Cells & DNA

• Cell: The basic unit of all living organisms, it is surrounded by a cell surface membrane and contains genetic material (DNA) and cytoplasm containing organelles.
• Organelle: A functionally and structurally distinct part of a cell, e.g a ribosome or mitochondria.
• Nucleus (plural nuclei): A relatively large organelle found in eukaryotic cells, therefore controls the activities of the cell, it is surrounded by two membranes which together form the nuclear envelope.
• Eukaryotic cell: An organism whose cells contain a nucleus and other membrane-bound organelles.
• Prokaryote: An organism whose cells do not contain a nucleus or any other membrane-bound organelles.
• The origins of cells go back to the early days of microscopy when an English scientist, Robert Hooke published a drawing of cork cells.
• In 1665, Robert Hooke published a drawing of cork cells.
• 200 years later, a general cell theory emerged from the work of two german scientists.
• A cell is surrounded by a thin membrane.
• The membrane is an essential feature of cells due to it controlling the exchange between the cell and its environment → Acts as a barrier + Control the movement of materials across the membrane in both directions.
• Without a membrane life wouldn't exist because the chemicals of the cell would simply mix with the surrounding chemicals by diffusion.
• Complex cells contain a nucleus (plural nuclei) surrounded by two membranes.
• Genetic material is also present in the nucleus.
• In simple cells the DNA was not surrounded by membranes but free in the cytoplasm.
• Organisms made of cells with membrane-bound nuclei are known as eukaryotes (e.g animals, plants,fungi etc.)
• Simplier cells lacking membrane-bound nuclei are known as prokaryotes (e.g bacteria)
• There are two fundamentally different types of microscopes, the light microscope and the electron microscope, which use radiation to see the specimen being examined.
• The light microscope uses light as a source of radiation.
• The electron microscope uses electrons as a source of radiation.
• One thousandth is represented as 0.001, 1/1000, or 10^-3.
• One millionth is represented as 0.000001, 1/1000000, or 10^-6.
• One thousandth milonoth is represented as 0.000000001, 1/1000000000, or 10^-9.
• The unit symbol for one micrometer is µm.
• The unit symbol for one nanometer is nm.
• The smallest structure visible to the human eye is about 50-100 μm in diameter.
• Grama (singular granum) :Stacks of membranes inside a chloroplast.
• Chromatin: The material of which chromosomes are made, consisting of DNA, proteins and small amounts of RNA; visible as patches or fibers within the nucleus when stained
• Chromosomes: In the nucleus of the cells of eukaryotes, a structure made of the term ‘circular DNA’ is now also commonly used for the cellular stand of DNA present in a prokaryotic cell
• Nucleolus: A small structure, one or more of which is found inside the function to manufacture ribosomes using the information in its own DNA
• Protoplasm: All the living material inside a cell (cytoplasm + nucleus = protoplasm)
• Cytoplasm: The contents of a cell, excluding the nucleus
• Mitochondrion (plural mitochondria)The organelle in eukaryotes in which aerobic respiration takes place
• Cell wall: A wall surrounding prokaryote, plant and fungal cells; the wall contains a strengthening material which protects the cell from mechanical damage, supports it and prevents bursting by osmosis if the cell is surrounded by a solution with a higher water potential.
• Plasmodesma (plural: plasmodesmata) A pore-like structure found in plant cell walls; plasmodesmata of neighboring plant cells line up to form tube-like pores through the cell walls, allowing the controlled passage of materials from one cell to another; the pores contain ER and are lined with the cell surface membrane
• Vacuole: An organelle found in eukaryotic cells; a large permanent central vacuole is a typical feature of plant cells, where it has a variety of functions, including storage of biochemicals (e.g salts, sugars and waste products);  temporary vacuoles, such as phagocytic vacuoles (also known as phagocytic vesicles), may form in animal cells
• Tonoplast: The partially permeable membrane that surrounds plant vacuoles
• Chloroplast: An organelle,bounded by an envelope, in which photosynthesis takes place in eukaryotes
• Photosynthesis: The production of organic substances from inorganic ones, using energy from light
• The eyepiece is where one views the enlarged object.
• The eyepiece contains a lens called the ocular that further magnifies the specimen by 10x.