Virus is non cellular, just some DNA or RNA surrounded by a protein coat…there is debate about whether it is alive or not.
Mitochondria and chloroplasts have their own DNA and can replicate themselves but they are organelles not cells. They are believed to have once been free living prokaryotic cells that formed a symbiotic relationship with a eukaryotic cell.
Multicellular cells show emergent properties Emergent properties are ones that come about when individual parts of a system interact with each other. On their own, the individual parts cannot do what they can do together. The whole is greater than the sum of its parts. A cell can do much more than the individual parts or organelles can do. A protein can do more than the amino acids that its made up of.
Think of these 3 parts: 1. A small metal cup 2. A glass bowl 3. A piece of tugnsten wire Individually they have no function, but when they are together:
Rate of heat and waste production and rate of resource consumption are functions that depend on its volume
Most chemical reactions takes place inside the cell and its size affects the rate of these reactions
The rate of exchange of substances therefore depends on the organisms surface area that is in contact with the surroundings
As the organism gets bigger, their volume and surface area both get bigger, but not by the same amount
Conclusion Large organisms, the rate of exchange of substances with their surroundings occurs more slowly Cell radius (r) 0.25 units 0.5 units 1.25 units Surface area 0.79 units 3.14 units 7.07 units Volume 0.06 units 0.52 units 1.77 units SA: Volume 13.17:1 6.04:1 3.99:1
Benefits of Light Microscope Benefits of Electron Microscope
Can see things in colour
Can look at live organisms
Much cheaper to buy & easy to operate
Comparisons of microscopes: Light microscope is more limited by its resolving power but allows observation of living organisms, movement and processes Transmission electron microscope is used to study the internal structure of the cell Scanning electron microscope is used to study the surface of a sample
Resolving power : a measure of the clarity of the image, the minimum distance two points can be and still be seen as two separate points
2. Magnification : how much bigger the image is, the ratio between the actual size and the image. The limiting factor for a microscope is the resolving power. For light microscopes the shortest wavelength of light enables discrimination of 0.2 microns, the size of a bacteria, magnification is limited to 1000X Electron microscopes use electrons and so their resolving power is 0.1 nanometers
First go through the virtual microscope tour. We do not have binocular microscopes, or light rheostat, otherwise same. Follow directions- you will get a green check when you have done the task successfully. View an image under 3 powers, adjusting light and focus.
Stems cells are unspecialized cells. They can reproduce indefinitely and have the capability of differentiation.
They have the ability to become any kind of cell. This is called totiopotency. Cells that can become almost any kind of cell are called pluripotent.
Human embryo is made up of stem cells up about 5 days old- called the blastula stage.
These cells can be made to differentiate into almost any cell type. This is why they are the focus of so much research.
Adults also have stem cells- these can’t make any kind of cell but they can make many different kinds. Ex: bone marrow stem cells can make all the different kinds blood cells as well as bone and muscle cells.
As the size of a sphere increases, the volume increases more than the surface area.
The surface area to volume ratio is important because materials must enter and leave the cell through the cell membrane. If the volume of the cell gets too big, the surface area can’t keep up with exchange of materials needed to support the metabolic activities of the cell.
So cells maintain a high surface area-to-volume ratio
Two kinds of cells: prokaryotic and eukaryotic Prokaryotic Small- 1 micron Lack nucleus and intermembranous systems Have cell wall DNA: one main circular chromosome and additional DNA in plasmid
Two kinds of cells: prokaryotic and eukaryotic Prokaryotic Eukaryotic Small- 1 micron Larger-10-100 microns Lack nucleus and intermembranous systems Organelles bound by membranes Have cell wall May have cell wall DNA: one main circular chromosome and additional DNA in plasmid DNA: in the nucleus, double stranded, no plasmid