Animal and plant cells PartFunction NucleusContains genetic material, which controls the activities of the cell CytoplasmMost chemical processes take place here, controlled by enzymes Cell membraneControls the movement of substances into and out of the cell MitochondriaMost energy is released by respiration here RibosomesProtein synthesis happens here Extra parts of plant cells PartFunction Cell wallStrengthens the cell ChloroplastsContain chlorophyll, which absorbs light energy for photosynthesis Permanent vacuoleFilled with cell sap to help keep the cell turgid
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Bacterial Cells A bacterium is a single-celled organism. A bacterial cell has a different structure to an animal or plant cell. It has cytoplasm, a membrane and a surrounding cell wall, but the genetic material in a bacterial cell is not in a distinct nucleus. Yeast Cells Yeast is a single-celled organism. Like bacterial cells, yeast cells have cytoplasm and a membrane surrounded by a cell wall. But unlike bacterial cells, yeast cells have a nucleus. Specialised cells Cells may be specialised for a particular function. Their structure will allow them to carry this function out.
Here are some examples: Examples of the functions of cells CellFunctionAdaption Leaf cellAbsorbs light energy for photosynthesisPacked with chloroplasts. Regular shaped, closely packed cells form a continuous layer for efficient absorption of sunlight. Root hair cellAbsorbs water and mineral ions from the soilLong ‘finger-like’ process with very thin wall, which gives a large surface area. Sperm cellFertilises an egg cell – female gameteThe head contains genetic information and an enzyme to help penetrate the egg cell membrane.
The middle section is packed with mitochondria for energy. The tail moves the sperm to the egg. Red blood cellsContains haemoglobin to carry oxygen to the cells. Thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus, so the whole cell is full of haemoglobin. Diffusion Dissolved substances have to pass through the cell membrane to get into or out of a cell. Diffusion is one of the processes that allows this to happen. Diffusion occurs when particles spread.
They move from
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a region where they are in high concentration to a region where they are in low concentration. Diffusion happens when the particles are free to move. This is true in gases and for particles dissolved in solutions. Particles diffuse down a concentration gradient, from an area of high concentration to an area of low concentration. This is how the smell of cooking travels around the house from the kitchen, for example. Examples of diffusion Two examples of diffusion down concentration gradients LocationParticles moveFromTo
GutDigested food productsGut cavityBlood in capillary of villus LungsOxygenAlveolar air spaceBlood circulating around the lungs Remember, particles continue to move from a high to a low concentration while there is a concentration gradient. In the lungs, the blood will continue to take in oxygen from the alveolar air spaces provided the concentration of oxygen there is greater than in the blood. Oxygen diffuses across the alveolar walls into the blood, and the circulation takes the oxygen-rich blood away. Photosynthesis Green plants absorb light energy using chlorophyll in their leaves.
They use it to react carbon dioxide with water to make a sugar called glucose. The glucose is used in respiration, or converted into starch and stored. Oxygen is produced as a by-product. This process is called photosynthesis. Temperature, carbon dioxide concentration and light intensity are factors that can limit the rate of photosynthesis. Photosynthesis summary Photosynthesis is the chemical change which happens in the leaves of green plants. It is the first step towards making food – not just for plants but ultimately every animal on the planet.
During photosynthesis: •Light energy is absorbed by chlorophyll, a green substance found inchloroplasts in some plant cells and algae •Absorbed light energy is used to convert carbon dioxide (from the air) and water (from the soil) into a sugar called glucose •Oxygen is released as a by-product This equation summarises what happens in photosynthesis: Some glucose is used for respiration, while some is converted into insolublestarch for storage. The stored starch can later be turned back into glucose and used in respiration. Storage and use of glucose
The glucose produced in photosynthesis may be used in various ways by plants and algae. Storage Glucose is needed by cells for respiration. However, it is not produced at night when it is too dark for photosynthesis to happen. Plants and algae store glucose as insoluble products. These include: •Starch •Fats and oils Use Some glucose is used for respiration to release energy. Some is used to produce: •Cellulose – which strengthens the cell wall •Proteins – such as enzymes and chlorophyll Plants also need nitrates to make proteins. These are absorbed from the soil as nitrate ions.