B1 Cells and Organisation

• light microscopes can magnify up to about x2000 and have a resolving power of about 200mm
• electron microscopes magnify up to about x2000000 and have a resolving power of about 0.2nm
• magification = image size/ real size
• an electron microscope uses electrons instead of light to form images
• a light microscope uses lenses made out of glass or plastic to focus visible light onto an object
• the nucleus control all the activities of the cell and contains DNA
• cytoplasm is where chemical reactions take place within the cell
• cell membrane controls what enters and leaves the cell, it is selectively permeable
• mitochondria are responsible for respiration which produces energy
• mitochondria are responsible for respiration, producing energy from glucose
• ribosomes make proteins
• chloroplasts contain chlorophyll which absorbs sunlight during photosynthesis
• a permanent vacuole is filled with cell sap storing water and waste products
• chloroplasts contain chlorophyll that absorbs sunlight during photosynthesis
• the nucleus contains genetic material (DNA)
• a permanent vacuole in a plant cell is a space in the cytoplasm filled with cell sap
• eukaryotic cells have a nucleus whereas prokaryotic cells do not
• prokaryotic cells' DNA is not enclosed in a nucleus and float in the cell freely (they are called plasmids)
• Bacterial cells use their flagella to move themselves around (long protein strands)
• As an organism develops, cells differentiate to form different types of specialised cells
• Most types of animal cells differentiate at an early stage of development, while many types of plant cells have to ability to differentiate at any stage in their life.
• nerve cells have adapted by having lots of dendrites to make connections with other nerve cells. 
• adaptations of nerve cells include an axon that carries the nerve impulse from one place to another. They can be very long e.g. your longest axon can be found from the base of your spine to your big toe. 
• muscle cells have adapted by having many mitochondria to transfer the energy needed for the chemical reactions that take place as the cells contract and relax.
• muscles can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer the energy needed for the muscles to contract. 
• muscles have special proteins that slide over each other making the fibres contract 
• sperm cells have a long tail that whips side to side to help the sperm move through the water in the female reproductive system
• in sperm cells the middle section is full of mitochondria, which transfer the energy needed for the tail to work. 
• in the sperm cell the acrosome stores the digestive enzymes for breaking down the outer layers of the egg 
• photosynthetic cells have specialised green structures called chloroplasts that have the chlorophyll needed to trap the light used for photosynthesis.
• Xylem is the transport in plants that carries water and mineral ions from the roots to the highest leaves and shoots
• Phloem cells are a specialised transport tissue that carries the food made by photosynthesis around the body of the plant.
• in phloem cells, the cell walls in between the cells break down to form special sieve plates, these allow water carrying dissolved food to move freely up and down the tubes to where it is needed. 
• phloem cells are are supported by companion cells that help keep them alive, the mitochondria of the companion cells transfer energy needed for the cell to be able to move dissolved food up and down the cell.
• mitochondria helps the sperm do its job by providing energy from respiration to the tail so it can flick from side to side and swim for long periods of time
• all plant cells' walls are made out of cellulose because it helps the plant remain stiff, rigid and strong
• the bacterial chromosome in a bacterial cell is found as a single DNA loop floating free in the cytoplasm
• nerve cell endings/ synapses are adapted to pass the impulses to another cell or between a nerve cell and a muscle in the body using special transmitter chemicals, they contain lots of mitochondria to provide the energy needed to make transmitter chemicals
• muscle cells are specialized cells that can contract and relax. striated (striped) muscle cells work together in tissues called muscles. muscles contract and relax in pairs to move the bones of the skeleton. smooth muscle layers also form one of the layers of tissue in your digestive system and they contract to squeeze food through your gut
• you find root hair cells close to the tips of growing roots (the meristem). plants need to take in lots of water and dissolved mineral ions, the root hair cells help the plant get this stuff more efficiently