GCSE Combined Science Biology Paper 1 Exam Date: 15 th May 2018 1
B1 - Cells 4.1.1.1 Eukaryotes and prokaryotes 1. State the 2 main types of cell Eukaryotic (with a nucleus), prokaryotic (without a nucleus) 2. State the cell organelles (parts) found in all eukaryotic cells (plant and animal). Cell membrane, cytoplasm, genetic material enclosed in a nucleus. 3. What is another name for bacterial cell? Prokaryotic cell 4. State two similarities between eukaryotic and prokaryotic cells They both have cytoplasm, cell membrane and genetic material. 5. State three differences between eukaryotic and prokaryotic cells. Bacterial cells (prokaryotic cells) are much smaller in comparison Bacterial cells (prokaryotic cells) have cell walls In a prokaryotic cell (E.g. Bacteria) the genetic material is not enclosed in a nucleus. It is single loop and there may be one or more small rings of DNA called plasmids in the cytoplasm. You should also be able to : 1. Carry out order of magnitude calculations using standard form 2. You should be able to use the terms centi, milli, micro and nano. 3. Demonstrate that you understand the size and scale of cells order in the correct sequence types of cell and cell parts 2
4.1.1.2 Animal and plant cells 1. State most components of animal cells: A nucleus, cytoplasm, cell membrane, mitochondria, ribosomes 2. State most components of plant cells: A nucleus, cytoplasm, a cell membrane, cell wall, mitochondria, ribosomes, chloroplasts, permanent vacuole filled with cell sap. 3. Which three parts are only found in plant cells? Cell wall, chloroplasts, permanent vacuole. 4. What is the cell wall made of in plant or algal cells? Cellulose, which strengthens the cell. 5. State the function of nucleus. Controls all the activities of the cell and it is surrounded by the nuclear membrane. It contains the genes on the chromosomes. This is the information on how to make a protein. 6. State the function of the cytoplasm. A liquid gel in which the organelles are suspended and where most of the chemical reactions take place. 3
7. State the function of the cell membrane. Controls the passage of substances such as glucose and mineral ions into the cell. It also controls the movement of substances such as urea or hormones out of the cell. 8. State the function of the mitochondria. Structures in the cytoplasm where aerobic reparation takes place, releasing energy for the cell. 9. State the function of the ribosomes. These are where protein synthesis takes place. 10. State the function of the cell wall. Made of cellulose to strengthen the cell and gives it support. 11. State the function of the chloroplasts. Found in the green parts of the plant. They are green because they contain chlorophyll. Chlorophyll absorbs light so the plant can make food by photosynthesis. 12. State the function of the permanent vacuole. It is a space in the cytoplasm filled with cell sap. It keeps the cell rigid to support the plant. You should also be able to: 1. Recognise types of cells from drawings, micrographs and photographs 2. Draw and label examples of different cells 3. Compare your drawings with real images of cells 4. Make estimations about size and use appropriately in judging relative size or area of sub-cellular structures. 5. Use a light microscope to observe, draw and label a selection of plant and animal cells including a magnification scale. 4.1.1.3 Cell specialisation 1. What is a specialised cell? A cell that is adapted to carry out a particular function. 2. State adaptations for muscle cells and describe how those adaptations help the cell carry out its function. 4 They contain many mitochondria, to transfer the energy needed for the chemical reactions that take place as they cells contract and relax.
They contain special proteins that slide over each other making the fibres contract. They can store glycogen, a chemical that can be broken down and used in cellular respiration to help cells to contract. 3. State adaptations for nerve cell and describe how those adaptations help the cell carry out its function. Lots of dendrites to make connections to other nerve cells to carry the message along. A long axon that carries the nerve impulse from one place to another. The nerve endings or synapses that are adapted to pass the impulses to another cell or between a nerve cell and muscle cell. They contain lots of mitochondria to provide the energy needed to make the transmitter chemicals. 4. State adaptations for sperm cell and describe how those adaptations help the cell carry out its function. A long tail whips from side to side to help move the sperm through water or the female reproductive system. The middle section is full of mitochondria, which transfer the energy needed for the tail to work. The acrosome stores digestive enzymes for breaking down the outer layers of the egg. A large nucleus contains the genetic information to be passed on. 5. State adaptations for root hair cells and describe how those adaptations help the cell carry out its function. They increase the surface area available for water to move into the cell. They have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell. They have many mitochondria that transfer energy needed for the active transport of mineral ions into the root hair cells. 6. State adaptations for xylem cells and describe how those adaptations help the cell carry out its function. They are alive when first formed but a special chemical called lignin builds up in spirals in the cell walls. The cells die and form long hollow tubes that allow water and mineral ions to move through them. The spiral rings of lignin make them very strong and help them withstand the pressure of water moving up the plant. They help to support the plant stem. 7. State adaptations for Phloem cells and describe how those adaptations help the cell carry out its function. 5
The cell walls between the cells break down to form special sieve plates. These allow water carrying dissolved food to move freely. Cells lose a lot of their internal structures but they are supported by companion cells to help to keep them alive. The mitochondria of the companion cells transfer energy needed to move dissolved food. 4.1.1.4 Cell differentiation 1. Why do cell need to differentiate. To form different types of cells so organism can develop and grow. 2. How is the process of differentiation different in plant and animal cells? Most types of animal cells differentiate at an early stage Many types of plant cells remain able to differentiate throughout their lifetime 3. What is the purpose of cell division in mature animals? Repair and replacement of damaged cells 4. What does a cell gain as it differentiates into a specialised cell? Different subcellular structures (E.g chloroplasts in palisade cells) to help it carry out a specialised function (job). 4.1.1.5 Microscopy 1. Explain the difference between resolution and magnification Resolution allows finer detail to be seen Magnification makes an image bigger 2. Describe how electron microscopes have allowed biologists to see and understand more sub-cellular structures Electron microscopes have a much greater resolving power than light microscopes and so cells can now be studied in much more detail 6 3. Describe key points in the development of microscopy techniques over time Improvements in technology and science knowledge enabled lenses to be developed.
Light microscopes first allowed us to form a magnified image of a specimen Using a light microscope we can see individual cells and larger cell organelles such as the nucleus Electron microscopes use electrons instead of light to form the image They have higher magnification and resolution than light microscopes Using electron microscopes we can see much smaller things in more detail like the internal structure of a chloroplast or a mitochondrion, ribosomes and plasmids. 4. What is the formula that you need to use to link magnification, size of microscope image and real size? Magnification = size of image size of real objects You should also be able to: 1. Write your answers to calculations in standard form if it is appropriate 2. Correctly use the prefix terms: centi, milli, micro and nano B2 Cell Division 4.1.2.1 Chromosomes 1. What is contained within the nucleus of a cell? Chromosomes made of DNA molecules, each chromosome contains a large number of genes. In body cells chromosomes are normally found in pairs You should also be able to: 1. Use analogies and models to explain how cells divide 4.1.2.2 Mitosis and the cell cycle 1. Describe the stages of the cell cycle Cell grows and increases the number of sub-cellular structure inside it (E.g. ribosomes, mitochondria) Genetic material in the nucleus is doubled when DNA replicates (gets copied) During mitosis (cell / nuclear division) one set of chromosomes is pulled to each end of the cell and the nucleus divides The cell divides into two identical cells when the cytoplasm and cell membranes divide 7
2. Why is mitosis an important process? It allows organisms to grow It enables multicellular organisms to develop You should also be able to: 1. Recognise and describe situations in which mitosis is occurring based on examples given to you in a question 4.1.2.3 Stem cells 1. What is a stem cell? An undifferentiated cell which is capable of producing many cells of the same type They can differentiate into other types of cells 2. What are embryonic stem cells? These are found in human embryos They can differentiate into most different types of human cells 3. How are adult stem cells different to embryonic stem cells? They are found in adult bone marrow Can form many types of cells including blood cells 4. Do plants have stem cells? Yes, they are found in the meristem and can differentiate into any type of plant cell throughout its life 5. Which conditions could stem cells be used to treat? 8
Diabetes Paralysis 6. Describe the process of therapeutic cloning. An embryo is produced with the same genes as the patient Stem cells from the embryo won t be rejected by the patients body and so can be used for medical treatment 7. Are there any risks of using stem cells? Transfer of viruses to the patient 8. Are the other issues with stem cell treatments? Some people have ethical or religious objections 9. How can plant meristem cells be used? To produce clones of plants quickly and economically To clone plant species to protect them from extinction Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers You should also be able to: 1. Evaluate the practical risks and benefits as well as social and ethical issues of stem cell use in medical research and treatments. B3a - Transport 4.1.3.1 Diffusion 9 1. What are the ways in which substances move in and out of cells? Diffusion Osmosis (Water only) Active transport
2. Describe the process of diffusion The spreading out of particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration 3. Give some examples of substances which move into / out of cells by diffusion Small molecules like amino acids Oxygen and carbon dioxide during gas exchange Waste product urea from cells into the blood plasma for excretion in the kidney 4. Explain how the concentration gradient affects the rate of diffusion The greater the difference in concentration between two sides of a membrane the faster the rate of diffusion will be 5. Explain how temperature affects the rate of diffusion A higher temperature means that particles have more kinetic energy and so the rate of diffusion will be greater 6. Explain how the surface area of the membrane affects the rate of diffusion The larger the surface area of the membrane the faster the diffusion rate as more particles can pass through at once. 7. Why is a simple single celled organism able to rely on simple diffusion as a way of getting molecules into and out of their cell? They have a relatively high surface area to volume ratio and this allows sufficient molecules into and out of the cell to meet the needs of the organism. 8. Explain how the small intestine is adapted for exchanging materials The inside surface is covered in millions and millions of tiny projections called villi. These increase the surface area so that digested food is absorbed more quickly into the blood They have a single layer of surface cells and a very good blood supply to assist quick absorption 9. Explain how the lungs in mammals are adapted for exchanging materials The lungs contain millions of little air sacs called alveoli where gas exchange takes place The alveoli are specialised to maximise the exchange of carbon dioxide and oxygen by having an enormous surface area, a moist lining to dissolve gases, very thin walls and a very good blood supply. 10. Explain how the gills in fish are adapted for exchanging materials Gills have gill filaments covered in lamellae to increase their surface area The lamellae have a very good blood supply To maintain a large concentration gradient the blood and water flow through and past the lamellae in opposite directions. 11. Explain how plant leaves are adapted as an exchange surface Air spaces in the leaf allow for rapid diffusion of gases into and out of the leaf 10
Stomata on the underside of the leaf allow gases to diffuse in and out Guard cells control the size of the stomata so that the leaf does not lose too much water by evaporation 12. Describe the four ways of increasing the effectiveness of a multicellular organisms exchange surface so sufficient molecules can be transported for the organisms needs Increase the surface area so more molecules can cross the membrane at once A thin membrane to reduce the distance molecules need to travel Animals need an efficient blood supply to the surface to supply and remove molecules effectively Animals need good ventilation at the gaseous exchange surface in their lungs You should also be able to: 1. Calculate and compare surface area to volume ratios 2. Use surface area to volume ratios to explain the need for exchange surfaces and a transport system in multicellular organisms 3. Recognise, interpret and draw diagrams to model diffusion 4. Explain the use of isotonic and high energy drinks in sports in terms of diffusion 4.1.3.2 Osmosis 1. Describe the process of osmosis Osmosis is the diffusion of water through a partially permeable membrane from a dilute solution to a more concentrated solution You also need to be able to: 1. Recognise, draw and interpret diagrams that model osmosis 2. Measure the rate of water uptake 3. Use percentages 4. Calculate percentage gain and loss of mass of plant tissue 5. Plot draw and interpret appropriate graphs 6. Carry out a practical to investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue 4.1.3.3 Active transport 1. Describe the process of active transport Move particles from an area of low concentration to an area of high concentration against a concentration gradient Energy is required to move the particles against the concentration gradient 2. Explain how plant roots are adapted as an exchange surface 11
Root hair cells have projections on them to increase their surface area for water and mineral ion absorption 3. Why do root hair cells need active transport for uptake rather than diffusion? They need to move substances from an area of low concentration in the soil to an area of higher concentration inside the cell. This is movement against a concentration gradient. 4. Why are sugar molecules absorbed form the gut into the blood by active transport? The concentration of sugars in the gut is less than the concentration of sugars in the blood. These sugar molecules are needed for respiration by cells You should also be able to: 1. Compare the transport of substances by diffusion, osmosis and active transport identifying similarities and differences between the three processes. 4.2.1 Principles of organisation 1. What are cells? Cells are basic building blocks of all living organisms 2. What are tissues? A tissue is a group of cells with a similar structure and function 3. What are organs? Organs are aggregations of tissues performing specific functions 4.What are organ systems? Organ systems are organised organs, which work together to form organisms. You should also be able to: 1. Develop a clear understanding of size and scale in relation to cells, tissues, organs and systems B3b - Organisation 4.2.2.1 The human digestive system 1. Explain the role of the digestive system 12
The digestive system is an organ system in which several organs work together to digest and absorbs food. 2. State two ways in which the rate of enzyme activity may change Temperature and ph changes If ph changes too far from the optimum the enzyme becomes denatured and it s active site changes shape and the substrate will no longer fit If temperature gets too high above the optimum the enzyme becomes denatured and it s active site changes shape and the substrate will no longer fit A too low temperature inactivates the enzyme but does not denature it 3. What is the role of enzymes? Enzymes are selective catalysts that speed up specific reactions 4. Describe the lock and key theory to explain enzyme action The molecules that enzymes work with are called substrates. Substrates bind to a region on the enzyme called the active site. Substrates and active sites must have specific shape in order for the binding and enzyme to work. 5. Describe the action of amylase (an example of a carbohydrase) An enzyme that catalyses the hydrolysis of starch into sugars. Amylase is produced in the salivary glands, small intestine and pancreas It breaks down starch into maltose 6. Describe the action of protease An enzyme that catalyses the breakdown of proteins into polypeptides or amino acids It is produced by the stomach, small intestine and the pancreas 7. Describe the action of lipase. An enzyme that catalyses the digestion of fats into glycerol and fatty acids It is produced in the pancreas and the small intestine 8. Describe the role of carbohydrase An enzyme that catalyses the breakdown of carbohydrates into simple sugars (amylase is one example) 9. Describe the role of digestive enzymes Digestive enzymes convert food into smaller molecules that can be absorbed into the bloodstream 10. What happens to the products after digestion? The products after digestion are used to build new carbohydrates, lipids, and proteins. Some glucose is used in respiration. 11. Where in the body is bile produced and stored? Bile is produced in the liver and stored in the gall bladder 12. What is the role of bile? 13
Bile neutralises the hydrochloric acid from the stomach. It also emulsifies fat to form small droplets to increase the rate of fat breakdown by lipase. You should also be able to: 1. Carry out rate calculations 2. Use word equations to describe a reaction 3. Use models to explain enzyme action 4. Carry out Benedict s test for sugars, iodine test for starch, Biuret test for protein 5. Investigate the effect of ph on amylase using a continuous sampling technique to determine the time taken to completely digest a starch solution at a range of ph values B3c Organisation in Plants 4.2.3.1 Plant tissues 1. Name some examples of plant organs 14
Leaf, root, stem 2. How is the structure of plant epidermal tissues related to its function? The upper epidermis on a leaf is thin and transparent which allows light through to reach the palisade cells. 1. How is the structure of palisade mesophyll tissue related to its function? This tissue is near to the top of the leaf to absorb light. The palisade cells contain many chloroplasts which increase the absorption of light. 2. How is the structure of spongy mesophyll tissue related to its function? The spongy mesophyll is inside the leaf, it is full of air spaces which allow carbon dioxide to diffuse through the leaf. The air spaces increase the surface area of mesophyll cells available to absorb carbon dioxide for photosynthesis by diffusion. 3. State adaptations for xylem cells and describe how those adaptations help the cell carry out its function. They are alive when first formed but a special chemical called lignin builds up in spirals in the cell walls. The cells die and form long hollow tubes that allow water and mineral ions to move through them. The spiral rings of lignin make them very strong and help them withstand the pressure of water moving up the plant. They help to support the plant stem. They transport water and mineral ions from the roots to the stem and leaves in the transpiration stream 6. How is the structure of phloem tissue related to its function? The cell walls between the cells break down to form special sieve plates. These allow water carrying dissolved food to move freely as cell sap through pores in the cell end sieve plates Cells lose a lot of their internal structures but they are supported by companion cells to help to keep them alive. The mitochondria of the companion cells transfer energy needed to move dissolved food. They transport dissolved sugars from the leaves to the rest of the plant for immediate use or storage in the process of translocation 1. How is the structure of meristem tissue at growing tips of shoots and roots related to its function? Plants cells are different to animal cells in another way. Unspecialised stem cells in plants are grouped together in structures called meristems. Cells produced by meristems ensure plants continue to grow in height and width throughout their life. Plant meristems divide to produce cells that increase the height of the plant, length of the roots and girth of the stem. They also produce cells that develop into leaves and flowers. You also need to be able to: 1. Draw and label a transverse section of a leaf 15
4.2.3.2 Plant organ systems 1. State adaptations for root hair cells and describe how those adaptations help the cell carry out its function. They increase the surface area available for water to move into the cell. They have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell. They have many mitochondria that transfer energy needed for the active transport of mineral ions into the root hair cells. 2. Describe the roles of the roots, stem and leaves in transporting substances around the plant In the stem xylem moves water and solutes (dissolved substances) from the roots to the leaves and phloem moves food substances from leaves to the rest of the plant. Both of these systems are rows of cells that make continuous tubes running the full length of the plant. Roots are adapted to allow efficient uptake of water (by osmosis) and dissolved minerals (by active transport) from the soil due to the root hairs Leaves are the site of evaporation of water from the leaf, this is a vital step in transpiration which draws water and dissolved substances through the plant. 3. Describe the process of transpiration Transpiration explains how water moves up the plant against gravity in tubes made of dead xylem cells without the use of a pump. Water on the surface of spongy and palisade cells (inside the leaf), evaporates and then diffuses out of the leaf. This is called transpiration. More water is drawn out of the xylem cells inside the leaf to replace what's lost. As the xylem cells make a continuous tube from the leaf, down the stem to the roots, acting like a drinking straw, producing a flow of water and dissolved minerals from roots to leaves. 4. How do changing temperature, humidity, air movement and light intensity affect the rate of transpiration? Temperature: transpiration is faster in higher temperature because evaporation and diffusion are faster. Humidity: Transpiration is slower in more humid condition because diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air. Air movement: Transpiration is faster in windy condition because water vapour is moved more quickly by air movement speeding up diffusion of more water vapour out of the leaf. Light intensity: In bright light transpiration is faster because the stomata are open wider to allow more carbon dioxide into the leaf for photosynthesis and so it is easier for water to leave the leaf by evaporation. 5. Describe the process of translocation Phloem transports sucrose and amino acids up and down the plant. This is called translocation. In general, this happens between where these substances are made (the sources) and where they are used or stored (the sinks). Applied chemicals, such as pesticides, also move through the plant by translocation. You also need to be able to: 1. Measure the rate of transpiration by the uptake of water 2. Investigate the distribution of stomata and guard cells 3. Explain the adaptations of xylem and phloem to their function (see previous section) 16
4. Process data from investigations involving stomata and transpiration rates to find arithmetic means, understand the principles of sampling 5. Calculate surface area and volumes B4 The Heart and Circulatory System 4.2.2.2 The heart and blood vessels 1. What is the role of the human heart? The human heart is an organ that pumps blood throughout the body via the circulatory system, supplying oxygen and nutrients to the tissues and removing carbon dioxide and other wastes. 2. Describe the difference between the left and right ventricle of the heart The right ventricle pumps blood to the lungs where gas exchange takes place. The left ventricle pumps blood around the rest of the body. The left ventricle has a thicker more muscular wall as it needs to pump blood a further distance around the body. 3. What is a double circulatory system? The blood travels through the heart twice on one complete circuit of the body (once on the way to the lungs and once on the way to the rest of the body). 4. Name the main blood vessels associated with the heart The aorta is the main artery leaving the heart, it carries out of the left ventricle and around the body The vena cava is the main vein from the body carrying deoxygenated body into the right atrium The pulmonary vein carries oxygenated blood from the lungs into the left atrium The pulmonary artery carries deoxygenated blood to the lungs from the right ventricle 5.What is the role of the lungs? The role of the lungs is to help oxygen from the air we breathe move into the red blood cells 6. Describe how the lungs are adapted for gaseous exchange They are folded, providing a much greater surface area for gas exchange to occur. The walls of the alveoli are only one cell thick. This makes the exchange surface very thin - shortening the diffusion distance across which gases have to move. Each alveolus is surrounded by blood capillaries which ensure a good blood supply. Each alveolus is ventilated, removing waste carbon dioxide and replenishing oxygen levels in the alveolar air. The alveoli walls are moist so gases can dissolve and diffuse more effectively through them 7. What are the key structures in the lungs? Air enters through the mouth and travels down the trachea to the lungs. The bottom of the trachea splits into a right and left bronchi Each bronchi branches into bronchioles which end in small bags called alveoli where gas exchange takes place 8. State three different types of blood vessel and their adaptations Arteries have a thick, elastic muscular walls and a small lumen to transport blood at high pressure from the lungs Veins don t carry high pressure blood so they have thinner wall and a larger lumen than the artery. They also have valves to keep lower pressure blood flowing in the right direction 17
Capillaries really tiny and carry blood really close every body cell so that substances can exchange between the body cells and the blood. They have permeable walls so that substances can enter and leave them by diffusion 9. How is the natural resting heart rate controlled? By a group of cells located in the right atrium that acts as pacemakers 10. What is the role of artificial pacemakers? An artificial pacemaker is an electrical device used to correct irregularities in the heart rate. You also need to be able to: 1. Use simple compound measures such as rate and carry out rate calculations for blood flow 4.2.2.3 Blood 1.What are the components in blood? Plasma Red blood cells White blood cells Platelets 2. What is the role of plasma? The role of plasma is the carry blood cells around the body and to maintain blood pressure and help regulate body temperature. It also transports dissolved nutrients, antibodies, hormones and waster products around the body 3. What is the role of red blood cells? The role of red blood cells is to carry oxygen around the body to the cells and to carry carbon dioxide from the cells to the lungs to be exhaled 4. What is the role of white blood cells? White blood cells are cells of the immune system that are involved in protecting the body against infectious diseases and foreign invaders 5. What is the role of platelets? The role of platelets is to stop bleeding 6. How are red blood cells adapted to their function? they contain haemoglobin - a red protein that combines with oxygen they have no nucleus so they can contain more haemoglobin 18
they are small and flexible so that they can fit through narrow blood vessels they have a biconcave shape (flattened disc shape) to maximise their surface area for oxygen absorption 7 How are white blood cells adapted to their function? They have a nucleus so they are able to synthesis proteins (antibodies) You also need to be able to: 1. Students should be able to recognise different types of blood cells in photographs or diagrams. 2. Evaluate the risks of using blood products 4.2.2.4 Coronary heart disease: a non- communicable disease 1. Describe how coronary heart disease occurs Layers of fatty material build up inside the coronary arteries narrowing them This reduced the flow of blood resulting in a lack of oxygen or the heart muscle 2. State the use of stents Stents are used to keep coronary arteries open 3. State the use of statins Statins are widely used to reduce blood cholesterol levels which slows down the rate of fatty material deposit 4. Describe the effect of faulty valves and how they can fixed Faulty valves might develop a leak. They can be replaced by using biological or mechanical valves. Faulty valves are a problem because they can cause: Chest pain or palpitations (rapid rhythms or skips) Shortness of breath Fatigue. Lightheadedness or loss of consciousness. 5. What can be done in the case of heart failure? In the case of heart failure, a donor heart, or heart and lungs can be transplanted Artificial hearts are occasionally used to keep the patients alive whilst waiting for a heart transplant, or allow the heart to rest as an aid to recovery. You also need to be able to: 1. Evaluate methods of treatment from given information bearing inmind the benefits and risks associated with the treatment. 2. Evaluate the advantages and disadvantages of treating cardiovascular diseases by drugs, mechanical devices or transplant. 19
B5 Communicable Disease 4.3.1.1 Communicable (infectious) diseases 1. What are pathogens? Microorganisms that cause infectious diseases Examples are bacteria, viruses, fungi and protists 2. How are diseases caused by pathogens spread? Direct contact, by water, by air 3. What can people do to reduce / prevent the spread of disease? Get the appropriate vaccine if available Wash your hands frequently Stay home if you are sick (so you do not spread the illness to other people). Use a tissue when you cough and sneeze. Dispose of the tissue immediately. Wash your hands after coughing, sneezing or using tissues. Do not touch your eyes, nose or mouth (viruses can transfer from your hands and into the body). 4. Why do people become ill quite quickly? Bacteria and viruses may reproduce rapidly inside the body 5. How do bacteria make people feel ill? They produce toxins that damage tissues 6. How do viruses make people feel ill? They live and reproduce inside cell causing cell damage 20
4.3.1.2 Viral diseases 1. Describe the cause, symptoms and prevention of measles. Measles is a viral disease spread by inhalation of droplets from sneezes and coughs Symptoms are: fever, red skin rash If complications develop the disease can be fatal Most young children are vaccinated against measles 2. Describe the causes, symptoms and control of HIV infection. HIV initially causes a flu like illness The virus attacks the body s immune system unless it is treated with antiretroviral drugs 21
Late stage HIV infection (AIDS) occurs when the body s immune system becomes so badly damaged it can no longer deal with other infections or cancers. HIV is spread by sexual contact or exchange of body fluids such as blood which occurs when drug users share needles. 3. Describe the cause and symptoms of Tobacco mosaic virus TMV is a widespread plant pathogen affecting many species of plant including tomatoes It gives a distinctive mosaic pattern of discoloration on the leaves which affects the growth of the plants due to lack of photosynthesis 4.3.1.3 Bacterial diseases 1. Salmonella is spread by bacteria in ingested food or on food prepared in unhygienic conditions In the UK we vaccinate poultry against salmonella to prevent its spread Symptoms of salmonella are fever, abdominal cramps, vomiting, diarrhoea. The symptoms are caused by the release of toxins by the bacteria. 2.Describe the cause, symptoms, spread and treatment of Gonorrhoea. Gonorrhoea is a bacterial sexually transmitted disease and is spread by sexual contact Symptoms include: thick yellow or green discharge from the vagina or penis and pain on urinating It was initially treated with antibiotic penicillin until resistant strains appeared and this treatment then became less effective. Spread can be controlled by treatment with antibiotics or the use of a barrier method of contraception such as a condom. 4.3.1.4 Fungal diseases 1. Describe the cause, symptoms and spread of Rose black spot It is a fungal disease where purple or black spots develop on leaves. This causes the leaves to turn yellow and drop early. Plants do not grow well as photosynthesis is reduced. The fungus is spread by water or wind. Fungicides can be used to treat the disease and affected leaves are removed and destroyed. 22
4.3.1.5 Protist diseases 1. Name the type of pathogen that causes malaria. Protist 2. How is malaria spread and how is spread controlled? The vector for malaria is the mosquito. Spread is controlled by preventing vectors, (mosquitos), from breeding and using mosquito nets to avoid being bitten. 3. What are the symptoms of malaria? Recurrent episodes of fever, and can be fatal. B6 Preventing Disease 4.3.1.6 Human defence systems 1. Describe the non-specific defence systems of the human body which prevent pathogens from entering. The skin covers the whole body. It protects the body from physical damage, microbe infection and dehydration. Its dry, dead outer cells are difficult for microbes to penetrate, and the sebaceous glands produce oils which help kill microbes. Nose, Trachea and bronchi (nasal hair, mucus and cilia) Stomach acid Tears, saliva and mucus contain an enzyme called lysozyme. This destroys microorganisms. 2. Explain how the immune system destroys pathogens that have entered the body. 23
White blood cells engulf and digest the pathogens (phagocytosis) White blood cells produce antibodies and antitoxins which destroy the pathogens. 4.3.1.7 Vaccination 1. Describe what a vaccination is. Small quantities of dead or inactive forms of a pathogen are introduced into the body so that their antigens can stimulate the white blood cells to produce antibodies. As this form of the pathogen is weakened or harmless the person is not at risk of catching the disease (some people may suffer a mild reaction). If the same pathogen re-enters the body the white blood cells respond quickly and reproduce rapidly to produce large quantities of the correct antibodies and prevent infection and illness. 2. How do are vaccinations used to prevent the spread of disease in a population? Disease epidemics can be prevented if a high proportion of the population has been vaccinated. This reduces the number of people who are able to catch the disease and pass it on to others. The more infectious the disease, the higher the proportion of the population that must be vaccinated to prevent the epidemic. An example: smallpox is the only disease that has been eradicated from the planet by vaccination. This was possible because smallpox is spread by direct contact, and not through the air. This made it possible to vaccinate enough people in the world to completely stop the disease from spreading. Some other diseases are more infectious but if we could vaccinate a sufficient number of the world s population we could, in theory, eliminate the disease. However, at the moment this is not technically feasible because we do not have enough vaccine, some areas of the world are at war and inaccessible, and some people would refuse to be vaccinated. You also need to be able to: 1. Evaluate the global use of vaccination in preventing disease 4.3.1.8 Antibiotics and painkillers 1. What is an antibiotic? A medicine that helps to cure bacterial diseases by killing infective bacteria inside the body (E.g. penicillin). Specific bacteria need specific antibiotics to treat them. They do not work against viruses. 2. Describe the key concern with the use of antibiotics. Over time, bacteria can become resistant to certain antibiotics: this is an example of natural selection. In a large population of bacteria, there may be some that are not affected by the antibiotic. These survive and reproduce, creating more bacteria that are not affected by the antibiotic. Mutations in bacteria can result in them becoming resistant to antibiotics, turning the bacteria into a superbug. Superbugs can develop while a person is taking a course of antibiotics. MRSA is methicillin-resistant Staphylococcus aureus. It is very dangerous because it is resistant to most antibiotics. To slow down or stop the development of other strains of resistant bacteria, we should always avoid the unnecessary use of antibiotics always complete the full course prescribed by a doctor. 24
(HIGHER TIER) The main steps in the development of resistance are: 1. Random changes or mutations occur in the genes of individual bacterial cells 2. Some mutations protect the bacterial cell from the effects of the antibiotic 3. Bacteria without the mutation die or cannot reproduce with the antibiotic present 4. The resistant bacteria are able to reproduce with less competition from normal bacterial strains 3. Can medicines that are produced to treat pain and symptoms of disease be used to kill pathogens? No, medicines only work for their specific purpose. 4. Why are viruses often tricky to treat? Drugs which kill viruses are difficult to produce as they often damage body tissues as well. You also need to be able to: 1. Link the ideas in this topic to the idea of resistant bacteria 4.3.1.9 Discovery and development of drugs 1. Traditionally drugs were extracted from plants and microorganisms, describe some examples. The heart drug digitalis originates from foxgloves The painkiller aspirin originates from willow Penicillin was discovered by Alexander Fleming from the Penicillium mould. 2. How are most drugs made today? They are synthesised by chemists in the pharmaceutical industry. The starting point for most drugs development is a chemical extracted from a plant. 3. How do we know a new medical drug is effective and safe to use? 25 They are extensively tested for toxicity, efficacy (does it do what it was designed to do?) and dose in a laboratory using cells and tissues and then live animals. Clinical trials are then carried out using healthy volunteers and patients.
4. The process of a clinical trial of a new drug in people is very structured, what the stages? Very low doses of drug are given at the start of a clinical trial If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug In double blind trials, some patients are given a placebo (tablet which looks exactly the same but contains none of the drug), neither the patients or the doctors know who has had the placebo and who has had the real drug. This prevents bias and makes the trials results more reliable. You also need to be able to: 1. Understand that the results of testing and trials and published only after scrutiny by peer review. B7 Non-Communicable Disease 4.2.2.5 Health issues 1. Define the term health Health is the state of physical and mental wellbeing 2. What can affect both physical and mental health? Diseases (communicable and non-communicable), diet, stress and life situations 3. How can ill heath arise from different types of disease interacting? Defects in the immune system can mean that an individual is more likely to suffer from infectious diseases. Viruses living in cells can trigger cancers Immune reactions initially caused by pathogens can trigger allergies such as skin rashes and asthma 26
Severe physical ill health can lead to depression and other mental illness You also need to be able to: 4. Students should be able to translate disease incidence information between graphical and numeral forms, Construct and interpret frequency tables and diagrams, bar hats and histograms and use a scatter diagram to identify a correlation between two variables 5. Students should understand the principles of sampling as applied to scientific data, including epidemiological data. 4.2.2.6 The effect of lifestyle on some non-communicable diseases 1. What are the risk factors that are linked to the increased rate of a disease? Lifestyle choices such as diet, alcohol and smoking Substances within the body or environment such as drugs, nicotine, alcohol, environmental toxins (E.g. heavy metals) 2. What is a causal mechanism? 27
For there to be a causal link/mechanism between a factor and an outcome there must be a scientifically proven mechanism which explains how the factor causes the outcome. 3. What are some examples of risk factors where a causal mechanism to disease can be proven: Diet, smoking and exercise on cardiovascular disease Obesity for Type 2 diabetes Effect of alcohol on the liver and brain Effect of smoking and alcohol on unborn babies Carcinogens (including ionising radiation) as a risk factor for cancer 4. What must be considered when selecting a scientific data sample when determining risk factors for disease The greater the sample size the more reliable outcomes will be A sample should represent adequately the population it is taken from You also need to be able to: 2. Discuss the human and financial coast of these non-communicable disease to individuals, local communities, a nation and globally. 3. Explain the effect of lifestyle factors including diet, alcohol and smoking on the incidence of noncommunicable diseases locally, nationally and globally. 4. Interpret data about risk factors for specified diseases 5. Appreciate that many diseases ae caused by the interaction of a number of factors 6. Translate information between graphical and numerical forms: and extract and interpret information from charts, graphs and tables in terms of risk factors 7. Use a scatter diagram to identify a correlation between to variables in terms of risk factors 4.2.2.7 Cancer 1. What is cancer? Cancer is the result of changes in cells that lead to uncontrolled growth and division 2. What is a benign tumour? Growths of abnormal cells which are contained in one area, usually with a membrane. They do not invade other parts of the body. 28
3. How is a malignant tumour different to a benign one? These are cancers. They invade neighbouring tissues and spread to different part of the body in the blood where they form secondary tumours. 4. What may increase your risk of cancer? Some types have been shown to have a genetic risk factor, other types are linked to a risk factor caused by lifestyle (E.g. diet, smoking) B8 Photosynthesis 4.4.1.1 Photosynthetic reaction 1. State the word equation for photosynthesis. carbon dioxide + water glucose + oxygen (light energy is required for the reaction to take place) 2. State the chemical symbols for the reactants and products in the photosynthesis reaction. CO 2 = carbon dioxide 29
H 2 O= water O 2 = oxygen C 6 H 12 O 6 = glucose 3. Why is photosynthesis an endothermic reaction? Energy is transferred from the environment to the chloroplasts by light (energy is taken in). 4.4.1.2 Rate of photosynthesis 1. Describe and explain the effect of temperature on the rate of photosynthesis. If the temperature is too low the enzymes needed for photosynthesis work more slowly. If the temperature gets too high the enzymes needed for photosynthesis denature and stop working (at approx. 45 C). 2. Describe and explain the effect of light intensity on the rate of photosynthesis. 30 Light provides the energy for photosynthesis. As the light level is raised the rate of photosynthesis increases steadily but only up to a certain point.
Beyond this point it won t make any difference as light intensity is increased as the rate will not increase any further as another factor such as temperature or CO 2 level will be limiting the rate of photosynthesis. 3. Describe and explain the effect of carbon dioxide concentration on the rate of photosynthesis. CO 2 is one of the raw materials for photosynthesis. The amount of CO 2 available will increase the rate of photosynthesis up to a point. After this point the rate of photosynthesis will no longer increase as another factor will have become limiting. 4. Describe and explain the effect of amount of chlorophyll on the rate of photosynthesis. If a plant is infected with a disease such as tobacco mosaic virus or suffers environmental stress (E.g. lack of nutrients), the chloroplast may become damaged or the plant will not make enough chlorophyll. This will reduce the rate of photosynthesis as the plant will not be able to absorb enough light. 5. (HIGHER TIER) What do we mean by the inverse square law when linked to photosynthesis and light intensity? Light intensity is inversely proportional to (the distance from a light source) 2. Light intensity α 1/d 2 This means that if you halve the distance the light intensity will be four times greater and if you double the distance the light intensity will be four times smaller. 6. (HIGHER TIER) Explain how limiting factors are overcome in greenhouses to maximise the rate of photosynthesis whilst still gaining profit. The glass traps the Sun s heat and ensures that low temperature does not become limiting. In winter farmers might use heaters in their greenhouses to keep the temperature at an ideal level. In summer it may become too hot and so they could use shades and ventilation to cool things down. Artificial lights can be used to increase the light intensity in the winter or at night. Carbon dioxide levels can be increased by using a CO 2 producing paraffin heater. Greenhouses make it easy for farmers to keep pests away and to add fertiliser to the soil. If the farmer controls all of the limiting factors really carefully then the additional money that they make from selling their crop will outweigh the money they have spent on the greenhouse adaptations. You should also be able to: Measure and calculate rates of photosynthesis Extract and interpret graphs of photosynthesis rate involving 1 limiting factor Investigate the effect of light intensity on the rate of photosynthesis using pondweed. (HIGHER TIER) Interpret limiting factor graphs to identify the limiting factor. (HIGHER TIER) Explain how limiting factors interact to control the rate of photosynthesis. (HIGHER TIER) Use data to relate limiting factors to the cost effectiveness of adding heat, light or carbon dioxide to greenhouses. 4.4.1.3 Uses of glucose from photosynthesis 1. Describe the uses of the glucose that is formed during photosynthesis. Respiration Converted into insoluble starch for storage. Used to produce fat or oil for storage Used to produce cellulose whch strengthens the cell wall Used to produce amino acids for protein synthesis (protein synthesis also needs nitrae ions which are absorbed from the soil). 31
B9 Respiration 4.4.2.1 Aerobic and anaerobic respiration 1. What happens in cellular respiration? It is an exothermic reaction continuously occuring in living cells. The enrgy that is transferred supplies an organism with all the energy needed for living processes. 2. What is the difference between aerobic and anaerobic respiration? Aerobic uses oxygen and transfers more energy than anaerobic respiration. Anaerobic does not require oxygen and transfers less energy than aerobic respiration. 32
3. Why do organisms need the energy transferred during respiration? Chemical reactions to build larger molecules For movement For keeping warm 4. State the word equation for aerobic respiration. Glucose + oxygen carbon dioxide + water 5. State the chemical formulae for glucose, water, carbon dioxide and oxygen. CO 2 = carbon dioxide H 2 O= water O 2 = oxygen C 6 H 12 O 6 = glucose 6. What is the word equation for anaerobic respiration in muscles? Glucose lactic acid 7. Why is less energy transferred during anaerobic respiration? The oxidation of the glucose is incomplete. 8. What is the word equation that represents anaerobic respiration in plant and yeast cells? Glucose ethanol + carbon dioxide 9. How do we use anaerobic respiration in yeast to make products? The process is called fermentation and it has economicc importance in the manufacture of bread and alcoholic drinks. 4.4.2.2 Response to exercise 1. Describe the changes in heart rate, breathing rate and breath volume during exercise. All increase in order to supply the muscles with more oxygenated blood. 2. Which process will occur in muscles to release energy if oxygen supply is limited? Anaerobic respiration 3. What happens to muscles during anaerobic respiration? 33 Lactic acid builds up (causes cramp) Oxygen debt is created