b1-9 triple paper 1

• Cell

  The basic unit of all forms of life
• Eukaryotic cells


  Cells with a genetic material enclosed in a nucleus – e.g. plant and animal cells
• Prokaryotic cells


  Bacterial cells; these don't have a nucleus to enclose their genetic material
• Cell membrane

  The border of all types of cell. The cell membrane separates the inside of the cell from the environment. It controls the movement of substances into and out of the cell
• Sub-cellular structure


  A part of a cell. (Sub- means less than – so these are the component parts of cells.) Also known as organelles
• Nucleus

  The enclosure for genetic material found in plant and animal cells. It controls the activities of the cell
• Cytoplasm


  The interior of a cell, where most of the chemical reactions needed for life take place
• Mitochondria


  The sub-cellular structure where aerobic respiration takes place
• Ribosome


  The sub-cellular structure where proteins are made (synthesised)
• Chloroplast


  A sub-cellular structure responsible for photosynthesis – only found in plant cells and algal cells
• Permanent vacuole


  A sub-cellular structure only found in plant and algal cells – it is filled with cell sap (a store of nutrients for the cell)
• Cell wall


  A sub-cellular structure that is never found in animal cells. It is made of cellulose, it is outside the cell membrane and it strengthens the cell
• DNA


  The molecule that holds the genetic information in a cell. In eukaryotic cells, it is one linear strand. In prokaryotic cells, the DNA forms a loop
• Plasmid


  A small loop of extra DNA, only found in prokaryotic cells
• Eukaryotic cells


  • They have a nucleus, unlike prokaryotic cells
• Prokaryotic cells


  • They are smaller and their genetic material (DNA) is not enclosed in a nucleus
• Bacteria are prokaryotic cells (all bacteria are single-celled organisms)
• Multicellular


  This describes an organism that is made of lots of cells – such as animals or plants
• Specialised cell


  Almost all cells in multicellular organisms have a particular job, or function
• Tissue


  A group of cells with similar structures and functions – i.e. a group of specialised cells
• Organ

  An organ is a collection (or aggregation) of tissues performing a specific function
• Organ system


  Organs don't operate alone: they work together to form organ systems
• Organism


  An organism has many organ systems, all contributing to its survival
• Light microscope


  A usual school microscope is a light microscope. You can see large sub-cellular structures like a nucleus with it, but not a lot more detail than that
• Magnification


  This is the measure of how much a microscope can enlarge the object you are viewing through it
• Resolution

  This is the measure of the level of detail you can see with a microscope
• Electron microscope


  A type of microscope with much high magnification and resolution than a light microscope. Essential for discovering the smaller sub-cellular structures
• The image is how it looks through the microscope. The real object is what you are looking at. The image and object must be measured with the same unit, e.g. both in µm or nm
• Cells become specialised by differentiation, which means they develop new features to help them perform a specific function
• Tissues are formed when cells with similar structures and functions work together
• Organs are formed from multiple tissues working together
• Organ systems are formed when multiple organs work together
• Centimetre

  1/100 metre (10-2). A centimetre is 1 one hundredth of a metre
• Millimetre

  1/1000 metre (10-3). A millimetre is 1 one thousandth of a metre
• Micrometre

  1/1 000 000 (10-6). A micrometre is 1 one millionth of a metre
• Nanometre

  1/1 000 000 000 (10-9) A nanometre is 1 one billionth of a metre
• Electron microscopes were a vital invention for understanding cells. They have higher magnification and more resolving power than light microscopes, so they let you see smaller structures
• Diffusion

  The net (overall) movement of particles from a higher concentration to a lower concentration. Diffusion happens across cell membranes. It does not require any energy from the cell
• Concentration gradient

  The difference in concentration of a substance between two places. A 'steeper' concentration gradient means there is a bigger difference in concentration
• Surface area to volume ratio


  The surface area divided by the volume of an organism, organ or cell. Generally, the smaller something is, the larger the surface area to volume ratio