Unit 2: Cell Structure and Function

Cytoplasm

The contents of the cell bounded by the plasma membrane; in eukaryotes, the portion exclusive of the nucleus.

Centrosome

Region where the cell's microtubles are initiated; contains centrioles in animal cells.

Golgi Apparatus

Modifies, sorts, and packages cell products such as proteins from the ER.

Cell Membrane

Thin, flexible barrier that surrounds a cell; regulates what enters and leaves.

Ribosomes

Assembles proteins; may be on the rough ER, nuclear envelope or free-floating in the cytosol

Chromatin/Chromosomes

DNA; contain genetic material that is passed from one generation to the next.

Cytoplasm

Portion of the cell between the nucleus and cell membrane.

Cytoskeleton

Helps a cell maintain its shape and functions in movement.

Smooth ER

Assembles membrane lipos, breaks down carbs, and detoxifies the cell of drugs; no ribosomes.

Cell Wall

Strong supporting/protecting layer surrounding the cell membrane in plant cells.

Rough ER

Chemically modifies new proteins, makes membrane components for the cell; covered in ribosomes.

Nucleolus

Begins the assembly of ribosomes; dense region in the nucleus.

Nucleus

Contain all of the cell's DNA; directs protein synthesis.

Vacuoles

Functions in storage, hydrolysis, and the breakdown of wastes.

Mitochondria

Involved in cellular respiration and the generation of ATP

Chloroplasts

Captures the sun's energy and converts it into chemical energy stored in sugar molecules in plant cells; photosynthesis

Lysosomes

Filled with enzymes to digest, or breakdown, lipids, carbs, and proteins in animal cells.

Flagellum

Used for movement; tail like in structure

Plasmodesmata

Channels through cell walls that connect the cytoplasms of adjacent cells; used for cell-to-cell communication withing plants.

Peroxisome

Has specialized metabolic functions; produces hydrogen peroxide as a waste product and converts it to water.

Free ribosomes

Produces proteins for use within the cell, suspended in the cytosol, consists of 2 subunits, and is composed of rRNA and proteins

Bound ribosomes

Produces proteins for export, attached to the rough ER, consists of 2 subunits, and is composed of rRNA and proteins.

Plasmodesmata

Found in plant cells, forms channels between cells, allows free passage of water and small solutes between cells. and permits intercellular transport.

Tight Junctions

Found in animal cells. holds cells tightly together, blocks intercellular transport of materials. found in epithelial layers that separate two kinds of solutions, found in the lining of the digestive tract and the blood-brain barrier, and found in skin cells.

Desmosomes

Found in animal cells, holds cells tightly together, rivets cells together, well developed in cells subjected to considerable mechanical force, and glycoprotein (intermediate) filaments penetrate and bind plasma membranes of two adjacent cells

Gap Junctions

Found in animal cells, forms channels between cells, allows free passage water and small solutes between cells, found in embryos, cardiac muscle tissue, and endocrine glands, and permits intercellular transport.

Cell Wall

A protective wall external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists. Polysaccarides such as cellulose (in plants and some protists), chitin (in fungi), and peptidoglycan (in bacteria) are important structural components of cell walls.

Endosymbiont Theory

The theory with mitochondria and plastids originated from prokaryotic cells engulfed by a host cell. The engulfed cell and its host cell then evolved into a single organism.

Extracellular Matrix (ECM)

The meshwork surrounding animal cells, consisting of glycoprotiens, polysaccarides, and proteoglycans synthesized and secreted by cells.

Cytoskeleton

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

Endomembrane System

The collection of membranes inside and surrounding a eukaryotic cell, related either though direct physical contact or by the transfer of membranous vesicles; includes the plasma membrane, the nuclear envelope, the smooth and rough endoplastic reticulum, the Golgi apparatus, lysosomes, vesicles, and vacuoles.

Integrin

In animal cells, a transmembrane receptor protein with two subunits that interconnects the extracellular matrix and the cytoskeleton.

Microfilament

A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction, also called an actin filament.

Centriole

A structure in the chromosome of an animal cell composed of a cylinder of microtuble triplets arranged in a "9+0" pattern. A centrosome has a pair of centrioles.

Chromosome

A cellular structure consisting of DNA molecule and associated protein molecules. A duplicated chromosome has two DNA molecules (in some contexts, such as genome sequencing, the term may refer to the DNA alone). A eukaryotic cell typically has multiple, linear chromosomes, located in the nucleus. A prokaryotic cell often has a single, circular chromosome, which is found in the nucleoid, a region that is not enclosed by a membrane.

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.

Phagocytosis

A type of endocytosis in which large particulate substances or small organism are taken up by a cell. It is carried out by some oritists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells)

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

Gap Junction

A type of intercellular junction in animal cells, consisting of proteins surrounding a pore that allows the passage of materials between cells.

Tight Junction

A type of intercellular junction between animal cells that prevents the leakage of material through the space between cells.

Plasmodesma

An open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some larger molecules to pass between the cells.

Amphiphatic

Having both a hydrophilic region and a hydrophobic region.

Concentration Gradient

A region along which the density of a chemical substance increases or decreases.

Active Transport

The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy.

Diffusion

The random thermal motion of particles of liquids, gases, or solids. In the presence of a concentration or electrochemical gradient, diffusion results in the net movement of a substance from a region where it is more concentrated to a region where it is less concentrated.

Facilitated Diffusion

The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.

Aquaporin

A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.

Endocytosis

Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.

Exocytosis

The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.

Plasmolysis

A phenomenon in waled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell looses water to a hypertonic environment.

Hypotonic

Referring to a solution that, when surrounding a cell, will cause the cell to take up water.

Hypertonic

Referring to a solution that, when surrounding a cell, will cause the cell to loose water.

Isotonic

Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.

Gated Channel

A transmembrane protein channel that opens or closes in response to a particular stimulus.

Ion Channel

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.

Osmoregulation

Regulation of solute concentrations and water balance by a cell or organism.

Passive Diffusion

When small and non-polar molecules cross the membrane without requiring a protein and energy.

Facilitated Diffusion

When charged and large polar molecules cross the membrane requiring a protein, but not requiring energy.

Active Transport

When ions cross the membrane, requiring both proteins and energy.

Bulk Transport: Endo- and Exocytosis

When large molecules cross the membrane, requiring both proteins and energy.