protons than the stroma. There is a proton gradient across the membrane (A store of energy). Protons move down the gradient via a proton pump - ATP synthase back into the stroma. This energy is used to make ATP.

Question 15

Energy from excited electrons generates reduced NADP
_______ energy is ___________by ___which ________the _____________to an even higher energy levels. These electrons are transferred to ______, along with a proton(H+) from the ______to form reduced NADP (NADPH)

Answer 15

Light energy is absorbed by PS1 which excites the electrons to an even higher energy levels. These electrons are transferred to NADP, along with a proton(H+) from the stroma to form reduced NADP (NADPH)

Question 16

Chemiosmosis
Movement of ___________ down the __________transfer chain is coupled to the transfer of __________into the thylakoid to build a proton gradient.
Movement of protons across a membrane generates ___.

Answer 16

Movement of electrons down the Electron transfer chain is coupled to the transfer of protons into the thylakoid to build a proton gradient.
Movement of protons across a membrane generates ATP. This process also happens in respiration

Question 17

Light energy excites the electrons in PS11 moving them…

Answer 17

to a higher energy level

Question 18

The excited electrons lose energy as they pass….

Answer 18

down the electron transport chain

Question 19

Cyclic photophosphorylation- produces ATP-uses only PS1
The electrons aren’t passed on to _____. They are passed back to ____via __________ ________. This means the ___________are recycled. Only small amounts of ___are generated. No ___________ _____or _________ are made

Answer 19

The electrons aren’t passed on to NADP. They are passed back to PS1 via electron carriers. This means the electrons are recycled. Only small amounts of ATP are generated. No reduced NADP or oxygen are made

Question 20

a) in which part of a chloroplast do the light dependent reactions occur

b) Name the substances A B and C
c) role of chlorophyll in photolysis?
d)how the energy of light is converted into chemical energyy in the light dependent reactions

Answer 20

Answer

Question 21

1a) What are photosynthetic pigments?
1b) Give one example of a photosynthetic pigment.
2) NADP is a coenzyme used in photosynthesis. What chemical group does it transfer between molecules?
3) Where in the chloroplast does the light-dependent reaction take place?
4) Describe what happens during the photoionization of chlorophyll.
5) What products of the light-dependent reaction are needed for the light independent reaction?
6) What is photophosphorylation?
7)What is the electron transport chain?
8) Name the products of the photolysis of water
9) Excited electrons lose energy as they move down the electron transfer chain. Explain how this leads to ATP synthesis.
10) Name the products of:
a) non-cyclic photophosphorylation
b) Cyclic phosphorylation

Answer 21

AO1-Fact Recall
1a) What are photosynthetic pigments? Coloured substances that absorb light energy for photosynthesis (1)
1b) Give one example of a photosynthetic pigment. Chlorophyll a, chlorophyll b, carotene (1)
2) NADP is a coenzyme used in photosynthesis. What chemical group does it transfer between molecules? Hydrogen (1)
3) Where in the chloroplast does the light-dependent reaction take place? Thylakoid membranes (1)
4) Describe what happens during the photoionisation of chlorophyll. Light energy excites the electrons in the chlorophyll molecule, giving them more energy, which eventually causes them to be released from the chlorophyll. The chlorophyll is left as a positively charged ion. (2)
5) What products of the light-dependent reaction are needed for the light independent reaction? ATP and reduced NADP (2)
6) What is photophosphorylation? The process of adding a phosphate group using light (1)
7)What is the electron transport chain? A chain of proteins down which the excited electrons flow (1)
8) Name the products of the photolysis of water. Protons, electrons and oxygen (3)
9) Excited electrons lose energy as they move down the electron transfer chain. Explain how this leads to ATP synthesis. The energy is used to transport protons into the thylakoid so that the thylakoid has a higher concentration than the stroma. This forms a proton gradient across the membrane. Protons move down their concentration gradient, into the stroma, via an enzyme called ATP synthase. The energy from this movement combines ADP and Pi to form ATP. (4)
10) Name the products of:
a) non-cyclic photophosphorylation ATP, reduced NADP and oxygen (3)
b) Cyclic phosphorylation ATP (1) Total 21 marks

Question 22

Plants produce ATP in their chloroplasts during photosynthesis. They also produce ATP during respiration. Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis (5 marks)

Answer 22

1.In the dark no ATP production in photosynthesis;
1. In context of in photosynthetic tissue / leaves
2.Some tissues unable to photosynthesise / produce ATP;
3.ATP cannot be moved from cell to cell / stored;
4.Plant uses more ATP than produced in photosynthesis;
5.ATP for active transport / synthesis (of named substance);

Question 23

Calvin Cycle diagrams

Answer 23

Question 24

REMEMBER

Answer 24

The Calvin cycle needs to turn 6 times to make 1 molecule of hexose sugar.

Question 25

What the Calvin Cycle can produce?

Answer 25

Question 26

Carbohydrates, Lipids and Proteins

______________- hexose sugars are made from 2 triose phosphate molecules. Larger molecules can be made by joining _______ sugars e.g. sucrose, cellulose, starch
______- These are made from ________ which is synthesised from TP and fatty acids, which are synthesised from GP
________ Acids- Some are made from glycerate 3 Phosphate (GP)

Answer 26

Triose phosphate (TP) and glycerate 3 phosphate (GP) are used to make carbohydrates, lipids and amino acids

Carbohydrates- hexose sugars are made from 2 triose phosphate molecules. Larger molecules can be made by joining hexose sugars e.g. sucrose, cellulose, starch

Lipids- These are made from glycerol which is synthesised from TP and fatty acids, which are synthesised from GP

Amino Acids- Some are made from glycerate 3 Phosphate (GP)

Question 27

Why is the Calvin cycle called carbon fixation?

Answer 27

Because C in the form of CO2 is removed from the air and joined to a 5C sugar – ribulose bisphosphate.

Question 28

How is a cycle defined?

Answer 28

The products of one reaction become the substrate for the next reaction

Question 29

Calvin cycle exam answer

Answer 29

) 1 5C / RuBP combines with CO2;
2 to form 3C compound / TP / GP;
3 using ATP;
4 and reduced NADP;
5 2 molecules of 3C compound / TP / GP form hexose;
6 all RuBP is regenerated;
7 10 molecules of 3C / TP / GP form 6 molecules of 5C / RuBP;

Question 30

Exam Tips

Answer 30

If you are asked to work out how many turns of the Calvin cycle are needed to produce a certain number of hexose sugars you need to remember that 5 of every 6 TP molecules are used to regenerate RuBP

Useful organic compounds have more than 1 carbon so the cycle needs to turn more than once

Six turns of the Calvin Cycle produce 12 GP molecules because 1 turn produces 2 GP, so 6 x 2 =12 GP

It is important that RuBP is regenerated. If it wasn’t then Glycerate 3 phosphate wouldn’t be formed. The Calvin cycle would stop and photosynthesis would be unable to continue

A diagram of the Calvin cycle in the examination might not look exactly the same…..so you need to learn the key points