Photosynthesis
Set of A2 Biology revision flash cards. Specifically for the Edexcel exam board. Only the first topic of Unit 5. 5.1 = Photosynthesis. Hope you find these helpful.
4.5 / 5 based on 3 ratings
- Created by: sadia123
- Created on: 30-09-12 21:45
What are AUTOTROPHIC organisms and what do they do?
They are organisms that make organic compounds from carbon dioxide by PHOTOSYNTHESIS. They trap energy from the sun and transfer it into chemical energy in the bonds of organic molecules. These are used as energy sources.
1 of 43
What are HETROTROPHIC organisms and what do they do?
They are organisms that eat plants or other animals that have eaten plants. They use the products of photosynthesis indirectly.
2 of 43
What is ATP (adenine triophosphate) made of?
A nucleotide with a ribose sugar and three phosphate groups attached. Chemical energy is stored in the phosphate bonds.
3 of 43
What happens to ATP when energy is needed?
The third phosphate bond is broken by hydrolysis. The reaction is catalysed by the enzyme ATPase. This results in ADP (adenine diphosphate) + a free inorganic phosphate group (Pi)
4 of 43
How much energy is released when ATP is broken down and where does this go?
34kj of energy is released per mole of ATP hydrolysed. Some of the energy is lost as heat or wasted but most of it is used for energy requiring biological activity in the cell.
5 of 43
How is ATP re-made?
The breakdown of ATP into ADP is reversible. It can be synthesised from ADP + inorganic phosphate group + 34kj of energy and the action of ATPase.
6 of 43
What drives the synthesis of ATP?
Energy from catabolic or redox reactions. Therefore ATP provides and immediate supply of energy.
7 of 43
Describe one way in which ATP is formed from ATP and an inorganic phosphate group
By using energy released from catabolic reactions. For example, respiration.
8 of 43
Describe the main way ATP is synthesised
When 2 hydrogen atoms are removed from a compound, they are picked up by a hydrogen carrier/acceptor. This becomes reduced. The electrons from the hydrogen atoms are passed along the electron transport chain.
9 of 43
Describe the main way ATP is synthesised... CONTINUED
components of the electron transport chain are reduced when they recieve the electrons and oxidised when they pass them on. These redox reactions release small amounts of energy used to drive the synthesis of ATP.
10 of 43
Define PHOTOSYNTHESIS
It is the process by which plants trap energy from the sun using chlorophyll and use it to convert carbon dioxide and water into glucose and oxygen.
11 of 43
Give the chemical and word equations of photosynthesis
Chemical = 6CO2 + 6H2O ----> C6H12O6 + 6O2. Word = Carbon dioxide + Water ----> Glucose + Oxygen
12 of 43
What is the energy from the light used for?
To break the strong O-H bonds in water. The hydrogen released combines with CO2 to form a fuel = glucose. The oxygen is released into the atmosphere as a waste product.
13 of 43
What are CHLOROPLASTS?
Large organelles found in the green areas of plants. An average plant contains 10-50 chloroplasts.
14 of 43
Describe the structure of CHLOROPLASTS
The membranes are arranged in stacks = grana. A granum is made up of membrane discs = thylakoids, this is where the chlorophyll is found. The membrane stacks are surrounded by a matrix = stroma, this contains all the enzymes needed for photosynthesis
15 of 43
What gives the colour of CHLOROPHYLL?
Chlorophyll is made up of five closely related pigments. Each pigment absorbs light from a different area of the spectrum so lots of energy from the sun can be absored and is used.
16 of 43
Name the pigments in Chlorophyll
It is made up of 5 pigments; Chlorophyll a = blue green, Chlorophyll b = yellow green, The Carotenoids = orange yellow + grey pigment.
17 of 43
Why are plant leaves green?
The most abundant pigment is Chlorophyll a (blue-green) and it is found in all photosynthesising plants. Hence, the green colour. The other pigments are found in varying proportions, this gives the variation of the green colour in plants.
18 of 43
How many Chlorophyll complexes are there and what are they called?
There are 2 complexes, PHOTOSYSTEM 1 and PHOTOSYSTEM 2
19 of 43
What are these Chlorophyll complexes?
They are systems which contain different variations of chlorophyll pigments. They absorb light from different areas of the spectrum. They have different roles in photosynthesis.
20 of 43
What have the complexes been identified as?
They have been identified as different sized particles attached to membranes in the chloroplasts.
21 of 43
Which areas of the Chloroplasts do the photosystems exist?
PSI are mainly the intergranal lamalle. PSII are mainly on the grana themselves.
22 of 43
How many stages is process of photosynthesis and what are the stages called?
There are two stages. Light independent stage and the light dependent stage.
23 of 43
When do the stages of photosynthesis occur?
LI takes place during the day and night, LD takes place during the day only.
24 of 43
Where does light dependent photosynthesis occur and what are its functions?
LDP takes place on the thylakoid membranes of the chloroplast. It has two main functions = to prodcue ATP and to split water molecules.
25 of 43
What is a PHOTON?
Smallest unit of light energy which comes from electromagnetic radiation.
26 of 43
What happens when a photon hits a Chlorophyll molecule?
The light energy is transferred to the electrons of the Chlorophyll. The electrons become excited and are raised to higher energy levels.
27 of 43
What happens when a photon hits a Chlorophyll molecule?... CONTINUED
If the electron is raised to a sufficiently high energy level, it leaves the chlorophyll molecule. The excited electron is picked up by an electron carrier/acceptor and used to synthesise ATP.
28 of 43
What are the two processes involved in the synthesis of ATP called?
NON-CYCLIC PHOTOPHOSPHORYLATION and CYLIC PHOTOPHOSPHORYLATION
29 of 43
Describe Cyclic Photophosphorylation
Involves only PSI. When light hits a chlorophyll molecule in PSI, the light excited electron leaves the molecule = picked up by an electron acceptor and passes through electron transport chain to produce ATP. Electron returns to PSI.
30 of 43
What is the ELECTRON TRANSPORT CHAIN?
A model that is used to describe the sequences of reactions by which ATP is made. It is a series of downward steps = each step is a different carrier molecule + represents an energy level. Electrons lose energy as they move down the ETC.
31 of 43
What is the energy lost from electrons in the ETC used for?
To drive the synthesis of ATP from ADP and an inorganic phosphate group.
32 of 43
Where do hydrogen ions in the Chloroplasts come from?
Water always dissociates spontaneously into hydrogen ions (H+) and hydroxide ions (OH-). So there are plenty in the cell.
33 of 43
Describe Cyclic Photophosphorylation
Involves both PSI + PSII. In light conditions photons are constantly hitting chlorophyll molecules in PSI and PSII = exciting electrons, An excited electron from PSI is picked up by NADP = electron acceptor, it also picks up a hydrogen ion = reduced
34 of 43
Describe Cyclic Photophosphorylation... CONTINUED
The reduced NADP = used as reducing power in LI reaction to produce glucose. At the same time an excited electron from PSII is picked up by an electron acceptor and is passed down ETC until it reaches PSI = electron lost from PSI is replaced.
35 of 43
Describe Cyclic Photophosphorylation... CONTINUED
Now the chlorophyll molecule in PSII is unstable because it is short of an electron. Electron has to be replaced to return it into its original state. The electron comes from photolysis. Once it is replaced the cycle can begin again.
36 of 43
How does the electron come from PHOTOLYSIS?
Photolysis = splitting of water. In cells many hydrogen ions are picked up and the hydroxide ions are left behind. These OH ions react with each other = oxygen + water. 4 electrons are freed during this reaction to return molecules to original states
37 of 43
Give the PHOTOLYSIS reaction equation
4OH- - 4e- ----> O2 + 2H2O
38 of 43
What does LIGHT INDEPENDENT PHOTOSYNTHESIS do?
Uses NADP and ATP from the LD stage. It consists of a series of reactions = CALVIN CYCLE = in the stroma. This results in reduction of CO2 from air to produce glucose. Each stage is controlled by enzymes.
39 of 43
Describe the stages of The CALVIN CYCLE
1) CO2 from the air combines with a 5 carbon compound called ribulose biophosphate (RuBP). The rate-limiting enzyme RUBISCO is needed. 2) = 6 Carbon compound 3) 6C splits into 2 3-Carbon compounds = glycerate 3-phosphate (GP)
40 of 43
Describe the stages of The CALVIN CYCLE... CONTINUED
4) GP is reduced, because hydrogen from NADP is added = glyceraldehyde 3-phosphate (GALP) 5) GALP undergoes a series of reactions to replace starting compound RuBP, but some of it is synthesised into 6 carbon simple sugar = GLUCOSE.
41 of 43
When does the Calvin Cycle occur?
It takes place both day and night but only stops when products of LD photosynthesis run out = no ATP or reduced NADP
42 of 43
What is Glucose used for?
As a fuel for respiration. It is converted into: double sugars = for transport around plant (e.g-sucrose), polysaccherides = for energy storage (e.g-starch), cellulose = for structural support. + Needed as building block for amino + nucleic acids
43 of 43
Other cards in this set
Card 2
Front
What are HETROTROPHIC organisms and what do they do?
Back
They are organisms that eat plants or other animals that have eaten plants. They use the products of photosynthesis indirectly.
Card 3
Front
What is ATP (adenine triophosphate) made of?
Back
Card 4
Front
What happens to ATP when energy is needed?
Back
Card 5
Front
How much energy is released when ATP is broken down and where does this go?
Back
Related discussions on The Student Room
- I enjoy chem practicals more than bio practicals. Is a chem degree right for me? »
- Advanced Higher Biology Project Ideas »
- OCR BIOLOGY PAPER 3 Predictions? »
- A level bio 20marker »
- AQA A-Level Biology Paper 3 [21st June 2023] Exam Chat »
- GCSE Biology AQA paper 1 (May 14th) Predictions »
- Dee’s A*AA Journey »
- Calvin Cycle »
- What is DNA repair »
- My attempt at not sabotaging my future career! »
Similar Biology resources:
3.0 / 5 based on 1 rating
2.5 / 5 based on 3 ratings
2.0 / 5 based on 1 rating
3.0 / 5 based on 2 ratings
4.0 / 5 based on 1 rating
3.0 / 5 based on 4 ratings
0.0 / 5
0.0 / 5
0.0 / 5
Comments
Report
Report
Report