- Created by: Mya Lane
- Created on: 20-01-20 11:40
B1.1 The world of the microscope.
- Light microscopes magnify up to about x2000, and have a resolving power of about 200nm.
- Electron microscopes magnify up to about x2,000,000 and have a resolving power of about 0.2nm.
- Resolving power affects how much detail the microscope can show.
- magnification= size of image / size of real object.
- The microscope consists of a stage, slide, light, coarse focus, fine focus, eyepiece and an objective lens.
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B1.2 Animal and plant cells.
- Animal cells contain a nucleus, cytoplasm, mitochondria, ribosomes and cell membrane.
- nucleus- controls all the activities of the cell and is surrounded by the necleus membrane and they contain the genes on the chromosomes.
- cytoplasm- Where most of the chemical reactions needed for life take place.
- cell membrane- controls the substances that enter and leave the cell.
- mitochondria- Where aerobic respiration takes place.
- ribosomes- These make the proteins for the cell.
- Plant cells contain a cell membrane, ribosomes, cellulose cell wall, mitochondria, cytoplasm, permanent vacuole, chloroplasts and a nucleus.
- chloroplasts- they contain chlorophyll which makes food by photosynthesis.
- permanent vacuole- This is important for keeping the cells rigid to support the plant.
- Animal and plant cells both have a nucleus, cytoplasm, cell membrane, ribosomes, mitochondria,
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B1.3 Eukaryotic and prokaryotic cells
- The difference between a eukaryotic cell and a prokaryotic cell is that eukaryotic cells have a nucleus but prokaryotic cells don't.
- Eukaryotic cells contain a cell membrane, cyptoplasm and gentetic material in the nucleus.
- Prokaryotic cells contain cyptoplasm and a cell membrane surrounded by a cell wall and the genetic material is formed as a single DNA loop.
- prokaryotic cells can contain extra loops of DNA called plasmids.
- Bacteria are all prokaryotes and they have a protective slime capsule and others have flagella.
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B1.4 Specialisation in animal cells
- As organisms develop, cells differentiateto form different types of cells.
- As an animal cell differentiates to form a specialised cell, it acquires different sub-cellular structures to enable it to carry out a certain function.
- Examples of specialised animal cells are nerve cells, muscles cells and sperm cells.
- Animal cells may be specialised to function within a tissue, an organ, organ systems, or whole organsims.
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B1.5 Specialisation in plant cells
- Some plant cells are specialised to carry out a particular function.
- Examples of specialised plant cells are root hair cells, photosynthetic cells, xylem cells and phloem cells.
- Plant cells may be specialised to function within tissues, organs, organ systems, or whole organisms.
- Root hair cells- a large surface area to allow water to move into the cell, mitochondria to transfer the energy needed for the active transport of mineral ions into the root hair cells.
- Photosynthetic cells- they contain chloroplasts which contain chlorophyll to trap the light needed for photosynthesis. They have a large permanent vacuole that helps keep the cell rigid
- Xylem cells- xylem tissue supports the cell and it transfers water and mineral ions from the roots to the stem and leaves.
- Phloem- a tissue that transports food made by photosynthesis to the rest of the plant.
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- Diffusion is the spreading out of particles of any substance, in solution or a gas, rsulting in a net movement from an area of high concentration to an area of low concentration, down a concentration gradient.
- The rate of diffusion is affectedd by the difference in concentrations, temperature and the available surface area.
- An increase in temperature causes the particles to move faster, which also increases the rate of diffusion.
- Examples of diffusion: oxygen and carbon dioxide in opposite directions in the lungs, known as gas exchange. The diffusion of oxygen and glucose into the cells of the body from the bloodstream for respiration.
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- Osmosis is a special case of diffusion. It is the movement of water from a dilute to a more concentrated solution through a partially permeable membrane that allows water to pass through .
- Differences in the concentrations of the solutions inside and outside a cell cause water to move into or out of the cell by osmosis.
- Animal cella can be damaged if the concentration outside the cell changes dramatically.
- If the solution around animal cells is hypertonic then water moves out of the cells and they shrink.
- If two solutions have the same concentrations they are Isotonic
- If a solution is more concentrated (has more solute and relatively less water) is Hypertonic.
- The solution that is more dilute (has relatively more water and less solution) is Hypotonic.
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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 effects of osmosis on plant tissues.
- Turgor pressure occurs when no more water can enter a cell due to the pressure inside.
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B1.9 Active transport
- Active transport moves substances from a more dilute solution to a more concentrated (against a concentration gradient).
- Active transport requires energy from respiration.
- Active transport allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil against a concentration gradient.
- 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
- Materials such as oxygen and soluble food molecules need to reach all cells, and metabolic waste materials must be removed efficiently.
- Single celled organisms have a relatively large surface area to volume ratio so all necessary exchanges with the invironment can take place over this surface.
- In multi-cellular organisms, many organs are specialised with effective exchange surfaces.
- Exchange surfaces usually have a large surface area and thin walls, which give short diffusion distnaces.
- In animals, exchange surfaces will have an efficient blood supply or, for gaseous exchnage, be ventilated.
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