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Biology Knowledge Organiser
B1 - Cell structure and transport
Cell The basic unit of all forms of life. Eukaryotic Cells Cells with a genetic material enclosed in a nucleus โ e.g. plant and animal cells. Prokaryotic Cells Bacterial cells; these donโt 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 โ 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 โ only found in plant cells and algal cells. Permanent Vacuole A sub-cellular structure only found in plant and algal cells โ 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
Eukaryotic cells include all plant and animal cells. Their most important feature is that they have a nucleus, unlike prokaryotic cells. Permanent vacuole ribosomes mitochondria
Prokaryotic Cells
Bacteria are prokaryotic cells (all bacteria are single-celled organisms). The most important differences to eukaryotic cells are that they are smaller and their genetic material (DNA) is not enclosed in a nucleus. Prokaryotic cells have DNA in a loop, and, in addition to the main loop of DNA, they have small loops of DNA called plasmids. Plasmids allow bacteria to swap genetic information between them. Cell membrane Cell wall Cytoplasm DNA Plasmid Ribosome Flagellum (tail)
Multicellular This describes an organism that is made of lots of cells โ 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 โ i.e. a group of specialised cells. Organ An organ is a collection (or aggregation) of tissues performing a specific function. Organ System Organs donโt operate alone: they work together to form organ systems. Organism (again) 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. Equation Meanings of terms in equation ๐๐๐๐๐๐๐๐๐๐ก๐๐๐ =
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 ฮผm ornm.
Multicellular Organisms
You are a multicellular organism, just like all animals, plants and many types of fungus. But, not all your cells are the same. Cells become specialised by differentiation , which means they develop new features to help them perform a specific function. E.g. sperm cells and root hair cells. Tissues are formed when cells with similar structures and functions work together. For example: muscle tissue in animals; phloem tissue in plants. Organs are formed from multiple tissues working together. For example: the stomach in animals; the leaf in plants. Organ systems are formed when multiple organs work together. For example: the digestive system in animals; the vascular (transport) system in plants.
Microscopy
Use of a microscope is called microscopy. Microscopes allowed scientists to discover cells and find all the sub-cellular structures. Because cells and their parts are very small, it is not useful to measure them in metres. Instead, we use small divisions of the metre as follows: Centi metre = 1/100 metre (10-^2 ). A centimetre is 1 one hundredth of a metre. (cm) Milli metre = 1/1000 metre (10-^3 ). A millimetre is 1 one thousandth of a metre. (mm) Micro metre = 1/1 000 000 (10-^6 ). A micrometre is 1 one millionth of a metre. (ฮผm) Nano metre = 1/1 000 000 000 (10-^9 ) A nanometre is 1 one billionth of a metre. (nm) 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.
Biology Knowledge Organiser
B1 - Cell structure and transport
Gas exchange in lungs Substance exchange in roo
Biology Knowledge Organiser
B1 - Cell structure and transport
Small intestine The organ in the digestive system where products of digestion are absorbed into the bloodstream. Lungs The organs were gas exchange takes place. The air sacs where gases are actually exchanged are called alveoli. Gills The organs in fish where gas exchange takes place. Oxygen is absorbed from the water into the blood, and carbon dioxide is transferred to the water. Leaves The plant organs responsible for gas exchange. Ventilation Technical term for breathing in and out. Breathing in brings fresh air, with a relatively high oxygen concentration, into the lungs, and breathing out removes the air with a relatively high concentration of carbon dioxide (and low concentration of oxygen). Gas exchange in gills Gas exchange in leaves
Specialised exchange surfaces
To be effective at exchanging substances with the environment, any exchange surface must have a large surface area , and a thin wall/membrane for a short diffusion pathway. In animals, a constant blood supply also increases effectiveness, and in the lungs, ventilation (breathing in and out) increases effectiveness by refreshing the concentration gradient with each breath.
Exchange in animals and plants
Gas exchange in many animals, including us, happens in the lungs. The structures in the lungs where it happens are the alveoli. There are millions of these tiny air sacs, so in total their surface area is gigantic. They also have a short diffusion pathway, a good blood supply and air supply due to ventilation. (look at the diagram of one alveolus) In fish, gills are where gas exchange takes place (see diagram). Again, a huge surface area increases the efficiency of gas exchange, along with a short diffusion pathway and good blood supply. The huge surface area comes from the division of gills into very thin plates of tissue called lamellae. This also creates the short diffusion pathway. In plants, the roots absorb water and mineral ions. The root hair cells have long projections that increase the surface area of this exchange surface, and shorten the diffusion pathway. The leaves are responsible for gas exchange, including oxygen out and water vapour out, and carbon dioxide in. Being flat and broad increases the effectiveness of the leaves as exchange surfaces, by increasing the surface area and shortening the diffusion pathway. In leaves, exchange happens through microscopic holes called stomata.
