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B1, B2: CELL STRUCTURE, TRANSPORT AND DIVISION - Coggle Diagram
B1, B2: CELL STRUCTURE, TRANSPORT AND DIVISION
CELL STRUCTURE
Animal Cell (Eukaryotic)
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Cytoplasm, where the cell's reactions take place.
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Plant Cell (Eukaryotic)
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Prokaryotic Cel
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CELL TRANSPORT
Diffusion
Diffusion is the passive movement of particles from where they are of a high concentration to where they are of a low concentration. It happens in the lungs in gas exchange, in the small intestine to absorb nutrients and in gills to absorb oxygen.
OSMOSIS
Osmosis is the movement of water from a dilute solution to a concentrated solution across a partially permeable membrane. It occurs in the roots of plants and in cells to maintain a good water level. When water moves into a cell, it is in a hypotonic solution and when water is moving out of a cell, it is in a hypertonic solution. If there is no net movement of water, then the solution is isotonic.
Animal cells will shrivel up in a hypertonic solution and will burst in a hypotonic solution as they have weak membranes. Usually, animal cells are in isotonic solutions.
Plant cells will become plasmolysed in a hypertonic solution and will wilt in an isotonic solution. Their vacuole needs to be pushing on the cell wall to maintain turgor. To be turgid, plants must be in a hypotonic solution.
ACTIVE TRANSPORT
Active transport is the movement of substance against a concentration graadient using energy in the form of ATP
Exchanging Materials
Larger animals have smaller Surface Area to Volume ratios which means they need specialised exchange systems, such as our lungs, to get the substances they need. Small animals have larger surface are to volume ratios so they can survive with simple diffusion across their skin.
Having a large surface area, good ventilation and blood supply, having thin walls to reduce diffusion distance and maintaining a large concentration gradient. These are adaptations of a good exchange system.
CELL DIVISION
Cells in your body are constantly getting damaged or dying. They need replacing with new cells. Cells grow and divide in a process called the cell cycle. All cells go through this cycle.
The cell cycle consists of the interphase, mitosis and the splitting phase (cytokinesis).
Inside the nucleus you have chromosomes with control your characteristics. You have 23 pairs, 23 from your mother and 23 from your father. Chromosomes are made up of genes which contain DNA. Genes code for the production of certain proteins.
Interphase: Cell growth stage, cell prepares for mitosis bt getting larger and duplicating organelles and chromosomes. Cells spend most of their time in this stage.
MITOSIS: PROPHASE: Chromosomes split and nucleus dissolves
METAPHASE: Chromosomes line up in the middle of the cell
ANAPHASE: Chromosomes are pulled to each side of the cell by centrioles and spindle fibres and so are the other organelles
TELOPHASE: Cytoplasm separates and membrane gets smaller around the middle
Cytokinesis: Cell splits and membranes separate. Nucleus forms again and cell has split into two identical daughter cells.
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STEM CELLS
Stem cells are unspecialised cells which have not been differentiated. Every cell in your body has come from stem cells. They make all types of cells by differentiating
Embryonic stem cells come from human embryos and bone marrow stem cells come from adult bone marrow. We also have stem cells in our skin, liver and brain.
Plants have stem cells in their meristems, roots and shoots. They can differentiate into any plant cell and they can also redifferentiatiate . They can be used to clone lots of the same type of plant. This is used to mass produce plants like disease resistant bananas.
Scientists have been researching ways in which to use stem cells to treat diseases like macular degeneration, cancer and blood poisoning. Stem cells can be encouraged to make certain cells which replace the damaged cells in the patients. However, there are problems with doing this. Using embryonic stem cells violates ethical and religious beliefs as the embryo technically cannot give consent. However embryonic stem cells can form any type of cell and they are less likely to be rejected. Bone marrow stem cells can only form blood cells, and they might even be rejected by the patient so immunosuppressants are needed. But the adult can give consent and they are effective ways of curing blood cancer.