Topic 1 : Cell Biology

• The five animal cell organelles are the nucleus, mitochondria, cytoplasm, cell membrane, ribosomes
• The three plant cell organelles are the chloroplasts, vacuole, cell wall.
• The five organelles of bacteria are the cytoplasm, cell membrane, cell wall, DNA strand, plasmid
• A eukaryotic cell has a membrane bound nucleus
• A prokaryotic cell has no membrane bound nucleus
• The formula for microscopy is magnification = image size / real size
• Differentiation is the process in which a cell changes to become specialised for a specific purpose
• The 3 adaptations of a sperm cell are : a long tail, lots of mitochondria, enzymes in the head
• the adaptation of a nerve cell is branched connections to allow it to send signals to many different parts of the body
• The adaptations of the muscle cell is a large surface area, lots of mitochondria
• The adaptation of the root hair cell is its large surface area
• Xylem are hollow in the centre
• Phloem have very few organelles to allow the flow of substances
• Pluripotent cells are found in early human embryos and can differentiate into any type of cell
• Multipotent stem cells are found in the bone marrow and can differentiate into many different types of cells
• In plants, stem cells are found in the meristems.
• Mitosis is a part of the cell cycle in which the cell separates into two identical daughter cells
• In mitosis, first the chromosomes duplicate, secondly, the chromosomes must line up in the middle of the cell, thirdly, membranes form around the 2 sets of chromosomes, lastly, the cell membrane and the cytoplasm divide
• In a culturing microorganisms practical, paper discs soaked in different types or concentrations of antibiotics are placed on an agar plate that has an even covering of bacteria. Antibiotic resistant bacteria will continue to grow on the agar, but non-resistant strains will die, a clear area will be left where the bacteria have died, this is the inhibition zone. A control paper disc soaked in no bacteria at all should also be placed on the agar. Leave for 48 hours at 28 degrees Celsius. The more effective the bacteria, the larger the inhibition zone
• Diffusion is the gradual movement of particles from an area of high to low concentration
• The bigger the concentration gradient, the faster diffusion occurs. A higher diffusion rate means a faster rate of diffusion
• Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of low concentration
• A partially permeable membrane is one with very small holes
• The water molecules pass both ways, because water molecules move about randomly in the liquid state.
• Because of the higher concentration on one side, there is a net flow of of water
• Active transport is the movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient
• Active transport requires energy (ATP)