Lecture notes
cellular organisation
- Module
- Foundations of life
- Institution
- University Of The West Of Scotland (UWS)
cellular organisation
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Cellular OrganisationLearning Outcomes
1. what are the main structures found in cells?
2. draw a labelled diagram of a prokaryotic cell.
3. draw a label diagram of a eukaryotic cell.
4. discuss the structure and function of endomembrane systems.
Basic Similarities
living organisms- archaea, bacteria and eukaryotes share the same basic needs.
they must ingest food, expel waste, and reproduce.
all cells reproduce by replicating DNA.
they make proteins from an RNA template using ribosomes.
the cytoplasm is enclosed within a lipid membrane (composition differs)
3 domains of life share these features:
a nucleoid or nucleus where DNA is located.
cytoplasm the semi fluid matrix of organelles and the cytosol
ribosome's for protein synthesis
plasma membrane, the phospholipid bilayer
these domains are evolutionary conserved.
little room from DNA, ribosomes, or membrane to improve their functioning.
although the location and organisation of genetic material is different, all cells use their DNA
as the genetic programme for building proteins.
3 domains all use ribosomes to assemble proteins, their ribosomes differ in structure but
work similarly.
Similarities of biochemistry at the very basic level support the hypothesis that cells derive
from a common ancestor.
In turn the vast array of cell types has arisen through evolution-countless selective events
and subsequent adaptation
Prokaryotic Cells
Prokaryotic= ‘before the nucleus’
Simplest organisms
Lack a membrane bound nucleus.
DNA is present in nucleoid.
Can also have numerous plasmids- small separate circular strands of DNA.
, Cell wall on outside of the plasma membrane
Contain ribosomes.
No membrane bound organelles.
2 domains of prokaryotes- archaea, bacteria
All cells have DNA, a plasma membrane, cytoplasm, and ribosomes.
Besides this cellular diversity is characterised by the presence or lack of internal structures
Flagella- long mobile projections used in moving cell (tail)
Fimbriae- short projections that attach them to surfaces.
Pilus- conjugative pili allow transfer of DNA between bacteria (process-bacterial conjugation)
Cell wall
Glycocalyx
Prokaryotic cells are very important in the ecology of all living organisms.
Harvest light by photosynthesis
Break down dead organisms and recycle their components.
Cause disease or have uses in many important industrial processes.
Plasmids
Plasmids are bonus DNA.
Carry information for additional functions e.g., Antibiotic resistance.
Not essential for life but favoured by selection if cell is exposed to antibiotic.
How bacteria acquire antibiotic resistance increasingly
Single cell with resistance gene on plasmid will pass gene to offspring.
Plasmids can be transferred between cells (conjugation pilus) one reason antibiotic
resistance can spread very quickly.
Bacterial Cell Walls
Most bacterial cells are encased in strong cell wall.
Composed of peptidoglycan (molecules composed of carbohydrates linked by peptides)
Cell walls of plants and fungi are chemically different.
Bacterial cells wall chemically more complex than plants algae and fungi.
Protect the cell maintain its shape and prevent excessive uptake or loss of water.
May have another layer called glycocalyx.
Susceptibility of bacteria to antibiotics often depends on the structure of their cell wall.
Penicillin- interferes with the ability of bacteria to cross-link the peptides in their
peptidoglycan cell wall.
Destroys the integrity of the structural matrix, which can no longer prevent water from
rushing in and swelling the cell to bursting.
Some bacteria also secrete a jelly-like protective capsule of polysaccharide around the cell.
Glycocalyx- carbohydrate-based outer covering that protects the cell.
Many disease-causing bacteria have such a capsule, which enables them to adhere to teeth,
skin, food.
Calyx= outer covering, glycol=sweet
Flagella
Some prokaryotes move by rotating the flagella.
Long threadlike structures protruding from the surface of a cell.
May be multiple.
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