Biology

• The cell theory states; that all living things are composed of cells, the cell is the smallest living organisational unit, all cells come from pre-existing cells
• All living things grow and develop over time. (characteristic of living things)
• all living things are capable of self generated movement. e.g individual bacteria swimming, plants growing towards a light source, animals moving to find food
• All living things sense and react to stimuli. e.g a plant reacting to the environment and growing towards the sunlight.
• All living things reproduce. e.g humans reproducing by sexual or asexual methods.
• all living things can extract energy from carbohydrates, fats and proteins through aerobic or anaerobic cellular respiration.
• Anaerobic respiration - no oxygen present so glucose reacts with pyruvate to form lactic acid which releases less ATP than aerobic respiration. Lactic acid builds up causing muscle fatigue.
• Cell membrane is made of phospholipids and cholesterol. It has hydrophilic heads that face outwards and hydrophobic tails that face inwards. The lipid bilayer forms a barrier between inside and outside of the cell.
• Cell membrane - controls what enters/leaves the cell. It also regulates the internal conditions of the cell such as pH and temperature.
• The plasma membrane contains embedded proteins such as channel proteins (allow substances to pass through) and carrier proteins (bind to substance on one side then change shape allowing it to cross).
• Plasma membranes have glycoproteins attached to them which act as recognition sites for other cells.
• Chloroplasts contain thylakoids stacked into grana. They have a stroma where photosynthesis takes place. Chlorophyll absorbs light energy and converts it into chemical energy stored as sugars.
• Mitochondria contains cristae (foldings) within its matrix. Mitochondria produce ATP during aerobic respiration using glycolysis and Kreb's cycle.
• all living things can maintain a relatively stable internal environment unique to individual species, which is known as maintaining Homeostasis. This allows organisms to tolerate environmental changes such as varying temperatures, or a lack of water availability.
• All living things produce wastes that must be removed. e.g urine or faeces or sweat, if these are not removed from the body, they can build up and become toxic to the body.
• all living things extract nutrients from the environment, which are used to produce cellular energy, grow and develop and maintain homeostasis. e.g some organisms gain nutrition via consumption of organic materials[heterotrophs] whereas others produce their own essential nutrients from simple inorganic molecules [autotrophs].
• milimetre to micrometre = 1000um = 1mm

  micrometre to nanometre = 1000nm = 1um
• all living things are chemically complex and highly organised
• A compound microscope has an objective lens that provides the main magnification, which is compounded by the eyepiece lens. Light passes through the specimen to produce an image
• Electron microscopes use electrons instead of light waves to form images. They have much greater resolving power than light microscopes because electron wavelengths are shorter than those of visible light. The two types of electron microscope are scanning electron microscopes(SEM) and transmission electron microscopes(TEM).
• Scanning Electron Microscopy uses a beam of high-energy electrons to scan across the surface of a sample. It produces a three dimensional image with great detail on the surface structure of cells and tissues.
• Transmission Electron Microscopy uses a beam of electrons to pass through thin sections of tissue or cells. This allows internal structures such as mitochondria and ribosomes to be seen clearly.
• hypertonic is a solution with a higher concentration of solute outside the solution and a lower concentration of free water molecules in the extracellular environment.
• hypotonic is a solution with a lower concentration of solutes compared to the surrounding fluid.
• isotonic is when there is no net movement of water into or out of the cell due to equal concentrations of solutes inside and outside the cell.
• Crenated - An animal cell in a hypertonic solution

  Plasmolysed - A plant cell in a hypertonic solution
• Lysed - Animal cell in hypotonic solution
• Turgid - Plant cell in hypotonic solution
• The process by which water moves down its concentration gradient, from areas of high water potential (low solute concentration) to areas of low water potential (high solute concentration), is called osmosis.
• A semi-permeable membrane allows some substances to pass through it but not others.
• the cell theory states that all organisms are made up of one (unicellular) or more cells (multicellular),cells are the basic structural and functional units of all life forms, all new cells are produced from exsisting cells