AP Biology Unit 2: Cell Structure and Function Key Terms

cell theory

a biological concept that states that one or more cells comprise all organisms; the cell is the basic unit of life; and new cells arise from existing cells

cell wall

rigid cell covering made of various molecules that protects the cell, provides structural support, and gives shape to the cell

central vacuole

large plant cell organelle that regulates the cell's storage compartment, holds water, and plays a significant role in cell growth as the site of macromolecule degradation

centrosome

region in animal cells made of two centrioles

chlorophyll

green pigment that captures the light energy that drives the light reactions of photosynthesis

chloroplast

a plant cell organelle that carries out photosynthesis

chromatin

protein-DNA complex that serves as the building material of chromosomes

chromosome

structure within the nucleus that is made up of chromatin that contains DNA, the hereditary material

cilium

short, hair-like structure that extends from the plasma membrane in large numbers and is used to move an entire cell or move substances along the outer surface of the cell

cytoplasm

the entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals

cytoskeleton

the network of protein fibers that collectively maintains the shape of the cell, secures some organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move independently

cytosol

gel-like material of the cytoplasm in which cell structures are suspended

desmosome

a linkage between adjacent epithelial cells that forms when cadherins in the plasma membrane attach to intermediate filaments

electron microscope

an instrument that magnifies an object using a beam of electrons passed and bent through a lens system to visualize a specimen

endomembrane system

the group of organelles and membranes in eukaryotic cells that work together to modify, package, and transport lipids and proteins

Endoplasmic Reticulum (ER)

a series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids

eukaryotic cell

cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs

extracellular matrix

the material, primarily collagen, glycoproteins, and proteoglycans, secreted from animal cells that provides mechanical protection and anchoring for the cells in the tissue

flagellum

long, hair-like structure that extends from the plasma membrane and is used to move the cell

gap junction

channel between two adjacent animal cells that allows ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate

Golgi apparatus

a eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution

intermediate filament

cytoskeletal component, composed of several intertwined strands of fibrous protein, that bears tension, supports cell-cell junctions, and anchors cells to extracellular structures

light microscope

an instrument that magnifies an object using a beam visible light passed and bent through a lens system to visualize a specimen

lysosome

organelle in an animal cell that functions as the cell's digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles

microfilament

narrowest element of the cytoskeleton system; it provides rigidity and shape to the cell and enables cellular movements

microscope

an instrument that magnifies an object

microtubule

widest element of the cytoskeleton system; it helps the cell resist compression, provides a track along which vesicles move through the cell, pulls replicated chromosomes to opposite ends of a dividing cell, and is the structural element of centrioles, flagella, and cilia

mitochondria

cellular organelle responsible for carrying out cellular respiration, resulting in the production of ATP, the cell's main energy-carrying molecule

nuclear envelope

the double-membrane structure that constitutes the outermost portion of the nucleus

nucleoid

central part of a prokaryotic cell in which the chromosome is found

nucleolus

the darkly staining body within the nucleus that is responsible for assembling the subunits of the ribosomes

nucleoplasm

semi-solid fluid inside the nucleus that contains the chromatin and nucleolus

nucleus

the cell organelle that houses the cell's DNA and directs the synthesis of ribosomes and proteins

organelle

compartment or sac within a cell

peroxisome

small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons

plasma membrane

phospholipid bilayer with embedded (integral) or attached (peripheral) proteins, and separates the internal content of the cell from its surrounding environment

plasmodesma

channel that passes between the cell walls of adjacent plant cells, connects their cytoplasm, and allows materials to be transported from cell to cell

prokaryotic cell

A unicellular organism that lacks a nucleus or any other membrane-bound organelle

ribosome

cellular structure that carries out protein synthesis

Rough Endoplasmic Reticulum (RER)

the region of the endoplasmic reticulum that is studded with ribosomes and engages in protein modification and phospholipid synthesis

Smooth Endoplasmic Reticulum (SER)

the region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface and synthesizes carbohydrates, lipids, and steroid hormones; detoxifies chemicals like pesticides, preservatives, medications, and environmental pollutants, and stores calcium ions

tight junction

a firm seal between two adjacent animal cells created by protein adherence

vacuole

membrane-bound sac, somewhat larger than a vesicle, which functions in cellular storage and transport

vesicle

small, membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and the membranes of the endoplasmic reticulum and Golgi apparatus

active transport

the method of transporting material that requires energy

amphiphilic

molecule possessing a polar or charged area and a nonpolar or uncharged area capable of interacting with both hydrophilic and hydrophobic environments

antiporter

transporter that carries two ions or small molecules in different directions

aquaporin

channel protein that allows water through the membrane at a very high rate

carrier protein

membrane protein that moves a substance across the plasma membrane by changing its own shape

caveolin

protein that coats the cytoplasmic side of the plasma membrane and participates in the process of liquid uptake by potocytosis

channel protein

membrane protein that allows a substance to pass through its hollow core across the plasma membrane

clathrin

protein that coats the inward-facing surface of the plasma membrane and assists in the formation of specialized structures, like coated pits, for phagocytosis

concentration gradient

area of high concentration adjacent to an area of low concentration

diffusion

a passive process of transport of low-molecular weight material down its concentration gradient

electrochemical gradient

gradient produced by the combined forces of an electrical gradient and a chemical gradient

electrogenic pump

pump that creates a charge imbalance

endocytosis

a type of active transport that moves substances, including fluids and particles, into a cell

exocytosis

process of passing bulk material out of a cell

facilitated transport

a process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins

fluid mosaic model

describes the structure of the plasma membrane as a mosaic of components including phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains attached to proteins or lipids, respectively), resulting in a fluid character (fluidity)

glycolipid

combination of carbohydrates and lipids

glycoprotein

combination of carbohydrates and proteins

hydrophilic

molecule with the ability to bond with water; "water-loving"

hydrophobic

molecule that does not have the ability to bond with water; "water-hating"

hypertonic

situation in which extracellular fluid has a higher osmolarity than the fluid inside the cell, resulting in water moving out of the cell

hypotonic

situation in which extracellular fluid has a lower osmolarity than the fluid inside the cell, resulting in water moving into the cell

integral protein

protein integrated into the membrane structure that interacts extensively with the hydrocarbon chains of membrane lipids and often spans the membrane; these proteins can be removed only by the disruption of the membrane by detergents

isotonic

situation in which the extracellular fluid has the same osmolarity as the fluid inside the cell, resulting in no net movement of water into or out of the cell

osmolarity

total amount of solutes dissolved in a specific amount of solution

osmosis

the transport of water through a semipermeable membrane according to the concentration gradient of water across the membrane that results from the presence of solute that cannot pass through the membrane

passive transport

method of transporting material through a membrane that does not require energy

peripheral protein

protein found at the surface of a plasma membrane either on its exterior or interior side; extra info: these proteins can be removed (washed off of the membrane) by a high-salt wash

pinocytosis

a variation of endocytosis that imports macromolecules that the cell needs from the extracellular fluid

plasmolysis

detaching of the cell membrane from the cell wall and constriction of the cell membrane when a plant cell is in a hypertonic solution

potocytosis

variation of pinocytosis that uses a different coating protein (caveolin) on the cytoplasmic side of the plasma membrane

primary active transport

active transport that moves ions or small molecules across a membrane and may create a difference in charge across that membrane

pump

active transport mechanism that works against electrochemical gradients

receptor-mediated endocytosis

variation of endocytosis that involves the use of specific binding proteins in the plasma membrane for specific molecules or particles, and clathrin-coated pits that become clathrin-coated vesicles

secondary active transport

movement of material that is due to the electrochemical gradient established by primary active transport

selectively permeable

the characteristic of a membrane that allows some substances through but not others (also known as semipermeable)

solute

substance dissolved in a liquid to form a solution

symporter

transporter that carries two different ions or small molecules, both in the same direction

tonicity

amount of solute in a solution

transport protein

membrane protein that facilitates passage of a substance across a membrane by binding it

transporter

specific carrier proteins or pumps that facilitate movement

uniporter

transporter that carries one specific ion or molecule