Cell Biology

• There are two types of cells, eukaryotes and prokaryotes
• The nucleus contains of genetic material and controls cell activity
• The cytoplasm is a gel like substance where most chemical reactions happen, it contains enzymes
• The cell membrane allows certain substances to enter and leave cell
• The mitochondria is the site of aerobic respiration
• Ribosomes are the site of protein synthesis
• A Cell wall is made of cellulose and provides structure and support for the cell
• The large permanent vacuole contains cell sap to keep the cell turgid
• Chloroplasts is the site of photosynthesis and contains chlorophyll
• There are two types of microscopes light and electron. Electron microscopes have a higher magnification and resolution and have 3D images that are black and white
• Magnification is equal to image size over real size
• To prepare a slide, add a drop of water on the slide and add epidermal tissue. Add iodine as a stain and place a cover slip carefully so air bubbles do not form
• Clip the slide onto the stage and select the lowest objective lens and use the coarse adjustment knob to move stage below the lens and adjust till image is roughly in focus. Adjust the focus using the fine adjustment knob and change objective lens if greater magnification is needed
• When drawing a diagram, the lines should be clear an unbroken with no shading. It should be drawn in proportion with labels and a title as well as the magnification
• Differentiation is the process by which a cell becomes specialised for a function. Undifferentiated cells are known as stem cells
• Sperm cells contain genetic information for fertilisation and has mitochondria to provide energy. It also has a tail to enable movement
• Nerve cells have a long axon to carry impulses over a long distance and are branched to pass signals. They're insulated with a fatty sheath to help impulses move quickly
• Muscle cells have a lot of mitochondria to provide energy for contraction and protein filaments to slide over other cells
• Root hair cells have a concentrated vacuole to provide a water potential gradient and lots of mitochondria to provide energy for active transport. There is also an elongated cell membrane for good absorbtion
• Xylem cells are responsible for transpiration they have dead and hollow walls and no top and bottom cell walls. It is unidirectional
• Phloem cells transport cell sap and are joined by sieve plates. Phloem is made of living cells
• Chromosomes are long strands of DNA wrapped in histones. There are 23 pairs of chromosomes in a nucleus
• In mitosis, the cell grows and sub cellular organelles replicate along with DNA. Chromosomes are pulled by cell fibres to opposite ends of the cell and a membrane forms around each set. The cytoplasm and cell membrane divide to form two identical daughter cells
• In binary fission, Nucleoid and plasmids replicate and the cell gets bigger and Nucleoids go to opposite poles. The cytoplasm and cell wall begin to divide
• Bacteria can be grown in a culture medium containing carbohydrates, minerals, proteins and vitamins. The medium is either agar jelly or a nutrient broth solution. The agar jelly is put in a petri dish and an inoculating loop is used to transfer microorganisms. In schools, cultures are kept at 25 degrees whilst in labs they are kept at higher temperatures
• To test the effect of antibiotics, paper discs can be soaked and placed on the petri dish with an even covering of bacteria. This will cause an inhibition zone to form. Sterile water can be soaked on placed on the dish as a control variable. The more effective, the larger the inhibition zone
• To prevent contamination, culture medium can be sterilised by heating at high temperatures, the inoculating loop can be passed through a flame, the lid can be secured by tape to prevent microorganisms from the air to come in and stored upside down to prevent drops of condensation
• A donor egg cells nucleus is removed and a body cell's nucleus is removed and added to an egg cell to prevent rejection
• Therapeutic cloning can help heal paralysis and diabetes
• Adult stem cells can only differentiate into cells associated with the tissue
• Embroyonic stem cells can differentiate into any cells
• Meristem cells can differentiate into any cell and can prevent extinction, grow plant economically and retain desired features
• Diffusion is the net movement of particles from a high to low concentration
• Osmosis is the net movement of water particles between a partially permeable membrane from a high to low concentration
• Active Transport is the movement of particles from a low to high concentration, it is an active process which requires energy
• Using a cork beaker, attempt to create 5 identical potato cylinders and use a ruler to make them the same size and record their weight. Get 5 beakers and fill them with distilled water, 0.2 mol, 0.4 mol, 0.6 mol, 0.8 mol, 1 mol. Place one potato in each and leave them for a day. Osmosis would have either drawn water in or out. When drawn on a graph, use percentage change and plot them on the graphs. Where it intersects at 0 means there is no change in mass and therefore no osmosis has occurred so it is the concentration of the potato.
• The small intestine is adapted for the absorption into blood. The small intestine has projections called villi which increase the surface area with each one having a single layer of surface cell for a short diffusion distance and a network of capillaries to provide a concentration gradient
• Alveoli provide a large SA and have a moist lining for dissolving gases. They have thin walls for a short diffusion distance and have a good blood supply to maintain a concentration gradient
• Gills have filaments covered in lamellae to provide a large SA. There is also a capillary network and a thin layer of cells. Blood also flows in the opposite direction to maintain a concentration gradient
• In leaves, the underside is covered in stomata to allow CO2 to enter and O2 and H2O to leave. Guard cells close the stomata to prevent wilting and control water loss and air spaces increase area where gas exchange occurs