ap bio unit 4 vocab

light microscope

an optical instrument with lenses that refract visible light to magnify images of specimens

electron microscope

a microscope that focuses an electron beam through a specimen, resulting great resolving power

cell fractionation

the disruption of a cell and separation of its organelles by homogenization and centrifugation

organelle

structure found within a cell that performs a specific task

centrifugation

a technique that uses spinning force to separate particles from a suspension

pellet

fraction of cell components that settles at the bottom of a tube after centrifugation

supernatant

liquid that collects above the pellet in a tube after centrifugation

scanning electron microscope (SEM)

a microscope that uses electrons to show the surface of a sample, useful for studying topography of a specimen

transmission electron microscope (TEM)

a microscope that uses electrons to study a thin specimen, used to study ultrastructure of cells

eukaryotic cell

cell that contains a nucleus and other structures (organelles) enclosed within membranes

prokaryotic cell

a cell that has no membrane bound organelles

cytosol

the semifluid portion of the cytoplasm

nucleoid

a dense region of DNA that is found in a prokaryotic cell

cytoplasm

the entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane

plasma membrane

the membrane at the boundary of every cell that acts as a selective barrier

nuclear envelope

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

nuclear lamina

a netlike array of protein filaments that maintains the shape of the nucleus

chromosome

a threadline, gene-carrying structure found in the nucleus or nucleoid. each consists of one very long coiled DNA molecule

chromatin

the complex of DNA and proteins that makes up a eukaryotic chromosome when it is not coiled

nucleolus

a specialized structure in the nucleus that is active in the synthesis of ribosomes

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

smooth endoplasmic reticulum (smooth ER)

endoplasmic reticulum (ER) that lacks ribosomes

rough endoplasmic reticulum (rough ER)

endoplasmic reticulum (ER) that contains ribosomes, manufactures membranes and secretory proteins

vesicle

a small sac surrounded by a membraine inside of cells

glycoproteins

proteins that have carbs covalently bonded to them

transport vesicle

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

golgi apparatus

an organelle that modifies products of the ER, such as proteins and sends them to other destinations in the cell

lysosome

a sac of hydrolytic enzymes that is used to digest macromolecules or cellular debris

phagocytosis

a method used by cells for engulfing large particles by surrounding them with the plasma membrane

autophagy

a process when lysosomes use their hydrolytic enzymes to recycle the cell’s own organic material

vacuoles

large vesicles derived from ER and golgi apparatus, mostly used to store materials or waste

endosymbiotic theory

explanation for how the early ancestor of eukaryotic cells engulfed prokaryotic cells that eventually evolved into the mitochondria and chloroplasts

cristae

infoldings of the inner membrane of a mitochondrion

mitochondrion

organelle that is the site of cellular respiration

mitochondrial matrix

the compartment of the mitochondrion enclosed by the inner membrane

thylakoid

a flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy

granum

a stack of thylakoids found in the chloroplast

stroma

the fluid outside the thylakoid found inside a chloroplast

plastid

members of a family of closely related plant organelles that contain pigments or reserve materials such as starch

photosynthesis

a process used by plants and other organisms to convert light energy, carbon dioxide and water into chemical energy

peroxisome

an organelle containing enzymes that degrade hydrogen peroxide into water and oxygen

microtubule

a hollow rod of tubulin protein in eukaryotic cells that forms part of cilia, flagella, and the cytoskeleton

centrosome

the microtubule organizing center, present in the cytoplasm of all eukaryotic cells, it is involved in cell division

centrioles

structures found in an animal cell composed of cylinders of microtubule triplets. an animal cell usually has a pair of them that are involved in cell division

flagella

long cellular appendages specialized for locomotion

cilia

short cellular appendages specialized for locomotion

basal body

a eukaryotic cell structure made out of microtubule triplets. they are part of cilia and flagella

microfilament

a solid rod of actin protein in the cytoplasm of eukaryotic cells, making up part of the cytoskeleton

actin

a globular protein that links into chains, forming microfilaments in muscle and other contractile elements in cells

myosin

the contractile protein that makes up the thick filaments of muscle fibers

pseudopodia

a cellular extension of cells used in moving and feeling

cytoplasmic streaming

a circular flow of cytoplasm that speeds the distribution of materials within cells

intermediate filament

a component of the cytoskeleton that includes all filaments with size between that of microtubules and microfilaments

primary cell wall

a relatively thin and flexible layer first secreted by a young plant cell

middle lamella

a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young plant cells

secondary cell wall

a layer of the cell wall that is rigid, used for plant cell protection and support in woody plants

extracellular matrix (ECM)

an intricate network of molecules, found outside the cell, that link together to form a stable layer

collagen

a glycoprotein in the ECM of animal cells that forms strong fibers; the most abundant protein in the animal kingdom

cell junctions

structures that provide contact between neighboring cells or a cell and the ECM

tight junctions

structures where plasma membrances of neighboring cells are pressed against each other, forming continuous seals around the cell

desmosomes

anchoring junctions that function like rivets, specialized for cell-cell adhesion

gap junctions

structures that provide cytoplasmic channel connections from one animal cell to an adjacent cell

plasmodesmata

an open channel in the cell wall of a plant through which the cytosol connects to the cytosol from an adjacent cell

amphipathic

a molecule that has both a hydrophilic region and a hydrophobic region

fluid mosaic model

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

integral proteins

proteins that extend entirely through the membrane with both hydrophobic and hydrophilic parts

peripheral proteins

protein loosely bound to the surface of the membrane and not embedded in the liquid bilayer

transmembrane proteins

a protein that goes from one side of the cell membrane to the other side

glycolipids

lipid substances with linked sugar groups

permeability

a measure of the rate of passive diffusion of molecules through the membrane

transport proteins

protein molecules that help to carry substances throughout the body and across cell membranes

channel proteins

a type of transport protein that functions by having a hydrophilic channel that certain molecules or ions use as a tunnel through the membrane

aquaporins

a transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across a membrane

diffusion

the process by which molecules spontaneously move from an area of higher concentration to an area of lower concentration

concentration gradient

the difference in the concentrations of a substance across a barrier or membrane

passive transport

the movement of substances with gradient across a cell membrane without the use of energy by the cell

osmosis

diffusion of water molecules through a semipermeable membrane until the concentration on both sides is equal

isotonic

having a solute concentration equal to that of another solution

hypertonic

when comparing two solutions, the solution with the greater concentration of solutes

hypotonic

when comparing two solutions, the solution with the lesser concentration of solutes

turgid

firm, walled cells become firm as a result of the entry of water from a hypotonic environment

flaccid

limp, lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell

plasmolysis

when a cell is in a hypertonic environment, the cell will lose water to its surroundings, shrink, and its plasma membrane will pull away from the wall

facilitated diffusion

the transport of substances through a cell membrane along a concentration gradient with the aid of transport proteins

ion channels

a transmembrane protein channel that allows a specific ion to flow across the membrane down its concentration gradient

gated channels

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

active transport

the movement of a substance across a biological membrane against its concentration of electrochemical gradient

sodium-potassium pump

a special transport protein in the plasma membrane of animal cells that transports sodium out of the cell and potassium into the cell against their concentration gradient

membrane potential

the voltage difference between a cell’s cytoplasm and the extrcellular fluid, due to the differential distribution of ions

electrochemical gradient

a transport force driven by both a difference in charges and in concentration

electrogenic pump

a transport protein that generates a voltage across a membrane

proton pump

an active transport mechanism in cell membranes that consumes ATP to force hydrogen ions out of a cell

cotransport

the coupling of the “downhill” diffusion of one substance with the “uphill” transport against its own concentration gradient

exocytosis

the process by which a substance is released from the cell through a vesicle

endocytosis

the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell

pinocytosis

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

receptor-mediated endocytosis

the 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

carrier proteins

proteins that bind to molecules and change shape to shuttle them across the membrane