- Created by: maddieecarr
- Created on: 25-11-19 16:11
B1.1 The World of the Microscope
- Light microscopes magnify up to x2000 and have a resolution of around 200nm.
- Electron microscopes magnify up to x2000000 and have a resolution of 0.2nm.
- magnification = size of image/ size of real object.
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B1.2: Animal and Plant Cells
- Animal cell features common to all cells: cytoplasm, cell membrane, mitchondria and ribosomes.
- Plant and algal cells contain the structures seen in animal cells as well as a cellulose cell wall.
- Many plant cells also contain choloroplasts and a permanent vacuole filled with sap.
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B1.3: Prokaryotic and Eukaryotic cells
- eukaryotic cells all have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus.
- prokaryotic cells consist of cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not in a distinct nucleus and may form a single DNA loop. Prokaryotes may contain one or more extra small rings of DNA called plasmids.
- bacteria are all prokaryotes.
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B1.4: Specialisation in Animal Cells
- as an organism develops, cells differentiate to form different types of cells.
- as an animal cells differentiates to form a specialised cell, it acquires different sub-cellular structures to enable it to carry out a certain function
- examples of specialised cells are nerve, muscle and sperm cells
- animal cells may be specialised to function within a tissue, organ, organ system or whole organism.
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B1.5: Specialisation in Plant Cells
- plant cells may be specialised to carry out a particular function.
- examples of specialised plant cells are root hair, photosynthetic, xylem and phloem cells.
- plant cells may be specialised to function within tissues, organs, organ systems, or whole organisms.
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- diffusion is the spreading out of particles of any substance, in a solution or a gas, resulting in a net movement of particles from a high concentration to a low concentration down a concentration gradient.
- the rate of diffusion is affected by difference in concentrations, temperatures and available surface area.
- dissolved substances such as glucose, urea, oxygen and carbon dioxide move in and out of cells by diffusion.
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- osmosis is a special case of diffusion.
- it is the movement of water from a dilute to a more concentrated solute solution through a partially permeable membrane that allows water to pass through.
- differences in the concentrations of solutions inside and outside a cell cause water to move into or out of the cell through osmosis.
- animal cells can be damaged if the concentration outside the cell changes dramatically.
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B1.8: Osmosis in Plants
- osmosis is important to maintain turgor in plant cells.
- there are a variety of practical investigations that can be used to show the effect of osmosis on plant tissues.
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B1.9: Active Transport
- active transport moves substances from a dilute solution to a more concentrated solution against the concentration gradient.
- active transport uses energy released from food in respiration to provide the energy required.
- active transport allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil.
- active transport enables sugar molecules used for cell respiration to be absorbed from lower concentrations in the gut into the blood where the concentration of sugar is higher.
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B1.10: Exchanging Materials
- single-celled organisms have a large surface area to volume ration so all the necessary exchanges with the environment take place over this surface.
- in multicellular organisms many organs are specialised with effective exchange surfaces.
- exchange surfaces usually have a large surface area and thin walls, which give short diffusion distances.
- In animals, exchange surfaces will have an efficient blood supply and/or be well ventilated.
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