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The simplest collection of matter that can live

cell theory

The theory that all living things are composed of cells and all cells come from other cells


an optical instrument used for viewing very small objects, such as mineral samples or animal or plant cells, typically magnified several hundred times.


An increase in the apparent size of an object

resolving power

A measure of the clarity of an image; the minimum distance that two points can be separated and still be distinguished as two separate points

light microscope

An optical instrument with lenses that refract (bend) visible light to magnify images of specimens

transmission electron microscope

A microscope that passes an electron beam through very thin sections, primarily used to study the internal ultrastructure of cells

scanning electron microscope

A microscope that passes an electron beam through very thin sections, primarily used to study the internal ultrastructure of cells


a microscopic single-celled organism, including the bacteria and cyanobacteria, that has neither a distinct nucleus with a membrane nor other specialized organelles


an organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleu


A cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm

plasma membrane

The membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell's chemical composition

cell wall

A fairly rigid, chemically complex structure that exists outside the plasma membrane of most prokaryotes


A long cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules, ensheathed in an extension of plasma membrane


a water based "jello" that organelles aer suspended in


the genetic control center of the cell that contains DNA


A threadlike, gene-carrying structure found in the nucleus

nuclear envelope

The membrane in eukaryotes that encloses the nucleus, separating it from the cytoplasm

endomembrane system

The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles

rough ER (endoplasmic reticulum)

That portion of the endoplasmic reticulum studded with ribosomes. Makes membranes and proteins that will be secreted by the cell and embedded in the cell.

smooth ER (endoplasmic reticulum)

That portion of the endoplasmic reticulum that is free of ribosomes. Synthesizes lipids and in muscle cells it stores calcium ions.

golgi apparatus

An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum

secretory protein

Proteins that are secreted by the cell via the endoplasmic reticulum


A tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell


A membrane-enclosd bag that contains enzymes and digests used up molecules and organelles for reuse


A membrane-enclosed sac containing a variety of substances

central vacuole

a membranous sac in plant cells that supports the cell and contains water


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


An organelle in eukaryotic cells that serves as the site of cellular respiration


A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions


hair like structures for movement


helps stick to surfaces in bacteria


organizes DNA during cell division


catalase is located here which helps break down hydrogen peroxide


dense region of nucleus where ribosomes begin to be made

cell junction

A structure that connects cells within a tissue to one another


An open channel in the cell wall of plants through which strands of cytosol connect from adjacent cells

extracellular matrix

layers of glycoproteins, helps cells stack together, assists in cell communication

selective permeability

A property of biological membranes that allows some substances to cross more easily than others


A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail


A protein that binds selectively to a specific molecule and initiates a biological response


The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area

passive transport

The diffusion of a substance across a biological membrane


The diffusion of water across a selectively permeable membrane


In comparing two solutions, referring to the one with a greater solute concentration


In comparing two solutions, the one with a lower solute concentration


The control of water balance in organisms living in hypertonic, hypotonic, or terrestrial environments

facilitated diffusion

The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients

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


The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane


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


A microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells that allows exchange between the blood and interstitial fluid

interstitial fluid

The internal environment of vertebrates, consisting of the fluid filling the spaces between cells


A type of connective tissue with a fluid matrix called plasma in which blood cells are suspended

open circulatory system

An arrangement of internal transport in which blood bathes the organs directly and there is no distinction between blood and interstitial fluid

closed circulatory system

Circulatory systems in which blood is confined to vessels and is kept separate from the interstitial fluid


A vessel that carries blood away from the heart to organs throughout the body


A vessel that returns blood to the heart


A chamber that receives blood returning to the vertebrate heart


A heart chamber that pumps blood out of a heart


A vessel that conveys blood between an artery and a capillary bed

pulmonary arteries

Carry deoxygenated blood to the lungs


The largest blood vessel of the cardiovascular system

superior vena cava

A large vein that channels oxygen-poor blood from the upper body

inferior vena cava

Another large vein that drains blood from the lower body

cardiac cycle

The alternating contractions and relaxations of the heart


The stage of the heart cycle in which the heart muscle is relaxed, allowing the chambers to fill with blood


The stage of the heart cycle in which the heart muscle contracts and the chambers pump blood

cardiac output

The volume of blood pumped per minute by the left ventricle of the heart

blood pressure

The hydrostatic force that blood exerts against the wall of a vessel


The rhythmic stretching of the arteries caused by the pressure of blood forced through the arteries by contractions of the ventricles during systole


The liquid matrix of blood in which the cells are suspended


A small enucleated blood cell important in blood clotting; derived from large cells in the bone marrow

red blood cell

A blood cell conaining hemoglobin, which transports oxygen

white blood cell

A blood cell that functions in defending the body against infections and cancer cells


A small and very toxic nitrogenous waste produced by metabolism


the main nitrogenous breakdown product of protein metabolism in mammals and is excreted in urine


The waste material produced by the excretory system


Fluid extracted by the excretory system from the blood or body cavity


function is to purify the blood by removing nitrogenous waste products and excreting them in the urine


A duct leading from the kidney to the urinary bladder

urinary bladder

The pouch where urine is stored prior to elimination


A tube that releases urine from the body


The tubular excretory unit of the vertebrate kidney


In the vertebrate kidney, the extraction of water and small solutes, including metabolic wastes, from the blood by the nephrons


The process by which water and valuable solutes are reclaimed from the filtrate and returned to the blood


the discharge of wastes from the blood into the filtrate from the nephron tubules


The disposal of nitrogen-containing waste products of metabolism


prepares nitrogenous wastes for disposal, detoxifies poisonous chemicals in the blood


The steady-state physiological condition of the body

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