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Cells (Bacteria (Practical "investigate the effect of antiseptics on…
Cells
Bacteria
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Microorganisms that cause infectious disease are called pathogens. Not all microorganisms are pathogenic. Bacteria and viruses may reproduce rapidly inside the body and may produce toxins that make us feel ill. Viruses damage the cells by reproducing inside them and bursting out of them, thus destroying the cell. Entry routes for bacteria include: food, inhalation, cuts and open wounds. People at risk of infection those that are very old or young and those already on medication.
Bacteria multiply by simple cell division called binary fission which can be as often as once every 20 minutes. This would only be if it had enough nutrients and a suitable temperature. Bacteria can be grown in a nutrient broth solution or as colonies on agar plates. Uncontaminated cultures of bacteria are required for investigating the action of disinfectants and antibiotics. If a culture becomes contaminated with another bacteria, this bacteria could be harmful and could also affect our results.
Aseptic- Free from contamination caused by harmful bacteria, viruses or other microorganisms; surgically sterile.
Practical "investigate the effect of antiseptics on bacterial growth using agar plates and measuring zones of inhibition"
To ensure the safety of ourselves and other, before completing this practical we must handle the equipment safely and wash our hands.
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We must tape the plate to ensure no bacteria get in or out. Afterwards we must also dispose of the agar plate properly.
Not using the aseptic technique can result in cultivating harmful microbes and therefore we must sure we are using aseptic technique and disinfect surfaces after use.
Bacteria make us feel ill as they reproduce quickly. Once in our bodies, they release toxins that make us feel ill.
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mean division time: bacteria at the end of growth period = bacteria at the beginning of growth period x 2 number of divisions
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Chain of Infection
Sources of infection include from people already infected, pets or animals and unclean surfaces.
Entrance routes for pathogens include through food, inhalation, cuts/sores and things we put in our mouths.
People at high risk of infection include old people, young children/babies and people already on medication.
Ways out for microbes include sneezing, coughing and bodily fluid.
Infection can be spread through making contact when you haven't washed your hands and through sexual transmission.
Bacterial Cells
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Bacteria are much smaller than human cells and can only be seen by the naked eye when in bacterial colonies which are made up of millions of bacteria.
Uses of bacteria include: making yoghurt and cheese, bacteria in our gut helps with digestion, making medicine (e.g. penicillin).
Bacteria have no nucleus. The DNA is circular and free in the cytoplasm, rings called plasmids which contain DNA carry extra genetic information. Flagella (tails) allow the bacteria to move. The slime capsule protects the bacteria. Bacteria are roughly 1-5 nanometres long.
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Orders of Magnitude
If one number is 10 times bigger than another, you say it is an order of magnitude bigger. Orders of magnitude are shown in powers of 10.
If one cell or organelle is 10 time bigger than another, it is one order of magnitude bigger. It is approximately 100 times bigger it is two orders of magnitude bigger and so on.
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Specialised cells
In mature animals, cell division is mainly restricted to repair and replacement. As a cell differentiates, it acquires different sub-cellular structures to enable it to carry out a certain function, meaning it has been specialised.
As an organism develops, cells differentiate to form different types of cells. Most animal cells differentiate at an early stage whereas plant cells retain the ability to differentiate throughout their lives.
Examples
Xylem cell: Xylem cells transport tissue in plants to carry water and mineral ions from the root to the leaves. Also important for support. Dead cells form long hollow tubes to allow water and mineral ions to move more easily. Spiral lignin make the cells very strong to support the plant.
Phloem cell: Phloem cells are specialised transport tissue that carry dissolved glucose around the plant. To achieve this, the cell wall breaks down between the cells to form special sieve plates. These allow water and the dissolved carbohydrates to move easily around the plant. Loss of internal structures allows for more room for ovement of water and dissolved carbohydrates. Companion cells are closely related to the phloem vessel, these cells contain many mitochondria which release the energy required for the phloem to perform its function.
Root hair cell: You find root hair cells close to the tips of growing roots. Plants need to take in lots of water and dissolved mineral ions. The root hair cells help them to take up water more efficiently because of its structure. The root hairs increase the surface area for water to move into the cell. Root hair cells are always close to the xylem tissue. The root hair cells have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell. They also have many mitochondria which allows for energy to be available for active transport of mineral ions into the root.
Sperm cell: Sperm cells are usually released a long way from the egg they are going to fertilise. They contain the genetic information from the male parent. Depending on the type of animal, they need to move through water or through the female reproductive system to reach an egg. Then they have to break into the egg. Long tail whips from side to side and helps move the sperm towards the egg for fertilisation. The middle section is full of mitochondria, which release the energy for the tail to work. The acrosome stores digestive enzymes for breaking down the outer layers of the egg. A large nucleus contains the genetic information to be passed on.
Nerve cell: A nerve cell (or a neurone) is an electrically excitable cell that processes and transmits information through electrical and chemical signals. These signals between neurones occur via synapses (specialised connections with other cells).
Neurones can connect to each other to form neural networks via dendrites. Neurones are the core components of the nervous system, which includes the central nervous system (CNS) and the peripheral nervous system (PNS). The axon is very long so can carry information quickly. The axon is also covered in a myelin sheath, which is a layer of fat, that speeds up the rate of electrical impulses.
Muscle cell: There are three different types of muscle cells, one being the striated muscle. Its function is to contract and relax. To help it to do this it contains special proteins that help the muscle contract and relax.
They contain many mitochondria to release energy so it can be used in contraction and relaxation.
Plant and Animal Cells
Plant cells
Parts of a plant cell
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Cytoplasm- Gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions.
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Chloroplast- This is where photosynthesis occurs. This contains a green substance called chlorophyll.
Cell wall- Made of cellulose in plants and algae, and chitin in bacteria. It supports the cell and strengthens it.
Ribosomes- This is where protein synthesis takes place. All the proteins needed in the cell are made here.
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Vacuole- Contains cell sap, a weak solution of sugars and salts. This is important for keeping the cells rigid to support the plant.
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