ENERGY Flashcards
How and why the efficiency of energy transfer is different at different stages in the energy transfer through an ecosystem:
Over 90% of the sun’s energy is reflected into space by clouds and dust
Not all wavelengths of light can be absorbed and used for photosynthesis
The light might not fall on the chlorophyll molecule
Efficiency of photosynthesis in plants is low – approximately 2% efficient
Some of the energy is lost by the consumers through release of heat, or by restoring heat depending on the environmental temperature
Some of the energy is lost by the consumers through faeces
Consumers may not eat all of their food/prey
Food consumed may not be fully absorbed and digested
Efficiency of energy transfer to consumers is greater than the efficiency of energy transfer to the producers
Efficiency of energy is lower in older animals
Carnivores use more of their food than herbivores
Percentage Efficiency of energy transfer
(Energy given out ÷ Energy provided) X 100
Intensive Rearing of livestock
Faster rate of growth
Slaughtered while young so more energy transferred to biomass
Fed on concentrated diets so higher proportion of food absorbed from gut i.e. higher proportion of food digested
Heating so that no energy wasted maintaining body temperature (mammals are Endotherms-have high body temp)
Reduced movement, therefore less respiratory losses
Plentiful food supply
High survival rate as no predators
Selective breeding
Gross Production
Total quantity of energy that the plants in a community convert to organic matter
Net Production
Gross Production – Respiratory losses
ATP
Provides energy in small, usable amounts for the wide variety of energy-requiring reactions
Is relatively small molecule that can diffuse around the cell quickly
It is soluble
Mainly found in mitochondria
Is extremely unstable and is constantly broken down and re-synthesised to and by ADP and Pi (free organic phosphate)
Therefore it cannot be stored
Reasons why ATP is a suitable source of energy
Energy released in small amounts Soluble Involves a simple reaction Makes energy available rapidly Lowers activation energy It is reformed
Why it is important to synthesise large amounts of ATP
ATP is unstable
ATP cannot be stored
ATP is needed for processes such as active transport, etc.
ATP only releases small amounts of energy
Why organisms need ATP
Metabolism such as polysaccharide synthesis from monosaccahrides, polypeptide synthesis from amino acids and DNA synthesis from nucleotides
Movement
Active Transport; provides the energy to change the shape of carrier proteins in a plasma membrane
Maintenance, Repair and Division
Secretion; ATP is needed to form the lysosomes necessary for the secretion of cell products
Production of substances such as enzymes and hormones
Maintenance of body temperature
Activation of molecules
The Light Dependent Reaction
Takes place in Thylakoids (membranes within the chloroplast that contain chlorophyll)
Light energy hits chlorophyll which then excites and emits 2 high energy electrons
These electrons pass down an electron transport system RELEASING ENERGY that is used by phosphorylation to make ATP from ADP and used to reduce NADP to become NADPH
Energy is also used to split water via the process of PHOTOLYSIS, which produces electrons to replace chlorophyll electrons. Photolysis also produces protons and Oxygen (2H2O → 4H+ + 4e- + O2)
The electrons are used to make reduced NADPH (NADP)
The Oxygen is released into atmosphere
DOES NOT depend on temperature as no enzymes involved
Light Independent Reaction: Stages of Calvin Cycle
CO2 combines with 5-carbon RuBP (Ribulose Bisphosphate) with the enzyme Rubisco as a catalyst, Oxygen acts a competitive inhibitor with CO2 for the active site of Rubisco
This produces 2 MOLECULES of 3 carbon compound GP (Glycerate 3-Phosphate)
ATP (provides energy) and NADPH used to reduce GP into 3 carbon compound TP (Triose Phosphate) – this process will not work in the dark, this is because ATP and NADPH cannot be made without light
Some of the TP is used to make carbohydrates like GLUCOSE, but MOST of it is used to make more RuBP for the next cycle
How the concentration of CO2 would fluctuate over 24 hours above ground level
Higher CO2 concentration at night as photosynthesis in plants which removes CO2 only takes place in the light
Respiration takes place throughout the 24 hours, therefore high CO2 at night
However, even in the dark plants DO take up CO2, but it is just significantly less than the amount they take up during the day
In light, the rate of photosynthesis will be higher than the rate of respiration
The higher you go above ground level, the lower the concentration of CO2 this is because the higher you go above ground level, the more leaves there will be, which will be carrying out photosynthesis which removes CO2
Glycolysis
one molecule of glucose oxidised to produce 2 molecules of Pyruvate (3 carbon ion)
The reaction YIELDS two molecules of ATP and two molecules of NADH
Takes place in the CYTOPLASM of cell as glucose is too large to enter the mitochondria
The process does NOT require Oxygen
Glycolysis is an oxidation reaction as it involves the removal of Hydrogen to form Pyruvate
ATP is necessary for Glycolysis as it activates the glucose to become phosphorylated glucose
Link Reaction
Also called Pyruvate Oxidation
Pyruvate used to produce Acetate and Carbon Dioxide, the Acetate is picked up by co-enzyme A forming Acetyl Co-enzyme A
No ATP is produced in the Link Reaction but 2 NADH molecules are formed as well as CO2 and Acetyl Co-enzyme A
Takes place in the Matrix of MITOCHONDRIA
Krebs Cycle
Electrons stripped from the Acetate, creating large amounts of electron carriers in the form of NADH and FADH2
Takes place in the Matrix of MITOCHONDRIA
Each cycle produces 1 ATP, 3 NADH, 1 FADH2 and 2 CO2
The cycle turns TWICE per molecule of glucose, therefore it produces 2 ATP, 6 NADH, 2 FADH2 and 4 CO2
The Krebs Cycle is a series of Oxidation and Reduction reactions
