Origin of Life Flashcards
What is special about earth that allowed life to emerge?
- the presence of water
- day/night cycle
Properties of Water
- high specific heat capacity
- undergoes two state transitions in the temperature range on Earth
- state changes require many times more heat than increasing the temperature
Why is water conducive to life?
- it controls the Earths temperature, can absorb a lot of energy to prevent fluctuations in temperature
- water condenses as it rises into the atmosphere and dissipates heat
- white clouds reflect light which has a cooling effect
Why is a day/night cycle conducive to life?
- regular cycle of hot and cold temperature
- could lead to continual break down and reassembly of molecules meaning useful molecules for life are more likely to be formed
- different enzymes can be active in day and night
Model
Definition
- attempt to explain a process which is not directly observable due to size or complexity
- a model can never be proved, only not yet disproven
What is a detergent?
a phospholipid composed of a hydrophilic head and hydrophobic tail
What are detergent cells and how are they formed?
- detergent monomers are placed in water
- detergent monomers line up to ‘hide’ hydrophobic parts from the water.
- under certain conditions this leads to the formation of a phospholipid bilayer enclosing a space, a cell
What two categories can lipids be divided into?
phospholipids and triglycerides
Structure of a Triglyceride
glycerol molecule attached to three fatty acid chains
Structure of a Phospholipid
glycerol molecule attached to two fatty acids and a phosphate
How is melting temperature related to carbon chain length?
the longer the carbon chain, the higher the melting point
Unsaturated
- has double bonds which causes bends in the chain
- lower melting temperature
- hard to form a solid as the bendy chains don’t line up very easily
- will only form a solid at very low temperatures
Saturated
- no double bonds
- straight chains
- easily form crystalline solid structures
What are the two types of phospholipid?
- glycerophospholipids
- -syphingolipids
Glycerophospholipids Structure
- glycerol backbone
- 2 fatty acid chains
Syphingolipid Structure
- sphingosine backbone with hydrophobic hydrocarbon tail
- one fatty acid tail
What came first, photosynthesis or chemolithotrophy?
It is generally believed that photosynthesis came befor chemolithotrophy as many chemolithotrophs are aerobic and there was no oxygen present on the early earth
Photosynthesis
- always occurs across a membrane as a proton gradient has to be maintained
- uses light as an energy source to create a proton gradient for ATP production
- autotroophic
Chemolithotrophy
- converts oxidations to biological fuel using oxygen or sometimes nitrate as an electron acceptor
- produces ATP
- uses ATP for the Calvin Cycle
- can function in the dark
- have internal membranes
Heterotrophy
- use of organic substances that can act as electron donors (can be oxidised)
- use glucose that autotrophs have made
- glucose is the most universal carbon and energy source
- if glucose is unavailable, heterotrophs will break down polysaccarides to form glucose
- don’t always require oxygen
Grotthus Mechanism
- the small size of protons cannot explain their unusually high diffusion rate in an electric field
- this mechanism describes ‘proton hopping’ between water molecules
- water is particularly good at conducting protons
The Fourth Phase of Water
- the structure of water is very complex due to the hydrogen bond network
- there are many different ways that water molecules can arrange themselves
- e.g. adding certain sugar molecules to water can cause it to become solid above its freezing point
ATP
- holds a lot of energy
- high energy phosphoryl bonds between phosphates
- large amounts of energy can be released through the hydrolysis of ATP
- ATP hydrolysis requires an enzyme and is an exergonic reaction
- as it requires an enzyme, ATP hydrolysis can be strictly controlled
Exergonic Reaction
Definition
- release energy
- usually spontaneous
- usually the break down of a molecule
