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
What is the relationship between natural selection and phenotypes?
Organisms with phenotypes that are advantageous to their survival will survive longer and have an increased chance of reproducing offspring or more of them, with the advantageous alleles (the fittest), continuing to be passed down from generation to generation whilst organisms with alleles that are not advantageous will be less likely to survive, and have a lower chance of survival and reproduction, with their phenotypes eventually tapering off.
This is natural selection.
What is evolution?
The change of inherited characteristics and traits found in populations over time
or
The change in frequency of particular alleles within the gene pool of a population through generations.
In Darwin’s theory, what three things are needed for evolution to occur?
- Competition and struggle for survival
- Variation between individuals of a species
- Characteristics being heritable
How do phospholipids form cell membranes?
Phospholipid bilayers form due to the hydrophobic tails pointing themselves inwards, away from surrounding water, whilst the hydrophilic heads point outwards towards the cytosol and the extracellular fluid. These phospholipid bilayers spontaneously form spherical membranes when put into aqueous environments.
What are organelles?
Compartments within a cell that are membrane-bound and possess specialist function/s.
Why could the formation of a lipid bilayer around organic molecules be theorised to lead to the formation of life?
If a phospholipid bilayer enclosed a range of organic molecules this would have promoted reactions between them as it increases the chance of reaction due to the higher concentration being fully enclosed. This may have lead to the formation of a cell that was capable of reproduction through binary fission.
What is the polarity of phospholipid heads and tails?
Phospholipid heads are polar (hydrophilic)
Phospholipid tails are non-polar (hydrophobic)
What is a heterotroph?
An organism that cannot form it’s own organic compounds and therefore must feed on organic matter produced by other organisms.
What is an autotroph?
An organism with the capability of synthesising it’s own organic molecules using light or other inorganic as an energy source.
What is a catabolic reaction?
A catabolic reaction is characterised by the breakdown of complex molecules into simple units which in turn releases energy.
What is an anabolic reaciton?
An anabolic reaction requires an energy input and is the building of complex molecules from simpler units
What are the components of an Adenosine 5’-triphosphate (ATP) molecule?
5 carbon sugar ribose (5’)
Adenine group (adenosine)
Chain of three phosphate groups with negatively charged oxygens (triphosphate)
What kind of reaction occurs to convert ATP to ADP?
Hydrolysis (addition of water molecule)
Define ‘metabolism’
Metabolism is the entirety of biochemical processes carried out by an organism necessary for the maintenance of life, growth, reproduction, and for responding to their environment.
What does it mean if an environment is anaerobic?
There is no readily available supply of oxygen .
State the term which describes respiration that utilises oxygen.
Aerobic respiration
What is the word equation for photosynthesis?
Water + Carbon dioxide + energy input → Glucose + Oxygen
What is the word equation for aerobic respiration?
Glucose + oxygen → carbon dioxide + water + energy as ATP
- What is one theory on the cause of the great oxygenation event?
- How may the increase of oxygen have lead to the presence of aerobic respiration?
- It is theorized that within Earth’s early anaerobic environment, heterotrophs used catabolic reactions to gain energy. A risk of organic material depletion needed by these heterotrophs may have led to the appearance of autotrophs able to synthesise organic molecules themselves using environmental energy, and with an increase in population came an increase in atmospheric oxygen levels.
- Oxygen is extremely reactive and increased levels may have increased the amount and range of chemical reactions occurring, with the eventual formation of a more efficient process of gaining ATP - aerobic respiration.
What is ‘LUCA’?
LUCA stands for the Last Universal Common Ancestor.
Theorized to have lived 3500 Ma, LUCA is a theorised singular common ancestor for all present-day organisms, most likely resembling a present-day bacteria.
Name 4 fundamental characteristics of living organisms.
- Composed of one or more membrane-bound cell
- Capable of growth and reproduction
- The ability to transform and utilise an external source of energy
- Possession of a heritable genetic code using 4 nucleotide bases
What are the 3 domains of organisms?
- Bacteria
- Archaea
- Eukarya
Define taxonomy
The classification of organisms, determined by shared characteristics or phylogenic relationships.
List the hierarchy used in taxonomy.
Top to bottom: Kingdom, Phylum, Class, Order, Family, Genus, Species
Bottom to top: Species, Genus, Family, Order, Class, Phylum, Kingdom
Define phylogeny
The evolutionary relationships between organisms, often shown as a type of illustrated ‘phylogenic tree’.
Which domains are eukaryotic and which are prokaryotic?
Prokaryotic: Bacteria, Archaea
Eukaryotic: Eukarya
Prokaryotes do not have a nucleus. What do they have instead and what is different about it compared to eukaryotes?
Prokaryotes have a nucleoid instead of a nucleus, in which their genetic material, usually circular DNA, is free floating within the cytosol of the cell.
What are pili?
Possessed by some bacteria, pili are short filament-like structures, formed of protein, protruding from their surface into the surrounding environment. Their main function is to facilitate adhesion to other cells and sufaces.
Sex pili are involved in the transfer of genetic material between bacterial cells during conjugation.
What are flagella?
Flagella are long whip-like structures formed of protein, that protrude from some cells. Their main function is movement but also are involved in signaling changes in the external environment to the interior of the cell.
Bacterial flagella and eukaryotic flagella have different structures, components, and different driving forces.
