Term
2.1 - 2.1.1 - carbohydrates
Complete the following table identify the major groups of substances in living cells, the elements present, their basic unit and their function in cells. |
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Definition
Elements present: carbon (C), hydrogen (H), oxygen (O)
Basic unit: glucose
Function in cells: glucose provides energy for cells in respiration. in plants polysaccharides are used for storage ( starch ) and for cell walls ( cellulose ) |
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Term
2.1 - 2.1.1 - proteins
Complete the following table to identify the major groups of substances in living cells, the elements present, their basic unit and their function in cells. |
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Definition
Elements present: C,H,O,N
Basic unit: amino acids
Funtion in cells: amino acids are the building blocks for cells being used for growth, repair and maintenance. |
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Term
2.1 - 2.1.1 - lipids
Complete the following table to identify the major groups of substances in living cells, the elements present, their basic unit and their function in cells |
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Definition
Elements present: C,H,O
Basic unit: lipids include fats, oils, waxes, and steroids. Fats and oils are used for storage of energy, plants usewaxes a as waterproofing as leaf cuticle. Many steroids are hormones which control body development. |
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Term
2.1 - 2.1.1 - nucleic acids
Complete the following table to identify the major groups of substances in living cells, the elements present, their basic unit and their function in cells. |
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Definition
Elements present: many element, mainly C,H,O,N,P
Basic unit: nucleotide with a sugar, nitrogenous base and a phosphate group.
Function in cells: contain hereditary information as DNA and RNA |
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Term
2.1 - 2.1.1 - inorganic substances
Completetable following table to identify the major groups of substances in living cells, the elements present, their basic unit and their function in cells. |
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Definition
Elements present: various with substance
Basic unit: many are ions
Function in cells: water is extremely important with most materials in the body dissolved in water, it is used for the transport of materials and water is required for many cell processes. Ions e.g.Calcium,iron,phosphate,sodium,magnesium,zinc are involved in many reactions and the synthesis of macromolecules and body components. |
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Term
2.2 - 2.2.1
List some of the molecules that move into/out of cells. |
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Definition
| Substances that move into/out of cells include water, oxygen, carbon dioxide, mineral ions, trace elements, organic molecules such as amino acids, simple sugars. |
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Term
2.3 - 2.3.1
ExplainHowe the following model is used to represent a cell membrane and how this structure allows movement of substances. |
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Definition
| The fluid mosaic model of the cell membrane is a lipid bilateral with the hydrophobic end of the phospholipids facing the middle of the membrane and the hydrophilic end facing towards the watery contents of the cell. In the lipid bilateral there are transmembrane proteins which are large protein molecules extending from one side to the other, integral proteins which extend only part way across the bilipid layer and peripheral proteins which are attached to the surface and part of the integral protein. This model explains movement by diffusion across the cell membrane as molecules soluble in lipids, e.g oxygen and carbon dioxide as these molecules dissolve in lipids. Water diffuses acrossa through small openings made by the movement othe fluid lipids. Large molecules, e.g. Amino acids and simple sugars combine with transport integral proteins and are "carried" across themembranes by facilitated diffusion. Very large molecules can enter when they are enclosed in a vesicles formed by the membrane and released on the other side ( endocytosis ) |
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Term
2.4 - 2.4.1
Distinguish between diffusion and osmosis. |
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Definition
| Diffusiondis the movement of particles from an area of high concerntration of particles to an area concentration of particles. Osmosis is a type of diffusion. In biology, osmosis refers to the movement of water, across a semipermable membrane from an area of high water concentration to an area of low water concerntaration. |
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Term
2.5 - 2.5.1
Explain why there is a maximum cell size and after this size many cells divide into two cells. |
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Definition
| Small cells have a larger surface area: volume ratio. This means that diffusion is more efficient allowing nutrients and oxygen into the cell and releasing wastes from the cell. As a cell grows in size the surface area: volume ratio becomes larger and diffusion becomes less efficient. If the cell becomes too large wastes may accumulate to toxic levels, oxygen and nutrients may be deficient for the cell's needs and the cell will not function properly and could die. To prevent this from occurring the cell will divide, makingtwo new cells and thus each cell now has a larger surface area: volume ratio. |
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Term
2.6 - 2.6.1 - glucose
Complete the following table to show the substance, the chemical used to test for the substance, the procedure and the positive test result. |
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Definition
Chemical used to test for the substance: Benedict's sollution
Procedure: add a few drops of Benedict's solution to sample and heat in a water bath
Positive test result: pale blue solution turns orange-red |
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Term
2.6 - 2.6.1 - starch
Complete the following table to show the substance, the chemical used to test for the substance, the procedure and the positive test result. |
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Definition
Substance: starch
Chemical used to test for the substance: iodine solution
Procedure: add afew drops of iodinesolution to sample.
Positive test result: yellow/brown solution turns blue/black |
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Term
2.6 - 2.6.1 - lipids
Complete the following table to show the substance, the chemical used to test for the substance, the procedure and the positive test result. |
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Definition
Chemical used totest for the substance: brown paper
Procedure: press the brown paper on the sample and rub gently.
Positive test result: opaque paper turns translucent . |
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Term
2.6 - 2.6.1 - proteins
Complete the following table to show the substance, the chemical used to test for the substance, the procedure and the positive test results. |
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Definition
Chemical used to test for the substance: biUret solution
Procedure: add equal amounts of sodium hydroxide and copper sulfate to make biuret solution. Add a few drops of biuret solution to sample.
Positive test results: pale blue solution turns mauve/purple |
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Term
2.6 - 2.6.1 - chloride ions
Complete the following table to show the substance, the chemical used to test for the substance, the procedure and the positive test results. |
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Definition
Chemical used to test for the substance: silver nitrate solution
Procedure: add a few drops of 1% silver nitrate solution to sample.
Positive testresults: clear solution to formation of a white precipitate. |
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Term
2.6 - 2.6.1 - lignin
Complete the following table to show the substance, the chemical used to test for the substance, the procedure and the positive test result. |
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Definition
Chemical used to test for the substance: phoroglucinol
Procedure: stain a thin section of plant tissue with 18% HCI saturated with phoroglucinol crystals.
Positive test result: lignin ( e.g. In xylem ) stains a reddish/purple color. |
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Term
2.7 - 2.7.1
Describe a model you constructed to show the selectively permeable nature of a cell membrane including one advantage and one limitation of your model. Draw a diagram to illustrate your model. |
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Definition
| To make a model to show the selectively permeable nature of a cell membrane, two plastic containers of the same size can be used. The lid is perforated with a dissecting needle to make a collection of holes that will let salt pass through but small enough to stop rice moving through. Salt is placed in one container and uncooked rice in the other container. The lid is placed on one container and the other container is taped to the first container so theKidd divides the two containers. The modelnew represents two sides of a semipermeable membrane. Shaking the model allows the salt to change sides, but therise is restricted to only one side. The advantage of this model is that it shows how small molecules canpast through a semipermeable membrane but large molecules cannot move through. A disadvantage is that outside energy must be applied ( shaking ) for the salt to move through, while osmosis of water is passive transport. |
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Term
2.8 - 2.8.1 - ( a )
Which experiment shows osmosis and which experiment shows diffusion? Explain your reasoning. |
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Definition
| Experiment a shows osmosisand experiment b shows diffusion. Osmosis involves the movement of small particles through a semipermeable membrane and the dialysis tubing in experiment a acts as the same semipermeable membrane. Experiment b involves diffusion of Condys crystals in water. |
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Term
2.8 - 2.8.1 - ( b )
Explain how each experiment shows biological process. |
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Definition
| Ina experiment a the bag with the starch solutionwill become more turgid showing osmosis as water moves into the bag, the contents of the bag will also turn blue-black showind diffusion of the iodine molecules into the bag ( they then react with the starch forming a large macromolecule and thus the iodine cannot move back again ) in experiment b, the Condys crystals ( potassium permanganate ) are dropped into the water, the straw slowly removed and diffusion can be observed as the red-purple potassium permanganate dissolves and spreads out by diffusion making the water red-purple. |
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Term
2.9 - 2.9.1 - ( b )
After removal from the acid, the cubes were cut and the depth of colour change was measured. The acid had penetrated to a depth of 3mm in each cupe |
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Definition
| The rate of diffusion of acid into the cubes is the same for all cubes. The acid penetrates to a depth of 3mm after four minutes. |
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Term
2.9 - 2.9.1 ( d )
Use the results of this experiment to explain how cell size is influenced by the rate of diffusion. |
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Definition
| The results of this experiment show that the rate of diffusion into the cubes was the same for all cubes. However, after four minutes the acid had reached 93.6% of small cube but only 48.8% of the large cube. The small cube had the largest SA:V (6:1) and the large cube had the smallest SA:V (2:1). This shows that cell size is influenced by the rate of diffusion as smaller cells, with larger SA:V have an advantage over larger cells. Materials and nutrients can reach all parts of the cell by diffusion more quickly than larger cells. |
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Term
2.9 - 2.9.1 - (e)
For this experiment describe two safety precautions that would need to have been taken. |
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Definition
| One of the safety precaution involves the use of acid e.g. HCI. Acid is corrosive to skin and clothing which means gloves, laboratory coat and goggles needed to be worn to protect eyes and skin from damage. When using knives to cut the jelly, care must be taken as sharp objects can cause injury and broken skin can lead to infection. |
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Term
2.10 - (a)
Define osmosis |
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Definition
| Osmosis is the movement of water across a semipermeable membrane from an are of high water concentration to an area of low concentration water. |
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Term
2.10 - (b)
What do you expect will happen to each potatcupe be? Explain why this should occur. |
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Definition
| In beaker a, you would expect the potato cube in the distiller water to remain turgid. The wateconcerned ration is greater outside the potato and so water willpotato into the potato by osmosis. In beaker b, the water concentration is greater inside the potatstand so the water will move from this potato to the salt water and this potato will shrivel. |
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Term
2.10 - (c)
Describe how you could improve the accuracy of this experiment. |
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Definition
| Yu could measure the size of each potato cube at the end of the experimentanswer well as at the beginning, and then calculate the amount if change in size. This will provide a more accurate description of the change in size. |
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Term
2.10 - (d)
Name 4 tests you could carry out to identify substances present in the potato tissue. |
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Definition
| To find out what substances are in thepotato you can carry out several distinguishing tests. To test for starch you can puta few drops if iodine on the potato. To test for glucose you can add a few drops of Benedict's solution and heat gently. To test for lipids you can rub brown paper against the potato. To teat for protein you can add a few drops of biuret solution. |
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