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B1: CELL STRUCTURE AND TRANSPORT (Features of Animal & Plant Cells…
B1: CELL STRUCTURE AND TRANSPORT
Microscopes
Electron microscopes magnify up to 2000000 and have a resolving power of around 0.2 nm
magnification = size of image/size of real object
Light microscopes magnify up to about x2000 and have a resolving of about 200nm
resolving power is the ability of a microscope to separate or distinguish small or closely adjacent images
Features of Animal & Plant Cells
cytoplasm
Most chemical processes take place here, controlled by enzymes
mitochondria
Most energy is released by respiration here
nucleus
Contains genetic material, which controls the activities of the cell
ribosomes
Protein synthesis happens here
cell membrane
Controls the movement of substances into and out of the cell
Features Exclusive to Plant Cells
chloroplasts
Contain chlorophyll, which absorbs light energy for photosynthesis
cell wall
Strengthens the cell
vacuole
Filled with cell sap to help keep the cell turgid
Eukaryotic and Prokaryotic Cells
Eukaryotic cells all have a cell membrane, cytoplasm and genetic material enclosed in a nucleus
Prokaryotic cells consist of cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not in a distinct nucleus- instead, it forms a single DNA loop. Some prokaryates have extra small rings of DNA called plasmids
Specialisation in Animal Cells
sperm cell
The middle section is packed with mitochondria for energy. The tail helps the sperm move to the egg.
red blood cell
Thin outer membrane to let oxygen diffuse through easily and the cell has a concave shape for more surface area to allow for more diffusion
Specialisation in Plant Cells
root hair cell
Long shape gives more surface area for the diffusion of mineral ions
palisade cell
Packed full of chloroplasts for more more photosynthesis
Diffusion
The rate of diffusion is affected by concentration, temperature and surface area
In the body diffusion takes place during gaseous exchange
Diffusion is is the overall movement of a substance from a region of high to low concentration
Osmosis
Osmosis is the movement of water from a less concentrated solution to a more concentrated solution through a partially permeable membrane
Differences in the concentrations of solutions inside and outside a cell cause water to move into or out of a cell by osmosis
Animal cells can be damaged is the concentration outside of cells changes dramatically
Plants gain water by osmosis through their roots. Water moves into plant cells by osmosis, making them turgid or stiff so that they are able to hold the plant upright.
Active Transport
Active transport is the movement of dissolved molecules into or out of a cell through the cell membrane, from an area of lower concentration to an area of higher concentration. The particles move against the concentration gradient, using energy released during respiration.
Examples of active transport include the uptake of ions from soil water by root hair cells in plants and the uptake of glucose by epithelial cells in the villi of the small intestine