Why are different organelles important?
Provide distinct environments and conditions for different cellular reactions
Nucleus
Contains genetic information in the form of genes
Nuclear envelope
DNA is contained within a double membrane to prevent damage in the cytoplasm
Nuclear pores
In the nuclear envelope- allows substances to move in and out of the nucleus since DNA is too large to leave the cell
How is DNA organised in the nucleus
DNA wraps around histones- forming chromatins- which coil and condense to form chromosomes
Nucleolus
Is an area within the nucleus responsible for producing ribosomes. Contains proteins and RNA.
Mitochondria
Is the site of respiration within a cell.
Inner membrane- cristae.
Fluid interior- matrix
Vesicles
Membranous sacs that are responsible for storage and transport within the cell
Lysosome
A specialised type of vesicle which have enzymes that break down waste material in cells (eg old organelles/ pathogens)
Cytoskeleton
Network of fibres helping maintain the shape and stability of the cell/ cell movement/ movement of organelles
Microtubules- scaffold like structure, act as tracks for movement of organelles, make up spindle fibres
Microfilaments- cell movement, cell contraction during cytokinesis
Intermediate fibres- mechanical strength
Centriole
Component of the cytoskeleton, assembly and organisation of spindle fibres
Flagella
Enable cell mobility, sensory organelle to detect chemical changes in the cell environment
Cilia
Hair like structure that beat to cause fluids/objects adjacent to the cell to move
Endoplasmic reticulum
Network of membranes connected to the outer membrane of the nucleus
Smooth ER- lipid/carbohydrate synthesis and storage
Rough ER- has ribosomes bound to surface, synthesis and transport of proteins
Ribosomes
The site of protein synthesis. Made up of equal amounts of protein and rRNA
Golgi apparatus
Modifying proteins then packaging them into vesicles
Describe the process of protein production
- DNA sequence of a gene is copied onto mRNA
- mRNA leaves the nucleus via the nuclear pore and attaches to a ribosome on the surface of RER
- Ribosome produces the protein and is enters the RER
- Proteins are packaged into vesicles and travel to the golgi apparatus via microtubules
- Vesicles fuse into the golgi, where they are further modified
- Proteins are packaged into vesicles again and leave the golgi
- Vesicles fuse with the cell surface membrane and release proteins via exocytosis
P- Cell wall
Surrounds the cell surface membrane
Made of cellulose
Gives the plant cell shape and rigidity because the contents of the cell push against the wall
Freely permeable
Prevents the cell from bursting
Acts as a defense mechanism, protecting the contents of the cell against invading pathogens.
P- Vacuole
Membrane lined sacs in the cytoplasm containing cell sap
Important in the maintenance of turgor (contents of the cell push against the cell wall to maintain rigidity)
P- Chloroplast
Responsible for photosynthesis
Can make their own proteins
What is the difference between prokaryotic and eukaryotic cells?
- Ribosomes in P cells are smaller than in E (70s and 80s)
- P cells have a cell wall made of murein/ peptidoglycan, plant cell walls are made of cellulose
- DNA in E cells exists in chromosomes in the nucleus and is wrapped around histones, P cells have DNA lying free in the cytoplasm and is only one molecule
- E cells have membrane bound organelles
- P cells reproduce via binary fission
