AP Biology: Chapter 4 & 5 Vocabulary

light microscope (LM)

optical instrument w/ lenses that bend visible light to magnify images of specimens

transport vesicle

small membranous sac in a eukaryotic cell's cytoplasm carrying molecules produced by the cell

resolving power

ability of microscope to distinguish between two adjacent structures/points separately

Golgi apparatus

organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products (i.e. noncellulose carbohydrates)

organelle

any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells

lysosome

membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists

electron microscrope (EM)

microscope that uses magnets to focus an electron beam on or through a specimen, resulting in resolution hundredfold greater than a light microscrope Notes: transmission EM (TEM) is used to study internal structures of sections in cellsscanning EM (SEM) is used to study fine details of cell surfaces

phagocytosis

type of endocytosis in which large particulate substances or small organisms are taken up by a cell

transmission electron microscope (TEM)

microscope that passes an electron beam through very thin sections stained with metal atoms and is primarily used to study the internal ultrastructure of cells

food vacuole

membranous sac formed by phagocytosis of microorganisms/particles to be used as food by the cell

scanning electron microscope (SEM)

microscope that uses an electron beam to scan the surface of a sample, coated with metal atoms, to study details of its topography

tonoplast

membrane that surrounds the central or a large vacuole of a plant cell

cell fractionation

disruption of a cell and separation of its parts by centrifugation at successively higher speeds

mitochondria

organelles in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP

cytosol

semifluid portion of the cytoplasm

chloroplast

organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water (photosynthesis)

prokaryotic cell

type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles organisms with pro. cells (i.e. bacteria and archaea) are called prokaryotes

crista

infolding of the inner membrane of a mitochondrion, the inner membrane houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase)

nucleoid

non-membranebounded region in a prokaryotic cell where the DNA is concentrated

mitochondrial matrix

compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle, as well as ribosomes and DNA

cytoplasm

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

plastid

family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts, plastids are found in cells of photosynthetic eukaryotes

nucleus

(physics) An atom's central core, containing protons and neutrons(biology) The organelle of a promoter, an operator, and a coordinately regulated cluster of genes whose products function in a common pathway

thylakoid

flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular "machinery" used to convert light energy to chemical energy

nuclear lamina

netlike array of protein filaments that lines the inner surface of the nuclear envelope and helps maintain the shape of the nucleus

granum

stack of membrane-bounded thylakoids in the chloroplast. Grana function in the light reactions of photosynthesis

chromatin

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

stroma

dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from carbon dioxide and water (photosynthesis)

chromosome

cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each of these consists of one very long DNA molecule and associated proteins. (A bacterial one usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded.)

peroxisome

organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2O2)

nucleolus

specialized structure in the nucleus, consisting of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm

cytoskeleton

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

ribosome

complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit In eukaryotic cells, each subunit is assembled in the nucleolus

centriole

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

endomembrane system

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

plasmodesmata

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

vesicle

membranous sac in the cytoplasm of a eukaryotic cell

tight junction

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

endoplasmic reticulum (ER)

extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions

desmosome

type of intercellular junction in animal cells that functions as a rivet, fastening cells together

smooth ER

portion of the endoplasmic reticulum that is free of ribosomes

gap junction

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

rough ER

portion of the endoplasmic reticulum with ribosomes attached

centrosome

structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles

glycoprotein

protein with one or more covalently attached carbohydrates

selectively permeability

ability of the cell membrane to control the flow of substances in and out of the cell

amphipathic molecule

a molecule having both a hydrophilic region and a hydrophobic region

fluid mosaic model

model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids

integral protein

transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein)

peripheral protein

protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer

transport protein

transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane

diffusion

spontaneous movement of a substance down its concentration or electrochemical gradient, from a region where it is more concentrated to a region where it is less concentrated

concentration gradient

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

passive transport

diffusion of a substance across a biological membrane with no expenditure of energy

hypertonic solution

solution that has a high solute concentration and low water concentration compared to body fluids

hypotonic solution

solution that has a low solute concentration and high water concentration compared to body fluids

isotonic solution

solution that has the same solute concentration and water concentration compared to body fluids

osmosis

diffusion of free water across a selectively permeable membrane

osmoregulation

regulation of solute concentrations and water balance by a cell or organism

turgid

swollen, distended, or firm, as in plant cells (A walled cell becomes firm if it has a lower water potential than its surroundings, resulting in entry of water.)

flaccid

limp; lacking turgor (stiffness or firmness), as in a plant cell in surroundings where there is a tendency for water to leave the cell (A walled cell becomes limp if it has a higher water potential than its surroundings, resulting in the loss of water.)

plasmolysis

phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment

facilitated diffusion

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

channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of free water across the membrane

gated channel

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

active transport

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

sodium-potassium pump

transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell

membrane potential

difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions. this affects the activity of excitable cells and the transmembrane movement of all charged substances

electrochemical gradient

diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force)

electrogenic pump

active transport protein that generates voltage across a membrane while pumping ions

proton pump

active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process

cotransport

coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient

exocytosis

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

endocytosis

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

pinocytosis

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

receptor-mediated endocytosis

movement of specific molecules into a cell by the inward budding of vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances

ligand

molecule that binds specifically to another molecule, usually a larger one