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24 Cards in this Set
- Front
- Back
outline cell theory |
• All living organisms are composed of cells, and the products of cells (e.g. hair and scales) |
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discuss the evidence for cell theory
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1590- The Dutch optician Zacharias Jansen invents the compound microscope. A compound microscope has 2 lenses which provide greater magnification |
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unicellular organisms carry out all functions of life, what are they?
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• metabolism which includes respiration and excretion |
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what is the approximate size of a Eukaryotic cell?
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10 - 100µm
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what is the approximate size of a Prokaryotic cell?
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1 - 5µm
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what is the approximate size of a Nucleus?
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10 - 20µm
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what is the approximate size of a Chloroplast?
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2 - 10µm
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what is the approximate size of a Mitochondrion?
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0.5 - 5µm
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what is the approximate size of
Bacteria? |
1 - 4µm |
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what is the approximate size of a large virus? (HIV)
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100nm
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what is the approximate size of a Ribosome?
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25nm
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what is the approximate size of a cell membrane? |
7.5nm thick
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what is the approximate size of a DNA Double Helix?
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2.5nm diamater
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what is the approximate size of a Hydrogen Atom?
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0.1nm
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what is the equation used to calculate the real size of an image?
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magnified size ÷ magnification
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explain the importance of the surface area to volume ratio as a factor limiting cell size
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The size of a cell is limited by its need to exchange materials with its environment. If a cell becomes too large, its diffusion distances becomes too long to be efficient and its surface to volume ration becomes too small to allow for the necessary exchange. |
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how can organisms deal with the problem of the surface area to volume ratio?
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By protruding extensions, or by flattening the cell. (e.g. a circulatory system - blood carries materials round the body, reducing the diffusion distance).
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multicellular organisms show emergent properties, but what does this mean?
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Emergent properties are those where the whole is more than the sum of their parts. This is caused by the fact that cells interact, allowing them to perform tasks together that they would not achieve, even in part, if they were alone
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Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.
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Cells differentiate by expression of some of their genes but not others. The genes which are not expressed by the cell, remain present in the nucleus but are packed away so tightly that they cannot be accessed. |
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How are stem cells different from normal cells?
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1. Stem cells are undifferentiated. This means that they have not yet specialised into a certain type of cell, as a result all (or most) of their genes can still be expressed. |
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What are totipotent stem sells?
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Cells that can become any type of cell (e.g. embryo)
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What are pluripotent stem cells?
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Cells that can become almost any type of tissue (e.g. blastocyst) |
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What are multipotent stem cells?
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Cells that can become a limited number of other particular types of cells (e.g. bone marrow)
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Outline a therapeutic use of stem cells.
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1. Also known as cell therapy, the most common example is a bone marrow transplant, which has been used for more than 40 years. Cells in the bone marrow produce blood cells, and people with leukemia can receive a transplant of healthy, functioning bone marrow which may cure their disease. |