Lecture 1 – Introduction to Cells
• Cell Theory
- Discovered by Robert Hooke ~ coined the term ‘cell’.
- Arises only from pre-existing cells.
- Cells are an organisms basic unit of structure and function.
- The cell is the lowest level of organisation that can perform all activities
required for life.
➢ Single cell (bacteria, protozoa)
➢ Multi-cellular (animals, plants)
- All enclosed by a membrane.
- DNA – Genetic information.
- Division of cells ~ basis of reproduction, growth and repair.
- Cell size is limited ~ as size increases, it takes longer for material to
diffuse from the cell membrane to the interior of the cell.
- SA:V Ratio ~ Cell increases in size, volume increases 10x faster than SA.
• Certain structures in common
1) Genetic material
➢ Information storage ~ DNA
➢ Duplicator of information ~ DNA replication enzymes
➢ Information translator ~ ribosome
2) Cytoplasm – Semifluid matrix.
3) Plasma membrane – phospholipid bilayer
• Grouping Species
Taxonomy – classifies species into groups of increasing breadth.
- Domain Bacteria
- Domain Archaea
- Domain Eukarya
• Types of Cells
PROKARYOTES
EUKARYOTES
• Prokaryotes
These cells thrive almost everywhere, e.g. too acidic, salty, cold or hot.
Mostly microscopic – More in a handful of fertile soil than the number of people
who have ever lived.
Structural and functional adaptations contribute to prokaryotic success:
- Unicellular.
- Variety of shapes:
➢ Spheres (cocci)
➢ Rods (bacilli)
➢ Spirals (spirillium)
, ➢ Curved (vibrio)
- Two types of prokaryotes
1) Bacteria
2) Archaea
Cell surface structures:
- Cell wall maintains shape, provides physical protection, and prevents the cell
from bursting in a hypotonic environment.
- Made of cellulose (chitin).
- Bacterial cell walls contain peptidoglycan (sugar polymers cross-linked by
polypeptides).
- Archaea contain polysaccharides and protein but lack peptidoglycan.
- Gram stain – used to classify bacterial species into gram-positive and gram
negative groups based on cell wall composition.
➢ Gram negative – Less peptidoglycan, outer membrane can be toxic,
antibiotic resistant.
➢ Gram positive –
- Some prokaryotes have fimbriae – allows them to stick to substrate or other
individuals.
- Sex pili are longer than fimbriae and allow DNA exchange.
Reproduction and Adaptation:
- Reproduce through Binary fission.
- Form endospores, which can remain viable in harsh conditions.
- They do have sex.
Motility (movement):
- Propel themselves by flagella.
- Heterogeneous environment = exhibit taxis, move toward/away from
stimuli.
Internal and genomic Organisation:
- Lack complex compartmentalisation.
- Some have specialised membranes that perform metabolic functions.
- Genome has less DNA than eukaryote genome.
- Genome consists mainly of circular chromosome.
- Genome = 1000-4000 genes.
• Eukaryotes
, Possess a membrane bound nucleus.
Compartmentalize many cellular functions within organelles and the
endomembrane system.
Possess a cytoskeleton for support and to maintain cellular structure.
Cytosol:
- Part of the cytoplasm that is not held by any of the organelles in the cell.
- Functions:
➢ Location of specific chemical reactions.
➢ Storage of fat, carbohydrates as inclusions.
➢ Storage of secretory vesicles.
- Cytoplasm: Cytosol and organelles.
Plasma Membrane:
- Surrounds cytoplasm, acts as a physical barrier.
- Site of attachment of cytoskeleton and membrane associated structures.
- Regulates movement of material in/out of cell, thus whole internal
environment.
- Such materials include oxygen, waste, nutrients.
- Double layer of phospholipids = structure.
Nucleus of eukaryotes:
- Contains most of the genes.
- Nuclear envelope ~ seperates from cytoplasm.
- Nuclear membrane ~ Double membrane (each consists of lipid bilayer).
- Pores regulate entry and exit of molecules.
- Shape maintained ~ nuclear lamina (composed of protein).
DNA
• Cell Theory
- Discovered by Robert Hooke ~ coined the term ‘cell’.
- Arises only from pre-existing cells.
- Cells are an organisms basic unit of structure and function.
- The cell is the lowest level of organisation that can perform all activities
required for life.
➢ Single cell (bacteria, protozoa)
➢ Multi-cellular (animals, plants)
- All enclosed by a membrane.
- DNA – Genetic information.
- Division of cells ~ basis of reproduction, growth and repair.
- Cell size is limited ~ as size increases, it takes longer for material to
diffuse from the cell membrane to the interior of the cell.
- SA:V Ratio ~ Cell increases in size, volume increases 10x faster than SA.
• Certain structures in common
1) Genetic material
➢ Information storage ~ DNA
➢ Duplicator of information ~ DNA replication enzymes
➢ Information translator ~ ribosome
2) Cytoplasm – Semifluid matrix.
3) Plasma membrane – phospholipid bilayer
• Grouping Species
Taxonomy – classifies species into groups of increasing breadth.
- Domain Bacteria
- Domain Archaea
- Domain Eukarya
• Types of Cells
PROKARYOTES
EUKARYOTES
• Prokaryotes
These cells thrive almost everywhere, e.g. too acidic, salty, cold or hot.
Mostly microscopic – More in a handful of fertile soil than the number of people
who have ever lived.
Structural and functional adaptations contribute to prokaryotic success:
- Unicellular.
- Variety of shapes:
➢ Spheres (cocci)
➢ Rods (bacilli)
➢ Spirals (spirillium)
, ➢ Curved (vibrio)
- Two types of prokaryotes
1) Bacteria
2) Archaea
Cell surface structures:
- Cell wall maintains shape, provides physical protection, and prevents the cell
from bursting in a hypotonic environment.
- Made of cellulose (chitin).
- Bacterial cell walls contain peptidoglycan (sugar polymers cross-linked by
polypeptides).
- Archaea contain polysaccharides and protein but lack peptidoglycan.
- Gram stain – used to classify bacterial species into gram-positive and gram
negative groups based on cell wall composition.
➢ Gram negative – Less peptidoglycan, outer membrane can be toxic,
antibiotic resistant.
➢ Gram positive –
- Some prokaryotes have fimbriae – allows them to stick to substrate or other
individuals.
- Sex pili are longer than fimbriae and allow DNA exchange.
Reproduction and Adaptation:
- Reproduce through Binary fission.
- Form endospores, which can remain viable in harsh conditions.
- They do have sex.
Motility (movement):
- Propel themselves by flagella.
- Heterogeneous environment = exhibit taxis, move toward/away from
stimuli.
Internal and genomic Organisation:
- Lack complex compartmentalisation.
- Some have specialised membranes that perform metabolic functions.
- Genome has less DNA than eukaryote genome.
- Genome consists mainly of circular chromosome.
- Genome = 1000-4000 genes.
• Eukaryotes
, Possess a membrane bound nucleus.
Compartmentalize many cellular functions within organelles and the
endomembrane system.
Possess a cytoskeleton for support and to maintain cellular structure.
Cytosol:
- Part of the cytoplasm that is not held by any of the organelles in the cell.
- Functions:
➢ Location of specific chemical reactions.
➢ Storage of fat, carbohydrates as inclusions.
➢ Storage of secretory vesicles.
- Cytoplasm: Cytosol and organelles.
Plasma Membrane:
- Surrounds cytoplasm, acts as a physical barrier.
- Site of attachment of cytoskeleton and membrane associated structures.
- Regulates movement of material in/out of cell, thus whole internal
environment.
- Such materials include oxygen, waste, nutrients.
- Double layer of phospholipids = structure.
Nucleus of eukaryotes:
- Contains most of the genes.
- Nuclear envelope ~ seperates from cytoplasm.
- Nuclear membrane ~ Double membrane (each consists of lipid bilayer).
- Pores regulate entry and exit of molecules.
- Shape maintained ~ nuclear lamina (composed of protein).
DNA
