A2 Flashcards
Define primordial soup
A solution of simple monomers including amino acids, and hydrogen and carbon chains. It is thought that the origin of living compounds began in this water based solution in the sea.
Define homeostasis
The maintainence of a consistent internal environment despite a changing external environment. It is an essential requirement of living organisms to maintain some constants.
Define vesicles
Vesicles are any small bubble of fluid surrounded by a phospholipid bilayer. Vesicles form automatically when phosphilipids are in water- this could model how cells could originate. Vesicles can also form by established membranes breaking off.
Define compartmentalisation
The seperation of functions for specific regions of the cell (organelles), allowing multiple distinct metabolic functions to occur at the same time.
Define coalescence
Coalescence is vesicle/ membrane formation. The natural coming together of things. In this context it refers to fatty acids/ phospholipids arranging themselves away from water, thus coming together and forming a ring.
How were the abiotic conditions of early Earth different from current conditions?
The abiotic conditions of early Earth allowed for spontaneous formation of compounds that occur now.
* The gases present included methane, ammonia and hydrogen sulfide- there was very little oxygen.
* There was high penetration of UV light (no ozone layer) leading to high temperatures.
* There was regular lighting
What are the requirements for something to be considered living?
- Metabolism
- Growth
- Reproduction (without a host)
- Respond to their environment
- Maintain homeostasis
- Use food for energy
What are the three principles of cell theory?
- All organisms are composed of one or more cells
- Cells are the smallest unit of life
- All cells come from pre-existing cells
What are the requirements necessary for cells to evolve?
- Catalysis (enzymes to speed up chemical reactions)
- Self-replication of molecules needed
- Self- assembly of those molecules into large polymers and structures/ organelles
- Compartmentalisation- functions assigned to organelles
What is the difference between an inorganic and an organic compound?
Organic- a generally complex carbon (and hydrogen) based compound- made in living organisms and play a crucial role in living processes
Inorganic- do not have to contain carbon (most do not) and are often found outside of living organisms as well as inside them- often simpler than organic
Explain the Miller-Urey experiment
- Wanted to test the hypothesis that inorganic gases could react (in early earth conditions) to create organic compounds.
- Tested this by creating 2 chambers, one with boiling water and one with gases (methane, ammonia, hydrogen) and electrodes to represent lightning
- The water vapour would travel though a tube and combine with the inorganic gases
- Once condensed into liquid, they found an aqueous solution containing amino acids and carbon hydrogen chains (primordial soup)
- This is evidence that there could have been spontaneous/ natural formation of biomolecules/ monomers in early Earth conditions.
Describe spontaneous vesicle formation
Phospholipids in aqueous solution naturally form a barrier to create a vesicle. If fatty acids were present in primordial soup, then this process could have created early cell membranes.
Define ribozymes
A special type of RNA that can act as a catalyst in protein synthesis. There is evidence they were the first catalyst, before protein based enzymes.
Define protocell
The general term for any unit contained by a membrane that completes cellular action. Thought to be the origin of life. They are likely the ancestors of modern cells, before compartmentalisation and self-replication to become ‘true cells’
What is a radioactive isotope?
An unstable form of an element that emits radiation, this radiation can be measured. Radioactive isotopes are used to date fossils by comparing the original amount to the current amount as it degrades steadily.
Define half-life (of a radioactive isotope)
The length of time it takes for a half of a radioactive isotope to turn into another stable element. This is known for the element, and used to date fossils, most commonly with C-14.
What are index fossils?
Distinctive, widespread fossils that are abundant but limited to a certain geological time. These can be used to compareto other fossils using the location in the rock layers.
What are hydrothermal vents?
Places where hot water come from beneath the ocean floor. They form cracks in the seabed which exposes the water to magma heated rocks. They are extremely hot and have low oxygen, but some organisms still live there
What is the RNA world hypothesis?
For primordial soup to progress to polymers through self-assemly, a catalyst is needed. The RNA world hypothesis states that RNA could have been the catalyst, and pre-dated DNA
What is the evidence for the RNA world hypothesis?
RNA is:
* A simple, single stranded nucleic acid
* Can spontaneously form from monomers
* Easily assembled
* Can act as a catalyst- we know this because of ribozymes currently doing this
* Can be used to make proteins and DNA
* Has self-replicating properties
What does LUCA stand for?
Last Universal Common Ancestor
What is the sequence of the major stages of the evolution of life?
- Abiotic chemical compounds existed
- Led to the creation of small, organic compounds (primordial soup)
- Assembled into polymers (aided by RNA catalysis)
- Membranes spontaneously formed
- Protocells exist
- Compartmentalisation
- A true cell with organelles form
What is LUCA?
The last common ancestor to all currently living organisms
What is the evidence for shared ancestry (LUCA)
- Universal genetic code
- Same biomolecules and metabolic processes
- 300 genes were tracked that are shared between all living organisms- genes involved in anaerobic processes (absence of oxygen)
Where is LUCA found?
- Low oxygen environment
- Other favourable conditions
- HYDROTHERMAL VENTS
- How do we know this? old fossils were found there
What is relative fossil dating?
Relative fossil dating considers whether a fossil is older or younger than nearby fossils, based on the placement in rock in relation to an index fossil (lower is older)
What is absolute fossil dating?
Absolute fossil dating attempts to determine an age of the fossil in years. This relies on carbon dating using the half-life of radioisotopes of carbon
Define cytology
Cytology is a branch of biology focused on the study of the cell, including cell structure and function. It heavily relies on the use of microscopes.
Define magnification
The increase in an objects image size compared to its actual size. How many times larger the viewed image is than the actual image
How do you calculate magnification?
Magnification= measured scale bar with ruler/ given size on bar
Define resolution
The minimum distance between two points/ objects at which they can be distinguished as two seperate objects.
What is a micrograph?
The image taken through a microscope to show the view of the microscope (light or electron).
Describe the process of freeze fracturing
- Cell is frozen
- Cell is broken at a plane known as the fracture plane
- Create an etching of the plane
- Observe the etching under an electron microscope
What has freeze fracturing helped us understand?
Freeze fracturing is how we have come to understand the bilayer
Describe the process of cryogenic electron microscopy (cryo-EM)
- A protein solution is frozen on a grid (in ethanol)
- The grid is placed in an electron microscope
- The pattern of the electron transmission reveals the structure of the protein, down to the atoms
- The software creates a 3D image
Describe the process of using flurescent stains
- Flurescent stain is added to the cells
- The stain sticks to a cellular component
- These are observed with a flurescent light with a UV light microscope