3.5 Energy Transfers in and between organisms Flashcards
What is the equation for photosynthesis?
6CO2 + 6H20 —-> C6H1206 + 6C02
What is photosynthesis?
Using light energy to make glucose
Occurs in plants and algae
What are adaptations of a plant for photosynthesis?
Leaf located near top of plant
Thin and wide = wider surface area, short diffusion pathway
Stomata for gas exchange
Air spaces - supports ease of gas-exchange
Palisade cells located near top of leaf
Large palisade cells are large = high S.A
Palisade contain many chloroplasts (site of photosynthesis)
Large Vacuole= pushes chloroplast to edge of cell closer
Structure of chloroplast?
Double membrane
Contains thylakoids
Granum
Thylakoids surrounded by stroma fluid
What is the light dependent reaction?
Stage of photosynthesis in which light energy is required to produce ATP and reduced NADP
Where does the light independent reaction take place?
The thylakoid membrane in the chloroplast
What are the products of the light independent reaction?
ATP, Reduced NADP and Oxygen (waste or respiration)
Describe photoionisation
- Chlorophyll (Photosystem) absorbs light energy which excited electrons to higher energy level
- Causes them to be released from the chlorophyll
Describe the production of ATP during the light dependent reaction
- Electrons travel down electron transfer chain from photosystem to photosystem, losing energy at each step
- Energy from this is used to transport/pump protons from stroma into the thylakoid
- This creates a proton gradient across the thylakoid membrane
- Proteins move by facilitated diffusion down the gradient into the stroma via ATP synthase embedded in thylakoid membrane
- Uses energy from this proton gradient to do photophosphorylation to make ATP: ADP + PI —> ATP
- Photolysis occurs and O2 given off as waste
- Electrons that are excited are transferred to NADP with a proton from photolysis to reduce NADP to form reduced NADP
What is photolysis?
The splitting of water using light energy
Describe the process of photolysis
Water splits to produce protons, electrons and oxygen
(2H20 —-> 02 + 4e- + 4H+)
Why does photolysis occur?
Electrons replace those lost from chlorophyll
How is reduced NADP formed?
In the second PS, the electrons are excited and transferred to NADP with a Proton from photolysis to reduce NADP and from reduced NADP
Describe the light independent stage?
- Involves the calvin cycle
- RuBP ( 5C) joins with CO2 to make 2X GP (3 Carbon)
- GP reduced to TP (3 Carbon)
Uses energy from ATP and hydrogen atom from reduced NADP - TP can be used to regenerate RuBP
- TP can be converted into useful organic substances eg. Glucose
What can TP produce as “useful organic substances”
Can produce hexose phosphates glucose, sucrose or cellulose
Fatty acids which join to form lipids for cell membranes
Production of amino acids for protein synthesis
Describe what is meant by Carbon Fixation within the Calvin Cycle
Carbon dioxide combines with RuBp
Uses enzyme Rubisco
Carbon has been fixed as it has been removed from external environment and is part of the cell
Name the limiting factors of Photosynthesis
Temperature, Light Intensity ,and Carbon Dioxide concentration
Effect of limiting Light on the calvin cycle?
RuBP decreases - being conveyed into GP but not reformed from TP
GP increases - not converted into TP but being formed from RuBP
Effect of limiting CO2 on the calvin cycle?
RuBP increases – not converted into GP (no CO2) but is being reformed from TP
GP decreases – not being formed from RuBP (no CO2) but being converted into TP
Effect of limiting Temperature on the Calvin cycle?
Increase = more Ek + More E-S complexes (rubisco)
Above Optimum= H bonds in tertiary structure break → active site changes shape → enzyme denatured + FEWER E-S Complexes
What is the compensation point in plants?
the point in the day (light intensity) when the CO2 taken in by photosynthesis equals the amount given out by respiration = no net gas exchange
How to measure the rate of photosynthesis?
measure amount of CO2 used or measure amount of O2 produced, in a certain time
How does a photosynthometer work?
measures amount of O2 produced
uses aquatic plants (e.g. elodea), as the O2 produced can be observed and collected
the plant is surrounded in sodium hydrogencarbonate solution (CO2 source)
the plant is kept in darkness before experiment runs (uses up all the O2 in the plant)
as the experiment runs, O2 will be produced, this will be collected in a capillary tube
the amount collected can be measured, this will be converted into a volume by multiplying length of oxygen bubble collected by πr2
volume of O2 collected can then be divided by time to calculate rate of photosynthesis
What does respiration produce?
ATP
What are the two types of respiration?
Aerobic and Anaerobic
What are the four stages of aerobic respiration?
Glycolysis
Link Reaction
Krebs cycle
Electron transport chain
What is glycolysis?
The first stage of anaerobic and aerobic respiration. It occurs in the cytoplasm and is an anaerobic process
Describe the stages of glycolysis
- Phosphorylation of glucose to glucose phosphate = using inorganic phosphate from 2 ATP
- Hydrolysed to 2x TP (triose phosphate)
- 2x TP → oxidised to 2x pyruvate
- 2 NAD reduced and 4 ATP regenerated
- Net production of 2 ATP