unit 1 science

• The cell is the fundamental unit of life, all organisms, whatever their type or size, are composed of cells.
• The modern theory of cellular organisation states that all living things are composed of cells and cell products, new cells are formed only by the division of pre-existing cells, the cell contains inherited information (genes), which is used as instructions for growth, functioning and development, and the cell is the functioning unit of life; the metabolic reactions of life take place within the cells.
• Eukaryotic cells make up multi-cellular organisms such as plants and animals, they are complex cells with a nucleus and membrane-bound organelles.
• Prokaryotic cells are single-celled organisms, they are simple structures and do not have a nucleus or any membrane-bound organelles.
• Robert Hooke first described cells in 1665.
• The first living cell was observed by Anton van Leeuwenhoek in 1674 – 1683.
• Matthias Schleiden suggested in 1831 that all plant material is composed of cells.
• Jan Purkyne observed in 1831 that animal tissue is composed of cells and the structure is similar to plant tissue.
• The scientist credited for the Universal Cell Theory is Theodor Schwann, a German physiologist, who proposed that 'all living things are composed of cells'.
• Fluorspar is made of calcium and fluorine and if 51% is calcium, its empirical formula is CaF 2.
• The relative atomic mass (A r) of an element on the periodic table tells you how much mass there is in one mole of the element.
• An oxide of carbon contains 27% carbon and 73% oxygen and its empirical formula is CO 2.
• The molar mass of a substance is equal to the mass of one mole of a substance.
• 1.68g of iron is combined with 0.48g of oxygen and the empirical formula of the new compound is FeO.
• The empirical formula of a compound can be calculated from the masses of each element in the compound.
• A compound contains 75% carbon and 25% hydrogen and its empirical formula is C H 4.
• The relative formula mass is the sum of all the relative atomic masses of all the atoms in the empirical formula (simplest formula) of a compound (M r).
• In a titration, a known volume of base is added to a measured volume of acid until a certain pH is reached.
• 3.2g of sulfur reacts with oxygen to produce 6.4g of sulfur oxide and the formula of the oxide is SO 2.
• Robert Remak observed cell division in animal cells in 1852.
• His findings were not accepted at the time, but in 1855 Rudolf Virchow published the findings as his own to show new cells form from existing ones.
• Neutrophils are a type of white blood cell and they play an important role in the immune system, with multi-lobed nuclei enabling them to squeeze through small gaps when travelling to the site of infection.
• In mammals, erythrocytes do not have a nucleus or other organelles, increasing space for the haemoglobin molecules inside the cell that carry oxygen.
• Erythrocytes are a type of blood cell that do not have a nucleus or other organelles, increasing space for the haemoglobin molecules inside the cell that carry oxygen.
• The cytoplasm of neutrophils holds lysosomes that contain enzymes used to digest pathogens that are ingested by the neutrophil.
• Coherent waves must share the same frequency and same wavelength and have a constant phase difference.
• Light from a sodium-vapour lamp passes through the slits in a diffraction grating and creates a pattern on a screen, which is called an emission spectrum.
• The diagram shows how a stationary wave on a stretched string might be studied.
• If a chemical element or compound is vaporised by heating in a flame, or if you pass an electric current at high voltage through a gas, you typically see light emitted of a characteristic colour, according to the chemical nature of the material you are testing.
• When a string on a guitar is plucked, a stationary wave is set up and a sound is produced.
• Stationary waves are seen only at certain frequencies because oscillations of different amplitudes occur along the length of the wave in a pattern that does not change over time.
• When light is emitted from or absorbed by matter, you can only explain what happens by thinking of light as being composed of tiny particles or 'packets of energy', which are called photons.
• Interference pattern is a stationary pattern that can result from the superposition of waves traveling in different directions, provided they are coherent.
• Path difference is the difference in length between two (straight line) rays, e.g. one from a particular grating gap to a given point in space and the ray from the next-door grating gap to the same point.
• On the diagram, label a node and an antinode.
• Superposition is the adding together of wave displacements that occurs when waves from two or more separate sources overlap at any given location in space.
• Some of the wave's energy may be absorbed in the grating itself, but the remainder of the energy is scattered backwards as a reflection.
• The quantum theory of light and other electromagnetic radiations is based on the experimental observation that there is a simple relationship between the frequency, f, of the radiation and the energy, E, carried by each photon: E = hf where h is the Planck constant, −6.626 070 10−34 Js.
• The function of red blood cells is to transport oxygen around the body.
• Eukaryotic ribosomes are deter- mined as 80S whereas prokaryotic cell ribosomes are smaller and are 70S.