Chapter 6,7,11 Flashcards
what are common features found in all cells?
cell membrane, cytoplasm, chromosomes, ribosomes, cytoskeleton
what does the cell membrane do?
separates and protects interior from exterior environment, selectively permeable
what is the fluid in the cytoplasm called?
cytosol
what are cytoskeletons?
dynamic network of fibrous proteins providing structural support in the cell
what properties would limit cells from being smaller?
cells have to be large enough to fit organelles and other important contents
what properties would impose upper limits on cell size?
surface area, cells want to have a high surface area: volume ratio
why does surface are impose an upper limit on size?
cell is limited by amount of surface area needed to obtain nutrients from environment and dispose of wastes
what is the fluid mosaic model of the cell membrane?
cellular membranes are fluid mosaics of phospholipids, proteins, cholesterols, and other components making membrane diverse
how are phospholipids amphiphatic?
they have a polar and hydrophilic head region with a glycerol,phosphate group and a polar group and a nonpolar tail region with fatty acid tails
what do phospholipids do in an aqueous solution?
spontaneously arrange themselves into enclosed bilayers which is energetically favourable
how do phospholipids move within the bilayer?
drifting laterally within membrane or by flip flopping transversely across membrane (rare)
what forces allow phospholipids to associate with one another?
Van der Waals forces between their fatty acid tails
why is the cell membrane fluid?
van der waal forces interactions are weak, membrane lipids are able to move
what two factors determine strength of interactions between fatty acid tails?
length and shape of the tails
how do kinks in fatty acid tails keep cell membrane more fluid?
more space to move, van der waals forces are also weaker
what properties do the membranes have?
membranes never have an open end or area due to cohesion, membranes spontaneously reseal, membranes can fuse with other membranes
what is cholesterol?
wedged between phospholipids in animal cell membranes, increases or decreases membrane fluidity depending on temperature
how does cholesterol act in room temp?
cholesterol restrains movement of phospholipids, reduces membrane fluidity
how does cholesterol act in colder temps?
cholesterol prevents phospholipids from packing tightly, increases membrane fluidity
is cholesterol amphiphatic?
yes, has hydrophilic head group with rigid planar group of rings and a hydrophobic hydrocarbon tail
what are transporter proteins?
channels or carriers, move ions and hydrophilic molecules across membrane
what are receptor proteins?
allows cell to receive signals from environment, does not let anything in, only transports signals
what are anchors?
anchor proteins attach to other proteins that help maintain cell structure and shape
what kinds of proteins are found in membrane?
transporter, receptor, enzymes, anchor proteins
what are integral membrane proteins?
permanently embedded in lipid bilayer
what are transmembrane proteins?
integral proteins that span entire membrane
what are peripheral membrane proteins?
loosely/temporarily associated/embedded in lipid bilayer and can be on internal or external side of membrane
what factors are a result of the selective permeability of the cell membrane?
permeability of bilayer and transport proteins
what does the cell membrane actively maintain?
homeostasis, a constant and stable environment within cell
what is passive transport?
diffusion of solute from a high solute conc. area to a low solute conc. area
does diffusion still occur at equilibrium?
yes, but no net movement
what is facilitated diffusion?
diffusion with the extra help of channel proteins, speeding up passive movement of hydrophilic molecules across plasma membrane
what is concentration?
the ratio of solute to solvent
why does water move quicker through aquaporins?
aquaporins are polar channels, water can interact easier with aquaporins than by simply diffusing through membrane
what is turgor pressure?
force exerted by water pressing against an object
what kinds of molecules can move through simple diffusion?
small molecules, nonpolar molecules
what transport proteins can do facilitated diffusion?
channel proteins and carrier proteins
what are channel proteins?
provides hydrophilic corridors allowing passage of ions and other polar molecules, specific only for one molecule
what are carrier proteins?
binds to ions and other polar molecules, changes shape to shuttle them across membrane so are specific only for one molecule
how can polar molecules pass through membrane without facilitated diffusion?
must go with the conc. gradient
passive facilitated transport only works when concentration gradient is
high to low
what is active transport?
movement of substances against concentration gradient which requires energy
what is an electrochemical gradient?
difference in protons, ex. higher conc of protons outside of cell compared to lower conc. of protons inside cell
what is primary active transport?
moving substances with a concentration gradient
what is secondary active transport?
moving substances with an electrochemical gradient
how do large substances move through membrane?
polysaccharides and proteins transported to an energy heavy process of exocytosis and endocytosis
what happens in endocytosis?
cell takes in macromolecules by forming vesicles from plasma membrane
what happens in exocytosis?
transport vesicles migrate to the membrane, fuse with it, and release contents to outside of the cell
why is it good that eukaryotic cells have membrane bound organelles?
can have multiple incompatible reactions occurring at the same time
how do membrane-bound organelles allow for greater efficiency of cellular activities?
increases rxn rates by clustering reactants and enzymes in close proximity, allows incompatible rxns to occur simultaneously by physically separating them in diff. compartments
what is the nucleus?
storehouse for cell’s genetic info and site for RNA synthesis
what is the endoplasmic reticulum?
involved in both protein and lipid synthesis
what is the mitochondria?
produces most of ATP that serves as energy currency of cell
what is the lysosome?
degrades macromolecules
what is the cytoskeleton?
network of dynamic filamentous proteins that provide structural support for cell
what is the golgi apparatus?
modifies and sorts proteins and lipids as they move to final destination in or out of cell
what is the plant cell wall?
rigid barrier composed of polysaccharides such as cellulose
what is the chloroplast?
enables plant cells to harness energy of sunlight to synthesize sugars
what is the central vacuole?
water-filled storage compartments that contribute to structural rigidty of plants and maintaining turgor pressure against cell wall
what is the endomembrane system?
system of interconnected organelles that communicate with each other through direct physical contact or exchange of membranous vesicles
what is the nuclear envelope?
double membrane enveloping nucleus perforated by protein openings called nuclear pores allowing molecules to move in and out of nucleus
what molecule commonly moves out of nucleus into the cytoplasm?
RNA
what is the outer membrane of the nuclear envelope connected to?
endoplasmic reticulum
what is the interior of the endoplasmic reticulum called?
lumen
how is the rough and smooth ER different?
rough ER has ribosomes, synthesizes proteins
smooth ER synthesizes lipids
where do the ER products go to for further processing?
golgi body
what are the functions of the golgi body?
chemically modifies proteins and lipids sent by ER, sorts proteins and lipids as they move to final destinations, synthesizes cell’s carbohydrates
what is the protein transport pathway of the endomembrane system?
proteins synthesized by rough ER end up within lumen of endomembrane system ending up in other organelles or excreted out
OR
end up as a membrane protein on membranes of other organelles or on cell membrane
where do proteins synthesized by free ribosomes end up?
stays in cytoplasm
where is cis and trans side of golgi body?
cis side is close to rough ER, trans side is close to cell membrane
how do lysosomes digest macromolecules?
specialized vesicles from golgi body that contain hydrolytic enzymes that animal cells use to digest all types of macromolecules and damaged organelles
how do lysosomes maintain a lower pH?
thanks to being membrane bound and it uses H+ pumps to transport H+ protons into inside of membrane
what is an autophagosome?
starts digesting its own organelles
what do the deep folds of the inner membrane cristae do in mitochondria?
provides more surface area for more cellular respiration reactions to occur
why do mitochondria and chloroplast have their own DNA?
theorized to have been separate organisms ingested by a larger one, forming the endosymbiosis theory
how many membranes do chloroplasts have?
three, the thylakoid membrane encompasses the small thylakoids
what is endosymbiosis?
belief that mitochondria and chloroplast were once bacteria engulfed by a eukaryotic cell and over time evolved their current functions within the cell
what type of chromosome do mitochondria and chloroplasts have?
circular
mitochondrial dna sequences are most closely related to _____
Typhus, a proteobacteria
chloroplast dna sequences are most closely related to ______
cyanobacteria
are mitochondria and chloroplasts part of the endomembrane system?
No
what evidence supports the endosymbiosis theory?
both contain own genomes, both have an outer and inner membrane, both grow and multiply independently of other membrane compartments
what types of skeletal proteins are there?
microtubules - thickest
intermediate filaments - middle
microfilaments - thinnest
what are microtubules?
tube-like structures that are polymers of tubulin dimers, radiates from a centrosome, supports cell shape and rigidity, separates replicated chromosomes, acts as tracks for movement of vesicles, found in cilia and flagella
flagella have a ____ motion
whip-like
cilia have a ______ motion
oar-like rowing
flagella and cilia are made of a ______________ sheathed by the plasma membrane
9 + 2 core of microtubules (9 pairs around 2 central microtubules)
are flagella and cilia considered organelles?
No
how do cilia and flagella move?
motor proteins will move pairs relative to one another, causing a bend
microtubules function as ________
tracks for transport within the cell using motor proteins kinesin and dynein
what are microfilaments?
polymers of actin subunits organized into a double helix, thinnest of three cytoskeletal fibres and are present in various locations in cytoplasm
what do microfilaments do?
form an extensive network just inside the plasma membrane to reinforce it and organize membrane proteins, also function as tracks for transport within cell but involves myosin
what are intermediate filaments?
polymers of intermediate filament proteins that combine to form cable-like structures providing mechanical strength
what are desmosomes?
cellular junctions between cells that intermediate filaments attach to, providing strong support for cells and greatly strengthening epithelial tissue
