Origin of Life and Cells Flashcards
What elements is living matter made from?
Carbon Nitrogen Oxygen Hydrogen Calcium Phosphorus = 97% dry weight
What was the Miller-Urey experiment?
They used a mixture of H20, CH4, NH3 and H2
They supplied it with an electric charge (lightening) and this yeilded soluble organic compounds including some amino acids
This could have taken place in hydrothermal vents - 400 degrees
In the prebiotic era how were simple organic molecules formed?
From monomers in a condensation reaction to form polymers
With the rate of condensation being greater than the rate of hydrolysis
Minerals in clays would have catalysed the reactions
What allows replication?
Association of complementary molecules as it can direct the assembly from smaller complementary molecules
e.g. bas pairing within DNA
What is natural selection?
The survival of the fittest organisms, due to variation in genes that are favourable to a changing environment, allowing them to survive and pass on their alleles to future generations
What did Darwin do?
Explored the Galapagos Islands collecting finch beaks to study
He published Origin of Species - about natural selection
And due to improved reproductive fitness, new species have arised
Evolution occurs due to variation in inherited characteristics
What is a species?
A group of organisms that can interbreed with each other and are reproductively isolated
What do cells do?
Carry out metabolic reactions within different compartments
What are the advantages of compartmentation?
Protection from environmental forces
Maintanence of high local concentrations of components - this helps as more concentrated substances react more readily = efficient polymerisation
What are the two types of cells?
Eukaryotic - a membrane enclosed nucleus holding the DNA
Prokaryotic - no nucleus
Describe Eukaryotes?
Uni or Multicellular Nucleus: condensed with proteins More complex 10-100 μm Diploid/Polyploid Division: mitosis - somatic and meiosis - gametes
Describe Prokaryotes?
Unicellular DNA is free in cytoplasm as 'nucleoid' No internal compartments 1-10 μm Normally haploid Simple division following DNA replication
How can we view cells/organelles?
Unaided eye
Light microscope
Electron microscope
What is the endosymbiotic theory?
Mitochondria and chloroplasts have been engulfed by an organism and been kept
They have their own DNA
What is significant about energy supply?
ATP demand is proportional to volume
Meaning supply depends on the membrane surface area
This is lead to cells being subdivided into organelles
Describe the mitochondria?
Double membrane (one invaginated)
Used for oxidative metabolism
Has an independent genome
The number of cristae per mitochondrion relates to energy demand so they can move to areas of need
Describe the endoplasmic reticulum?
Smooth ER - synthesises lipids and steroids, regulates Ca2+ conc, detoxifys drugs and is used in gluconeogenesis
Rough ER - Facilitates protein synthesis/folding and transports synthesised proteins
Describe the nucleus?
DNA is packed by histones into chromatin
Surrounded by a nuclear membrane containing pores to allow communication between the cytoplasm and nucleus
Heterochromatin - tightly coiled
Euchromatin - unwound and DNA can be accessed to transcribe
Decribe the Golgi apparatus?
Functions in secretion and intracellular tracking of new synthesised proteins
Proteins are sorted, modified and packaged
5 functional regions of cisternae stack: cis-golgi, cid-golgi network, medial-golgi, trans-golgi and trans-golgi network
This is like a postcode (cis to trans)
How can we categorise organisms?
Taxonomy - the science of biological classification
Phlogeny - relationships between organisms based on their evolutionary history
What are the domains of life?
Eubacteria
Archaea
Eukarya
What are the 4 key points of evolution?
Evolution is not directed towards a particular goal
Variation is among individuals
The past determines the future - preexisting elements lead to developed ones
Evolution is on going
What biochemical tools can we use to study cells?
Subcellular fractionation: two types
- Differential centrifugation
- Isopycnic centifugation (sucrose density)
Describe differential centrifugation?
- Break open the cells in a blender/homogeniser/french press (to break the cell membrane)
- Further homogenisation: crush and strain
- Cetrifuge the homogenate - due to different sizes they have different sediment rates
Large cell fragments will emerge first, then heavier organelles, lighter orangelles etc.
- Resuspend the supernautent and further isolate
Describe isopycnic centrifugation?
The further purification of organelles
They are separated on a density gradient due to different buoyant densities
How can different organelles be identified?
Functional assays, size and concentration of antibody binding:
Marker enzymes SDS PAGE Fluoresence Antibodies Live cell imaging
What are marker enzymes?
Located exclusively in target organelles with a known activity
Therefore we can monitor enzyme activity in each fraction, this can also help indicate purity
What is live cell imaging?
Using fluoresence microscopy we can track movements in real time
GFP - Green Fluorescent protein, taken from a jellyfish
GFP can be mutated to different colours
