Studied by 3 people
high SA:V ratio
allows for specialization
in order to get enough nutrients, be able to reduce waste, get resources, acquire or dissipate thermal energy, etc
higher efficient exchange of materials with the environment
endosymbiotic theory
led to the evolution of complex eukaryotic cells with compartmentalization
a free-living aerobic prokaryotic cell was engulfed by an anaerobic cell through endocytosis
electron microscope
allowed for scientists to figure out the exact functions of cells
prokaryotes
only in domains bacteria and archaea
circular DNA in nucleoid region, no nucleus
cell wall- made of peptidoglycans
filled with semi-fluid cytosol
no membrane bound organelles
eukaryotes
more complex, ordered into smaller structures called organelles
DNA in nucleus bounded by a membranous nuclear envelope
cytoplasm between plasma membrane and nucleus
plasma membrane
complex outer envelope
composed of phospholipid bilayer
regulates movement in/out of cell.
flexible due to weak bonds holding it together, has higher fluidity when phospholipids have double bond (bend in tail) or when it has cholesterol in it
amphipathic
a molecule containing both hydrophilic and hydrophobic parts
semipermeable membrane
only small hydrophobic molecules can pass through unaided
anything large/hydrophilic must pass through active/passive transport
water can’t move through easily due to its polarity
fluid mosaic model
describes the fluid and flexibility of the membrane, and also the components its made from.
peripheral proteins
are loosely associated with the lipid bilayer
located on inner/outer surface (the hydrophilic head part of the plasma membrane)
is polar and hydrophilic
integral proteins
firmly bound into the plasma membrane
some extend all the way through the membrane
amphipathic to allow anchoring
hydrophilic with charged and polar side groups, but also hydrophobic with nonpolar side groups that penetrate the hydrophobic interior of the bilayer
6 major protein functions
transport
cell to cell recognition
enzymatic activity
signal transduction
intercellular joining
attachment to ECM and cytoskeleton for anchoring
adhesion proteins
membrane proteins form junctions between adjacent cells
helps cells interact with each other and with the extracellular matrix
receptor proteins
serve as docking sites for arrivals at the cell
ex: horomones
transport proteins
form pumps that use ATP to actively transport solutes across the membrane (active transport)
hydrophilic channel that certain molecules/ions can use as a tunnel
specific for the substance it moves
carrier proteins
bind to molecules and change shape to shuttle molecules across the membrane
channel proteins
selectively allow the passage of ions/molecules
hydrophilic tunnel
cell surface marker
exposed on cellular surface
play a role in cell recognition/adhesion
ex: glycoproteins, glycolipids, proteins
carbohydrate side chains
attached to surface of some proteins
found only on outer surface
cholesterol
a type of steroid that maintains fluidity in the plasma membrane by increasing the space between phospholipids due to bend
can also prevent plasma membrane from becoming too fluid in hot conditions
randomly distributed and wedged between phospholipids in the cell membrane of eukaryotic cells
nucleus
largest organelle of cell
directs what goes on in cell
responsible for cell’s ability to reproduce
home of hereditary information (DNA)
DNA organized into large structures called chromosomes
nucleolus
is the most visible structure of nucleus, which is where rRNA is made and ribosomes are assembled
nuclear envelope
a highly regulated membrane barrier that separates the nucleus from the cytoplasm in eukaryotic cells
ribosomes
sites of protein synthesis
manufacture all proteins required/secreted (discharged) by the cell
bind messenger RNA (mRNA) and transfer RNA (tRNA) to synthesize proteins
round structures consisting of 2 subunits: the large subunit and the small subunit. composed of RNA and proteins
can either be free floating or attached to the endoplasmic reticulum (ER)
endoplasmic reticulum
continuous channel that extends into many regions of the cytoplasm
lipid proteins synthesis/transport
rough endoplasmic reticulum
attached to nucleus
studded with ribosomes, which makes it appear ‘rough’
proteins generated here are trafficked to/across plasma membrane, or used to build Golgi bodies, lysosomes, or the ER.
smooth endoplasmic reticulum
lacks ribosomes
makes: lipids, hormones, steroids
breaks down toxic chemicals (detoxify)
golgi complex
Once the ribosomes on the rough ER have completed synthesizing proteins, the Golgi bodies modify, process, and sort the products (proteins, lipids, etc)
packaging/distribution centers for materials destined to be sent out of cell
package final products into vesicles, which carry products to plasma membrane
involved in production of lysosomes
mitochondria
responsible for converting the energy from organic molecules (glucose) into useful energy for the cell
energy molecule in the cell is adenosine triphosphate (ATP). ATP production.
unique oblong shape and characteristic double membrane consisting of an inner portion and an outer portion
mitochondria structure
inner membrane forms folds called cristae
separates innermost area (called the matrix) from the intermembrane space
outer membrane separates the intermembrane space from the cytoplasm
production of ATP done on the cristae
lysosomes
tiny sacs that carry digestive enzymes
break down old/worn out organelles/debris/large ingested particles
cells clean-up crew
keep cytoplasm clear of unnecessary flotsam
sometimes contain hydrolytic enzymes that function only at an acidic pH, which is enclosed inside the lumen of the lysosome
centrioles
small, paired, cylindrical structured often found within microtubule organizing centers (MTOCs)
Most active during cellular division
When cell is ready to divide, centrioles produce microtubules, which pull the replicated chromosomes apart and move them to opposite ends of the cell
common in animal cells but not in plants
centrisomes
pair of centrioles
vacuoles
latin for “empty cavity”
large vesicles, fluid-filled sacs that store water/food/wastes/salts/pigments for later use/removal
larger in plant cells (plant cells have a central vacuole) to take up cytoplasm space to increase intracellular transport speed
peroxisomes
uses peroxide to break down molecules
breakdown of long fatty acids through beta-oxidation
cytoskeleton
network of fibers that maintain cell shape (microfilaments and microtubules)
microtubules
made up of protein tubulin
participate in cellular division/movement
integral part of centrioles/cilia/flagella
microfilaments
important for movement
composed of protein actin
actin monomers joined together and broken apart as needed to allow microfilaments to grow and shrink
assist during cytokinesis/muscle contraction/formation of pseudopodia extension during cell movement
cilia
allow motion in cells
in respiratory tract, cilia sweep constantly back and forth to keep out pathogens/dust
flagella
allow for motion in cells
every sperm cell has flagellum, enabling it to swim through the female reproductive organs to fertilize the waiting ovum
extracellular matrix
also known as ECM
molecules secreted by cell, mostly glycoproteins or other carb/containing molecules, especially collagen
provides structure/biochemical support
plasmodesmata
connections between plant cells that allow communication amongst them
cell wall
rigid layer of cellulose (polysaccharide) in plant cell walls, chitin in fungi cell walls, and peptidoglycan in bacterial cell walls
outside of plasma membrane
provides support for cell and prevents lysis
comprised of complex carbohydrates
chloroplasts
contain chlorophyll, making them green
involved in photosynthesis
part of plastid family, has double membrane
central vacuole
takes up most of cytoplasm and crowds out other organelles
contains cell sap in mature plants
full vacuole means plant is not dehydrated
facilitated transport
substances must pass through a specific channel protein instead of directly through the membrane due to its hydrophilic/charge/etc.
depends on a number of proteins that act as tunnels through the membrane
ex: aquaporins are water specific-channels
diffusion
a substance will move down its concentration gradient
simple diffusion
if the diffusion molecule is hydrophobic, the nonpolar molecule can drift through the membrane unaided
facilitated diffusion
diffusion of a substance requires the help of a channel protein
passive transport
when the substance is moving down its concentration gradient
no energy required
dynamic equilibrium
as many molecules cross the membrane in one direction as the other
osmosis
process where water is diffused
water always moves from areas where it is more concentrated to where it is less concentrate
water moves to dilute solid particles
tonicity
describes osmotic gradients
isotonic
the solute concentration is the same inside as outside
no net water movement
plant cells become flaccid in an isotonic environment, normal for animal cells
hypertonic
solution has more total dissolved solutes than the cell
cell loses water
plant cells experience lethal plasmolysis in a hypertonic environment. In animal cells it is called crenatation
hypotonic
solution has less total dissolved solutes than the cell
cell gains water
plant cell in a hypotonic solution swells until the wall opposes uptake, becoming turgid/firm (which is optimal); while an animal cell in a hypotonic solution will lyse/burst since their membrane are not as strong
water potential
Ψ
is the measure of potential energy in water and describes the eagerness of water to flow from an area of high water potential to an area of low water potential
affected by pressure potential Ψp and solute potential Ψs
active transport
allows a substance to move against its concentration gradient by using energy to help it along
Performed by specific proteins along membrane
ion pumps
membrane potential = voltage difference across a membrane
voltage created by difference in the distribution of positive/negative ions across a membrane
2 combined forces (electrochemical gradient) drive diffusion of ions across a membrane
electrogenic pump is a protein that generates voltage across a membrane
ex: sodium-potassium pump, which pushes out 3 Na+ and brings in two K+ and depends on ATP
cotransport
occurs when active transport of a solute indirectly drives transport of other solutes
symport
a process by which two different molecules are transported across a cell membrane in the same direction
antiport
a process that moves two or more different molecules in opposite directions across a cell membrane
endocytosis
when the particles that want to enter a cell are too large to be transported by a channel protein, the cell uses a portion of the membrane to engulf that substance
Membrane forms a pocket, pinches in, and eventually forms a vacuole/vesicle
pinocytosis
the endocytosis of liquids
phagocytosis
the endocytosis of solids
receptor mediated endocytosis
cell surface receptors work with endocytic pits that are lined with a protein called clathrin
when a ligand binds to one of these receptors, it is brought into the cell by the folding in of the cell membrane
vesicle forms around incoming ligand and carries it to cell’s interior
exocytosis
large particles transported out of cell ex. waste, specific secretion products (like hormones)
fusion of a vesicle with plasma membrane
reverse endocytosis
bulk flow
one-way movement of fluids brought about by pressure
ex. movement of blood through a blood vessel
dialysis
diffusion of solutes across a selectively permeable membrane
cell junctions
result of cells in close contact with each other
allow neighboring cells to form strong communication connections/nutrient flow
fastens cells to each other
provide contact between neighboring cells or cell and extracellular matrix
3 types
desmosomes
hold adjacent animal cells tightly together
pair of discs associated with the plasma membrane of adjacent cells + intermediate filaments within cells that are also attached to discs
gap junctions
protein complexes that form channels in membranes and allow communication between cytoplasm of adjacent animal cells for the transfer of small molecules/ions
tight junctions
tight connections between membranes of adjacent animal cells
so tight that there is no space in between cells
seal off body cavities
prevent leaks
go all around cells rather than random spots like desmosomes
Note 
Flashcard (71)