Chapter 1: The first cells Flashcards
What is the basic composition of a cell?
Water (60 - 80%), Ions, Organic molecules (proteins, lipids, polysaccharides, nucleic acids - and their monomers)
What is the difference between Unicellular and Multicellular organisms?
Unicellular organisms are composed of a single cell.
Multicellular organisms are composed or more than one cell, and often composed of a range of cell types.
What makes water such a good medium for chemical reactions?
Water is formed of one oxygen covalently bonded to two hydrogen atoms. Due to significant differences in the electronegativities the shared electrons between them are more drawn to the atom with higher electronegativity - in this case, Oxygen. This causes the oxygen to have a slight negative charge (δ-) and the hydrogen’s to have a slight positive charge (δ+), and this polarity allows weak hydrogen bonds to form between the hydrogen atom of a water molecule to the oxygen atom of another, as their differences in charge act as an attractive force. These bonds allow water to exist as a liquid over a range of temperatures, and act as an efficient solvent to dissolve other substances in, forming a reliable medium for chemical reactions to occur.
What are the monomers of these macromolecules:
- Proteins
- Lipids
- Polysaccharides
- Nucleic acids
- Proteins are formed of Amino acids
- Lipids are formed of fatty acids and glycerol
- Polysaccharides are formed of monsaccharides
- Nucleic acids are formed of nucleotides
What is the Oparin-Haldane hypothesis?
The hypothesis states that chemical reactions between inorganic gaseous molecules in the atmosphere, promoted by solar energy or energy from lightning, formed a ‘prebiotic soup’ of organic molecules that are the building blocks of complex molecules we see in present-day.
What is the general term for the formation of polymers from monomers?
Polymerisation
What are some of the functions of proteins within a cell?
- Enzymes/catalysts
- Structural proteins
- Contractile proteins
- Transporters
- Receptors
What are glycoproteins and what is their function?
Glycoproteins are formed of a protein and attached polysaccharide.
Used by the cell surface for
- adhesion
- recognition
- lubrication
What are the functions of Lipids in a cell?
- Energy storage
- Signalling molecules
- Cell membrane components
What are the functions of polysaccharides within a cell?
- Provide energy
- Store energy
- Cell wall support
What are the functions of Nucleic acids in cells?
- Storage of genetic information needed for protein synthesis and characteristic inheritance.
Harold Urey carried out an experiment recreating the life conditions of early earth using Ammonia, Methane and Hydrogen and simulating the ocean and lightning through refluxed water and an electrical discharge - all within a closed circuit.
What did Urey detect and what is the significance of this?
Urey detected:
- Significant amounts of organic molecules
- Five types of amino acids
Demonstrated how simple chemical reactions can form the reactive intermediates that can subsequently react and form amino acids and other organic building blocks.
(Reminder: Current geological evidence suggests this may have not been able to happen, and the earth’s atmospheric gases were much less reactive. No universal accepted theory exists on how these molecules formed)
Describe the structure of DNA.
- Nucleic acid
-Two polymer chains in the shape of a double helix - Polymer chains formed of 4 types of nucleotides (Cytosine, Guanine, Thymine and Adenine) in a specific sequence
DNA replication allows the use of encoded information in protein synthesis. Specific enzymes are crucial in the process of DNA replication.
How was the polymerisation of nucleotides possible in early cells that lacked protein enzymes?
RNA molecules, with similar catalytic activity to an enzyme, are capable of catalysing the polymerisation of nucleotides.
(Also suggests that RNA may have been the first basis of life)
What is ‘The Central Dogma’?
DNA –> RNA –> Protein
How does genetic variation arise? What does this give rise to?
Genetic variation arises through the rearrangement and errors in the nucleotide sequence of genetic material during replication.
It gives rise to phenotypic variation between the offspring and parent with possible phenotype differences, allowing for adaptation to changing environments.
What makes a set or organisms a ‘species’?
- Similar characteristics
Ability to reproduce and birth fertile offspring
What drives speciation?
Natural selection