BIOL10004 Final: Biology of Cells and Organisms: Exam Notes of examinable material
16 Jun 2018
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Biology: Cells and Organisms Notes
Lecture 1
Evolution – the great unifying theory of biology:
• That the earth has a long history.
• All living organisms arose in the course of this history from earlier, more primitive forms.
• As a consequence of this theory, all organisms are related or share a common ancestor.
• As such – all life shares biochemical processes – also, all organisms have cells
Oldest life known – fossilised cyanobacteria in Grand canyon parallel to Stromatolites in WA
Lecture 2
Prokaryotes
– First inhabitants of earth, primitive compared to highly complex eukaryotes.
Eg/ Cyanobacteria – contain chlorophyll a – first to photosynthesise and produce oxygen.
This caused an increased level of oxygen in the atmosphere, decreasing UV due to O2 to O3 conversion which protected and
facilitated life.
Prokaryotes – contain no organelles or nucleus, have circular DNA as a single molecule, and have specifically prokaryotic
ribosomes. Cell is surrounded by selectively permeable plasma membrane and peptidoglycan wall. Size ranges from 1 to 10
micrometres.
Bacteria – produce resting spores that can be dormant for long periods –
spores can then wake and become functioning bacteria. Divide extremely
fast – only have 0.1% the amount of DNA as eukaryotes – divide every 20
minutes.
Prokaryotes can survive in almost every niche on earth as they have a high
diversity of biochemical processes and tolerances.
The flagella of a prokaryote are a single protein – flagellin, a sheath and a
rotary motor.
Prokaryotic cellular division is Binary fission STEPS:
1. Replicates genome that is always attached at plasma membrane
2. The two loops of DNA are attached at different points
3. Cell wall and membrane grows in between, pulling apart DNA loops
4. Cell wall splits – results in two equally sized prokaryotes. – FtsZ protein
Two super kingdoms – Prokaryote (Archaea, Bacteria) and Eukaryote.
Differences between Archaea and Bacteria:
Morphologically similar
Over half of Archaean genes were new to science when discovered
Biochemically very different
Transcription and translation more similar to EU than BA – Eg/ use Methionine as staring amino acid
Lack peptidoglycan wall, they have different features of lipids
Don’t produce resting spores
Found everywhere (thought they were only extremophiles)
There are NO KNOWN Archaean pathogens
Archaeans have histones linked to their DNA
Not affected by antibiotics
The cell theory says that:
• Living matter is composed of cells;
• The chemical reactions of living
organisms take place in cells;
• Cells only arise from other cells;
• Cells contain the hereditary
information of the organism of which
they are a part, and this information
is passed from parent cell to
daughter cells.
Phylogeny of superkingdoms:
Root Archaea
Bacteria Eukarya
Bacteria:
• Ubiquitous and metabolically diverse
• Cause of many diseases
• Decomposers, recyclers – critical roles in removal and waste decontamination
• Nitrogen fixation in root nodules
• Have many biotech applications
Lecture 3
Eukaryotes - Organelles
Nucleus
• Contains DNA
• Covered in pores (~75nm in diameter) for communication
• Contains nucleoli (packets of jumbled protein and RNA – contain ribosome genes – transcription occurs here)
More nuclear pores if highly active and connect outer and inner membranes of nuclear envelope (continuous). Pores are
selective – RNA passes through. Long strands of DNA are covered in globular proteins – histones. DNA double wraps
around histone to form a nucleosome. Histones are +ve, DNA –ve. A core of histones = several nucleosomes.
Euchromatin – loosely packed DNA so it can be accessed / Heterochromatin – tightly packed →chromosome.
Mitochondria –cell powerhouse
• Cells may have several hundred, or a single large one
• Contains its own circular DNA and ribosomes(prokaryotic)
• Surrounded by two membranes, outer and highly convoluted inner (cristae – SA)
• Carry out aerobic respiration of all eukaryotes
• Inner membrane – matrix- many enzyme complexes
• Intermembrane space has very different environment
• Mitochondria are highly dynamic, always moving around a cell.
Chloroplasts
• In plant cells – one or many
• Outer and highly folded inner membrane – forms complex internal thylakoid network, stack to form grana
• Responsible for photosynthesis – produces sugars.
• Only chlorophyll a can be used for PHS, accessory pigments transfer energy to CPA
• Has own circular DNA and prokaryotic ribosomes.
Origin of Plasmids – mitochondria and chloroplasts
Plasmids are believed to be derived from relic endosymbionts. M – Purple bacteria, C- cyanobacteria. Basic process of
endosymbiosis – primitive eukaryote absorbed prokaryote was not digested, survived in eukaryote – formed into organelle.
Mitochondria from primary endosymbiosis, Chloroplasts from secondary – Primary: A absorbs B, does not digest, mutual
benefit – some DNA lost to host nucleus – therefore not completely autonomous. Secondary: Eu A absorbs Eu B, steals and
uses its organelles.
Evidence for primary endosymbiosis is that some chloroplasts have been found to still have a bacterial peptidoglycan wall
between the inner and outer membranes (in cyanophora).
For secondary endosymbiosis – some chloroplasts found to have 3, or even 4 outer membranes (membrane from original
engulfed cell). Organisms that carry this out are protistan pirates.
Other evidence includes degenerated peptidoglycan wall around chloroplasts of cyanophora, and in cryptomonads there is
a second, degenerated nucleus (nucleomorph).
Lecture 4
Endomembrane system:
System of compartments that generally includes all membrane bound components – excluding M&C
Major functions of the intracellular membranes:
• -provides service for biochemical reactions
• -Establishes a number of compartments to prevent mixing
• -Provides transport of materials within a cell/to adjacent cell.
• Membranes always includes a space than ever are demanded on west the cell is damaged
• Biological membranes another four T junctions
• Membranes are the consistency of oil in water not stiff barriers.
Endoplasmic reticulum-is continuous with the nuclear envelope.
Connects all membranes of the cell and consists of cisternae that ramify through the cytoplasm and result in
compartments and channels.
The ER is dynamic, constantly changing structure. It has a high surface area to volume ratio. Rough and smooth
endoplasmic reticulum are biochemically very different.
Rough – present ribosomes, synthesises and transports proteins.
Smooth – no ribosomes, synthesises lipids and carbohydrates.
