Title: Cell types and subcellular structures
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Markdown Content:
Cells in their environment
Lecture 3
4BBY1030 Cell Biology & Neuroscience
> FoLSM/IoPPN
> Neuroscience Education
Prof Clemens Kiecker
and Dr Suba
Poopalasundaram
> 3rd and 4 th October 2024 Dr Clemens Kiecker Topic title: Cells in their environment
## Learning outcomes
By the end of this lecture, you should be able to:
Speculate on the origins of cellular life forms on earth
Explain the concept of cellular specialisation in the context of multicellularity
Provide an overview of cellular and subcellular pathogens Dr Clemens Kiecker Topic title: Cells in their environment 3
Theodosius Dobzhansky (1900-1975) geneticist and evolutionary biologist Dr Clemens Kiecker Topic title: Cells in their environment 4
## Chapter 1
# The origins of cellular life Dr Clemens Kiecker Topic title: Cells in their environment
## The phylogenetic tree of cells
5Dr Clemens Kiecker Topic title: Cells in their environment
## Earths early atmosphere
Conditions on Earth before life forms existed:
- Lots of methane
- Increased amounts of carbon dioxide
- Little/no oxygen
- Higher temperatures
- Lots of lightning and volcanic eruptions (energy)
- No UV protection from atmosphere (no ozone)
Conditions to promote spontaneous reactions.
Formation of carbon compounds.
Living organisms changed spontaneous conditions.
> 6Dr Clemens Kiecker Topic title: Cells in their environment
## Where did the first cell come from?
How could non-living things form a living cell?
- Ideal reaction conditions (high temperature and pressure)
- Catalysts (metals)
- Self-assembly of polymers
- Self-replicating molecules (RNA)
- Compartmentalisation (membrane formation by
phospholipids; partially permeable )
> 7Dr Clemens Kiecker Topic title: Cells in their environment
## The first genetic material - RNA
RNA:
- can store genetic information
- is self-replicating
- can act as an enzyme
- mutates at a higher rate and is more prone to mutations
> 8Dr Clemens Kiecker Topic title: Cells in their environment 9
## Evolution of LUCA (the last universal common ancestor of cells)
HCHO, HCN, cyanamide, glyceraldehyde, PO 43- etc.
Minerals as catalysts, high temperatures in hydrothermal vents
RNA world, ribozymes
DNA more stable
Lipid bilayers spontaneously form vesicles
[Pollard (2017) Cell Biology] Dr Clemens Kiecker Topic title: Cells in their environment
## The phylogenetic tree of cells
10
LUCA Dr Clemens Kiecker Topic title: Cells in their environment 11
## Bacteria and archaea
One cellular compartment, no membrane-bound
organelles
Specialisations: e.g. flagella
Huge variety (approx. 1 million species known)
Archaea can adapt to extreme environments
(extremophiles; halophiles, thermophiles,
acidophiles etc.) and sources of energy (hydrogen,
methane, sulfate etc.)
Reproduction: error-prone, but fast
Our microbiome: 40,000 species, 30-50 trillion
bacterial cells
Scanning electron micrograph of E. coli [New Scientist (2019)] Dr Clemens Kiecker Topic title: Cells in their environment 12
## The endosymbiotic theory
Mitochondria: symbiotic
relationship between an
anaerobic ancestral
eukaryote and aerobic
bacterium
endosymbiotic theory
Chlorophyll-based
photosynthesis
Photosystem I green
sulfur bacteria and
heliobacteria
Photosystem II purple
and green filamentous
bacteria
Cyanobacteria Dr Clemens Kiecker Topic title: Cells in their environment 13
## How did mitochondria and chloroplast evolve?
Transmission electron
micrograph of a mitochondrion Dr Clemens Kiecker Topic title: Cells in their environment 14
## The endosymbiotic theory
Mitochondria: symbiotic
relationship between an
anaerobic ancestral
eukaryote and aerobic
bacterium
endosymbiotic theory
Chlorophyll-based
photosynthesis
Photosystem I green
sulfur bacteria and
heliobacteria
Photosystem II purple
and green filamentous
bacteria
Cyanobacteria Dr Clemens Kiecker Topic title: Cells in their environment 15
## Protozoans
Single-celled eukaryotes
Motility, predation
Not animals, plants (algae) or fungi Dr Clemens Kiecker Topic title: Cells in their environment 16
## Chapter 2
# Multicellularity Dr Clemens Kiecker Topic title: Cells in their environment
## Cellular specialisation
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Heart cells Blood cells Kidney cells
Neurons Bone cells Gut epithelial cells Dr Clemens Kiecker Topic title: Cells in their environment 18
## Ex ovo omnia
Lat. Everything from the egg
William Harvey (1651)
Asexual reproduction (eg hydra and yeast)
Sexual reproduction versus parthenogenesis
(eggs can give rise to an organism without
undergoing fertilisation only contains maternal
genetic information)
Embryogenesis requires tight control of cell
division, morphogenesis and differentiation
(Lecture 18 and 4BBA1010)
Sea urchin
Mouse Dr Clemens Kiecker Topic title: Cells in their environment 19
## Budding in hydra and yeast asexual reproduction Dr Clemens Kiecker Topic title: Cells in their environment 20
## Ex ovo omnia
Lat. Everything from the egg
William Harvey (1651)
Sexual reproduction versus parthenogenesis (eggs
can give rise to an organism without undergoing
fertilisation only contains maternal genetic
information)
Embryogenesis requires tight control of cell division,
morphogenesis and differentiation (Lecture 18 and
4BBA1010)
Formation of an organism involves cell proliferation,
differentiation and morphogenesis.
Sea urchin
Mouse Dr Clemens Kiecker Topic title: Cells in their environment 21
## Origins of multicellularity
Volvox ( Volvox carteri ): colonial green alga
Two cell types: somatic cells (differentiated, mortal) and germ
cells (gonidia, reproductive, immortal)
[Matt & Umen (2016) Dev Biol 419 :99-113] Dr Clemens Kiecker Topic title: Cells in their environment 22
## Origins of social behaviour
Dictyostelium discoideum : slime mold, social
amoeba
Motility and chemotaxis (Lectures 4 and 14)
Cell adhesion (Lecture 5)
Phagocytosis, micropinocytosis, autophagy
(Lecture 15)
Pattern formation (Lecture 18)
Cell death (Lecture 17)
Display characteristics of multicellular organisms!
[Bozzaro (2019) Int J Dev Biol 63: 321-31] Dr Clemens Kiecker Topic title: Cells in their environment
## Chapter 3
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# Pathogens Dr Clemens Kiecker Topic title: Cells in their environment
## Pathogens
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Pathogens - disease causing microorganisms or infectious agents.
Examples of pathogens include bacteria, viruses, fungi and protozoans.
Salmonella SARS-CoV-2
Athletes foot - fungi Protozoans Dr Clemens Kiecker Topic title: Cells in their environment
## Bacterial pathogens
Robert Koch (1884): cholera is caused by a rod-shaped bacterium ( Vibrio cholerae )
Paul Ehrlich (1910): Salvarsan (antibiotic drug)
Alexander Fleming (1928): penicillin Nobel Prize for Medicine 1945
Methicillin-resistant Staphylococcus aureus (MRSA; resistant to antibiotics)
Cyanobacteria: produce toxins (BBC - 30 th September 2020: Elephants die from
bacterial disease)
Archaea are not known to cause diseases (extreme environments) unlikely exposure
> 25 Dr Clemens Kiecker Topic title: Cells in their environment 26
## Viruses
Outside of host cell: virion (DNA or RNA + protein
coat/capsid + sometimes lipid envelope)
Retroviruses, lentiviruses (e.g. HIV) integration
events can be mutagenic
Dormancy (e.g. herpes virus, varicella-zoster virus)
2014 identification of 30,000 year old Pithovirus
sibericum
Origins: virus first versus cellular origin
hypotheses
Usually very small (only visible in EM)
2013 Science : pandoravirus (2,500 genes) Dr Clemens Kiecker Topic title: Cells in their environment
## Other pathogens
Fungi: Candida albicans (yeast), Cryptococcus gattii (yeast), coccidioidomycosis (Valley
fever), athletes foot
Approx. 1 million deaths per year globally (usually patients with weakened immune
system)
Protozoans: malaria ( Plasmodium falciparum and Plasmodium vivax ), toxoplasmosis
(Toxoplasma gondii; undercooked meat ), giardiasis ( Giardia species; beaver fever),
cryptosporidiosis ( Cryptosporidium; diarrheal illness )
> 27 Dr Clemens Kiecker Topic title: Cells in their environment
## Recommended reading
Pollard, Earnshaw, Lippincott-Schwartz, Johnson, Pollard (2017) Cell Biology. 3 rd ed. Elsevier, PA.
Please note that the content of this book is broader than the learning outcomes of this module. Thus, do not
panic we do not expect you to study this book from the first to the last page. You should rather use it to
supplement your learning and as a resource if you have a question or if you find a particular topic interesting
and would like to learn a little bit more about it.
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# Thank you for your attention
[email protected]
subathra.poopalasundaram@@kcl.ac.uk
Kings College London. All rights reserved