BIO 1140 Lecture Notes - Lecture 4: Chitin, Actin, Liposome

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What distinguishes eukaryotes from bacteria and archea?
1. Nuclear envelope (separating DNA from rest of intracellular components)
2. Membranous compartments with specific roles (E.R., mitochondria, etc.)
All eukaryotic cells have some sort of energy-transforming unit (mitochondria,
chloroplasts)
Could this be the key to evolving the common ancestor
Theory of Endosymbiosis
The mitochondrion is thought to have originated from an aerobic prokaryote that
lived as an endosymbiont within an anaerobic prokaryote. The chloroplast is
thought to have originated from a photosynthetic prokaryote that became an
endosymbiont within an anaerobic cell that had mitochondria. (looks like
membrane in a capsule, divide by binary fission like prokaryotes, have a genome,
can produce their own protein)
Simpler to more specialized cell
Endo: within, inside + symbiosis: working together = Working inside a cell
together
Mitochondria first, chloroplasts after
Theory of Endosymbiosis: Evidence
1. Morphology: Shape of mitochondria and chloroplasts and size (μm) are
similar to bacteria and archea
2. Reproduction: Only by binary fission
3. Genome: circular mDNA and cpDNA
4. Transcription and translation: machinery in place
5. Electron transport: double membrane with ETC
6. Sequence: bacterial branch on tree of life (mitochondria=proteobacteria;
chloroplasts = cyanobacteria
Examples of Endosymbiosis in Nature
The spotted salamander Amystoma masculatum and green algae are
endosymbiotic; algae cells infiltrate the embryos.
They provide the O2, while they use the N2 produced by the salamanders
Elysia chlorotica (Sea slug) steals the chloroplasts from Vaucheria litoriea
(process is termed Kleptoplasty)
Macromolecules
Objectives
Understand and evaluate polarity of molecules
What are the types of chemical bonds relevant to biology
Discuss the importance of water in biology
What are the main classes of macromolecules, their structures, and their roles in
cell
Important Macromolecules in Biology
Sugar Carbohydrates
oMono, di or poly-saccharides
oFuel source for chemical energy
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oStructural molecules (know them: alpha both OH on same side
DDUD/beta  OH on two sides UDUDU) *Exam question*
oCellular recognition and communication
oPolysaccharides
From 3 to millions of single sugar units attached together
Storage
Glycogen (animals)
Starch (plants)
Structure
Cellulose
Chitin
Recognition
Can trigger immune reaction
Lipids
oSmall to large hydrophobic molecules
oNot polymers
o4 main groups
1. Fatty acids and triglycerides
oFatty Acids
Structure: long chain, amphipathic (a molecule that has a
polar and non-polar region)
Saturated chain (line up well  solid)
Unsaturated chain (when there’s a kink/double bond, enzyme
that does this is called a desaturase, don’t line up well  liquid)
Found in plasma membrane
oTriglycerides
Structure: lots of space for storing triglycerides (thin membrane
and small nucleus)
Stored in specialized cells (adipocytes)
Can serve as energy reserves (1g of fat can produce 2x the
energy from 1g of carbs)
Also play an important role in thermal regulation and isolation,
as well as protection against mechanical pressure
Unsaturated = double bonds: more stable and requires more
energy to break, are also liquid because the kinky bonds cannot
be packed
Saturated: solid because straight bonds can be packed tightly
2. Phosphoglycerolipids
Amphipathic molecules placed in water will spontaneously
arrange in a bi-layer
Made up of a hydrophilic head and a hydrophobic tail
oHydrophilic head = positive charge + negative charge
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Document Summary

Theory of endosymbiosis: the mitochondrion is thought to have originated from an aerobic prokaryote that lived as an endosymbiont within an anaerobic prokaryote. Objectives: understand and evaluate polarity of molecules, what are the types of chemical bonds relevant to biology, discuss the importance of water in biology, what are the main classes of macromolecules, their structures, and their roles in cell. Important macromolecules in biology: sugar carbohydrates, mono, di or poly-saccharides, fuel source for chemical energy, structural molecules (know them: alpha both oh on same side. Ddud/beta oh on two sides ududu) *exam question: cellular recognition and communication, polysaccharides. From 3 to millions of single sugar units attached together. Recognition: can trigger immune reaction, lipids, small to large hydrophobic molecules, not polymers, 4 main groups, fatty acids and triglycerides, fatty acids. Structure: long chain, amphipathic (a molecule that has a polar and non-polar region) Saturated chain (line up well solid)

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