Biology: B1 - Cell Structure and Transport Combined Science AQA
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- Biology: B1 - Cell Structure and Transport
- 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 around 0.2nm.
- magnification =size of image size of real object
- Animal and Plant Cells
- Animal cell features common to all cells:
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
- Plant and algal cells contain all the structures seen in animal cells as well as a cellulose cell wall.
- Many plant cells also contain chloroplasts and a permanent vacuole filled with sap.
- Animal cell features common to all cells:
- Eukaryotic and Prokaryotic 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 bu a cell wall.
- The genetic material is not in a distinct nucleus. It forms a single DNA loop.
- Prokaryotes may contain one or more extra small rings of DNA called plasmids.
- Bacteria are all prokaryotes.
- The genetic material is not in a distinct nucleus. It forms a single DNA loop.
- Bacteria are all prokaryotes.
- Specialisation in Animal Cells
- As an organism develops, cells differentiate to form different types of cells.
- As an animal cell differentiates to from a specialised cell it acquires different sub-cellular structures.
- These sub-cellular structures carry out a certain function.
- Examples of specialised animal cells are:
- Nerve cells
- Muscle cells
- Sperm cells
- Examples of specialised animal cells are:
- These sub-cellular structures carry out a certain function.
- As an animal cell differentiates to from a specialised cell it acquires different sub-cellular structures.
- Animal cells may be specialised to function within:
- Tissue
- Organs
- Organ systems
- Whole Organisms
- As an organism develops, cells differentiate to form different types of cells.
- Specialisation in Plant Cells
- Plant cells may be specialised to carry out a particular function.
- Examples of specialised plant cells are:
- Root Hair cells
- Photo synthetic cells
- Xylem cells
- Phloem cells
- Examples of specialised plant cells are:
- Plant cells may be specialised to function in:
- Tissue
- Organ systems
- Whole organisms
- Organs
- Plant cells may be specialised to carry out a particular function.
- Diffusion
- Diffusion is the spreading out of particles of any substance, in a solution or a gas.
- This results in a net movement from an area of higher concentration to an area of lower concentration, down a concentration gradient.
- Dissolved substances such as glucose and urea as well as gases such as oxygen and carbon dioxide, move in and out of cells by diffusion.
- The rate of diffusion is affected by the difference in concentration, the temperature, and the available surface area.
- The rate of diffusion is affected by the difference in concentration, the temperature, and the available surface area.
- Diffusion is the spreading out of particles of any substance, in a solution or a gas.
- Osmosis
- Osmosis is a special case of diffusion.
- Diffusion
- Diffusion is the spreading out of particles of any substance, in a solution or a gas.
- This results in a net movement from an area of higher concentration to an area of lower concentration, down a concentration gradient.
- Dissolved substances such as glucose and urea as well as gases such as oxygen and carbon dioxide, move in and out of cells by diffusion.
- Diffusion is the spreading out of particles of any substance, in a solution or a gas.
- 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.
- Diffusion
- Animal cells can be damaged if the concentration outside the cell changes dramatically.
- Differences in the concentration of solutions inside and outside a cell cause water to move into or out of the cell by osmosis.
- 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.
- Osmosis is a special case of diffusion.
- Osmosis in Plants
- Osmosis is important to maintain turgor in plant cells.
- Osmosis is a special case of diffusion.
- Osmosis is a special case of diffusion.
- There are a variety of practical investigations that can be used to show the effect of osmosis on plant tissues.
- Salt and sugar
- Potato
- Sweet potato and beetroot
- Osmosis is important to maintain turgor in plant cells.
- Active Transport
- Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient).
- Active transport uses energy released from food in respiration to provide the energy required.
- Allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in the soil against the concentration gradient.
- Enables sugar molecules used for cell respiration to be absorbed from a lower concentration in the gut into the blood where there is a higher concentration.
- Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient).
- Exchanging Materials
- Single-celled organisms have a relatively large surface area to volume ratio so all 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 or, for gaseous exchange, be ventilated.
- The World of the Microscope
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