BIOL1020 Lecture Notes - Lecture 5: Human Microbiota, Halobacterium, Dna Replication
L5 - Life and cellular functions !
Origin of cells
•All cells are believed to have originated from a common universal ancestor believed to
be 2.8 billion years ago called LUCA
Lipid membranes
Membranes regulate exchange of nutrients and other compounds with the environment. All
cells have lipid membranes and they are made up of:
• Phospholipids!
• Cholesterol!
• Membrane proteins (integral and peripheral)
•Carbohydrates attached to the outside of the membrane
•Attachment sites for the cytoskeleton (inside of the membrane
Bacteria
•extremely simple but also extremely versatile regarding the environments in which they
can occur
• Bacteria (and Archaea that also evolved early in earth’s history) can survive in
inhospitable environments. Eg: Halobacterium – salt-tolerant Archaea can survive in
37% salt concentration.
•Bacterias has been linked to obesity, type II diabetes autism and other conditions not
generally associated with bacteria
•These diseases appear to be caused by interactions between commensal bacteria and
the human body
•Another disease associated with the human microbiome is kwashiorkor that has been
linked to malnutrition in African children.
The bacterial cell components
•The bacterial cell is a single chamber: all processes occur in the same space
•All metabolic reactions occur in the same space, i.e. the cytoplasm or in the cell
membrane
•Energy generation, Protein synthesis (ribosomes), DNA replication, Synthesis of cell
components
•The bacterial chromosome is (usually) a single, circular molecule
•The area in which the bacterial chromosome is located is called nucleoid
How did they find the link between bacteria and this disease?!
They looked at twin boys with same diet but one twin got the disease. so it cant be the dna or
the environment that caused the disease. so the disease was attributed to the bacteria.
find more resources at oneclass.com
find more resources at oneclass.com
•In addition to a chromosome bacteria may contain small circular DNA molecules
called plasmids
•our cells try to destroy foreign DNA but because bacterial DNA is more plastid,
foreign DNA can be incorporated much faster
Cell wall !
•The exterior of the bacterial cell is rigid and multilayered
•There are two main types of bacterial cells that differ in their cell wall structure
•the peptidoglycan layer is a ridgid matrix that defines the cell shape.
•The layer in gram negative bacteria is thinner than the gram positive bacteria. !
Flagella and pili !
•both used for mobility and
movement
•Pili (or fimbriae) are used for
adhesion to surfaces
•Flagella generate movement and
motion (allows bacteria to swim)
They are ‘nanomachines’ and they
even have a clutch protein that puts
the flagellum into gear or into
neutral.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Origin of cells: all cells are believed to have originated from a common universal ancestor believed to be 2. 8 billion years ago called luca. Membranes regulate exchange of nutrients and other compounds with the environment. All cells have lipid membranes and they are made up of: phospholipids, cholesterol, membrane proteins (integral and peripheral, carbohydrates attached to the outside of the membrane, attachment sites for the cytoskeleton (inside of the membrane. Bacteria: extremely simple but also extremely versatile regarding the environments in which they can occur, bacteria (and archaea that also evolved early in earth"s history) can survive in inhospitable environments. Eg: halobacterium salt-tolerant archaea can survive in. They looked at twin boys with same diet but one twin got the disease. so it cant be the dna or the environment that caused the disease. so the disease was attributed to the bacteria.
