Stage 1 Biology Cells and Microorganisms L Notes
Topic One: Cells & Microorganisms
Introduction to Cell Theory
Living things can be distinguished from non-living things
Characteristics
Living things Non-living things
Grow Do not grow
Absorbs nutrients Do not require nutrients
Reproduce Do not reproduce
The cell theory states that:
- All living things are made up of one or more cells (contain hereditary material)
- All cells derive from pre-existing cells
- The cell is the smallest structural and functional unit of life
Cell Characteristics
- Cells are a tiny volume of fluid which contain a cell membrane
- The cell membrane separates the cell from its surroundings
- Cells contain organelles (small structures). All cells contain an organelle named a ribosome
The two major cell types are:
- Prokaryotic
Organisms with one cell/unicellular
Smaller than eukaryotic cells
They contain:
Ribosomes
Cell membrane
Cytosol
Single Circular DNA Chromosome
Plasmid DNA
They lack: A nucleus and internal organelles containing membrane
- Eukaryotic
Can be either unicellular or multicellular
They contain: Organelles and nucleus (containing linear DNA chromosomes)
Similarities and Differences
Similarities of both cell types:
- Cell membrane
- Nucleic acids
- Proteins
- Ribosomes
, Stage 1 Biology Cells and Microorganisms L Notes
Differences:
Prokaryotes Eukaryotes
Small (1 – 10m) Large (10 – 100m)
Circle DNA Linear DNA
No nucleus Nucleus
No internal organisation High level of internal organisation
Single chromosome Two or more chromosomes
No organelles Organelles
Plant & Animal cells
Animal Cells Plant Cells
Don’t have a rigid shape Do have a rigid shape
Don’t have chloroplasts or a large vacuole Do have chloroplasts and a large vacuole
Don’t have a cell wall Do have a cell wall
Do have lysosomes Don’t have lysosomes
Organelles
Nucleus
Structure
→ contains the nuclear membrane (double membrane)
→ Comprised of DNA and proteins, containing many genes
Function
→ Controls cell activities
→ Stores genetic information
Cell Membrane
Structure
→ A thin, semi-permeable barrier made of lipids and proteins
→ Lipid bi-layer (two layers)
→ Fluid Mosaic Model
Function
→ Controls which substances enter and leave the cell
Cytoplasm/cytosol
Structure
→ A fluid matrix comprised mostly of water and a complex network of protein chains
→ Cytosol
Cytoskeleton
→ Holds organelles in place with the cytoplasm, maintaining cell shape
→ Involvement in cell divisions, endocytosis, and exocytosis.
→ Functions:
Support
Movement
Regulation
Topic One: Cells & Microorganisms
Introduction to Cell Theory
Living things can be distinguished from non-living things
Characteristics
Living things Non-living things
Grow Do not grow
Absorbs nutrients Do not require nutrients
Reproduce Do not reproduce
The cell theory states that:
- All living things are made up of one or more cells (contain hereditary material)
- All cells derive from pre-existing cells
- The cell is the smallest structural and functional unit of life
Cell Characteristics
- Cells are a tiny volume of fluid which contain a cell membrane
- The cell membrane separates the cell from its surroundings
- Cells contain organelles (small structures). All cells contain an organelle named a ribosome
The two major cell types are:
- Prokaryotic
Organisms with one cell/unicellular
Smaller than eukaryotic cells
They contain:
Ribosomes
Cell membrane
Cytosol
Single Circular DNA Chromosome
Plasmid DNA
They lack: A nucleus and internal organelles containing membrane
- Eukaryotic
Can be either unicellular or multicellular
They contain: Organelles and nucleus (containing linear DNA chromosomes)
Similarities and Differences
Similarities of both cell types:
- Cell membrane
- Nucleic acids
- Proteins
- Ribosomes
, Stage 1 Biology Cells and Microorganisms L Notes
Differences:
Prokaryotes Eukaryotes
Small (1 – 10m) Large (10 – 100m)
Circle DNA Linear DNA
No nucleus Nucleus
No internal organisation High level of internal organisation
Single chromosome Two or more chromosomes
No organelles Organelles
Plant & Animal cells
Animal Cells Plant Cells
Don’t have a rigid shape Do have a rigid shape
Don’t have chloroplasts or a large vacuole Do have chloroplasts and a large vacuole
Don’t have a cell wall Do have a cell wall
Do have lysosomes Don’t have lysosomes
Organelles
Nucleus
Structure
→ contains the nuclear membrane (double membrane)
→ Comprised of DNA and proteins, containing many genes
Function
→ Controls cell activities
→ Stores genetic information
Cell Membrane
Structure
→ A thin, semi-permeable barrier made of lipids and proteins
→ Lipid bi-layer (two layers)
→ Fluid Mosaic Model
Function
→ Controls which substances enter and leave the cell
Cytoplasm/cytosol
Structure
→ A fluid matrix comprised mostly of water and a complex network of protein chains
→ Cytosol
Cytoskeleton
→ Holds organelles in place with the cytoplasm, maintaining cell shape
→ Involvement in cell divisions, endocytosis, and exocytosis.
→ Functions:
Support
Movement
Regulation
