Introductory (1.1) Flashcards
What is the cell theory?
A scientific theory that states all living organisms are:
1 - Composed of one or more cells — cells are building blocks of organisms;
2 - A cell is the smallest unit of life — that is, a cell is the most basic unit capable of carrying out all the functions of a living organism;
3 - Cells come from pre-existing cells (Omni cellulae e cellula) – that is, cells do not show spontaneous generation.
What made the development of the cell theory possible?
Advances in microscopy. As the quality of light microscopes improved, more and more information about the structure of organisms and cells was collected.
Divide these into living and non-living: Animals, Plants, Bacteria, Viruses, and Fungi.
Animals, Plants, Bacteria, Fungi: living
Viruses: non-living
How are cells formed?
They don’t spontaneously appear; they are always formed by the division of preexisting cells
(Prokaryotic cells divide by binary fission, while eukaryotic cells can divide through fission, mitosis, or meiosis)
Outline evidence that supports the cell theory.
No evidence proves the cell theory to be incorrect.
Subcellular components have never been seen to perform the functions of life, whereas full cells have.
From the 17th century on, biologists examined tissues from plants and animals (later from fungi, bacteria, and protists) and saw that every specimen contained at least one or more cells.
We have observed cells coming from other cells but never observed spontaneous generation.
What is the difference between theory in daily use and scientific environments?
In daily use: there are doubts, a guess
Scientific: a theory is true through repeated observations and experiments. There is no current doubt. As of yet, no evidence has been collected that does not support the idea.
Describe the features of striated muscle fibers that make them a discrepancy from a typical cell.
Striated muscle fibers are large cells that have multiple nuclei (while most eukaryotic cells have one nucleus, each cell is multinucleated, and the average muscle fiber cell is about 30 mm long, which is much larger than a typical cell).
Describe features of red blood cells that make them a discrepancy from a typical cell.
Red blood cells have no nucleus (while most eukaryotic cells have one nucleus).
Describe features of aseptate fungal hyphae that make them a discrepancy from a typical cell.
Aseptate fungal hyphae are tube-like structures that contain no cell membranes between the many nuclei.
Aseptate hyphae are not divided up into individual cells, resulting in a continuous cytoplasm along the length of the hyphae.
Describe features of giant algae (acetabularia) that make them a discrepancy from a typical cell.
Giant algae can be a large, single-celled organism with a single nucleus.
Organisms as large as giant algae would be expected to be multicellular, but they have only one cell with one nucleus.
As a single-celled organism, Acetabularia challenges two widely accepted notions about cells: that they must be simple in structure and small in size.
Outline the functional characteristics of life.
1) All life has a cellular structure (according to the cell theory, all living things are composed of cells).
2) All life exchanges energy and matter with the environment (including intake of nutrients and excretion of waste).
3) All life has a metabolism (chemical reactions within the organism).
4) All life can recognize and respond to changes in environmental conditions.
5) All living things can grow and/or develop through the lifespan (increase in size, mass, or number of cells within the organism)
6) All life has the capability for reproduction (production of similar cells/organisms from existing ones).
7) All life has maintenance of homeostasis (regulating for a stable interior environment).
8) At the population level, life adapts and changes over time.
Why are viruses not considered living organisms?
A single living cell is capable of carrying out all life functions. In contrast, a virus is a non-living example because it cannot carry out all the processes of life. A virus has a protein coat and, like living organisms, has genetic material (DNA or RNA). However, viruses do not metabolize or reproduce – this function is carried out by the infected host cell. Because they exhibit no properties of life outside the host cell and do not have a cellular structure, viruses are not regarded as living entities.
1 um = ?nm
1000 um =?mm
1000 nm (nanometres) = 1 μm (micrometre)
1000 μm (micrometres) = 1 mm (millimetre)
(The size of a typical animal cell ranges from 10 to 20 μm in diameter.)
Describe the “SAM” Triangle
Why can’t a cell just keep growing?
Just like a balloon, as a cell grows, its volume increases much more than the surface area in the cell. To survive, a cell needs to import molecules and expel waste products through its plasma membrane. If a cell’s surface area is too small compared to its volume, not enough of the necessary molecules can get in, and not enough waste (including heat) can get out.
What is the ratio between Volume and Surface Area (SA:V)?
While volume increases cubically, the surface area increases quadratically.
Cite cell adaptations that can occur to provide more surface area for faster exchange of material.
1 - The folds in a human brain increase the surface area and allow more brain tissue to fit in a smaller area;
2 - The small intestine has small folds that increase the surface area exposed to the digested food. These folds are called villi and are where nutrients are absorbed in the body. The villi increase the surface area and allow more absorption to take place. Additionally, the cells making up the villi have microvilli, which are small folds on their cell membranes that increase the surface area even more. This allows nutrients to be absorbed more efficiently.
Outline the activities occurring in the volume of the cell.
The cell volume is full of cytoplasm in which many metabolic reactions are occurring. The metabolic reactions require reactants (i.e. nutrients and oxygen) and may produce waste (i.e. urea and CO2).
Outline the activities occurring at the surface of the cell.
The cell surface area is the cell membrane, through which reactants and waste enter and leave the cell.
Calculate the surface area, volume, and SA:V ratio of a cube.
Surface area= side length^2
Volume= side length^3
SA:V ratio = [length^2 / length^3]
