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Biology
Cells, Tissues and Organs
The Cell Membrane.
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All living organisms are made up of cells. Many cells have a membrane that surrounds the
cytoplasm.
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It can also be known as a plasma membrane and is partially permeable. This means that it only
allows small particles or substances to pass into or out of the cell.
The Nucleus.
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This contains the DNA and chromosomes that are necessary for growth, development and
reproduction.
The Cytoplasm.
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This makes up most of the cell.
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It provide a protective place for organelles, such as the mitochondria and ribosomes, to sit and
safely carry out their function.
The Mitochondria.
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This part of the cell is used during cell respiration and the release of energy within the body.
The Ribosomes.
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Ribosomes are responsible for making and assembling proteins within a cell.
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This is known as protein synthesis.
The Cell Wall.
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This is a feature that only plant cells have.
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The cell wall is a layer that surrounds the outside of the cell.
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It is made up of cellulose and allows many particles and substances to passes freely across into or
out of the cell.
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Its purpose is to help the cell to keep its shape.
The Vacuole.
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This is a feature that only plants cells have.
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Its purpose is to store dissolved sugars, mineral ions and other substances in a watery liquid known
as cell sap.
Chloroplast.
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This is a an organelle, only found in plant cells.
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Its function is to absorb light which can them be converted into food and energy for the plant.
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Chloroplast contains a green pigment known as chlorophyll.
The Nerve Cell.
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This is known as a specialised cell, this is because it has a specific function.
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Nerve cells are also known as neurones, they conduct an electrical impulse which travels through
the body, stimulating glands, organs, cells or tissues to perform their function.
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Part of the nerve cell called the nerve fibre, can vary in length but it is usually very long, allowing
the electrical impulse to travel grate distances in the body.
The Palisade Cell.
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This is a specialised cell found in plants.
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Its function is to absorb light for photosynthesis.
The Ciliated Cell.
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This is a cell that can be found in the human respiratory and digestive system.
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It has tiny hairs on its surface which are used to waft particles along the respiratory and digestive
tract, keeping them clean.
Tissues.
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Tissues are made up of all the cells that perform the same or similar function.
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There are three main groups of tissues:
1. Epithelial Tissue – made up of a thin layer of cells that are used to line the mouth, air and food
passages, protecting them from damage.
2. Muscular Tissue – made up of cells that contract and relax during movement.
3. Glandular Tissue – made up of cells that produce the chemicals used in the body.
Once the cells are organised into tissues, tissues are organised into organs. Organs can be made up of
many different types of tissues depending on their particular function.
Organs.
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Some organs within the body work together to perform functions.
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Two or more organs working in this way is known as a system.