cell membrane & organelles

dat bio ch. 2

cell membrane

selective permeable barrier regulating movement of substances in/out of the cell

→ phospholipid bilayer, proteins, carbs, cholesterol

→ regulates cell signaling & comms

phospholipid bilayer

cellular membrane componend that contains hydrophilic heads & hydrophobic tails

membrane proteins

faciliate transport, used as receptors & provide structural support

2 types of membrane protiens

• integral: embedded in membrane

  • peripheral membran proteins: on the membrane surface

carbohydrates

attached to membrane surface

→ important for cell recog, signaling, adhesion

cholesterol

help stabilize membrane fluidity

→ embedded w/in cell membrane & found only in eukary cell membranes

role of integral proteins

amphipathic proteins aid in cell signaling and transport of substances in/out of cell

role of peripheral membrane proteins

gen hydrophilic proteins functioning as receptors, aid in cell recog, work as enzymes, or help w/ cell adhesion

receptors (int/perip)

transmit signal to cell

transmembrane proteins

span entire membrane

agonists

molecules binding to receptors & activate biological response

antagonists

molecules binding to receptors & prevent other molecules from binding , inhibiting bio response

ahdesion

proteins attac cells to toher things and anchor the cytoskeleton

cellular recog

glycoproteins used for cells to recognize each other

fluid mosaic model

describes how cell membrane components can move freely

• fluid = free movement

  • mosaic = mult cell membrane structures

how does temp impact fluidity

higher temps increase fluidity

how does cholesterol impact fluidity

holds membrane together @high temp; keels membrane fluid @low temp

how does degrees of unsaturation impact fluidity

saturated fatty acids pack more tightly than unsaturated fatty acids

which describes how temp affect cell membrane fluidity?

• fluidity increases as temp increases

• fluidity increases as temp decreases

• fluidity is not impacted by temperature

• fluidity increases as temp increases

how are substances transported across cell membrane

• simple diffusion

• facilitated transport

• active transport

simple diffusion

small uncharged molecules (o2, co2, h2o) or lipid-soluble molecules travel across membrane along conc gradient (high to low)

• no energy req

facilitated tranpsort

large/charged molecules travel across cell membrane thru channel proteins along conc gradient

• no energy req

  • glucose, sucrose, Na+ K+ Cl- ions

active transport

molecules traveling along cell membrane against conc gradietn

• primary & secondary active transport

• req energy

primary active transport

membrane transport proteins uses ATP hydrolysis to pump molecules against conc gradient

• Na+ K+ pump

secondary active transport

uses energy from molecule moving down its electrochemical gradient to drive transport of another molecule against conc gradient

endocytosis

cell membrane internalizes extracellular substances

• phagocytosis

• pinocytosis

• receptor-mediated endocytosis

phagocytosis

cellular eating

pinocytosis

cellular drinking

receptor-mediated endocytosis

endocytosis initiated by dissolved molecules binding to peripheral membrane receptor proteins

clathrin-mediated endocytsosi

clathrin(protein) facilitates endocytosis → results with coated vesicle intracellular space

exocytosis

internal substances released to extracellular space

which type of transport is characterized by the travel of small, uncharged molecules across the cell membrane along the concentration gradient without the use of channel proteins

simple diffusion

cellular components

• organelles

• cytosol: aq intracellular fluid

• cytoplasm

nucleus

protects & stores DNA

• DNA rep & transcript occur in nucleus and translation occur in cytoplasm

  • prokaryotes have nucleoids → not organelle

nucleus components

• nucleoplasm: cytoplasm of nucleus

• nuclear envelope: encapsulates nucleus; contains inner outer phospholipid bilayer

• nuclear pores: channels in nuclear envelope

• nucleolus: produces components of ribosomes (rRNA)

ribosomes

produces proteins via translation

eukaryotic ribosomal subunits

60S and 40S assemble in nucleoplasm and are exported to cytosol to combine and form full ribosome 80S

prokaryotic ribosomal subunits

50S and 30S assemble and combine in cytosol 70S

free floating ribosomes

produce proteins that function in cell

rough ER ribosomes

produce proteins for extracellular or cellular membrane use

endomembrane system

nucleus, rough smooth ER, golgi apparatus, lysosomes, vacuoles, and cell membrane work together to modify, package, and transport proteins and lipids

rough ER

organelle attached to outer membrane of nuclear envelope

• rough bc of embedded ribosomes → produce proteins that travel to lumen for mods, proteins then sent to cell membrane or extracellular

  • composed of cisternae (flattened sacs)

smooth ER

extends off rough ER

• synthesize lipids, produces steroid hormones, detoxifies cells

golgi apparatus

stores, modifies, and exports proteins to be secreted from cell

• composed of cisternae

proteins from rough ER enter at the cis face and exit from trans face

peroxisomes

perform hydrolysis, break down stored fatty acids, help w/ detox

• processes generate hydrogen peroxide, which is broken down by catalase

lysosome (animal cells)

membrane-bound organelles that break down cellular waste via hydrolytic enzymes and help facilitate apoptosis

vacuoles

membrane-bound vesicles used for storage or transport

• plant cells use this to main cell rigidity and break down waste

mitochondria

produces ATP via cellular respiration

• mitochondrial DNA inheritance is maternal

chloroplast

perform synthesis

• type of plastid (double membrame organelle found in only plant cell & algae)

centrosomes

organelles found in animal cells

• contain a pair of centrioles that act as microtubule organizing centers during cell replication

proteins that will be secreted are produced in the ___, processed and modified in the ___, and then transported to the cell membrane via ___.

ER, gogi apparatus, vesicle

cytoskeleton

provides structural support within the cytoplasm

• composed of several cytoskeletal proteins

microfilaments

smallest cytoskeletal structure

• composed of actin

  • essential for cell movement

functions of microfilaments

• cleavage furrow: myosin and actin aid in cell division via contractile rings

• cyclosis: actin myosin “stir” cytoplasm

• muscle contraction: actin myosin motor proteins essential for muscle contration

intermediate filaments

medium-sized cytoskeletal filament used for structural support

keratin

intermediate filament found in skin, hair, and nails

microtubules

largest cytoskeletal filament that stabilizes and shapes the cell

• composed of tubulin

• form centrioles

• essential for movement

flagella

long, hair-like structures

• cell movement

• prokaryotic: composed of flagellin

• eukaryotic: composed of tubulin polymers

cilia

small, hair-like projections composed of tubulin

• function in locomotion of whole cell or extracellular fluids

  • ony in eukaryotes

kinesin & dynein

motor proteins that travel on microtubules and are used for transport

microtubule organizing centers (MTOCs)

organize microtubule extensions

centrioles

hollow cylinders composed of microtubules found in animal cells

centrosomes

pair of centrioles oriented at 90 degree angles to one-another

which of the following plays a role in generating cleavage furrow

• intermediate filaments

• microfilaments

• microtubules

microfilaments

which two cytoskeletal elements have an active role in cell division

• microfilaments and intermediate filaments

• microfilaments and microtubules

• intermediate filaments and microtubules

microfilaments and microtubules

extracellular matrix (ECM)

provides support on the outside of the cell

• contains porteins and glycoproteins

components of ECM

• proteoglycan

• collagen

• integrins

• fibronectin and laminin

proteoglycan

ECM glycoprotein with a lot of carbohydrates

collagen

ECM structural protein secreted by fibroblast;

• collagen molecules form polymers called collagen fibrils

integrins

transmembrane proteins that control ECM adhesion and work as cell receptors

fibronectin and laminin

proteins attached to integrins

• fibronectin: helps with signal transduction

• laminin: essential for cell differentiation, ahdesion, and movement

cell wall

carbohydrate based structure that acts like ECM but more rigid

• provide structural support to cells lacking or have minimal ECM

plant cell walls

composed of cellulose

fungi cell walls

composed of chitin

bacteria cell walls

composed of peptidoglycan

archaea cell walls

composed of polysaccharides

cell matrix junctions

connect extracellular matrix to the cytoskeleton

focal ahdesions

actin microfilaments attach ECM to inside of cell

hemidesmosomes

intermediate filaments connect ECM to inside of cell

cell cell juntions

connect adjacent cells to each other

ex: tight junctions, desmosomes, adherens junctions, and gap junctions

tight junctions

form watertight seals between cells to make sure materials are passed thru the cells rather than between

• make a barrier

gap junctions

adhere cells together via connexons (transmembrane proteins)

• not watertight; allow substances to pass between cells

  • only in animal cells

desmosomes

connect adj cells with intermed filaments

• provide structural support against mechanical stress

adherens junctions

connect adj cells with actin filaments (like focal adhesions)

plant junctions

• middle lamella

• plasmodesmata

middle lamella

adheres adj cells walls together

plasmodesmata

similar to gap junction in animal cells; allow cytosol fluids to travel between plant cells

which cell matrix junction connects extracellular matrix to actin filmaents in cytoskeleton

adherens junctions

what is the most common fibrous structural protein in the ECM

collagen

tonicity

extracellular solutio influences water movement across cell membrane via osmosis due to solute concentration gradient

osmosis

water flow from low to high solute concentration thru semipermeable barrier

isotonic solution

solution and cell have same solute concentration

hypertonic solution

solution has higher solute concentration than the cell so water exits the cell

animal cells in hypertonic solution ….

lose volume and shrivel

in hypertonic solution, cells with cell walls experience

plasmolysis → interior of the cell shrinks away from cell wall as water exits the cell

hypotonic solution

solution that has lower solute concentration than the cell, so water enters the cell

in hypotonic solution, animal cells ….

gain volume and can burst and experience lysis

• lysis: cell membrane breaks down

in hypotonic solution, plant, bacterial, and fungal cells can beomce

turgid

A cell enclosed by a semipermeable membrane has an internal concentration of 0.5 M fructose, 0.2 M glucose, and 0.1 M sucrose. It is placed into a solution of fructose, glucose, and sucrose and starts to shrivel. Which of the following conclusions can be made?

A. The cell is placed in a hypertonic solution

B. The cell is place in a hypotonic solution

C. The cell is placed in an isotonic solution

D. The membrane is impermeable to water

A. The cell is placed in a hypertonic solution

epithelial tissue

sheet of cells that lines the organs and body that functions in protection, absorption, secretion, and sensation