Biology AQA 3.1.3 Cells

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Unit 1 Biology, Aqa specification 3.1.3

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Question Answer
Structure of an epithelial cell from the small intestine. quest24a.jpg (image/jpg)
images.jpg (image/jpg) PLASMA MEMBRANE: Appearance: found on the surface of animals cells and inside the wall of plant cells and prokaryotic cells. It is made up of proteins and lipids. Function: regulates movement of substances in and out of cells. it also has receptors which responds to hormones and chemicals.
villi2.gif (image/gif) MICROVILLI: Appearance: These are folds in the plasma membrane Function: Involved in processes like absorption and they increase the surface area of the plasma membrane
0318_Nucleus.jpg (image/jpg) NUCLEUS: appearance: A large organelle surrounded by a nuclear envelope( double membrane) It contains many pores and the nucleus contains chromatin and often a nucleolus Function: Chormatin is made from proteins and this makes up DNA which controls the cells activities. The pores allow substances to move in and out and the nucleus makes ribosomes.
cell_lysosome1.gif (image/gif) LYSOSOME: Appearance: A round organelle surrounded by a membrane with no clear internal structure. Function: Contains digestive enzymes and are used during phagocytosis and they digest invading cells or break down worn components of the cell.
cell_ribosome3.jpg (image/jpg) RIBOSOME: Appearance: A small organelle that floats free or is attached to a rough endoplasmic reticulum. Function: This is the site where proteins are made.
download.jpg (image/jpg) ENDOPLASMIC RETICULUM: Appearance: SMOOTH: system of membranes enclosing a fluid filled space ROUGH:Is similar to smooth but is covered in ribosomes. Function: SEM synthesises and processes lipids. REM folds and processes proteins that have been made by ribosomes.
download__1_.jpg (image/jpg) GOLGI APPARATUS; Appearance: A group of fluid filled flattened sacs. Function: Processes and packages new lips and proteins. It also makes lysosomes.
download__2_.jpg (image/jpg) MITOCHONDRION: Appearance: They have a double membrane and the inner membrane is folded to form cristae, inside this is the matrix which contains enzymes involved in respiration. Function: The site of aerobic respiration. Found in large numbers are active and require lots of energy.
Prokaryote: Before nucleus Eukaryote: After Nucleus
Transmission Electron Microscopes Electrons are fired onto the specimen which then absorbs electrons. this then causes an image to be produced on a screen *The whole thing must be in a vacuum *A complex staining process *Image is black and white * Specimen must be thing *Image might contain artefacts Scanning Electron Microscopes Same limitations as a transmission. However the specimen doesnt need to be thin as a 3D image can be produced.
Magnification: Magnification= Size of image/ size of object M= I/o (MILO) Resolution: The minimum distanceof two objects for them to appear seperate
Cell Fractionation: the process where cells are broken up in a c cold, isotonic and buffered solution. Cold: Reduce enzyme activity Isotonic: To prevent organelles bursting or shrinking Buffered: to maintain a constant PH
Ultracentrifugation: Process by which fragments are seperated. 1. The tube is spun at a slow speed. 2. The heaviest organelles (the nucleus) are forced to the bottom of the tubes, they then form a sediment. 3. The fluid at the top is removed leaving the nucleus 4. the fluid is then spun again and the heaviest sinks and the organelles continue to be seperated