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30 Cards in this Set

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  • Back
active transport
The movement of a substance across a biological membrane against its concentration or electrochemical gradient, with the help of energy input and specific transport proteins.
cell
A basic unit of living matter separated from its environment by a plasma membrane; the fundamental structural unit of life.
cell membrane
The outer membrane of the cell; the plasma membrane.
cell theory
All living things are composed of cells; cells arise only from other cells. No exception has been found to these two principles since they were first proposed well over a century ago.
cell wall
A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists. In the case of plant cells, the wall is formed of cellulose fibers embedded in a polysaccharide-protein matrix. The primary cell wall is thin and flexible, whereas the secondary cell wall is stronger and more rigid, and is the primary constituent of wood.
chloroplast
An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists as a mass of very long, thin fibers that are not visible with a light microscope.
chromosome
A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins. See chromatin.
cytoplasm
The entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane.
cytoskeleton
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions.
diffusion
The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area.
endocytosis
The cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicle.
eukaryote
An organism whose cells contain membraine-bound organelles and whose DNA is enclosed in a cell nucleus and is associated with proteins.
exocytosis
The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane.
facilitated diffusion
The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients.
Golgi apparatus
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum.
lysosome
A membrane-enclosed bag of hydrolytic enzymes found in the cytoplasm of eukaryotic cells.
microfilament
A solid rod of actin protein in the cytoplasm of almost all eukaryotic cells, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction.
microtubule
A hollow rod of tubulin protein in the cytoplasm of all eukaryotic cells and in cilia, flagella, and the cytoskeleton.
mitochondrion pl. mitochondria
An organelle in eukaryotic cells that serves as the site of cellular respiration.
nuclear envelope
The membrane in eukaryotes that encloses the nucleus, separating it from the cytoplasm.
nucleolus
A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes.
organ
A specialized center of body function composed of several different types of tissues.
organelle
One of several formed bodies with a specialized function, suspended in the cytoplasm and found in eukaryotic cells.
osmosis
The diffusion of water across a selectively permeable membrane.
phagocytosis
A type of endocytosis involving large, particulate substances.
ribosome
A cell organelle constructed in the nucleolus, functioning as the site of protein synthesis in the cytoplasm. Consists of rRNA and protein molecules, which make up two subunits.
selective permeability
A property of biological membranes that allows some substances to cross more easily than others.
tissue
An integrated group of cells with a common structure and function.
vacuole
A membrane-enclosed sac taking up most of the interior of a mature plant cell and containing a variety of substances important in plant reproduction, growth, and development.