biology revision

CELL STRUCTURE

animal and plant cells:

how do we view them? - we use a light microscope to examine, observe and draw scale diagrams of animal or plant cells. we do this by transferring what we are trying to observe onto a slide and placing it under the lense of the microscope. the onbjective lense should be set to low power before hand along with the stage which should be as close as possible to the lense. the slide should be clamped into place using the stage clips so that it is in the centre of the stage where the light passes through. once these steps are complete you then need to make the image clearer by first turning the coarse focus adjustment, straight after which you should draw a low power image before changing the objective lense to the high power setting and using the fine focus adjustment to bring the slide back into view. make sure to label all of your images/diagrams.

contents of a cell - all cells must contain the following: cell membrane, cytoplasm, DNA, and ribosomes. but what are their functions?

cell membrane - controlls what goes in and out of a cell

cytoplasm - a jelly like substance where the chemical reactions in the cell occur

DNA - the genetic material of the cell

ribosomes - site of protein synthesis

there are 2 types of cell: eukaryotic and prokaryotic

eukaryotic cells - Plant and animal cells are both eukaryotic cells. They have the components listed above, as well as others. A defining feature of eukaryotic cells is that their genetic material (DNA) is enclosed within a nucleus

prokaryotic cells - Bacterial cells are a type of prokaryotic cell. A defining feature of prokaryotic cells is that their genetic material is not enclosed within a nucleus, it is found as a single loop of DNA within the cytoplasm. Additional smaller, circular pieces of DNA called plasmids may also be present in prokaryotic cells. The cell membranes of all prokaryotic cells are surrounded by a cellulose cell wall. 

animal cells - they are a type of eukaryotic cell cointaning a nucleus, cell membrane, mitochondria, ribosomes, cytoplasm

mitochondria - powerhouse of the cell, where most of the reactions that are involved in aerobic respiration occur and where energy is produced. usually found in cells with lots of reactions taking place

plant cells - another type of eukaryotic cell containing the same as animal cells along with a cell wall, choloroplasts and a permanent vacuole

cell wall - keeps the cell rigid and gives it support as it is strong and made of cellulose

choloroplasts - contain green chlorophyll pigments that absorb light energy and also contain the enzymes used in photosynthesis

permanent vacuole - contains cell sap, used for the storage of certain materials and helps support the shape of the cell.

SPECIALISED CELLS

specialised cells - cells designed and adapted to carry out a particulare role in the body. they can specialise by undergoing a process known…