AP Bio Unit 2: Cell Structure

Amphipathic

Amphipathic

having both a hydrophilic region and a hydrophobic region

Fluid Mosaic model

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

integral proteins

a 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 soln on one or both sides of the membrane (consists of nonpolar amino acids usually cooled into alpha helixes)

transport

spans the membrane and provides hydrophilic channel across the membrane that is selective for a particular solute; others can shuttle a substance from one side to another by changing shape (hydrolyze atp)

enzymatic activity

built into membrane may be enzyme with active side exposed to substances in the adjacent soln

signal transduction

membrane protein (receptor) may have binding site with a specific shape that fits the shape of a chemical messenger (hormone)

cell-cell recognition

some glycogen proteins serve as identification tags that are specifically recognized by proteins of other cells

intracellular joining

membrane proteins of adjacent cells may hook together in various kinds of junctions such as gap junctions or tight junctions

attachment to cytoskeleton and extracellular matrix (ECM)

microfilaments or other elements of the cytoskeleton may be noncovalently bonded to membrane proteins. helps maintain the cell shape and stabilizes locations of certain membrane proteins. Proteins that can bind to ECM molecules can coordinate extra and intracellular changes

glycolipids

a lipid with one or more covalently attached carb

glycoproteins

a protein with one or more covalently attached carb

transport protein

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

auquaporins

a channel protein ion the plasma membrane that specifically facilitates osmosis, the diffusion of free water across the membrane (consists of 4 identical polypeptides)

diffusion

the random thermal motion of particles of liquid, gases, or solids. moves from a certain region that is more concentrated to a region less concentrated with the gradient

concentration

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

passive transport

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

osmosis

the diffusion of free water molecules across a semi-permeable membrane

tonicity

the ability of a solution surrounding a cell to cause that cell to gain or lose water (iso, hypo, hyper)

isotonic

referring to a soln that when surrounding a cell causes o net movement of water into or out of the cell

what happens to the cell membrane if it consists of unsaturated fats?

it keeps the membrane fluid at room temp

hypertonic

referring to a soln that when surrounding a cell will cause the cell to lose water

hypotonic

referring to a soln that when surrounding a cell will cause the cell to take up water

osmoregulation

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

turgid

swollen or distended (a water cell becomes turgid if it has a lower water potential than its surroundings resulting in entry of water)

plasmolysis

a 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

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

ion channels

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

gated channels

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

active transport

the movement of a substance across the cell membrane against its concentration or electrochemical gradient mediated by specific transport proteins and requiring 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 protein

the difference in electrical charge across a cells plasma membrane due to a differential distribution of ions

electrochemical gradient

the diffusion gradient of an ion which is affected by both the concentration difference of an ion across a membrane and the ions tendency to move relative to the membrane potential

electrogenic pump

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

proton pump

an 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

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

exocytosis

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

endocytosis

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

phagocutosis

a cell engulfs a particle by extending pseudopodia around it and packaging it with in a membraneous sac called a food vacuole the particles will be digested after the food vacuole fuses with a lysosome containing hydrolytic enzymes

pinocytosis

s cell continually gulps droplets of extracellular fluid into tiny vesicles formed by infolding of the plasma membrane. the cell obtains molecules dissolved in the droplets

eukaryotic cell

type of cell with a membrane enclosed nucleus and membrane enclosed organelles

prokaryotic cell

type of cell lacking a membrane enclosed nucleus and membrane enclosed organelles

nucleoid

a non membrane enclosed region in a prokaryote cell where chromosomes are located

fimbriae

attached structure on surface of some prokaryotes

glycocalyx

outer coating of many prokaryotes consisting of a capsule or a slim layer

cytoplasm

the contents of the cell enclosed by the plasma membrane (in eukaryotes exclusive of nucleus)

nucleus

the organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes made up of chromatid

nuclear envelope

the double membrane that surrounds the nucleus perforated with pores that regulate traffic with the cytoplasm; the outer membrane is continuous with the outer membrane

nuclear lamina

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

chromosomes

a cell structure consisting of one DNA molecule and associated protein molecules

chromatin

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

nucleolus

a specialized structure in the nucleus consisting of chromosomal regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasm; site of rrna synthesis and ribosomal subunit assembly

endomembrane system

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

vesicles

a membraneous sac in the cytoplasm of a eukaryotic cell

Endoplasmic reticulum

an extensive membraneous network in eukaryotic cells, continuous with the outer nucleus membrane and composed of ribosome studded and ribosome free regions

Golgi apparatus

an organelle in eukaryotic cells consisting of stacks of flat membraneous sacs that modify, store, and route products of the er and synthesize some products notably non cellulose carbs

lysosome

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

autophagy

lysosomes using their hydrolytic enzymes to rescue the cells own organic material

vacuole

a membrane bound vesicle whose specialized function varies in different kinds of cells

food vacuoles

membraneous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell

contractile vacuoles

membraneous sac that helps move excess H2O out of certain freshwater protists

central vacuole

in mature plant cells, a large membraneous sac with diverse roles in growth, storage, and sequestration of toxic substances

mitochondria

an organelle in eukaryotic cells that serves as site of cellular respiration; uses oxygen to break down organic molecules and synthesize atp

chloroplasts

found in plants and photosynthesis protists that absorb sunlight and uses it to drive the synthesis of organic compounds from CO2 and H2O (dbl membrane)

endosymbiont

a cell living with another cell

cristae

an 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)

thylakoids

a flattened membraneous sac inside a chloroplast. thylakoids often exist in stacks called grand that interconnected; their membranes contain molecular machinery used to convert light energy to chemical energy

granum

a stack of membrane bounded thylakoids in the chloroplast. they function in the light reactions of photosynthesis

stroma

the dense fluid with in the chloroplasts surrounding the thylakoid membrane and containing ribosomes and dna; involved in the sythesis of organic molecules from CO2 to H2O

plastids

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

chromoplasts

has pigment that give fruit and flowers their hues

peroxisome

an organelle containing enzymes that transfer hydrogen atoms from various substances to oxygen, producing and then degrading hydrogen peroxide

cytoskeleton

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

motor proteins

protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell

microtubules

(tublin polymers) hollow tubes that maintain the cell shape; help with chromosome movement in cell division

microfilaments

(actin filaments) 2 intertwines strands of actin that maintains cell shape, changes cell shape, muscle contraction, cytoplasmic streaming (plants), cell motility, and cell division (animal)

intermediate filaments

fibrous paths coiled into cables made up of several different proteins that help maintain cell shape, ancrage of nucleus and certain other organelles, and the formation of the nuclear lamina

centrosomes

a structure present in the cytoplasm of animal cells that functions as a microtubule organizing center and is important during cell division; has 2 centrioles

centrioles

structure in chromosomes of an animal cell composed of a cylinder of microtubule triplets arranged in a 9+0 pattern

flagella

long cellular appendage specialized for locomotion. like motile cilia, eukaryotic flagella have a core with 9 outer doublet microtubules and 2 inner single microtubules (9+2 arrangement) (prokaryotic flagella have different structure)

basal body

eukaryotic cell structure consisting of 9+0 arrangement of microtubule triplets. the basal body may organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole

myosin

type of motor protein that associates into filaments that interact with actin filaments, causing cell contraction

cell wall

protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists. polysaccharides such as cellulose, chitin, and peptidoglycan are important structural components of cell walls

primary cell wall

in plants, relatively thin and flexible layer that surrounds the plasma membrane of a young cell

middle lamenta

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

secondary cell wall

in plant cells a strong and durable matrix that is often deposited in several laminated layers around the plasma membrane that provides protection and support

collagen

glycoproteins in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone

proteoglycan

large molecule consisting of a small core protein with many carb chains attached, found in the extra cell matrix of animal cells. a proteoglycan may consist of up to 95% carbs

fibronectin

extra cell glycoprotein secreted by animal cells that helps them attach to the extracellular matrix

plasmodesmata

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

tight junctions

plasma membrane of neighboring cells are tightly pressed against each other bound together by specific proteins (prevents leakage)

desmosomes

function like rivers fastening cells together into strong sheets through the filaments

gap junction

(communicating junctions) provides cytoplasmic channels from one cell to an adjacent cell and in this way are similar to the plasmodesmata in plants