Cell Anatomy & Transport

https://quizlet.com/170251548/ap-biology-chapter-11-multiple-choice-cell-communication-flash-cards/

micrometer to millimeter conversion

micrometer to millimeter conversion

1,000 um = 1 mm

a cell that is 1-10 um is probably…

bacteria/prokaryote

a cell that is 10-100 um is probably…

eukaryote

cell size is determined by…

• surface area to volume ratio

• You MUST have a larger surface area than volume to survive as a cell

  • plasma membrane must be large enough relative to cell volume to regulate passage of materials

  • volume inc faster than surface area so cell must DIVIDE

• cell size & shape is related to its function

prokaryotes & eukaryotes both have…

• plasma membrane

• cytosol that contains organelles

• chromosomes which have genes in form of DNA

• ribosomes

where is DNA located in a prokaryote vs eukaryote?

E:

• LINEAR chromosomes contained in membrane-enclosed organelle (nucleus)

P:

• DNA concentrated in nucleoid region w/o membrane separating it from rest of cell (all jumbled up chromatin)

free ribosomes

• STAY IN THE CELL

• synthesize proteins that function within the cytosol

bound ribosomes

• Proteins attached to the rough ER will either go into the membrane (and stay there) or be exported out of the cell

smooth ER

• rich in enzymes & plays role in metabolic processes

• enzymes of smooth ER synthesize lipids (e.g. oils, phospholipids, steroids, sex hormones, etc.)

• also catalyzes key step in mobilization of glucose from stored glycogen (carbohydrate) in liver

  • other enzymes in smooth ER of liver detoxify drugs, poisons, alc, etc

  • frequent exposure leads to proliferation of smooth ER, inc tolerance to target & other drugs

rough ER

• esp abundant in cells that secrete proteins

• as polypeptide is synthesized by ribosome, it’s threaded into cisternal space thru pore in ER membrane

• these secretory proteins are packaged in transport vesicles that carry them to their next stage

• also a membrane factory

  • membrane-bound proteins are synthesized directly into membrane

  • enzymes in rough ER also synthesize phospholipids

  • as ER membrane expands, parts can be transferred as transport vesicles to other components of endomembrane system

Golgi apparatus

• many transport vesicles from ER travel to golgi for modification of their contents

• golgi = center of manufacturing, warehousing, storing, & shipping (thru transport vesicles)

• esp extensive in cells specialized for secretion (bound ribosomes)

• cis side receives material; trans side buds off vesicles that travel to other sites (products modified in btwn)

• golgi can also manufacture its own macromolecules, including pectin & other non-cellulose polysaccharides

lysosomes

• animal cells ONLY

• lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, & nucleic acids (e.g. digest food)

• enzymes work best at pH 5

• proteins in lysosomal membrane pump hydrogen ions from cytosol to lumen of lysosomes

• while rupturing one or a few lysosomes has little impact on cell, but massive leakage from lysosomes can destroy cell by autodigestion

• used to destroy old cells (cell death)

• lysosomal enzymes & membrane synthesized by rough ER then transferred to Golgi

phagocytosis

• process wherein a cell binds to the item it wants to engulf on the cell surface

• draws the item inward while engulfing around it

• often happens when the cell is trying to destroy something (e.g. virus/infected cell)

• often used by immune system cells (e.g. white blood cells)

mitochondria

• sites of cellular respiration & generating ATP

chloroplasts

• found ONLY in plants & eukaryotic algae

• sites of photosynthesis

  • convert solar energy to chem energy for food

endosymbiotic theory (name at least 3 justifications)

• mitochondria & chloroplasts evolved from prokaryotes

• justifications:

  • both have small quantities of DNA that direct synthesis of polypeptides produced by internal ribosomes

  • both can grow & reproduce as semi-autonomous organelles

  • both organelles around size of prokaryotic cell

  • have 2 layers for plasma membrane, similar to prokaryotes

peroxisomes

• contain enzymes that transfer H from various substrates to O2

• an intermediate product of this process is hydrogen peroxide (H2O2), but the peroxisome has another enzyme that converts H2O2 to water

• sometimes breakdown fatty acids to smaller molecules that are transported to mitochondria for fuel

• some detoxify alc & other harmful compounds

• NOT formed by endomembrane system, but by incorporation of proteins & lipids from cytosol

cytoskeleton functions

• maintains shape of cell

• fibers act like a geodesic dome to stabilize balance btwn opposing forces

• provides anchorage for many organelles & cytosolic enzymes

• dynamic, dismantling one part & reassembling in another to change shape of cell

• cell mobility (location o cell & limited mvmts of parts of cell)

• interacts w/ motor proteins

motor protein

• carry vesicles or organelles to various destinations along “monorails” provided by cytoskeleton

• interactions of motor proteins & cytoskeleton circulate materials within cell via streaming

• recently, evidence is accumulating that cytoskeleton may transmit mechanical signals that rearrange nucleoli and other structures

• requires ATP

3 main types of fibers in cytoskeleton

• microtubules

• microfilaments

• intermediate filaments

microtubules

• thickest fibers

• hollow rods abt 25 microns in diameter

• move chromosomes during cell division

• acts as tracks that guide motor proteins carrying organelles to destination

• grow out from centrosome near nucleus

• resist compression to the cell

• central structural supports in cilia & flagella

centrioles

• in ANIMAL cells, centrosome has pair of centrioles

• found inside centrosome

• each w/ 9 triplets of microtubules arranged in ring

• during cell division, centrioles replicate

cilia vs flagella

• cilia usually occur in large numbers on cell surface

  • abt 2-20 microns long

• usually just one or few flagella per cell

  • 10-200 microns long

  • e.g. sperm cell

• hwvr, both have same ultrastructure

  • core microtubules sheathed by plasma membrane

  • can move unicellular/small multicellular organisms by propelling water past organism

microfilaments

• thinnest class of cytoskeletal fibers

• solid rods

• provide rigidity and shape to the cell and facilitate cellular movements

• w/ other proteins, they form 3D network inside plasma membrane

intermediate filaments

• intermediate size of all cytoskeletal fibers

• bear tension and anchor the nucleus and other organelles in place

• more permanent fixtures of cytoskeleton than are the other two classes

cell wall

• found in prokaryotes, fungi, some protists, & plant cells

• in plants:

  • protects cell

  • maintains its shape

  • prevents excessive uptake of water

  • supports plan against force of gravity

• consists of microfibrils of cellulose embedded in matrix of proteins & other polysaccharides

• mature cell wall → primary cell wall, middle lamella w/ sticky polysaccharides that hold cell together, & layers of secondary cell wall

extracellular matrix (ECM)

• lacking cell walls, animal cells do have elaborate ECM

• contains primarily glycoproteins, esp collagen fibers, embedded in network of proteoglycans

• fibronectins in ECM connect to integrins (intrinsic membrane proteins)

• integrins connect ECM to cytoskeleton

in what ways can the ECM regulate cell behavior?

• interconnections from ECM to cytoskeleton via fibronectin-integrin link permit interaction of changes inside & outside cell

• embryonic cells can migrate along specific pathways by matching orientation of microfilaments to “grain” of fibers in extracellular matric

• extracellular matric can influence activity of genes in nucleus via combo of chemical & mechanical signaling pathways

  • this may coordinate all cells within a tissue

plasmodesmata

• plant cells have this

• channels that allow cytosol to pass btwn cells

• allows neighboring cells to communicate thru direct physical contact

animal cells’ 3 main types of intercellular links

• tight junctions

• desmosomes

• gap junctions

tight junctions

• membranes of adjacent cells are fused, forming continuous belts around cells

• prevents leakage of extracellular fluid

desmosomes

• also called anchoring junction

• fastens cells together into strong sheets, like rivets

• intermediate filaments of keratin reinforce desmosomes

gap junctions

• also called communicating junctions

• provide cytoplasmic channels btwn adjacent cells

• special membrane proteins surrounding these pores

• salt ions, sugar, amino acids, & other small molecules can pass

phospholipids

• most abundant lipid in plasma membrane

• amphipathic

  • hydrophilic head

  • 2 hydrophobic tails

fluid mosaic model

• membrane is fluid structure w/ “mosaic” of various proteins embedded in it when view from top

• phospholipids can more laterally (left/right)

• membrane proteins also move side to side or laterally, making membrane fluid

how do different types of hydrocarbon tails affect the fluidity of the plasma membrane?

• unsaturated hydrocarbon tails w/ kinks → more fluid

• saturated hydrocarbon tails w/ no kinks → less fluid

• cell should have good mix of both

integral proteins

• penetrate hydrophobic core of lipid bilayer

• often transmembrane proteins, completely spanning membrane

peripheral proteins

• appendages loosely bound to surface of membrane

six major functions of membrane proteins

• transport to substances in and out of cell

• enzymatic activity

  • protein built into membrane may be enzyme

• signal transduction

  • protein may have binding site w/ specific shape that fits shape of chemical messenger, such as hormone

• cell-to-cell recognition

• intercellular joining

  • membrane proteins of adjacent cells may hook together

• attachment to cytoskeleton and extracellular matric

  • elements of cytoskeleton may be bonded to membrane proteins

  • helps maintain cell shape & stabilizes location of certain membrane proteins

what is the role of membrane carbohydrates in cell-to-cell recognition?

• cell-cell recognition → cell’s ability to distinguish one type of neighboring cell from another

• interact w/ surface molecules of other cells, helping facilitate cell-to-cell recognition

how would you expect the saturation levels of membrane fatty acids to differ in plants adapted to cold environments and plant adapted to hot environments?

• cold → more unsaturated → more fluidity

• hot → more saturated → less fluidity

carbs are attached to proteins and lipids in ER & Golgi; the new membrane them forms transport vesicles that travel to cell surface and will merge w/ cell membrane. on which side of the vesicle membrane are the carbs?

inside

polar vs nonpolar molecules passing thru plasma membrane

• nonpolar = hydrophobic; lipid soluble and can pass thru membrane rapidly

• polar molecules do NOT cross membrane rapidly

transport proteins

• allow passage of hydrophilic substances across membrane

passive transport

• diffusion of substance across membrane w/o energy (including osmosis)

• e.g. CO2, H2O, O2

osmosis

• diffusion of water

• affected by concentration gradient of dissolved substances called solution’s tonicity

• aquaporin proteins move polar water molecules past phobic tails (high to low concentration)

diffusion

• tendency for molecules to spread evenly into available space

• move from HIGH to LOW concentration

• DOWN concentration gradient

• NO ENERGY NEEDED

tonicity

• ability of solution to cause cell to gain or lose water

• has great impact on cells w/o walls

• 3 states of tonicity:

  • hypertonic

  • isotonic

  • hypotonic

isotonic

• concentration of solutes inside cell is same as outside

• no net mvmt of water

hypertonic

• concentration of solutes outside is greater than inside

• cell will lose water (plasmolysis)

hypotonic

• concentration of solutes is less outside than inside the cell

• cell will gain water

turgor pressure

pressure of water inside plant cell pushing outward against cell membrane

if a plant cell is turgid, it’s in a ____ environment

• hypotonic

• firm, healthy state in most plants

if a plant cell is flaccid, it’s in a ____ environment

• isotonic or hypertonic

animal cells survive best in which tonicity?

isotonic

how will water move across semi-permeable membrane?

solution A: 100 molecules of glucose/mL

solution B: 100 molecules of NaCl/mL

• each molecules of NaCl will dissociate to form Na+ ion & Cl- ion

  • → final concentration of solutes is 200 molecules/mL

• therefore, there will be net mvmt of water from solution A to solution B until both solutions have equal concentrations of solute

facilitate diffusion

• type of PASSIVE transport aided by proteins

• transport proteins speed mvmt of molecules across plasma membrane

• channel & carrier proteins

channel proteins

• facilitated diffusion

• provide corridors that allow specific molecule or ion to cross membrane

carrier proteins

• undergo subtle change in shape that translocates solute-binding site across membrane

• protein can transport solute in either direction (in or out of cell) w/ net mvmt being DOWN concentration gradient of solute

active transport

• uses energy to move solutes against concentration gradient

• requires energy, usually ATP

• e.g. sodium-potassium pump

• sometimes move against concentration gradient

sodium-potassium pump

• active transport

membrane potential

voltage difference across membrane

electrochemical gradient

caused by concentration electrical gradient of ions across membrane

electrogenic pump

transport protein that generates voltage across membrane

proton pump

cotransport

• occurs when active transport of specific solute indirectly drives active transport of another solute

• involved transport by membrane protein

• driven by concentration gradient

bulk transport

• occurs by exocytosis & endocytosis

• large proteins cross membrane by diff mechanisms

exocytosis

transport vesicles migrate to plasma membrane, fuse w/ it, & release their contents

endocytosis

cell takes in macromolecules by forming new vesicle from plasma membrane

cell theory

• all living things are made of cells

• cells = basic unit of structure & function of life

• cells are derived from reproduction of existing cells

light microscope

• visible light passes thru specimen; then thru glass lenses

• can see nucleus/chromosomes in dividing cells/central vacuole/NOT other organelles

• can observe LIVING cells

electron microscope

• electromagnets focus beam of electrons

• better resolution than light microscope

• can only observe organelles in DEAD cells

transmission electron microscope

• thin sections of specimen are stained w/ heavy metals for contrast

• can see organelles (ultrastructure) of cells

scanning electron microscope

• useful for studying surface structure

• sample surface = covered w/ thin film of gold

• image appears 3D

cell fractionation

• uses machine (ultracentrifuge) to separate major organelles for study

• separates by size/mass (bigger/heavier organelles sink to pellet'; lighter ones in supernatant)

nuclear envelope

• contains genes in eukaryotes (additional genes in mitochondria & chloroplasts)

• surrounded by DOUBLE MEMBRANE separated by 20-40 nm space

• nuclear pores lined by proteins (nuclear pore complex) → regulates passage of molecules in & out

• nuclear side of envelope lined by network of protein filaments (nuclear lamina) → maintains shape

• chromatin fibers - DNA + histone proteins

  • wraps into chromosomes (more tightly packed form) during cell division

• nucleolus → site of ribosome (rRNA) production

endomembrane system

• directly continuous or connect via transfer of membrane sacs (vesicles)

• includes nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, & plasma membrane

vesicles & vacuoles

• vacuoles = larger vesicles

• membrane-bound sacs w/ varied functions

• contractile vacuoles in freshwater protists → pump excess water out/maintain water-salt balance

• large CENTRAL vacuole in many mature plant cells

purpose of central vacuole

• stockpile proteins or inorganic ions

• dispose metabolic byproducts

• hold pigments

• store defensive compounds to defend plant against herbivores

• large vacuole reduces area of cytosol, so surface area/volume ratio inc

• water storage makes plants TURGID

facilitated diffusion w/ ion channels

• transmembrane proteins form “tunnels” across membrane

• moves from high to low concentration

• moves charged ions (Na+, K+, Ca++, Cl-) past hydrophobic tails in center

• can be “gated” or not

  • gates can open/close in response to electrical/chemical changes

water potential

• solute potential (always neg) + pressure potential (always pos) = water potential

• the greater the concentration of a solute, the lower the water potential (INVERSE relationship)

pinocytosis

• cell “gulps” droplets of extracellular fluid into tiny vesicles

• not the fluid itself that is needed by cell, but molecules inside droplet

• b/c any & all included solutes are taken into the cell, pinocytosis is nonspecific in the substances it transports

receptor-mediated endocytosis

• enables cell to acquire bulk quantities of specific substances, even tho those substances may not be very concentrated in extracellular fluid