Patterns in Nature Summary

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Patterns in Nature
1. Organisms are made of cells that have similar structural characteristics * Outline the historical development of the cell theory, in particular the contributions of Robert Hooke and Robert Brown Robert Hooke was the first person to observe a cell through a compound microscope in 1665. Franscesco Redi used a microscope to observe that flies do not spontaneously appear but develop from eggs laid by other flies. Many years later, Robert Brown observed a large body in both animal and plant cells that he named the nucleus. M. Schleiden and T. Schwann came up with the first two points of cell theory; 1. Cells are the smallest units of life and 2. All living things consist of one or more organised structures called cells. Rudolf Virchow later added the third point to the cell theory; 3. All living things arise from pre-existing cells. * Describe evidence to supports the cell theory

* Discuss the significance of technological advances to developments in the cell theory

* Identify cell organelles seen with current light and electron microscopes In light microscopes the organelles that could be seen were cell wall, cytoplasm, nucleus, nucleolus, chloroplast, water vacuole and cell membrane. * Describe the relationship between the structure of cell organelles and their function

2. Membranes around cells provide separation from and links with the external environment * Identify the major groups of substances found in living cells and their uses in cell activities The major group of substances found in living cells are carbohydrates, lipids, proteins and nucleic acids. Carbohydrates are used as nutrients for cells, cellular respiration, provide energy for the body to function and live off, give structure to cell walls and store glucose. Lipids are a structural component of cell membrane and modulator of cell activity. Proteins regulate the immune system and signal pathways. Nucleic acids are used for the growth repair and reproduction of cells and are also used in DNA and RNA. * Identify that there is movement of molecules into and out of cells Passive transport is the movement of molecules across the cell that doesn’t require expenditure of energy. Active transport on the other hand is the movement of molecules across cell membranes requiring energy and proteins that act as carriers * Describe the current model of membrane structure and explain how it accounts for the movement of some substances into and out of cells

The cell membrane is mainly composed of integral proteins and lipid bilayer. The phospholipids form a bilayer with the hydrophilic head facing outwards and the hydrophobic tails facing inwards. This model for the cell membrane is called the fluid mosaic model. The fluid mosaic model demonstrates the semi permeable nature of membrane. Polar molecules have trouble passing though non-polar parts of the membrane but can easily pass through the polar parts of the membrane, therefore to move through the membrane they require protein channels to provide a path through it. Water molecules pass through pores in the lipid and protein channels allow certain substances pass through the membrane; once the molecule enters the protein channel; the protein undergoes a conformational change so that the molecule can pass through.

* Compare the processes of diffusion and osmosis
Diffusion is the movement of molecules from an area of high concentration to an area of low concentration whereas osmosis is the movement of water across a semi-permeable membrane from an area of high concentration to an area of low concentration; they both use passive transport * Explain how the surface area to volume ratio affects the rate of movement of substances into and out of cells All nutrients and gases needed by a cell have to pass across the cell membrane as do all waste materials when leaving the cell. The requirements of a cell can quickly outstrip the rate at which the...
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