Cells as the basis of life

• There are two types of cells: prokaryotic and eukaryotic
• Prokaryotic cells exist as single cells and have no membrane-bound nucleus or organelles
• Bacteria and Archaea kingdoms contain prokaryotic cells
• Eukaryotic cells have a membrane-bound nucleus and membrane-bound organelles
• Prokaryotic cells are simpler and more common in life on earth than Eukaryotic cells
• All cells have a cell membrane, cytoplasm and ribosomes
• Prokaryotic cells are 0.1 - 5.0 µm, eukaryotic cells are 10 - 100 µm
• Genetic material forms a large loop called the "bacterial chromosome" and also forms small rings called "plasmids"
• Structures of a prokaryotic cell float in fluid-like cytoplasm
• Organelles have specific functions in a eukaryotic cell, but must work together for successful functioning in a cell like respiration and photosynthesis
• In a light microscope, a light source is focused by a condenser lens to illuminate a thin specimen. Then the light passes through a convex objective lens to magnify and focus the image
• Resolution (resolving power) is the ability to distinguish details when imaging a specimen in a microscope
• Light microscopes can magnify images up to 1500x, and the max resolution is 200nm
• Fluorescence microscopes are similar to a light microscope, but allow for structures beyond the limit of resolution to be seen by labelling cell structures with fluorescent substance
• Electron microscopes use an electron beam instead of light to view cell structures
• The two main types of electron microscopes are scanning electron microscope (SEM) and transmission electron microscope (TEM)
• TEM is the most common microscope and transmits electrons through the specimen, producing a 2D image
• TEM magnifies an image up to 1500000x and the resolution is 2nm
• SEM bombards specimen with a beam of electrons, causing secondary electrons to be emitted from the specimen's surface layer, and creating a 3D image of surfaces
• SEM has magnification up to 500000x and a resolution of 10nm
• Computer-enhanced technology produces a 3D representation of cell structure
• A confocal laser produces an intense beam of light to focus on the sample at many levels, then an image reconstruction program generates the 3D image in a computer-enhanced technology
• Scale = actual length (of cell) / length of drawing
• Organelles have internal structures enclosed by own membrane
• A light microscope allows viewing of the nucleus, vacuoles, and chloroplasts
• An electron microscope allows viewing of mitochondria and ribosomes
• A plant cell has a cell wall, chloroplasts, and a large-permanent vacuole
• An animal cell has centrioles and lysosomes
• Plant and animal cells have a cell membrane, cytoplasm, cytoskeleton, nucleus, mitochondria, endoplasmic reticulum, golgi body, and ribosomes
• A cell membrane surrounds and separates the contents of the cell
• Cell membranes are selectively permeable
• Selectively permeable means the organelle only allows passage some molecules like water or chemical substances to be in or out of the cell
• The protoplasm is the living content of the cell, and carries out essential functions to life e.g. making cellular products and respiration
• Cytoplasm consists of dissolved chemical substances called cytosol (e.g. ions like chloride ions), suspended organelles and granules. It is 90% water
• The nucleus stores information in order to control all cell activities
• The nucleus communicates by the surrounding cytoplasm
• The nucleus is surrounded by a double nuclear membrane, that is pierced by tiny pores
• The pores in a double nuclear membrane regulate the passage of substances between the nucleus and cytoplasm, allowing for communication
• The nucleoplasm is the liquid portion of the nucleus that contains the chromatin material
• The chromatin is made up of protein and nucleic acid