Topic 1 - Cell Biology

Question	Answer
What is a Prokaryote?	A single celled organism (bacteria).
What is a Eukaryote?	An organism made up of complex cells (animal/plant).
Name all of the subcellular strucures of an animal cell?	1. Nucleus - Contains genetic material. 2. Mitochondria - Site of aerobic respiration. 3. Cytoplasm - Site of most chemical reactions and enzymes. 4. Cell membrane - Controls what goes in and out of the plant. 5. Ribosomes - Make proteins.
Name all the subcellular structures of a plant cell?	All of the animal cell and: 1. Rigid cell wall - Made of cellulose and supports/strengthens the cell. 2. Chloroplasts - Site of p.syn and contains pigment called chlorophyll that absorbs light. 3. Permanent vacuole - Contains cell sap, a weak solution of sugar and salt.
Name all the sub cellular structures of a bacteria cell?	1. Cell membrane. 2. Cytoplasm. 3. Cell wall. 4. Single circular strand of DNA. 5. Small rings of DNA called plasmids.
What is the formula for magnification?	Magnification= Image size/Real size.
How do you convert micrometers to millimetres?	Divide by 1000.
What is differentiation?	Differentiation is the process by which a cell changes to become specialised for its job.
How are sperm cells specialised for reproduction?	Sperm cell - Long tail for swimming, lots of mitochondria to provide energy, carries enzymes in head to digest egg membrane.
How are nerve cells specialised for rapid signalling?	Nerve cells - Long to cover large distance, branched connections allow ends to connect and form a network.
How are muscle cells specialised for contraction?	Muscle - Long for space to contract, lots of mitochondria to generate energy for contraction.
How are root hair cells specialised for mineral and water absorption?	Root hair cell - Big surface area for absorbing.
How are phloem and xylem cells specialised for transporting substances?	Phloem and Xylem cells - Long and joined end to end to form tubes, xylem are hollow and phloem have few subcellular structures so substance can flow through.
What is a stem cell?	Stem cells are undifferentiated so can deferentiate into different types of cells. Stem cells are found in early embryos (embryonic) and in adult bone marrow. However adult stem cells can only change into one type of cell. They can be grown in a lab and made to differentiate into specialised cells to use in medicine/research.
How can stem cells cure a disease?	1. Healthy bone marrow containing stem cells replace faulty blood cells. 2. Insulin producing cells for diabetes, nerve cells for paralysis etc.
Why are some for/against stem cell research?	1. Potential human life. 2. More important to cure those who already 'exist'. 3. Could use unwanted ones from fertility clinics so less wasteful.
What are stem cells in plants (meristems) used for?	Stem cells are found in meristems. Produce clones of plants quickly and cheaply. Produce more of a rare species. Farmers grow identical crops with desirable features.
What are chromosomes?	Chromosomes are coiled up lengths of DNA molecules. Each one contains genes that determine characteristics. There are 23 pairs of chromosomes.
Explain the process of mitosis?	1. the cell duplicates its DNA. 2. the chromosomes line up in the centre of the cell and the cell fibres pull them apart so each arm is at opposite sides of the cell. 3. membranes form around each set and these become the nulei of each cell. (the nucleus has divided.) 4. the cytoplasm and cell membrane also divide to produce two identical daughter cells.
Explain the process of binary fission (prokaryotes replace by this)?	1. the circular DNA and plasmids replicate. 2. the cell gets bigger and the circular DNA strands move to each end of the cell. 3. the cytoplasm begins to divide and two cell walls begin to form. 4. the cytoplasm divides and two daughter cells are produced. Each daughter cell has a single strand of DNA and can have a varied number of copied plasmids.
What is diffusion?	Diffusion is the spreading out of particles from and area of high concentration to an area of low concentration.
How does surface area affect the rate of diffusion?	The larger the surface area the, the faster the rate of diffusion as more particles can pass through at once.
What is a cell membrane?	The cell membrane holds a cell together but lets stuff in and out via diffusion/osmosis. Only very small molecules can diffuse through a cell membrane (not starch and proteins).
What is osmosis?	Osmosis is the movement of water molecules across a semi-permeable membrane from a region of high water concentration to a region of low water concentration.
How do you make sure your bacteria cultures are uncontaminated?	1. the Petri dish must be sterilised to kill unwanted microorganisms. 2. the inoculating loop should pass through a hot flame. 3. after transferring the bacteria the lid should be lightly tapped on to stop microorganisms in the air from getting in. 4. Petri dish should be stored upside down to stop condensation dripping onto agar jelly. Not stored above 25oC.
What is active transport?	Active transport is the process by which dissolved molecules move across a semi-permeable membrane from a lower to higher concentration, against the concentration gradient so it needs energy.
Give two examples of when active transport is needed?	Root hairs - low conc of minerals in soil to high conc in roots. Needs energy from respiration in mitochondria. Gut - sometimes low conc of glucose/amino acids in gut so goes into blood against the conc gradient.
How has the alveoli adapted for a gas exchange?	Large surface area more diff at once, moist lining for dissolving gases, thin walls for shorter diff dist, good blood supply for carrying material to/away quickly.
How has the villi adapted for nutrient exchange?	Thin walls, large surface area, good blood flow.
How has the leaf adapted for the exchange of substances?	Stomata allows gases in and out, guard cells efficiently stop water from being lost, flat shape increases surface area, air spaces increase contact with gases, water vapour evaporates in leaf then diffs out.
How has gills adapted for the exchange of gases?	Water (containing oxygen) passes through mouth and gills, as this happens oxygen diffuses out of water and into blood and carbon dioxide diffuses out of blood and into water. The gill filaments have large surface area, lamellae increase surface area, good blood supply, thin surface layer, blood and water flows in opposite direction to maintain conc grad (conc of oxygen in water>conc of oxygen in blood).
Explain how you would prepare a microscope slide?	1. add a drop of water to the middle of a clean slide. 2. cut open an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers. 3. using the tweezers, place the epidermal tissue into the water on the side and add a drop of iodine solution. Stains are used to highlight objects in a cell by adding colour to them. 5. place a coverslip on top by standing the coverslip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles under there, they will obstruct the view.
What are the six parts of a light microscope?	eyepiece coarse adjustment knob (big) fine adjustment knob (small) light stage high and low power objective lenses
How do you use a light microscope to look at a slide?	1. clip the slide you've prepared onto the stage. 2. select the lowest-powered objective lens (lowest magnification). 3. use the coarse adjustment knob to move the stage up to just below the objective lens. 4. look down the eyepiece, use the coarse adjustment knob to move the stage downwards until the image is roughly in focus. 5. adjust the focus with the fine adjustment knob, until you get a clear image of what's on the slide. 6. if you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus.
What are the main points when drawing your observations?	1. use a pencil with a sharp point. 2. make sure it takes up at least half of the space available and that it's drawn with clear, unbroken lines. 3. no clouring or shading. 4. draw the subcellular structure in proportion to the cell. 5. title and state magnification. 6. label important features with straight, uncrossed lines.
Explain how you would investigate the effect of antibiotics on bacterial growth?	1. place paper discs soaked in different types (or different concs) of antibiotics on an agar plate that has an even covering of bacteria. Leave some space between the discs. 2. the antibiotic should diffuse (soak) into the agar jelly. Antibiotic-resistant bacteria will continue to grow on the agar around the paper discs, but non-resistant strains will die. A clear area will be left where the bacteria have died (inhibition zone). 3. make sure you use a control, soak in sterile water instead, so you can see the difference in growth of the bacteria not affected by anything that may be on the paper only the antibiotic. 4. leave the plate for 48 hours at 25oC. 5. the more effective the antibiotic against the bacteria, the larger the inhibition zone will be.
Explain how you can observe the effect of sugar solutions on plant tissue?	1. cut up a potato into identical cylinders, and get some beakers with different sugar solutions in them. One should be pure water and another should be a very concentrated sugar solution (1mol/dm^3). Then you can have a few others with concentrations in between. 2. you measure the mass of the cylinders, then leave one cylinder in each beaker for 24 hours. 3. take them out, dry them and measure their masses again. 4. if the cylinders have drawn in water by osmosis, they'll have increased in mass. If water has been drawn out, they'll have decreased in mass. You can calculate the percentage change in mass then plot graphs etc. Dependent variable is the chip mass. Independent is the concentration of the sugar solution. Control are; the volume of solution, temp, time, type of sugar used etc.
Name some errors with the potato experiment?	Some potato cylinders were not fully dried, the excess water would give a higher mass, or if water evaporated from the beakers, the concentrations of the sugar solutions would change. You can reduce the effect of these errors by repeating the experiment and calculating a mean percentage change at each concentration.

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Topic 1 - Cell Biology

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	Created by finn squires over 6 years ago