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N5- Unit 1 How do we improve the reliability of Repeat the experiment the results of an experiment? Why do we repeat experiments? To improve the reliability of the results How do we improve the validity of an By improving its design. For example, having experiment? all the reagents at the same temperature to start with, making sure that all conditions are the same (controlled variable) except for what is changed (independent/input variable). Why do we use % or % change as a To allow comparison between tissues which way to compare results? were different in their mass/ volume/ length at the start of the experiment. Why do we use different To prevent cross-contamination between the pipettes/syringes/measuring cylinders solutions. when setting up an experiment with If you have only one measuring cylinder, you solutions of different concentrations? need to start measuring the least concentrated solution first so that the cross contamination has a limited effect. Unit 1 – Key area 1- Cell structure To magnify an object so it appears larger 1-Why do we use a microscope? than it is. 2-More powerful lenses allow you to see more/less of the sample 3-Why do we use stains? 4-Why do we use coverslips? 5-To convert 1 mm into 1 μm (micrometer)… 6-To convert 1 μm into 1 mm 7-To calculate the total power of the microscope Less but in greater detail. So that cell parts stand out. So that the sample does not dry out. X 1000 ÷ 1000 Multiply the power of the eyepiece lens and the power of the objective lens. Animal cell: 1-mitochondrion, 2-cell membrane, 3-cytoplasm, 4-nucleus, 5ribosomes. 1 Plant cell: 1-cell wall, 2-mitochondrion, 3chloroplast, 4-cell membrane, 5-cytoplasm, 6vacuole, 7-nucleus, 8-ribosomes. 2 Bacterial cell: 1-cell membrane, 2-cell wall, 3ribosome, 4-nucleoid, 5-cytoplasm, 6-plasmid 3 Fungal cell: 1-cell wall, 2-mitochondrion, 3cell membrane, 4-cytoplasm, 5-vacuole, 6nucleus, 7-ribosome. 4 5-Function of cell membrane 6-Function of cytoplasm 7-Function of nucleus 8-Function of vacuole 9-Function of ribosome 10-Function of mitochondria 11-Function of cell wall 12-Function of chloroplast 13-Function of plasmid 14-Similarity/ difference between plant and fungal cell 15-Similarity/ difference between animal and fungal cell 16-Plant cell wall structure compared to fungal and bacterial cells 17- What is characteristic of a bacterial cell compared to all other cells? Controls the movement of substances into and out of the cell. Where most chemical processes take place. Contains genetic material which controls the activities of the cell. Contains cell sap and can help keep cell structure rigid. Where protein synthesis happens Where most of the energy is released by respiration It strengthens and supports the cell. Contain the pigment chlorophyll. Photosynthesis happens here. Small circular piece of DNA in bacteria. Similar structures except that plant cell wall is made of cellulose and fungi have no chloroplasts. Similar structures except that animals cells have neither cell walls nor vacuoles. Only plant cell wall is made of cellulose. Absence of organelles (membrane bound structures such as mitochondrion, vacuole, nucleus) and a different cell wall structure to plant and fungal cells Unit 1 - Key area 2- Transport across the cell membrane 1-Composition of the cell membrane 1- Phospholipids (in a bilayer). 2- Proteins. These can be on the inner or outer surface of the membrane or embedded within the membrane surface. These proteins can help move molecules into or out of the cell. 2-Property of the cell membrane 3-Characteristics of passive transport 4-Fluid mosaic model 5-Diffusion 6-Importance of diffusion 7-Osmosis 8-Effect of osmosis on animal cells 9-Effect of osmosis on plant cells 10-In experiments, the diffusion of substances is usually demonstrated by… 11-In experiments, osmosis is usually demonstrated by… It is selectively permeable (only let molecules smaller than a certain size go through) Passive transport happens down a concentration gradient and does not require energy. The molecules which form the cell membrane move constantly with respect to each other. Diffusion in cells is the movement of molecules down a concentration gradient, from an area of high concentration to an area of low concentration It is how gases (CO2, O2) and some other substances, e.g. water, glucose, urea and amino acids move in and out of cells. O2 and glucose are needed by animal cells for respiration. Water and CO2 are needed by plants for photosynthesis. Osmosis is the movement of water molecules down a concentration gradient through a selectively permeable membrane. Water loss: cells shrink. Water gain: cells burst. Water loss: cells plasmolysed (cell shrinks away from the cell wall, cell wall caves in) Water gain: cells turgid (swollen cell which does not burst due to the support of the cell wall). A reagent changing colour. 12-Define active transport A change in mass of a piece of potato or a model cell or the change of volume of a solution (visible on a graduated tube). Transport against the concentration gradient. 13-Requirements for active transport Energy is required as well as protein carriers. 14-Examples of molecules and organisms using active transport Transport of sodium and potassium in nerve cells, or iodine in seaweeds. Unit1-Key area 3- Producing new cells 1-State the function of cell division 2-State the biological name for cell division 3-State what is the store of hereditary information? 4-What is meant by “chromosome complement”? 5-Describe how the daughter cells compare to the original cell To increase the number of cells in an organism so that growth and cell replacement/repair can take place. Mitosis Chromosomes, DNA Number of chromosomes characteristic to a species, e.g. humans have 46 chromosomes They have an identical set of chromosomes which carry the same information as the original cell. 6-Explain why it is important that the chromosome complement of daughter cells in multi-cellular organisms is maintained To obtain two identical sets of chromosomes, the genetic material contained in a nucleus is replicated (copied) before mitosis. If not, cells might die or grow and/or function abnormally. 1-Chromatids 2-Centromere (Keeps the chromatids together) 7 8-Recognise the stages of mitosis in an animal cell and in a plant cell 1- Duplicated chromosomes get shorter and fatter. The cell is ready for mitosis. 2- Chromosome are attached to spindle fibres at the centromere and positioned at the equator (plane at the centre of the cell). They can be seen to be made of two chromatids. 3- Spindle fibres contract, chromatids are pulled apart towards opposites poles. 4- Two nuclei form at each end of the cell 5- The cytoplasm starts to divide 6- Two daughter cells are formed Same as above except for 5: 5- New cell wall forms on a plane at the centre of a cell. What is meant by a “diploid cell” Cell culture 1-Why is cell culture done? 2-What is needed for cell culture? 3-Explain how glassware can be sterilised Diploid cells have two matching sets of chromosomes. - Make food & drink (e.g. beer, wine). - Test antibiotic, vaccines, medicine. - Aseptic techniques. - Appropriate medium . - Control of other factors (e.g. availability of oxygen, temperature, pH). Heat glassware in an autoclave (pressure cooker) to 121oC. 4-Explain how hands and surfaces need to be prepared before an experiment. - Hands need to be washed before an experiment to remove microorganisms from skin. - Surfaces are disinfected before and after experiment to kill microbes on work area. Hold the lid over an opened petri dish. 5-Explain how microbes can be prevented to contaminate an opened petri dish 6-Explain how the inoculating can be Flame the inoculating loop. sterilized? 7-Why are lids held onto inoculated To prevent entry OR exit of microbes from petri dishes with tape agar. Unit 1- Key Area 4 - DNA and the production of proteins 1-Describe the structure of a DNA Double stranded/ double helix. molecule. Made of sub-unit called nucleotides. Each nucleotide consists of: - phosphate - desoxyribose sugar - a base (adenine, thymine, guanine or cytosine). Bases on each strand form complementary pairs. 2-What holds a DNA strand together? A bond between the sugar of one nucleotide and the phosphate of the adjacent nucleotide. 3-What type of bond holds the two Hydrogen bonds. strands together to form the double helix? 4-What is determined by the base The genetic code. In proteins, the base sequence? sequence determines amino acid sequence. 5-Complementary rule A-T and G-C. Protein synthesis 1-What are the chemical elements C-H-N-O and some sulfur. found in proteins? 2-Structure of proteins is determined DNA sequence which itself determines the by… order of amino acids. 3-Name of the type of bond between Peptide bond. amino acids 4- Give 5 examples of types of Enzymes: speed up chemical reactions. proteins and their function Hormones: carry chemical messages around the body (e.g. insulin) Antibodies: recognize molecules of invading organisms to defend the body against disease. Structural: connect and support tissues (e.g. 5-Where does protein synthesis take place? 6-What carries the sequence information from where it is stored (i.e. in the nucleus) to where it is needed (ribosome) 7-Characteristics of RNA collagen). Receptors: participate in cell signaling. In ribosomes in the cytoplasm. mRNA= messenger RNA - Single stranded - sugar is ribose - Uracil (U) is found in place of thymine (T). Unit 1 –Key Area 5 – Proteins and enzymes 1- Describe a chemical reaction in A substrate is chemically altered into a product general terms A catalyst is a substance which speeds up the rate 2- Explain the meaning of the term (i.e. the speed) of a chemical reaction without being “catalyst”. changed or used up. (i.e. a catalyst is neither a substrate nor a product as it is unaffected by chemical reactions). An enzyme is a biological catalyst made up by all living 3-State what an enzyme is. cells. It speeds up reactions and is left unchanged. 4-Which part of the enzyme binds The active site. The shape of the active site is to the substrate? complementary to that of its specific substrate. 5-Explain the word “specific” as Each enzyme only works on one substrate because the applied to enzymes and their shape of the active site is only complementary to substrate that of its specific substrate. E.g. Amylase only breaks down starch. Enzymes and substrates have matching shapes like a “lock and key”. 6-Explain why enzymes are required The cell processes necessary for life would happen too for the functioning of living cells. slowly without enzymes. 7-Give an example of an enzyme C-L-A-P - Catalase: breaks down hydrogen peroxide into water involved in a degradation reaction. and oxygen - Lipase: breaks down fats into fatty acids and glycerol - Amylase: It breaks down starch into maltose. - Pepsin: breaks down proteins into polypeptides and amino acids. Potato phosphorylase: in potatoes, joins molecules of 8-Give an example of an enzyme involved in synthesis (building up) Glucose-1-phosphate to form starch. Enzymes are proteins. 9-State what type of molecule enzymes are. 10-Describe the effect of At low temperatures, enzymes do not work effectively temperature on enzyme activity (molecules move too slowly). Enzymes work best at a temperature called the optimum. Beyond that temperature, the shape of the enzyme and its active site change which slows down reaction rate. Above a certain temperature, an enzyme becomes denaturated, i.e. it is irreversibly damaged. 11-Describe the effect of a range of Each enzyme has an optimum pH, i.e. a pH at which it pH on the activity of an enzyme works most effectively (faster rate of reaction). Enzyme may work at other pH but the rate of the chemical reaction that they control is usually not as fast. 12-Explain the term “optimum” as The conditions at which enzymes works best are called optimum conditions: optimum pH and optimum applied to the activity of enzymes temperature. 13-Explain what a control is. A repeat of an experiment to show that the effect observed is only due to the factor being investigated (e.g. activity of an enzyme). Unit 1 – Key area 6 – Genetic engineering 1-State in general terms how genetic - naturally information can be transferred - by genetic engineering 2-Give examples of natural genetic - by bacterial plasmid engineering - by viruses 3-State in general terms how human By transferring a piece of chromosome from can engineer bacteria to make new an organism to bacteria. substances 4-Stages in genetic engineering 1- Gene from other organism cut by 1 2 enzymes. 2- A plasmid extracted from a vector/bacterial cell is cut open. 3 3- Gene is inserted into vector/bacterial plasmid by an enzyme. 4 5 4- Plasmid is introduced back into host bacteria and forms a genetically modified (GM) organism 5- Bacteria allowed to reproduce, produce new desirable substance from information contained in the new gene. 5-State what is the advantage of Obtain large quantities in short time. genetic engineering for the production of substances from genes 6-Give examples of products of Insulin to help treat diabetes. genetic engineering used by humans Human growth hormone for children who do not make enough of their own. Unit 1 –Key area 7 - Photosynthesis 1-Word equation of photosynthesis 2-Number of stages and their name 3-Description of first stage 4-Description of second stage 5-Explain the transfer of energy from the light arriving at the leaf to the formation of sugar. Light energy Carbon dioxide + water → sugar + oxygen Chlorophyll 2 stages Light reaction Carbon fixation The light energy from the sun is trapped by chlorophyll in the chloroplasts and is converted into chemical energy in the form of ATP. Water is split to produce hydrogen and oxygen. Hydrogen attaches to hydrogen acceptor molecules. Excess oxygen diffuses from the cell. A series of enzyme-controlled reactions which use hydrogen and ATP (produced by the light reactions) with carbon dioxide to produce sugar. Light energy is trapped by chlorophyll. Light energy is then converted to chemical energy used to regenerate ATP. ATP goes from stage 1 to stage 2 of photosynthesis where glucose is formed. C-H-O 6-What are the elements found in a carbohydrate? 7-What are the 3 fates of the glucose - used directly in respiration to provide produced by photosynthesis? energy for cell processes. - converted to a storage carbohydrate, e.g. starch. - converted to a structural carbohydrate, e.g. cellulose. 8-How are factors affecting starch By testing leaves with starch. usually investigated? 9-Chlorophyll? Name of a green pigment found in chloroplasts which captures light energy. 10-Describe the process of Raw materials: carbon dioxide and water photosynthesis in terms of raw Products: oxygen (waste) and sugar (glucose) materials and products. 11-Explain what is meant by a limiting Something which, when in short supply, will factor and describe the main limiting slow down or stop photosynthesis resulting in factors in the process of the decrease of growth. photosynthesis. Main limiting factors are: carbon dioxide concentration, temperature and light intensity, Unit 1- Key area 8 - Respiration 1-State 5 reasons why living cells need energy. 2-Give an example of an energy transformation in a plant and in an animal. 3-State what cells need in order to release the energy from food. 4-Describe aerobic respiration in terms of a word equation 5-What is produced by all respiring animals and plants? 6-What is the link between energy producing and energy demanding reactions? 7-Write the equation of ATP breakdown and regeneration 8-How many ATPs are regenerated during aerobic respiration? 9-Breakdown of ATP production during aerobic respiration 10-Which cells need lots of mitochondria? 11-State what is produced by respiration in addition to carbon dioxide 12-Give another word for anaerobic respiration in plants and yeast 13-Characteristic of anaerobic respiration 14-Where does anaerobic respiration take place and how many ATPs does it release? 15-Products of anaerobic respiration in plants and yeast (fungi) 16- Products of anaerobic respiration in animals 17-State which of these types of food contains more energy per gram: proteins, fats, carbohydrates. Cell division Muscle contraction Active transport Protein synthesis Transmission of nerve impulse Plants: light energy → chemical energy (starch) Animal: chemical energy (fat) → heat energy Cells need oxygen (found in air) to release the energy from food in “aerobic respiration” glucose + oxygen → energy + carbon dioxide + water Carbon dioxide and water. ATP Breakdown: ATP → ADP + Pi : releases energy Regeneration: ADP +Pi → ATP : requires energy (Pi stands for inorganic phosphate) 38 ATP per molecule of glucose. 2 ATP are produced when glucose is broken down into 2 molecules of pyruvic acid in the cytoplasm. 36 ATP are produced when respiration is completed after entry of the 2 molecules of pyruvic acid in the mitochondria. Cells with high energy needs such as muscle cells, nerve cells, sperm cells. Heat energy and water will be produced by aerobic respiration. Fermentation. It takes place in the absence of oxygen. Only in the cytoplasm, 2 ATP molecules. Ethanol and carbon dioxide. Lactic acid Fats contain about twice as much energy as proteins and carbohydrates (sugars, starch)