Biology - Paper 1

• Microscopy involves the use of two types of microscopes: the light microscope, which uses light to form an image and can be used to view live specimens, and the electron microscope, which uses electrons to form an image and cannot be used to view live specimens.
• The light microscope has a resolving fire of around 200 nanometers and can magnify up to 2,000 times.
• The electron microscope has a resolving fire of 0.2 nanometers and can magnify up to two million times.
• The cell membrane is the inner layer of the two layers that you can see in a plant cell.
• The nucleus controls the cell's activities and contains genetic material.
• The cytoplasm is a liquid gel that fills up the entire cell and is where chemical reactions occur.
• The mitochondrion is where aerobic respiration occurs and releases energy for the cell.
• The ribosome's function is protein synthesis, which is a fancy way of saying making proteins.
• Limiting factors can and do interact with each other, for example, if a plant receives a high light intensity but has a low concentration of carbon dioxide, the rate of photosynthesis will be low because carbon dioxide concentration is limited.
• Carbon dioxide concentration can be increased in a greenhouse to maximize the rate of photosynthesis.
• Greenhouses naturally trap heat from the Sun, which increases the temperature and causes a higher rate of photosynthesis.
• The final limiting factor in photosynthesis is the amount of chlorophyll in the leaves of the plant, which can be reduced in variegated leaves and when a plant is deficient in magnesium ions.
• Gardeners can provide higher carbon dioxide concentrations within greenhouses using paraffin heaters, which release carbon dioxide as they burn and provide heat.
• Greenhouses can be ventilated using open windows to cool them in very hot conditions.
• If a greenhouse gets too hot, it can be ventilated using open windows or heaters can be used to provide warmth, ensuring that the optimum temperature for photosynthesis is maintained.
• The higher carbon dioxide concentration increases the rate of photosynthesis.
• Temperature increases the rate of photosynthesis until it reaches the optimum temperature, after which the enzymes that catalyze this reaction become denatured.
• Prokaryotic cells may also have a slime layer for protection, a flagellum or plural flagella for movement, and some bacterial cells may have a large nucleus to contain DNA which can then be passed on to create offspring.
• Prokaryotic cells have a cell membrane, cytoplasm, ribosomes, and a cell wall, unlike eukaryotes which only sometimes have a cell wall.
• Eukaryotic and prokaryotic cells share features such as a cell membrane, cytoplasm, and genetic material found inside a nucleus.
• Cellulose is a component of the cell walls of plants, fungi, and some bacteria, providing strength and support.
• The genetic material of prokaryotic cells is not enclosed in a nucleus, instead it's found as a single loop of DNA inside the cytoplasm, and may also have one or more small rings of extra DNA called plasmids.
• Animal and plant cells are both eukaryotic cells, as are fungi and protista.
• Specialized plant cells include root hair cells and xylem cells, each with structures that help them carry out their specific functions.
• Specialized animal cells include sperm cells, muscle cells, and nerve cells, each with structures that help them carry out their specific functions.
• The nucleus, mitochondrion, and ribosomes are all organelles that can be found in animal and plant cells.
• Measles is a viral disease that is spread by droplet infection in the air and symptoms include fever, cough, red skin rash, and it can be fatal if complications arise.
• Tobacco mosaic virus affects many species of plants including tobacco plants and tomatoes and is spread by vectors which are other organisms that can carry the disease pathogen.
• Salmonella is a bacterial disease that causes food poisoning and is a common form of food poisoning it's a bacterium found in the guts of many different animals.
• Bacteria are larger than viruses and there are many good bacteria that play an important role in our digestive system.
• Viruses are a lot smaller than bacteria and live inside the body cells of the hosts once there they also reproduce rapidly but they require the hosts body cell to actually do this they damage and eventually destroy the host cell.
• The four main ways to reduce the spread of disease are simple hygiene measures, destroying vectors, isolating infected individuals, and vaccinations.
• HIV is a viral disease that is spread by sexual contact or by the exchange of body fluids such as blood and it initially causes flu-like symptoms but if not caught early it can develop into late stage HIV or AIDS.
• Bacteria can reproduce rapidly in the process of binary fission and can purchase poisons called toxins that damage the tissues of the body.
• Communicable diseases are caused by bacteria and viruses.
• Osmosis is important in animal cells for maintaining the correct concentration of solutes like glucose and salts inside the cell.
• Eventually, the water concentration will be equal on both sides of the membrane, and the water molecules will continue to move back and forth across the partially permeable membrane, but there will be no further net movement of water.
• Active transport is the movement of substances from where they are in a low concentration to where they are in a high concentration, against the concentration gradient, and it requires energy from respiration.
• In active transport, mineral ions move from a dilute solution in the soil into a more concentrated solution in the root hair cells, against the concentration gradient, requiring energy from respiration.
• In osmosis, the dilute side of the membrane has a higher concentration of water molecules, while the concentrated side has a lower concentration of water molecules.