Photosynthesis

HideShow resource information
What is the definition of photosynthesis?
The process whereby light energy from the sun is transformed into chemical energy and used to synthesise large organic molecules from inorganic substances.
1 of 55
What is an autotroph?
An organism that can synthesise complex organic molecules from inorganic molecules and an energy source. So, they make their own food.
2 of 55
What is a heterotroph?
An organism that ingests and digests complex organic molecules and released chemical potential energy that is stored in them.
3 of 55
Where does photosynthesis take place?
In chloroplasts.
4 of 55
Is the inner or outer membrane of a chloroplast more permeable to small ions?
The outer membrane.
5 of 55
What is the structure of the inner membrane of a chloroplast?
It is folded into lamellae which are stacked in grana. It contains transport proteins which are embedded in it.
6 of 55
What is between the grana?
Intergranal lamellae.
7 of 55
Where do the light-independent stage's reactions occur?
In the fluid-filled matrix: the stroma.
8 of 55
What is in the stroma?
Enzymes for the light-independent stage, starch grains, oil droplets, DNA and prokaryote-type ribosomes.
9 of 55
Where does the light-dependent stage take place?
In the grana on the thylakoid membranes.
10 of 55
What are the grana?
Stacks of flattened membrane compartments, the thylakoids.
11 of 55
What are photosynthetic pigments?
Substances that absorb certain wavelengths of light and reflect others so that they appear to us as the colour of the wavelength they are reflecting.
12 of 55
What is a photosystem?
A group of photosynthetic pigments in the thylakoid membrane held in place by proteins. Consists of a primary reaction centre and accessory pigments.
13 of 55
Where is P680 found and what is its peak wavelength absorption?
Found in photosystem II and peak is 680nm (red light).
14 of 55
Where is P700 found and what is its peak wavelength absorption?
Found in photosystem I and peak is 700nm (red light).
15 of 55
What are the 2 forms of chlorophyll a?
P680 and P700.
16 of 55
What light does chlorophyll a absorb and what colour does it appear?
Blue light of wavelength around 450nm. Appears yellow-green.
17 of 55
What light does chlorophyll b absorb and what colour does it appear?
Light of wavelengths around 500nm and 640nm. Appears blue-green.
18 of 55
What light do accessory pigments, carotenoids, reflect and absorb?
Reflect yellow and orange. Absorb blue.
19 of 55
What to accessory pigments do?
Absorb light that are not well absorbed by chlorophylls and pass the energy to chlorophyll a at the base of the photosystem.
20 of 55
Where do photosystems I and II occur?
I mainly on intergranal lamellae. II mainly on granal lamellae.
21 of 55
What is photolysis?
The splitting of water into H+ ions, electrons and oxygen in the presence of light, catalysed by an enzyme in PSII.
22 of 55
What is water used for in photosynthesis?
Electrons from it are used to replace those lost by oxidised chlorophyll. H+ ions are used in chemiosmosis to produce ATP and to be accepted by NADP in the light-independent stage.
23 of 55
What is photophosphorylation?
The making of ATP from ADP and Pi in the presence of light.
24 of 55
Where are protons pumped across and where do they accumulate during the light-dependent stage?
Pumped across the thylakoid membrane. Accumulate in the thylakoid space.
25 of 55
What is chemiosmosis?
The flow of H+ ions through ATP synthase enzymes to produce a force that allows ATP production.
26 of 55
Where does chemiosmosis occur in the light-dependent stage?
Across the thylakoid membranes.
27 of 55
What photosystem does cyclic photophosphorylation use?
PSI.
28 of 55
What photosystem does non-cyclic photophosphorylation use?
Both PSI and PSII.
29 of 55
What is the other name for the light-independent stage?
The Calvin Cycle.
30 of 55
Why is carbon dioxide used in the light-independent stage?
It is the source of carbon for the production of large molecules.
31 of 55
Where does carbon dioxide enter the plant?
It diffuses through open stomata in the leaves. Then diffuses through air spaces in spongy mesophyll. Then diffuses through thin cellulose walls in the palisade mesophyll layer, cell surface membrane, cytoplasm and chloroplast envelope into stroma.
32 of 55
What 5-carbon compound does carbon dioxide combine with in the stroma?
Ribulose bisphosphate (RuBP) which is a carbon dioxide acceptor.
33 of 55
What enzyme catalyses the combination of carbon dioxide and RuBP?
Rubisco (ribulose bisphosphate carboxylase-oxygenase).
34 of 55
What is produced when carbon dioxide is combined with RuBP?
Glycerate 3-phosphate (GP) (3C).
35 of 55
What is GP reduced and phosphorylated into?
Triose phosphate (TP) (3C).
36 of 55
What are used when GP is reduced and phosphorylated into TP?
ATP and reduced NADP from the light-dependent reaction.
37 of 55
How many molecules of TP are recycled by phosphorylation and into what are the recycled?
5 out of 6 are changed to 3 molecules of RuBP (5C).
38 of 55
What can GP be used for?
To make amino acids or fatty acids.
39 of 55
What can pairs of TP molecules combine to form?
Hexose sugars (6C).
40 of 55
What can TP be converted into?
Glycerol.
41 of 55
What can glucose been isomerised into?
Fructose (6C).
42 of 55
What is formed when glucose and fructose are combined?
Sucrose, which is a disaccharide.
43 of 55
What is formed when hexose sugars are polymerised?
Polysaccharides.
44 of 55
What is a limiting factor?
The factor that is present at the lowest or least favourable value for a metabolic process.
45 of 55
What are the 3 main effects light has?
Causes stomata to open so carbon dioxide can enter. It is trapped by chlorophyll and excites elections. It splits water molecules to produce protons in photolysis.
46 of 55
Above what temperature does rate of photosynthesis level off and then fall?
25 degrees Celsius.
47 of 55
Why does the rate of photosynthesis fall at high temperatures?
Enzymes involved in the Calvin cycle are denatured (such as rubisco as it cannot accept carbon dioxide). Also causes water loss from stomata so they close and limits carbon dioxide availability.
48 of 55
What are there high/low levels of when there is bright light?
High: RuBP and TP / Low: GP as it is reduced to TP.
49 of 55
What are there high/low levels of when there is dim light?
High: GP as it cannot be reduced to TP / Low: RuBP and TP.
50 of 55
What are there high/low levels of when there is a high carbon dioxide concentration?
High: GP and TP / Low: RuBP as it is carboxylated to GP.
51 of 55
What are there high/low levels of when there is a low carbon dioxide concentration?
High: RuBP as there is little carbon dioxide to combine with it / Low: GP and TP.
52 of 55
What happens if water loss by transpiration exceeds water uptake?
The stomata close in a stress response due to a release of abscisic acid.
53 of 55
Why does an increase in temperature have little effect on the light-dependent reaction?
Because only photolysis in this stage is dependent upon enzymes.
54 of 55
What happens in the light-independent stage if temperature rises about 25 degrees?
Oxygenase activity of rubisco increases more than its carboxylase activity, so ATP and reduced NADP from the light-dependent reaction are wasted.
55 of 55

Other cards in this set

Card 2

Front

What is an autotroph?

Back

An organism that can synthesise complex organic molecules from inorganic molecules and an energy source. So, they make their own food.

Card 3

Front

What is a heterotroph?

Back

Preview of the front of card 3

Card 4

Front

Where does photosynthesis take place?

Back

Preview of the front of card 4

Card 5

Front

Is the inner or outer membrane of a chloroplast more permeable to small ions?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Photosynthesis resources »