Cell Theory & Eukaryotic Structures Cell theory – All living things are made of cells – Cells are the basic unit of life – New cells come from existing cells Study called cytology – Light microscopy - a device using light and mirrors to magnify an object. Its resolution (measure of clarity) is limited to 0.2 mm. good for seeing the gross structure of most cells and bacteria most appropriate for viewing live specimens – Electron Microscopy - a device that concentrates a beam of electrons onto a plated surface. Its resolution is to around 2nm. (good for seeing organelles and some macromolecules ) (SEM) scanning electron microscope - good for detailed investigation of surface structure (TEM) transmission electron microscope - good for seeing internal structures of cells – Cell fractionation uses a centrifuge to separate the parts of the cell by mass

Prokaryote vs Eukaryote Prokaryotes - no true nucleus – DNA is not separated from the rest of the cell (no nuclear membrane) but is concentrated in a nucleoid region Eukaryote - true nucleus – DNA is located in a membrane bound compartment called the nucleus – area between the nucleus and the plasma membrane is called the cytoplasm contains the membrane bound organelles

Prokaryote vs Eukaryote Common features – plasma membrane - all cells are bound by a plasma membrane functions as a selective barrier - hydrophobic interior with hydrophilic exterior which is embedded with channel proteins used to transport materials. has a very large surface to volume ration in order to efficiently transfer gases, nutrients, & waste in and out of the cell – cytosol - semi fluid medium contained within the plasma membrane – chromosomes - structures containing genetic information (DNA) – ribosomes - tiny structures that assemble proteins

Nucleus The nucleus houses the genetic information of the cells. It is responsible for directing protein synthesis which effects every function of the cell. Its structures include: – Nuclear envelope - double membrane that separates its contents from the cytoplasm contains pores that regulate the entrance and exit of macromolecules – Nuclear lamina - lines the nuclear side of the nucleus contains a netlike structure of filaments that helps maintain the shape of the nucleus

DNA – Chromosomes - basic structure of inheritance made of chromatin - a complex of DNA and proteins 46 chromosomes present in the normal human cell (2n, diploid, 44 autosomes, 2 sex chromosomes) 23 chromosomes are present in the sex cells (1n-haploid) – Nucleolus - region of the nucleus containing ribosomal RNA (rRNA) directs the formation and assembly of the ribosomal subunits

Ribosomes Site of protein synthesis. Most ribosomes are attached to the endoplasmic reticulum while some float freely in the cytosol. – Free floating ribosomes make proteins that are destined to function in the cytoplasm – Bound ribosomes make membrane bound proteins and proteins destined for the organelles of the cell