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4.1 Cell Biology (4.1.1 Cell Structure (4.1.1.4 Cell Differentiation (As…
4.1 Cell Biology
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4.1.2 Cell Division
4.1.2.1 Chromosomes
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In body cells, the chromosomes are usually found in pairs.
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4.1.2.3 Stem Cells
A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
Functions of Stem Cells
Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
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Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of a plant.
Uses of Stem Cells...
...In Plants
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
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Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
...In Animals
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In therapeutic cloning, an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient's body so they may be used for medical treatment.
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4.1.3 Transport in Cells
4.1.3.1 Diffusion
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Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of low concentration.
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4.1.3.3 Active Transport
Active transport moves substances from a more dilute solution to a more concentrate solution (against the concentration gradient).
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Examples
Allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Plants require ions for healthy growth.
Allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
Summary:
Cells are the basic unit of all forms of life. Structural differences between types of cells enables them to perform specific functions within the organism. These differences in cells are controlled by genes in the nucleus. For an organism to grow, cells must divide by mitosis producing two new identical cells. If cells are isolated at an early stage of growth before they have become too specialised, they can retain their ability to grow into a range of different types of cells. This phenomenon has led to the development of stem cell technology. This is a new branch of medicine that allows doctors to repair damaged organs by growing new tissue from stem cells.