AS OCR Biology - Chapter 1 - Cell Structure Notes on first chapter of AS OCR Biology. 4.0 / 5 based on 3 ratings ? BiologyCellular processes and structureASAll boards Created by: AliceCreated on: 14-05-11 13:30 Cell Organelles - Nucleus Nucleus - Only a few eukaryotes without nucleus; RBC's, phloem, etc. Contains chromosomes - form tangle known as chromatin. DNA carries code that instrucs cells about making proteins. Nuclear Envelope - pair of membranes with gaps inbetween - gaps in envelope are nuclear pores. Nucleolus - contains DNA being used to make ribsomes. 1 of 10 Cell Organelles - Endoplasmic Reticulum Smooth Endoplasmic Reticulum - no ribosomes not joined to nuclear envelope Rough Endoplasmic Reticulum - coverered in ribsomes usually joined to nuclear envelope Cisternae - enclosed spaces formed by membranes. 2 of 10 Cell Organelles - Golgi Apparatus Golgi Apparatus - Not stable, always moving and changing. Sacs join and break away all the time. Used in protein synthesis. Protein Synthesis Overview - Protein made by ribosomes of RER. Vesicles carry protein and join to Golgi. Protein modified in Golgi, e.g. sugars added. Vesicles carry modified proteins. Secretion from cell by exocytosis. 3 of 10 Cell Organelles - Lysosomes Lysosomes - Tiny bags of digestive enzymes. 0.5 micrometre diameter. Used for digestion - by fusion with bacteria, old/worn out organelles etc. Enzymes in lysosome break down large molecules into soluble substances. Substances disperse into the cytoplasm. 4 of 10 Cell Organelles - Mitochondia Mitochondria - Site of aerobic respiration. ATP made in them. Lots of mitochondria in places where lots of energy is needed, e.g. muscle cells. Each cell makes its' own ATP as it has to provide own energy. Double membrane - inner membrane folded to form cristae. Matrix is background material. 5 of 10 Cell Organelles - Plasma (Cell Surface) Membrane Plasma (Cell Surface) Membrane - Thin layer of phospholipid molecules. Phospholipids - Hydrophobic tails (water-hating). Hydrophilic heads (water-loving). Tails closest together, heads on outside. 6 of 10 Cell Organelles - Centrioles Centrioles - Make and organise microtubules made of tubulin. Microtubules form spindle to move chromosomes in cell division. 7 of 10 Cell Organelles - Cytoskeleton Cytoskeleton - Network of microfilaments. Gives cell mechanical strength. Provides 'tracks' for organelles to move along. ATP needed, because energy needed to pull organelles. Can help whole cell to move. 8 of 10 Prokaryotic Cells Prokaryotic Cells - Always contain - Circular DNA (no nucleus) - sometimes referred to as chromosome. Peptidoglycan cell wall - crosslinked peptidoglycan. ~20nm ribsomes - smaller than eukaryotic ribsomes. Cytoplasm. Plasma membrane. Sometimes contain - Pili - attachment to other cells or surfaces. Plasmid of DNA - several may be present. Capsule - additional protection. Mesosome - associated with DNA during cell division. Infolded plasma membrane - photosynthetic membrane. Flagellum - movement of cell. 9 of 10 Microscopes Light - 1400 x mag. Use glass lenses to refract light rays. Living specimens. Cheap. Unable to show objects smaller than 200nm across. Electron - TEM - pass electrons through thin specimen. Very thin specimens, and stained. 300,000 x mag. Much finer detail - better resolution. Dead specimens. MAGNIFICATION = IMAGE SIZE / ACTUAL SIZE 10 of 10
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