These are fingerlike catchers. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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If no button appears, you cannot download or save the media. Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. A cell is one of the building blocks of life. Cells are membrane-bound groups of organelles that work together to allow it to function.
Some of the major organelles include the nucleus, mitochondria, lysosomes, the endoplasmic reticulum, and the Golgi apparatus. Plant cells also include chloroplasts, which are responsible for photosynthesis. Use these classroom resources to examine how cells function with your students. Cells function differently in unicellular and multicellular organisms. A unicellular organism depends upon just one cell for all of its functions while a multicellular organism has cells specialized to perform different functions that collectively support the organism.
Organelles are specialized structures that perform various tasks inside cells. Join our community of educators and receive the latest information on National Geographic's resources for you and your students.
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Related Resources. Cell Functions. After an egg cell and sperm cell unite to begin forming a new organism, all of the DNA in each cell of that organism will be virtually identical. If every part of the DNA in each cell is the same, then how do cells become different types of cells? DNA is wound tightly into chromosomes. Different regions of the chromosome code for every different function and cell type. Not all sections of a chromosome are turned on, or expressed, at the same time.
Only the regions that are needed to perform a specific function are expressed in each cell. These regions are often depicted as bands or stripes on a drawing of a chromosome. These bands are called genes, and whether or not a gene is expressed determines what type of cell will be created. For example, genes that are expressed turned on in a nerve cell are different from the genes that are expressed in a muscle cell. Both cells have the same DNA, but expressing different genes generates different cell types.
This process by which information from a gene is used to make the structures of a cell is called gene expression. Since RNA translates and transcribes the DNA code into proteins the structures of a cell , it also plays a role in cell differentiation. Environmental factors can also influence gene expression and cell differentiation.
For example, available nutrients, salinity, and temperature are all factors that can influence gene expression in organisms.
In Himalayan rabbits, genes that code for fur color are turned on and off depending on temperature. The Himalayan rabbit shown below lost black fur on her ears due to an infection. Another example of environmental factors influencing gene expression is metamorphosis.
Metamorphosis is regulated by external and internal factors, including temperature, available resources, and hormones. Unicellular organisms include bacteria, protists, and yeast.
For example, a paramecium is a slipper-shaped, unicellular organism found in pond water. It takes in food from the water and digests it in organelles known as food vacuoles. Nutrients from the food travel through the cytoplasm to the surrounding organelles, helping to keep the cell, and thus the organism, functioning.
Multicellular organisms are composed of more than one cell, with groups of cells differentiating to take on specialized functions. In humans, cells differentiate early in development to become nerve cells, skin cells, muscle cells, blood cells, and other types of cells. One can easily observe the differences in these cells under a microscope.
Their structure is related to their function, meaning each type of cell takes on a particular form in order to best serve its purpose. Nerve cells have appendages called dendrites and axons that connect with other nerve cells to move muscles, send signals to glands, or register sensory stimuli. Outer skin cells form flattened stacks that protect the body from the environment. Muscle cells are slender fibers that bundle together for muscle contraction.
The cells of multicellular organisms may also look different according to the organelles needed inside of the cell. For example, muscle cells have more mitochondria than most other cells so that they can readily produce energy for movement; cells of the pancreas need to produce many proteins and have more ribosomes and rough endoplasmic reticula to meet this demand. Although all cells have organelles in common, the number and types of organelles present reveal how the cell functions.
The ECM consists of a mixture of proteins and polysaccharides produced by the endoplasmic reticula and Golgi apparatuses of nearby cells. Once synthesized, these molecules move to the appropriate side of the cell — such as the basal or apical face — where they are secreted. Final organization of the ECM then takes place outside the cell. To understand how the ECM works, consider the two very different sides of the gut endothelium.
One side of this tissue faces the lumen, where it comes in contact with digested food. The other side attaches to a specialized ECM support structure called the basal lamina. The basal lamina is composed of collagen and laminin proteins, as well as various other macromolecules. On this side of the endothelium, adhesive junctions attach cells to the ECM. Transmembrane integrin proteins in the junctions bind components of the ECM and recruit signaling proteins to their cytoplasmic sides.
From there, the signals travel to the nucleus of each cell. This page appears in the following eBook. Aa Aa Aa. Cell Differentiation and Tissue. The gut contains a mixture of differentiated cells and stem cells. Figure Detail. Tissues are communities of cells that have functions beyond what any single cell type could accomplish.
Healthy tissues require the proper mix of cells, and the cells within them must be oriented correctly and dividing at an appropriate rate. In order to coordinate their function, organization, and rates of death and division, the cells in a tissue are constantly processing and responding to signals from one another and from the ECM around them.
Cell Biology for Seminars, Unit 5. Topic rooms within Cell Biology Close. No topic rooms are there. Or Browse Visually. Student Voices. Creature Cast. Simply Science. Green Screen.
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