biology

• cells are the building blocks of every organisms on the planet
• all living things are made of cells
• Eukaryotic cells are complex. All animal and plant cells are Eukaryotic
• Prokaryotic cells are smaller and simpler. Bacteria are prokaryotic cells.
• the different parts of a cells are called subcellular structures.
• most animal cells have these subcellular structures: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
• Nucleus - contains genetic material the genetic material controls what the cell does
• Cytoplasm - where most of the chemical reactions happen
• Cell membrane - controls what goes in and out of the cell
• Mitochondria - where most aerobic respiration takes place.
• Ribosomes - these are where proteins are made in the cell
• plant cells usually have all the bits that animal cells have.they also have: cell wall, permanant vacuole, chloroplasts
• A cell wall - made of cellulose. it supports the cell and strengthens it
• A permanent vacuole - contains cell sap
• Choroplasts - where Photosynthesis happens. Photosynthesis makes food for the plant
• Bacterial cells have these subcellular structures: cytoplasm, cell wall, cell membrane, a single loop of DNA. Bacteria don't have a 'true' nucleus, plasmids
• Plasmids - small rings of extra DNA
• light microscopes can be used to look at cells
• Electron microscopes have a higher resolution than light microscopes
• microscope prepare: 1)add a drop of water to the middle of the clean slide, 2)cut up an onion and take one layer off
• microscope using: 3)use tweezers to peel off some epidermal tissue(the clear 'skin') from the bottom of the layer, 4)using the tweezers, place the skin into the water on the slide, 5)add a drop of iodine solution. Iodine solution is a stain. Stains can make different parts of a cell easier to see, 6)Place a cover slip on top. Try not to get any air bubbles under it.
• light microscope: 1)clip the slide onto the stage, 2)select the objective lens with the lowest magnification, 3)use the coarse adjustment knob to move the stage up to just below the objective lens, 4)look down the eyepiece. Move the stage up and down until the image is clear, 5)move the fine adjustment knob, until you get a clear image of what's on the slide, 6) if you want a bigger image, use an objective lens with a higher magnification and refocus
• sperm cells: 1)a sperm cells has a tail to help it swim to the egg, 2)it has a lot of mitochondria. These provide energy for swimming
• sperm cells take the DNA to the egg
• nerve cells carry electrical signals around the body
• nerve cells: 1)nerve cells are long to cover more distance in the body, 2)they have branches at the end to connect to other nerve cells
• muscle cells contract (shorten)
• muscle cells: 1)muscle cells are long so they have space to contract, 2)they have lots of mitochondria. These provide energy for muscle contraction
• root hair cells absorb water and minerals: 1)root hair cells grow into long hairs 2) hairs have large surface area
• phloem cells transport food and xylem cells transport water
• 1)phloem and xylem cells form phloem and xylem tubes, 2) to form the tubes, the cells are long and joined end to end, 3) xylem cells are hollow and phloem cells have very few subcellular structures. so there's lots of space inside the cells for stuff to flow through them.
• chromosomes contain genetic information: 1) the nucleus of a cell contains chromosomes. 2) chromosomes are coiled up lengths of DNA molecules. 3) each chromosomes carries a large number of genes. 4) different genes control the development of different characteristics. 5) body cells normally have two copies of each chromosome. 6) there are 23 pairs of chromosomes in a human cells
• the cell cycle makes new cells: 1) body cells in multicellular organisms divide to make new cells. this is part of a series of stages called the cell cycle. 2) the stages of the cells cycle when the cell divides is called mitosis. 3) multicellular organisms use mitosis to grow and develop
• growth and DNA replication: 1) the cell grows and increases the amount of subcellular structures such as ribosomes and mitochondria. 2) the DNA is replicated so there's one copy for each new cells. 3) the DNA forms X-shaped chromosomes. each 'arm' of the chromosomes is an exact copy of the other.
• Mitosis:(the cell is now ready for dividing) 1) the chromosomes line up at the centre of the cell. 2) the two arms of each chromosome are pulled apart to opposite ends of the cell. 3) this divides the nucleus. 4) each set of chromosomes become the nucleus of a new cell. 5) the cytoplasm and cell membrane divide. 6) the cell has now produced two new cells: they both contain the same DNA-they're identical. they're also identical to the original cell.