1. “Structure and Function in Organisms
Life Science
“Structure and Function in Organisms

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Active Transport
The movement of molecules or ions against a concentration gradient, that is, from an area of lower concentration to higher concentration, and therefore requiring energy.
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3. Adenosine Triphosphate (ATP)
The molecule that carries the energy produced by respiration in its third, high-energy phosphate bond; used by cells to provide energy necessary for chemical reactions.
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Autotroph
An organism that produces its own food, including photosynthetic organism such as green plants and phytoplankton and chemosynthetic organisms such as sulfur bacteria.
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5. Capsule Click here to reveal the definition!
The outermost protective layer found on some prokaryotic cells.
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Cell Wall
A structure in plant cells that surrounds the cell membrane, important for external cell structure and the protection of the cell’s contents; also present in algae and certain bacteria.
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Cellular Respiration
The process in which carbon-rich sugar molecules react with oxygen to make energy for a cell’s use; occurs in heterotrophs and autotrophs.
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Centriole
A cell structure that helps separate the contents of the nucleus during cell divisions.
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Chloroplast
The structure in plants that contains chlorophyll and is the site of photosynthesis.
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10. Concentration Gradient
The varying levels of concentration of a substance on either side of a membrane or in an area.
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Cytoplasm
A jellylike material that surrounds the nucleus of a cell and contains most of the cell’s organelles.
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Cytoskeleton
The support framework inside the cell made up of microfilaments and microtubules.
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Diffusion
The general process by which all materials transfer passively in and out of cells.
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Eukaryote
A cell that has membrane-bound organelles and generic material contained inside a nucleus.
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Flagella
The whiplike structures on some prokaryotic cells that help the organism move.
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Glucose
A six-carbon sugar that is the usual form in which organisms process carbohydrates.
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Golgi Apparatus
An organelle that stores, modifies, packages, and ships enzymes and other molecules.
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Heterotroph
An organism requiring complex organic compounds of nitrogen and carbon for metabolic synthesis; it must get its energy from plants or animals.
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19. Homeostasis Click here to reveal the definition!
Detection and maintenance of a body’s internal environment.
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20. Instinct Click here to reveal the definition!
A complex animal behavior triggered by external stimuli.
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21. Lysosome Click here to reveal the definition!
A membrane-bound organelle that digests sugars and wastes.
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22. Mitochondrion Click here to reveal the definition!
A membrane-bound organelle that is the site of aerobic respiration.
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23. Nucleoid Click here to reveal the definition!
The bundle of fibers of DNA found within a prokaryotic cell.
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24. Nucleus Click here to reveal the definition!
The control center of a eukaryotic cell that contains the cell’s DNA.
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25. Organ Click here to reveal the definition!
A group of tissues that works together to complete a specific task.
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26. Organ System Click here to reveal the definition!
A group of organs that works together to complete a specific task.
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Organelle
A compartmentalized structure in eukaryotic cells that performs a specific function for the cell.
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28. Osmosis Click here to reveal the definition!
The passive transport of water molecules through a membrane.
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Passive Transport
The movement of molecules from higher concentration to lower concentration; does not require energy.
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Peroxisome
A membrane-bound organelle containing enzymes that break down peroxides, which can damage cells.
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Photosynthesis
The process by which plants make high energy carbohydrates in their chloroplasts from sunlight, water, and carbon dioxide.
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32. Pili Click here to reveal the definition!
Hollow, hairlike structures used by bacteria to attach to other cells.
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Plasma Membrane
A combination of lipids and proteins that separates the cell from its environment and helps regulate the traffic of molecules between the inside and the outside of the cell.
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Prokaryote
A cell that does not have a nucleus in which its hereditary material in stored; a single-celled organism such as bacteria.
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Protein Channel
A membrane passageway that opens and closes to allow necessary molecules to move in and out of the cell.
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Ribosome
An organelle, made of RNA and proteins, that is involved in protein synthesis.
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37. Rough Endoplasmic Reticulum (RER)
A series of membranous sacs that are covered with ribosomes and are an important producer of proteins.
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38. Smooth Endoplasmic Reticulum (SER)
A series of membranous tubules that assist in the synthesis of lipids and other molecules needed by the cell.
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Stimulus
A change in the internal or external environment, detectable by an organism or a cell within an organism.
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Tissue
A group of cells that works together to perform a task that requires many cells.
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Vacuole
A membrane-bound organelle in a cell that serves as a storage area for materials such as water, food, and waste products; helps to maintain cell rigidity in plants.
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Virus
A particle consisting of DNA encased in a protein coat that must inject its DNA into a living cell in order to reproduce.
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