Edexcel: Additional Biology (B2)

There's an awful lot of information which you need to retain in Additional Science. This slideshow is based solely on Biology, covering the contents of Edexcel's exam board material. I have also included a few past paper exam questions, to give you a little insight of what to expect in the exam, and what the questions may want you to include in your answer. 

EDEXCEL: ADDITIONAL BIOLOGY (B2)

Animal Cells

In an animal cell, there are four features you need to know. You will also need an understanding of the definition of each feature, so here they are!: Cell Membrane - the cell membrane separates the contents of the cell from its surroundings. The cell membrane also controls the movement of different substances such as oxygen, carbon dioxide and glucose into and out of the cell. Cytoplasm - at the cytoplasm, chemical reactions which are essential for human processes occur. The cytoplasm also contains organelles (organelles are tiny structures which carry put specific jobs).Mitochondria - this is where most energy is released by respiration. It's very hard to see mitochondria in animal cells under a light microscope at low magnification as they are very tiny.Nucleus - the nucleus contains genetic information for the cell, which also controls activities of the cell. 

Image of an animal cell

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Caption: : A generalised animal cell. You could be asked in an exam to label a part of an animal cell.

Plant cells compared to animal cells

Plant cells contain a nucleus, a cell membrane, a cytoplasm and mitochondria too, however there are a few features only plant cells have. These are:Cell wall - the cell wall strengthens/supports a plant cell, and is made of tough cellulose. This also allows the cell to keep its shape.Chloroplasts - chloroplasts contain chlorophyll, a green substance which absorbs light energy used in photosynthesis. Large/permanent vacuole - this is a space in the cytoplasm which is filled with cell sap and helps support the plant by keeping cells turgid and rigid.

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Caption: : An animal cell compared to plant cell (mitochondria is not included in this diagram, but it is in a plant cell nevertheless).

Microscopes

Hans and Zaccharias Janssen were credited with the invention of the first microscope. Early microscopes could not magnify to a great extent, but scientists have worked hard to improve this. In fact, now, the best modern light microscopes can magnify specimens more than 1,500 times. Microscopes have allowed scientists to identify cell structures in much greater detail. Magnification calculationsTo calculate the length of magnified object:Length of magnified object = length of object  × magnificationAnd then, by knowing this formula, we can rearrange it to get the length of an object:Length of an object = length of magnified object ÷ magnification