Making New Cells. Proteins DNA. Photosynthesis. Genetic Engineering. Respiration

Transcription

1 Cell Structure Transport Making New Cells DNA Proteins + + Genetic Engineering Photosynthesis Respiration

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3 1.1 Cell Structure Cells are the basic structures which make up all living organisms. Different types of cells are made up of different structures to carry out the functions needed by the cell to keep the organism alive Structures which make up cells and there Functions The table below shows the most common structures found in cells and their functions: Cell Structure Cell Membrane Nucleus Cell Wall Function(s) of Cell Structure Boundary around the cell which controls the substances that can enter or leave the cell. Controls the activities carried out by the cell. Contains genetic information in the form of DNA. Provides cells with a strong boundary and helps to maintain the cell s structure. The cell walls of plant cells are made of Cellulose. The cell walls surrounding fungal and bacterial cells are not made of cellulose and have a different structure to the cell walls of plant cells. Chloroplasts Contain chlorophyll to capture light energy. The light energy is used to create chemical energy, in the form of sugars, by the chemical reaction photosynthesis. Vacuole Membrane enclosed fluid-filled sac used for storage. Cytoplasm Ribosome Mitochondria Plasmid The site of the chemical reactions which occur within the cell. The structure at which new proteins are formed by the process of Protein Synthesis. Generates most of the cell's supply of energy, in the form of Adenosine Triphosphate (ATP), by Aerobic Respiration. A ring of DNA that can control some of the cell s functions. A plasmid may contain genes acquired from other bacteria. 1.

4 The Diagrams below show the structures which are most commonly are found in different types of cells: Structures in a Typical Plant cell Ribosome Mitochondrion Nucleus Chloroplast Cell Membrane Cell Wall Cytoplasm Vacuole Structures in a Typical Animal cell Mitochondrion Nucleus Cytoplasm Ribosome Cell Membrane Structures in a Typical Fungal cell Cytoplasm Vacuole Nucleus Ribosome Cell Membrane Mitochondrion Cell Wall Structures in a Typical Bacterial cell Cell Membrane Plasmid Cytoplasm Cell Wall Ribosome 2.

5 1.2 Transport across the Cell Membrane Structure of the Cell Membrane The cell membrane is made up of 2 layers of phospholipids, a type of fat, and proteins. Surface Protein Phospholipids Pore Channel-forming Protein Properties of the Cell Membrane The cell membrane can be described as Selectively Permeable because it controls which substances can move into and out of the cell. Small, soluble molecules, such as glucose, carbon dioxide, oxygen and amino acids, can pass easily across the cell membrane. Large, insoluble molecules, such as starch, proteins and fats cannot pass easily across the cell membrane. Movement of Substances across the Cell Membrane The method by which a substance is transported across the cell membrane may depend on the concentration of the substance on the inside of the cell and on the outside of the cell Concentration Gradient The concentration of substance on the inside of a cell and on the outside of a cell maybe different depending, causing a Concentration Gradient. A Concentration Gradient is the difference in the concentration of a substance on the inside of a cell and the concentration of the same substance on the outside of the cell. The concentration gradient of the substance across the cell membrane will determine if a substance can move across the cell membrane by either passive transport or active transport Passive Transport Passive transport is the movement of a substance down a concentration gradient; from an area where the substance is at a high concentration to an area where the substance is at a low concentration. Energy is not required for a substance to move by passive transport. 3.

6 1.2.5 Definition of Diffusion Diffusion is an example of the movement of substances across a cell membrane by passive transport. Diffusion is the movement of a substance from an area of high concentration to an area of low concentration, down a concentration gradient. Diffusion will stop when their is no concentration gradient; the concentration of the substance is equal on both sides of the cell membrane. Area of high concentration Concentration Gradient No Concentration Gradient Area of low concentration Substances which move across the cell membrane by diffusion Glucose Carbon dioxide Oxygen Amino acids Importance of Diffusion Diffusion is important to organisms because it allows: Useful substances to move into cells: Glucose moves into cells so they can make energy by respiration. Oxygen moves into cells so they can make energy by aerobic respiration. Amino acids move into cells so they can make the proteins needed by the organism. Waste substances to leave the cell, preventing the cell being damaged: Carbon dioxide is a waste product made during aerobic respiration. 4.

7 1.2.8 Definition of Osmosis Osmosis is the name given to the movement of water across the cell membrane by diffusion. Osmosis is the movement of water molecules from an area of high concentration to an area of low concentration, down a concentration gradient, across a selectively permeable membrane. Osmosis is an example of passive transport; as the water is moving down a concentration gradient the process does not require energy. Effects of Osmosis on Plant and Animal cells: Effects of Osmosis in Animal cells If an Animal cell is surrounded by a solution with a lower water concentration and a higher solute concentration: High Water Concentration inside the cell Low Water concentration outside the cell Water moves out of the cell by osmosis. The cell shrinks. If an Animal cell is surrounded by a solution with an equal water concentration and an equal solute concentration: There is no concentration gradient across the cell membrane; there is no osmosis. The cell remains unchanged. If an Animal cell is surrounded by a solution with a higher water concentration and a lower solute concentration: Low Water concentration inside the cell High Water concentration outside the cell Water moves into the cell by osmosis. The cell bursts. 5.

8 Effects of Osmosis in Plant cells If a Plant cell is surrounded by a solution with a lower water concentration and a higher solute concentration: High Water concentration in the vacuole of the cell. Low Water concentration outside the cell. Water moves out of the vacuole of the cell by osmosis. The vacuole shrinks, pulling the cell membrane away from the cell wall. This process is called Plasmolysis. A cell with this appearance is described as being Plasmolysed. A cell with this appearance can also be described as being Flaccid; meaning the cell has become soft and unsupportive. If a Plant cell is surrounded by a solution with an equal water concentration and an equal solute concentration: There is no concentration gradient across the cell membrane; there is no osmosis. The cell remains unchanged. If a Plant cell is surrounded by a solution with a higher water concentration and a lower solute concentration: Low Water Concentration in the vacuole of the cell. High Water Concentration outside the cell. Water moves into the vacuole of the cell by osmosis. The vacuole expands, pushing the cell contents hard against the cell wall. The strong cell wall prevents the cell from bursting. A cell with this appearance is described as being Turgid; meaning the cell has become hard and supportive. A cell with this appearance cannot take any more water into its vacuole. 6.

9 Active Transport Active Transport is the process in which substances can be moved across the cell membrane against a concentration gradient Definition of Active Transport Active transport is the movement of a substance from an area of low concentration to an area of high concentration, across a cell membrane, against a concentration gradient Resources needed for Active Transport Cell Membrane Proteins Active transport is carried out by some of the proteins which make up the cell membrane. As the cell membrane proteins use energy to move substances against a concentration gradient they are sometimes known as Protein pumps. Area of high concentration Phospholipids Concentration Gradient Protein pump Area of low concentration Energy (ATP) To move substances against a concentration gradient, by active transport, the protein pumps in the cell membrane need to use energy, in the form of a high energy molecule called ATP Examples of Active Transport Active transport is used to move sodium and potassium across the cell membrane of nerve cells to produce nerve impulses. Active transport is used by seaweeds to move iodine from sea water into the cells of the seaweeds. 7.

10 1.3 Producing New Cells What is cell division? Cell division is the process by which a parent cell divides to produce 2 daughter cells, which contain the same number of chromosomes in their nuclei as the parent cell. Parent cell Cell makes a copy of its nucleus Cell contents start to divide Two identical Daughter Cells produced Why do organisms need to produce new cells? An organism needs to produce new cells to allow the organism to grow; by increasing the number of cells in the organism repair tissues which have been damaged e.g. cuts in skin or broken bones Cancer: A problem with cell division Cancers are caused when cell division is not controlled by the nucleus: due to a fault which has developed in the DNA. This causes a large number of cells to be made which form a tumour. The tumour can interfere with the normal functioning of the organ and so causing the individual to become ill. Diploid cells Inside the nucleus of every cell there are the instructions which tell the cell what functions to carry out. The instructions are coded into long strands of DNA called Chromosomes Diploid cells A cell which has two sets of chromosomes in its nucleus is described as being a Diploid cell. Before a cell can divide it needs to make a copy of its chromosomes so that the new cells produced containing the same genetic information. 8.

11 1.3.5 What is Mitosis? Mitosis is the process by which a cell makes an identical copy of its nucleus, including all the DNA it contains, to pass on to the daughter cells made by cell division. Stages of Mitosis: Mitosis 1: Interphase During this phase the cell looks inactive but it is making exact copies of its chromosomes. At the start of this stage the chromosomes in the nucleus are long and thin and not visible using a microscope. By the end of this stage each chromosome has made a copy of its DNA and is now made up of 2 identical chromatids. Chromatid Chromosome Chromosome Mitosis 2: Prophase The Chromosomes coil up, becoming shorter and fatter; making them visible when viewed through a microscope. Cell membrane Nucleus Chromatid Cytoplasm Mitosis 3: Metaphase The membrane around the nucleus disappears. The chromosomes move to the equator (middle) of the cell. Spindle fibres form from the end of the cell and join to the chromosomes. Spindle fibres 9.

12 1.3.9 Mitosis 4: Anaphase The chromosomes are pulled apart by the spindle fibres and move to the opposite ends (poles) of the cell Mitosis 5: Telophase The membrane reforms around the separated chromosomes to form 2 new nuclei. The rest of the cell contents are copied and the cell starts to divide. 2 new identical nuclei Mitosis 6 The 2 new daughter cells will have the identical genetic information and cell structures as the parent cell. This means the daughter cells can carry out exactly the same functions as the parent cell. 2 new identical daughter cells Maintaining the Chromosome complement during Mitosis After cell division is complete the number of chromosomes in the nucleus of the daughter cells is identical to the number of chromosomes in the nucleus of the parent cell Maintaining the Chromosome Complement in Daughter cells The daughter cells produced by cell division must have exactly the same number of chromosomes, containing the identical genetic information, in their nuclei as the parent cell so that they have the same instructions as the parent cell to enable them to carry out exactly the same functions as the parent cell. 10.

13 Commercial Cell Production A number of different commercial and medical processes require the production of large numbers of specific types of cells: Yeast cells- for brewing beer or baking bread. Fungal cells- for antibiotic production or mycoprotein production (Quorn). Genetically engineered bacterial cells- for insulin production etc. Stem cells- for research or medical treatment, for burns etc. Tissue culture- for producing cloned plants Cell Culture Cell culture is the process by which the large numbers of cells needed for commercial or medical processes are produced. This is achieved by providing a very small number of cells with the correct conditions to allow them to divide quickly and so produce the large number of cells required. Health and Safety precautions needed during Cell Culture Aseptic Technique Aseptic technique is a term used to describe the precautions taken during cell culture to prevent the risk of: the cells being made during cell culture being contaminated by unwanted, and potentially harmful cells, from the environment. the cells being made during cell culture being accidentally released and contaminating the environment Precautions taken during Aseptic Technique Keep windows and doors closed when working with microorganisms; to reduce draughts which might spread cells about. Wash your hands before and after working with cells. Wipe the surface you are working on with disinfectant before and after working with cells. Keep the lids of containers with cells or growth medium in them closed when not in use and open the containers for the minimum amount of time. Work close to a blue bunsen burner flame; so that the air currents are drawn upwards, away from your work area. All equipment which has come in contact with cells during the experiment must be sterlised using an autoclave. 11.

14 Conditions required to increase the rate of Cell Division during Cell Culture. During cell culture the cells are given the optimum conditions they need to carry out cell division, so that the number of cells can be increased as quickly as possible Growth Medium Growth medium is a liquid or gel designed to support the growth of microorganisms or cells. As different types of cells contain different structures, made from different substances, each type of cell will need to be given a growth medium containing the correct nutrients and raw materials to allow it to divide Factors used to select a growth medium for Cell Culture Liquid or solid media: Some types of cell will only grow in a liquid media, such as nutrient broth, and some types of cell will only grow on solid media, such as agar. Energy Source: If the growth medium does not contain the correct food source; the cell will not be able to produce the energy it needs to divide. Cell metabolism: If the growth medium does not contain the raw materials substances the cells needs to carry out their chemical reactions the cells will not be able to divide. Cell components: If the growth medium does not contain the correct raw materials the cell won t be able to make the components to it requires for cell division to take place. Additional extracellular components required for cell division: Cells from multicellular organisms may require growth factors and/or hormones, produced by a different type of cell within the organism, so that they can divide. If the correct growth factors or hormones are not present in the growth medium the cells will not be able to carry cell division Factors which are controlled to promote cell division Temperature The temperature of the cells must be controlled to keep the enzymes, which control cell division, at their optimum (best) temperature, speeding up the rate at which new cells will be produced. Oxygen Concentration The oxygen concentration around the cells must be controlled to ensure the cells have enough oxygen to carry out aerobic respiration, to make the energy required for cell division. The more energy the cells can make the more quickly they will divide. ph The ph of the growth medium must be controlled to keep the enzymes which control cell division at their optimum (best) ph, speeding up the rate at which new cells will be produced. 12.

15 1.4 DNA and the Production of Proteins What is DNA? DNA is found in the nucleus of cells, in long strands called Chromosomes. The chromosomes are formed from many smaller areas of DNA called Genes. The genes in the DNA contain the instructions needed to make proteins. Genes are passed from the parents to their offspring. Each individuals DNA is unique DNA Structure A DNA molecule is made from two strands. Each strand has an outer backbone which is linked to a series of molecules called Bases. The two strands are twisted to form a spiral. This arrangement is known as a double-helix. Backbone Bases Bonds Strand 1 Strand 2 The two strands are joined together by bonds which form between the bases on opposite strands Complementary Base Pairs DNA contains 4 different bases. These bases are known by the letters A, T, G and C. The bases in DNA can only join together in a one way: the base A can only join to the base T the base G can only join to the base C. The bases that can join together are known as complementary base pairs. The diagram shows how the bases on the opposite strands of the DNA join together in complementary base pairs. A G C T T C G A 13.

16 Making Proteins (Protein Synthesis) using DNA Protein Structure Proteins are large molecules which are made up of many smaller molecules called Amino Acids. The amino acids which make up a protein are joined together by peptide bonds. The diagram below shows a section of a protein made up of amino acids joined together by peptide bonds: Peptide Bonds Amino Acids Different proteins will have a different arrangement of amino acids The effect of the Base Sequence in DNA on Protein structure The information stored in the DNA is split into many smaller areas called genes. The information in each gene carries the instructions to make a particular protein. The order of the bases that make up the DNA in a gene acts as a set of instructions which is used to control the order in which the amino acids are arranged when the protein is made. The base sequence in each gene is different; this means there will be different arrangement of amino acids in each protein produced by each different gene. This means each protein produced by each different gene will have a different structure, and so will have a different function. The diagram below shows how rearranging the same bases into a different base sequence changes the order of the amino acids and so changes the protein structure: Strand A: Base sequence A T A A G C G T A C G C T A G C A G G T T C A G C A T G C A Order of Amino Acids Strand B: Base sequence T A G C A G A G C A T A G C A C G C C A T G T T C A G G T A Order of Amino Acids 14.

17 1.4.6 DNA to mrna; mrna to Protein The instructions to build a protein are stored, in the nucleus of the cell, as the base sequence of a gene on the DNA. The structures required to assemble amino acids into a protein, are called Ribosomes; they are found in the cytoplasm of the cell. The diagram below shows how the instructions to build a protein are moved from the DNA, in the nucleus, to a ribosome, in the cytoplasm: Nucleus Cytoplasm 1 3 New Protein 4 DNA mrna 2 Ribosome Amino Acids 1. In the nucleus; a section of the DNA s base sequence is copied to make a new molecule containing the instructions to make a protein. The new molecule is called messenger Ribonucleic Acid (mrna). 2. The mrna carries the instructions, to make the protein, out of the nucleus into the cytoplasm; through a small hole in the membrane which surrounds the nucleus. 3. The mrna joins to a ribosome in the cytoplasm. 4. The ribosome uses the base sequence of the mrna as a set of instructions to control the order in which free amino acids in the cytoplasm join together; this will produce the correct arrangement of amino acids needed to form the protein required by the cell. 15.

18 1.5 Proteins Different types of cells need to produce different types of proteins so they can perform different functions Why do different Proteins have different functions? The order in which the amino acids are joined together, when the protein is made, determines the structure of the protein. The structure of the protein determines the function of the protein. The functions of the proteins made by a cell determines the functions of the cell. Types of proteins and their functions. A large variety of different proteins are needed to keep the cell, and the organism they are a part of, alive Structural Proteins Structural Proteins have a long and fibrous structure and are very strong. Examples of structural proteins: Keratin: forms the long strands found in hair and finger nails. Collagen: forms the fibres which make up tendons and ligaments Hormones Hormones are proteins which act as chemical messengers. Hormones are made and released by the cells in one organ of an organism and then move to act on the cells in another organ of the organism. Examples of hormones: Insulin: helps to control blood sugar levels. Indole Acetic Acid (IAA): controls growth in plants Enzymes Enzymes are proteins which act as biological catalysts. This means an enzyme can speed up a chemical reaction in a cell and remain unchanged after the reaction. Examples of enzymes: Catalase: breaks down hydrogen peroxide, made in the liver, into water and oxygen. Starch phosphorylase: converts glucose, made by photosynthesis, into starch, in the tubers of plants such as potatoes Antibodies Antibodies are proteins which can identify harmful microorganisms and substances, within an organism, and destroy them. Antibodies are made by some types of white blood cells. 16.

19 1.6 Enzymes Properties of Enzymes Enzymes are made of Proteins. Enzymes are required for the functioning of all living cells. Enzymes function as Biological Catalysts: This means an enzyme can: 1. Speed up the rate of chemical reactions. 2. Remain unchanged by the chemical reaction so the enzyme can be used again Enzyme Reactions All enzyme controlled chemical reactions have the same pattern: Substrate Enzyme Product(s) A Substrate is the substance with which an enzyme carries out a chemical reaction. The Product(s) is (are) the substance(s) produced by an enzyme after it acts on a substrate. Specificity of Enzymes Mechanism of Enzyme Specificity For an enzyme to be able to speed up a chemical reaction it has to join on to its substrate molecule. The area of the enzyme that joins to the substrate is called the Active Site. Enzyme Active Site Complimentarybinding Site Substrate The area on the substrate which the enzyme joins onto is called the Complimentarybinding site. An enzyme can only join to a substrate molecule that has a complimentarybinding site that is the correct shaped to fit into the enzymes active site. As an enzyme can only join to one substrate molecule an enzyme is described as being Specific to that substrate. Depending on the enzyme; there are two different types of chemical reaction which an enzyme can speed up: -Degradation reactions -Synthesis reactions 17.

20 1.6.4 Degradation reactions 17. In a Degradation reaction an enzyme breaks down large, complex molecules into small, simple molecules. The diagram below shows how an enzyme carries out a degradation reaction: Complimentary binding Site Enzyme Active Site Substrate Enzyme/Substrate complex Product The Enzyme and Substrate bind together forming an Enzyme/substrate complex. 2. The enzyme acts on the substrate to make break down the large, complex substrate molecule into smaller, simpler product molecules. 3. The enzyme releases the products. 4. As the enzyme is not changed during the chemical reaction it can join to another substrate molecule and repeat the chemical reaction. Examples of Degradation reactions carried out by enzymes: Substrate Enzyme Product(s) Starch Hydrogen Peroxide Amylase Catalase Maltose Oxygen + Water Synthesis reactions A Synthesis reaction is a chemical reactions in which an enzyme uses small, simple molecules to build large, complex molecules. The diagram below shows how an enzyme carries out a synthesis reaction: Enzyme Complimentary binding Sites Enzyme/Substrate complex Product Active Sites Substrate 1. The Enzyme and Substrates bind together forming an Enzyme/substrate complex. 2. The enzyme acts on the substrates to join together the small, simple substrate molecules into a large, complex product molecule. 3. The enzyme releases the product. 4. As the enzyme is not changed during the chemical reaction it can join to another substrate molecule and repeat the chemical reaction. Example of a Synthesis reaction carried out by an enzyme: Glucose-1-Phosphate Starch Substrate Enzyme Product 4. Starch Phosphorylase 18.

21 Factors affecting enzyme activity: To understand enzyme activity it is especially important to know the meaning of 2 words Denatured An enzyme is Denatured when extreme conditions damage the structure of the protein from which the enzyme is made. This damage alters the shape of the enzyme s active site; preventing the enzyme joining to the complimentary binding site of the substrate. The diagram below shows the change in the structure of an enzyme under extreme conditions: Favourable Conditions Extreme Conditions Enzyme Substrate Enzyme Substrate Active Site Complimentary binding site Active Site Complimentary binding site As the enzyme cannot join to its substrate it cannot carry out the chemical reaction; so the enzyme becomes inactive. The damage to the enzyme s active site is permanent so the enzyme cannot become active again, even if it is put into favourable conditions Optimum The Optimum conditions for an enzyme are those at which the enzyme is most active (will work the best). The optimum conditions for an enzyme will depend on the type of enzyme and where it is found. If an enzyme is put into conditions above its optimum conditions it may be denatured and become inactive. The speed at which an enzyme can carry out its reactions can be affected by a number of different factors such as temperature and ph The effect of temperature on enzyme activity The graph below shows how changing the temperature will cause a change in the activity of an enzyme: Rate of Reation A. Temperature O C A. At low temperatures the rate of the enzyme reaction is very slow; the enzyme s activity Is low. B. As the temperature increases the rate of the enzyme reaction increases; the enzyme is becoming more active. C. At 40 o C the rate of the enzyme reaction is the highest; this is the optimum temperature for enzyme activity where the enzyme is most active. B. D. At temperatures above 40 o C the rate of the enzyme reaction decreases; the enzyme is less active as the enzyme is being denatured by the higher temperatures. 19. C. D.

22 1.6.9 The effect of ph on enzyme activity The graph below shows how changing the ph will cause a change in the activity of an enzyme: B Rate of Reaction A C A. As the ph increases the rate of the enzyme reaction increases; the enzyme is becoming more active. B. At ph 7 the rate of the enzyme reaction is the highest. This is the optimum ph for this enzyme; where the enzyme is most active. C. As the ph rises above 7 the rate the enzyme of reaction decreases; the enzyme is less active. The enzyme is being denatured, by the higher ph. ph Industrial and Commercial uses of Enzymes: Enzyme can be used in a number of different biotechnology industries: Making biological washing powders: Enzymes are added to detergents to form biological washing powders. The advantages of having enzymes in washing powders are: o Enzymes can breakdown stains more efficiently and more quickly than detergents alone. o Enzymes allow stains to be removed at lower temperatures. This has the advantages of: a) using less energy to heat the water, so it is more environmentally friendly. b) using less energy to heat the water, so it saves money. c) reduces damage which could be caused to delicate fabrics by high temperatures. Cheese making: Rennet is a complex mixture of enzymes which is used in cheese making. o The enzymes in rennet cause the milk to coagulate; dividing into a solid part, called Curds, and a liquid part, called Whey. o The curds are separated from the whey. o The curds are compressed to form the cheese. o The whey is discarded or used as a raw material in other biotechnology industries. Producing fruit juices: The enzymes pectinase and cellulase are used in the production of fruit juices from fresh fruit: o The enzymes pectinase and cellulase are added to the fruit before it is squashed. The enzymes breakdown the cell wall in the fruit; breaking open the cells and releasing the cell contents. When the fruit is squashed more juice is released from inside the cells and so more fruit juice is produced. o Pectinase is also added to the fruit juice to make it clear. 20.

23 1.7 Genetic Engineering Natural transfer of genetic information Genetic information, in the form of DNA, can be transferred naturally between cells in 2 different ways: 1. Transfer of genetic information between cells by Viruses. 2. Transfer of genetic information between cells by Bacterial Plasmids. Scientists can make use of the natural abilities bacteria and viruses have evolved to transfer genetic information between cells in the process of Genetic Engineering What is Genetic Engineering? Genetic Engineering is the artificial transfer of genetic information, usually DNA, between organisms of different species. Genetic engineering allows the organism receiving the genetic information to carry out a process it could not perform naturally Examples of Genetically Engineered organisms The table below shows some examples of organisms which have been genetically engineered: Genetically Engineered Organism Organism(s) providing Donor Genes Beneficial Product Advantage(s) of genetic modification Golden rice Daffodil Maize E. coli Vitamin A Golden Rice can be used to prevent malnutrition in developing countries. Oilseed rape Soil bacteria Resistance to weed killers Increased crop yield as weeds, which compete with the crop plants, can be easily removed. Potato Wild South American Potatoes Blight (fungi) resistant potatoes Environmental benefits, higher crop yields and decreased costs from less use of fungicides. Tomato Artificially produced DNA Deactivated gene Tomatoes cannot make an enzyme involved in ripening and so have a longer shelf life. Atlantic salmon Chinook salmon Ocean Pouter Salmon grow more quickly Salmon grow quickly and so can be sold more quickly with decreased production costs. Yeast Hepatitis B virus Hepatitis B antigen protein The protein produced is used to make a vaccine against the Hepatitis B virus. Bacteria Human Insulin Human insulin can be made in large quantities, quickly using genetically engineered bacteria. 21.

24 1.7.4 Producing Genetically Engineered Bacteria The diagram below shows the different stages required to produce a genetically engineered bacteria which is able to produce a useful product using genetic information from a different organism: Plasmid 1. Gene Chromosome 2. Bacterial Cell Product 1. The gene containing the genetic information to produce the protein that is to be manufactured is identified on the genetic information of an organism. 2. The gene is cut out of the DNA and copies are made. 3. A plasmid is removed from the bacterial cell and the ring of DNA is cut open using an enzyme. 4. The gene is inserted into the plasmid using an enzyme; to produce a genetically modified plasmid. 5. The modified plasmid is put back into a bacteria cell to create a modified bacterial cell. 6. The modified bacteria cell is encouraged to divide to produce many more cells containing the modified plasmid. 7. The modified bacteria cells are given the correct conditions and raw materials so the gene added to the plasmid can make the desired protein. 8. The protein is extracted from the growth media surrounding the genetically modified bacteria and is then purified and packaged ready for use. Examples of products produced using this technique: Human insulin, Human growth hormone, Factor VIII 22.

25 1.8 Photosynthesis What is Photosynthesis? Photosynthesis is a series of enzyme controlled chemical reactions used by some organisms to convert light energy into chemical energy, usually a sugar, which the organism uses as food source. All plants can carry out photosynthesis Word equation for Photosynthesis Light energy Carbon Dioxide + Water Glucose + Oxygen Chlorophyll Raw materials Product Waste Product Photosynthesis occurs in a series of 2 enzyme-controlled reactions called: o The Light reaction o Carbon Fixation The Light Reaction 1.. Chlorophyll (in chloroplasts) Hydrogen 2. Water (H 2 O) Oxygen Used in the second stage of photosynthesis Carbon Fixation. ADP + P i 3. ATP 1. Light energy is absorbed by chlorophyll, in the chloroplasts. Excess oxygen diffuses out of the cell and is released into the air as a waste product. 2. The chlorophyll releases energy which is used to splits a water molecule into hydrogen and oxygen. Splitting the water molecule releases energy. 3. The energy released by splitting the water molecule is used to form a high energy molecule called ATP. The ATP made is used to provide the energy required for to the second stage of photosynthesis, Carbon Fixation. 4. The excess oxygen produced by splitting the water molecule is a waste product which released into the air. 5. The hydrogen produced by splitting the water molecule is used in Carbon Fixation, the second stage of photosynthesis. 23.

26 1.8.4 Carbon Fixation Carbon Fixation is the second stage of photosynthesis. During Carbon Fixation the carbon dioxide from the air is combined with hydrogen, made during photolysis (the light reaction), to make the sugar glucose. The energy needed to carry out this reaction is provided by ATP, made during photolysis (the light reaction). The word equation for carbon fixation is: Carbon Dioxide + Hydrogen ATP (made during Photolysis) Glucose (from the air) (from Photolysis) Uses for the Glucose produced by Photosynthesis The glucose produced by photosynthesis can be used by a plant cell in a number of different ways: 1. Producing energy; the chemical energy stored in the glucose can be released by the plant cell using the chemical reaction Respiration. 2. Converting into Cellulose; a structural carbohydrate which is used to make the cell walls for new plant cells produced by cell division. 3. Converting into Starch; a storage carbohydrate which is used by the plant cell as an energy store. Factors that can limit the rate of Photosynthesis: If certain raw materials needed for photosynthesis are not available to a plant or the external conditions are not correct then the rate at which photosynthesis within a plant cell can happen will decrease Limiting factors for Photosynthesis Limiting factors for Photosynthesis include: 1. Light intensity: If the levels of light reaching a plant are low then the cells will not be able to carry out the Light Reaction, decreasing the rate of photosynthesis. 2. Carbon dioxide concentration: If the Carbon dioxide concentration in the air surrounding a plant is low then the cells will not be able to carry out Carbon Fixation, decreasing the rate of photosynthesis. 3. Temperature: The rate of the reactions which take place during photosynthesis are controlled by enzymes. If the temperature surrounding a plant is below the optimum temperature required by the enzymes the Light reaction and Carbon Fixation will occur more slowly, decreasing the rate of photosynthesis. 24.

27 1.8.7 Effects of Limiting Factors on Plant Growth If the rate of photosynthesis is reduced, by one or more limiting factor, then the amount of glucose produced by the plant will decrease. Decreasing the amount of glucose produced by the plant will have two effects: o o Decrease the energy available for cell division. Decrease the amount of Glucose available which can be converted to cellulose to make cell walls for new cells. These two effects will combine to decrease the plant s ability make new cells by cell division and so reduce the plants ability to grow Effect of decreasing Limiting Factors for photosynthesis By carefully controlling the conditions in which plants are grown the effect of limiting factors can be decreased, this will result in an increased rate of photosynthesis leading to an increased rate of plant growth and an increase in crop production. 25.

28 1.9 Aerobic and Anaerobic Respiration What is Respiration? Respiration is a series of enzyme controlled chemical reactions in which the energy stored in Glucose molecules is released to produce molecules of a high energy substance called Adenosine Triphosphate (ATP) Importance of Respiration All living cells need to carry out respiration to make the energy required to carry out the processes needed to keep the cell and/or organism alive. These cell processes include: o Cell division (mitosis) for growth and repair of tissues. o Contraction of muscle fibres, to produce movement. o Creating and sending nerve impulses. o Carrying out protein synthesis; to make enzymes, hormones, antibodies etc. Making Energy by Respiration: During respiration the energy released by the breakdown of Glucose is used to form a high energy bond between a molecule of Adenosine Diphosphate (ADP) and a molecule of inorganic phosphate (P i ) to form an Adenosine Triphosphate (ATP) molecule Making ATP The diagram below shows how ATP is made: Adenosine P i P i + Energy from the breakdown of Glucose P i High Energy Bond Adenosine P i P i P i Adenosine Diphosphate phosphate Adenosine Triphosphate The word equation for the formation of ATP is summarised below: ADP + P i ATP Releasing Energy from ATP: When the cell needs energy, the energy stored in ATP can be released by breaking the high energy bond between the last phosphate molecule and the rest of the ATP molecule. This releases the energy stored in the bond and breaks the ATP molecule into a molecule of Adenosine Diphosphate (ADP) and a molecule of inorganic phosphate (P i ) Releasing energy from ATP The diagram below shows the reaction by which energy is released from ATP High Energy Bond Adenosine P i P i P i Energy from the breakdown of Glucose Adenosine P i P i + P i Adenosine Triphosphate Adenosine Diphosphate phosphate The word equation for releasing energy from ATP is summarised below: ATP ADP + P i 26.

29 1.9.5 Regenerating ATP After the ATP molecule has been broken down the ADP and the Pi can be used by the respiration reaction to regenerate a new molecule of ATP. The diagram shows how ATP is Regenerated from the products made after it has been broken down, to release energy. ATP ADP + P i Types of respiration The type of chemical reaction used to break down glucose to make ATP will depend on the availability of oxygen to the organism. Aerobic Respiration: Definition of Aerobic Respiration Aerobic respiration is a series of enzyme controlled chemical reactions in which the energy stored in Glucose molecules is released to produce Adenosine Triphosphate (ATP), when Oxygen is available Aerobic Respiration word equation Glucose + Oxygen Raw materials Carbon Dioxide + Water + ATP Products Aerobic respiration occurs in 2 stages: Aerobic respiration: Stage 1 A glucose molecule is broken down into 2 smaller Pyruvic Acid molecules. This reaction also makes 2 molecules of ATP. The word equation for this reaction is summarised below: Glucose Pyruvate + 2 ATP molecules This stage of aerobic respiration takes place in the cytoplasm of the cell Aerobic respiration: Stage 2 The Pyruvate, from Stage 1, is combined with Oxygen to make Carbon Dioxide and Water. This reaction makes 36 molecules of ATP. The word equation for this reaction is summarised below: Pyruvate + Oxygen Carbon Dioxide + Water + 36 ATP molecules This reaction takes place in the mitochondria of the cell. 27.

30 Total Energy produced by Aerobic Respiration During aerobic respiration; each Glucose molecule is completely broken down to produce 38 ATP molecules. Anaerobic Respiration: Definition of Anaerobic Respiration Anaerobic respiration is a series of enzyme controlled chemical reactions in which the energy stored in Glucose molecules is released to produce Adenosine Triphosphate (ATP), when Oxygen is not available. The chemical reactions which take place and the products which are produced during Anaerobic Respiration depend on the organism making ATP using this reaction. Anaerobic Respiration in Animal cells: Anaerobic Respiration in Animal Cells word equation Glucose Raw material Lactic Acid + 2 ATP molecules Products Anaerobic respiration in animal cells occurs in 2 stages: Anaerobic Respiration in Animal Cells: Stage 1 A glucose molecule is broken down into 2 smaller Pyruvic Acid molecules. This reaction also produces 2 molecules of ATP. The word equation for this reaction is summarised below: Glucose Pyruvate + 2 ATP molecules This reaction takes place in the cytoplasm of the cell Anaerobic Respiration in Animal Cells: Stage 2 The pyruvic acid from stage 1 is converted into Lactic Acid. This reaction does not produce any molecules of ATP. The word equation for this reaction is summarised below: Pyruvate Lactic Acid This reaction takes place in the cytoplasm of the cell Total Energy produced by Anaerobic Respiration in Animal Cells During anaerobic respiration in animal cells; each Glucose molecule is partially broken down to produce 2 ATP molecules. 28.

31 Anaerobic respiration in Plant Cells and Yeast cells: Fermentation Anaerobic respiration in Plant Cells and Yeast cells is also called Fermentation Anaerobic respiration in Plant and Yeast cells (Fermentation) word equation Glucose Raw material Ethanol + Carbon + 2 ATP (Alcohol) Dioxide molecules Products Anaerobic respiration Plant Cells and Yeast cells (fermentation) occurs in 2 stages: Anaerobic respiration in Plant and Yeast cells: Stage 1 The glucose molecule is broken down into 2 smaller Pyruvic Acid molecules. This reaction also produces 2 molecules of ATP. The word equation for this reaction is summarised below: Glucose Pyruvate + 2 ATP molecules This reaction takes place in the cytoplasm of the cell Anaerobic respiration in Plant and Yeast cells: Stage 2 The pyruvate from stage 1 is converted into Ethanol (alcohol) and Carbon Dioxide. This reaction does not produce any molecules of ATP. The word equation for this reaction is summarised below: Pyruvate Ethanol and Carbon Dioxide Total Energy produced by Anaerobic respiration in Plant and Yeast cells (Fermentation) During anaerobic respiration in yeast and plant cells; each Glucose molecule is partially broken down to produce 2 ATP molecules. 29.

32 Respiration summary The table below summarises the different types of respiration reactions which take place in different types of organisms: Type of Respiration Type of Organism Raw Materials Product(s) Molecules of ATP produced Area(s) in the cell where the reaction takes place. Aerobic Animals Plants Yeast Glucose + Oxygen Carbon Dioxide + Water 38 Cytoplasm and Mitochondria Anaerobic Animals Plants Yeast Glucose Glucose Lactic Acid Ethanol + Carbon Dioxide 2 2 Cytoplasm Cytoplasm Mitochondria and Energy Production: Most of the ATP produced by aerobic respiration is produced in the mitochondria of a cell Factors which affect the number of Mitochondria in a cell Cells which use a lot of energy need more mitochondria so they can make more ATP, so they have enough energy to carry out all the processes they need to work efficiently. Examples of cells which use a lot of energy, and so have a large number of mitochondria, are: o Muscle cells need a large amount of energy to bring about movement. o Nerve cells need a large amount of energy to create nerve impulses. o Liver cells need a large amount of energy to carry out chemical reactions. 30.

33 1.10 Properties of microorganisms and their use in industries Microorganisms are very small living things which can only be seen using a microscope. Bacteria, viruses and fungi are all examples of microorganisms Properties of Microorganisms Microorganisms have a number of properties which can make them useful including: o having the ability to increase in number very quickly; by producing new cells. o having the ability to use of large number of different food sources. o having the ability to create a wide range of products. Using Yeast in industry: What is Yeast? Yeast is a single celled fungus Fermentation by yeast When oxygen is not available yeast can make energy by the process of anaerobic respiration. Anaerobic respiration by Yeast cells is also called Fermentation Fermentation by Yeast cells word equation Glucose (Sugar) Raw material Ethanol + Carbon + Energy (Alcohol) Dioxide Products The products made by yeast from anaerobic respiration can be used in industrial processes to make useful products The use of yeast in bread making Product: Bread Product of yeast fermentation used: Carbon Dioxide Explanation: Bread is made using a basic dough of flour, water, salt and yeast. Inside the dough there is very little oxygen so the yeast produces bubbles of carbon dioxide by fermentation. The bubbles of carbon dioxide, produced by the yeast, get trapped in the dough and this makes the dough rise. 31.

34 Yeast can also be used to make alcoholic drinks such as beer and wine The use of yeast in beer making Product: Beer Product of yeast fermentation used: Alcohol (ethanol) Explanation: 1. Barley is allowed to germinate (start growing); this converts the starch in the barley to sugars, which the yeast can use for fermentation. 2. The barley is crushed and mixed with hot water. The sugars from the barley are dissolved in the water. 3. The sugary water is mixed with yeast. 4. The yeast uses the sugars in the water to produce alcohol by fermentation The use of yeast in wine making Product: Wine Product of yeast fermentation used: Alcohol 30. (ethanol) Explanation: 1. The fruit, usually grapes, is picked and squeezed to remove the juice; which contains sugars. 2. The juice is mixed with yeast. 3. The yeast uses the sugars in the juice to produce alcohol by fermentation. Using Bacteria in industry: Fermentation by bacteria When oxygen is not available bacteria can make energy by the process of anaerobic respiration. Anaerobic respiration by bacterial cells is also called Bacterial Fermentation Bacterial Fermentation of milk The word equation for the bacterial fermentation of milk reaction is summarised below: Lactose (Sugar in milk) Lactic Acid Raw material Product 32.

35 The products made by bacteria during the fermentation of milk can be used in industrial processes to make useful products The use of bacteria in yoghurt making Product: Yoghurt Product of bacterial fermentation used: Lactic acid Explanation: o The bacteria break down the lactose sugar, in the milk, to produce Lactic Acid. o The Lactic Acid causes a decrease in the ph (increased acidity) of the milk; this causes the milk to sour and curdle, becoming thicker, producing the yoghurt. o The increase in acidity prevents other bacteria growing in the milk and so helps to preserve the yoghurt. The lactic acid also contributes to the yoghurt s flavour The use of bacteria in Cheese making Product: Cheese Product of bacterial fermentation used: Lactic acid Explanation: o The bacteria break down the lactose sugar, in the milk, to produce Lactic Acid. o The Lactic Acid causes a decrease in the ph (increased acidity) of the milk; this causes the milk to sour and curdle, becoming thicker and starts the process of separating the milk into a solid part (curds) and a liquid part (whey). o The enzyme rennet can also be added to the milk to speed up the process of producing the curds and whey (also see ). o The curds are separated from the whey. o The curds are compressed to form the cheese. o The increase in acidity, caused by the lactic acid produced by the bacteria, prevents other bacteria growing in the cheese and so helps to preserve the cheese and contributes to the cheese s flavour The use of bacteria in making biogas Product: Biogas Product of bacterial fermentation used: Methane Explanation: o Organic wastes, such as paper, food wastes, and sewage, are collected and stored in a sealed tank, called a Biodigester. o The bacteria in the organic wastes decompose it, by anaerobic respiration, to produce methane gas. o The methane gas is collected and can be used as a fuel for heating and cooking or to run a generator to produce electricity. 33.