Jeff Kerr; Week 1 MED1011; Anatomy
General cell structure is DNA and RNA in the nucleus and cytosol, organelles and inclusions in the cytoplasm.
1mm = 1000um; 1um = 1000nm; 1nm = 10A
If cells were the size of golf balls, they would contain 600 square meters of membranes. Proteins and nucleic acids are found at concentrations of 300mg/mL (like dissolving an aspirin in 1mL of water). Cells must generate order out of potential chaos (entropy), compartments ensure components are in the right place at the right time.
Nucleus contains a nuclear membrane to separate contents from the cytoplasm, contains chromatin in two forms, heterochromatin where DNA is not transcribed, and euchromatin where DNA is transcribed. Nucleolus is where ribosomal genes make rRNA that is combined with proteins to produce ribosomes.
- Heterochromatin is packed DNA, 'silent'; euchromatin is uncoiled DNA, appears white on film
About 2m of DNA can be packed into a structure 4-5um in diameter
Cytosol is a sol-gel liquid where metabolic reactions and protein synthesis occur. Has a self-maintenance role where proteins are produced that repair plasma membrane, made inside the endoplasmic reticulum
Rough endoplasmic reticulum is used in protein synthesis, covered in ribosomes and has cisternae, smooth endoplasmic reticulum is not covered by ribosomes. Rough ER transports formed proteins in vesicles to the 'cis' end of the Golgi apparatus to be packaged, modified and sorted for use inside or outside the cell. Proteins leave the Golgi apparatus from the 'trans' end, and are either secreted or used within the cell. Smooth ER is a compartment for steroid synthesis and detoxification of drugs. Rough ER is prolific in cells that use lots of proteins, such as B cells, and smooth ER is prevalent in liver cells for detoxification of drugs.
Mitochondria produce ATP which serves as an energy source for mechanical work, has matrix in the centre and infoldings of cristae. It is abundant in heart muscle and the tails of sperm.
Peroxisomes oxidate toxic materials, kill bacteria; lysosomes formed by Golgi and contain digestive enzymes to break down unwanted/foreign ingested material.
Inclusion bodies are intert, stored materials such as fat or lipid droplets (stored triglyceride/cholesterol for energy source and biosynthetic reactions), glycogen granules (major form of stored carbohydrate), pigment/lipofuscin (undigested waste materials)