BIOL10004 Lecture Notes - Lipid Bilayer, Cell Membrane, Archaea
14 Jun 2018
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BIOL – Lecture 2
Prokaryotes
Prokaryotic cell features
• No nucleus or compartments
• Semi-rigid cell wall – gives support and structure to the cell
• Plasma membrane – semi-permeable made of phospholipid bilayer
• Outer capsule – can allow bacteria to survive in difficult environments
• Flagellum – whip-like appendage that can spin fast and create motion so the cell can
move through its environment
o Composed of a single protein, unlike those in eukaryotic cells
• DNA – double-stranded loop within the nucleoid region
• Pili – important for transferring genetic info between prokaryotic cells
• Ribosomes – attaching to mRNA to translates proteins
o Number of them within a cell can change depending on how young or old a
cell is or how active it may be
• Can have different shapes – spherical, rod or spiral shaped
• Very small and range from less than 1 micron up to 10
• Produe restig spores that a e oke up after ay years he the ell is i a
difficult environment
• Divide very rapidly as there is less material within the cell compared to eukaryotes
• Can tolerate all kinds of environments and niches
Replication – Binary fission
1. Double stranded loop of DNA becomes embedded in the plasma membrane
2. The loop then replicates
3. Cell wall and plasma membrane elongates
4. Cytokinesis – cell wall pinches together to split cell into two daughter cells
Taxonomy of prokaryotes
Two of the three domains of life are prokaryotes: Bacteria and Archaea
• Archaea are more closely related to Eukarya that Bacteria
How do bacteria differ from archaea? (table 35.2)
• Morphologially they dot differ
• The comparison on nucleic acid sequences allows us to construct phylogenetic trees
• Biochemically, Archaea are very different from the other two domains
• The two central processes in archaea (genetic transcription and translation) are
more similar to those of eukaryotes than bacteria
• Features of Archaean lipids and their membranes are unusual
• Archaea have not been found to produce resting spore
• There are no Archaean pathogens – all pathogens are in the bacteria domain
Prokaryotes
• Ubiquitous (found anywhere) and metabolically diverse
• Cause of many diseases
• Biotech applications
• Decomposers and recyclers`
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find more resources at oneclass.com
BIOL Lecture 3
Eukaryotes 1
When did they evolve?
• First eukaryotic fossils may be from 1.3-1.8 billion years ago
• First animal embryo-like fossils are 600 million years old
Nucleus
• Surrounded by double membrane (nuclear envelope)
o Continuous at pores
• Presence of nuclear (annular) pores (50nm diameter)
o All over surface of nucleus → communication
o More active the nucleus, the more pores
• Nucleolus – sub-region of nucleus containing ribosome genes
• linear DNA in long strands covered with histones (proteins) = chromosomes
• different organisms have different numbers of chromosomes
• RNA transcribed from DNA leaves nucleus via pores and is translated in cytoplasm
Mitochondria
• All eukaryotes have them, and some cells may have several, or one large one
• Surrounded by two membranes
o Smooth non-folded outer membrane
o Highly convoluted inner membrane, whose inward projections are called
cristae
o They carry out aerobic respiration
• Matrix fluid is different to between the outer and inner membranes
Chloroplasts
• Cells may contain one or many
• Surrounded by two membranes
o Smooth other membrane, not folded
o Inner membrane that forms a complex internal network of
lamellae/thylakoids
• The photosynthetic pigments are located within the thylakoids
• They are responsible for photosynthesis
• Stacks of thylakoids (grana) are important for photosynthesis
• Fluid within the organelle is called stroma, while fluid within the thylakoid
membranes is called lumen
Accessory pigments
• All photosynthetic organisms have chlorophyll A, and some have B that allow them
to trap energy from different wavelengths of light (B has a slightly different green
colour to A)
• Brown algae – chlorophyll C plus fucoxanthin
• Red algae – phycoerythrin and phycocyanin
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Replication binary fission: double stranded loop of dna becomes embedded in the plasma membrane, the loop then replicates, cell wall and plasma membrane elongates, cytokinesis cell wall pinches together to split cell into two daughter cells. Two of the three domains of life are prokaryotes: bacteria and archaea: archaea are more closely related to eukarya that bacteria. Eukaryotes 1: first eukaryotic fossils may be from 1. 3-1. 8 billion years ago, first animal embryo-like fossils are 600 million years old. Chloroplasts: cells may contain one or many, surrounded by two membranes, smooth other membrane, not folded. Secondary (or eukaryotic) endosymbiosis: chloroplast derived from an endosymbiotic, eukaryotic cell rather than a prokaryote, eukaryote stealing a chloroplast from another eukaryote, several protest groups obtain chloroplasts this way. Making, packaging and shipping proteins and molecules: a system of compartments that generally includes all of the membrane-bound components of the cell (including nuclear envelope) except for the mitochondria and chloroplasts.
