Biology of Living Things - Cell Structure Flashcards
characteristics of life
- complexity and organization (requires energy to maintain)
- responds to environment (homeostasis - maintains constant internal conditions)
- growth and metabolism
- reproduction/hereditary
- evolve
cell types
Prokaryotes - bacteria and archaea
Eukaryotes - animals, plants, fungi, protists
major differences b/n eukaryotes and prokaryotes
Eukaryotes - have nucleus and an internal membrane system
Prokaryotes - lack both
Eukaryotes cells can be up to 1000X larger than prokaryote cells
cell volume represents
demand
cell surface area represents
supply
in order for cell to survive…
supply ≥ demand
as cell size increases…
cell volume (demand) increases faster than cell surface area (supply)
best way for cells to maintain workable SA to Vol. ratio
remaining small
prokaryotic cells divided into 2 domains
Bacteria AKA eubacteria
Archaea - extremophiles
prokaryotic structure (different from eukaryotes)
no nucleus
genetic material found in nucleoid
no internal membrane system
cell wall - proactive outer barrier composed of peptidoglycan
prokaryotic structure (similar to eukaryotes)
have plasma membrane (phospholipid bilayer)
cytoplasm: semi-solid gel (cytosol) contains all the cell’s internal components
has ribosomes (universal organelle - responsible for building proteins)
structure of prokaryotic cells
pili
nucleoid (DNA)
ribosomes
capsule
cytoplasm
plasma membrane
cell wall
flagellum
eukaryotic cells (characteristics)
membrane-bound nucleus
membrane-bound organelles –> internal membrane system
more complex
larger
compartmentalization
compartmentalization
most distinctive feature of euk. cells
compartments are membrane-bound (internal membrane)
different compartments in cell perform different functions
compartments are called organelles
structure of animal cell
nucleus
nucleolus
nuclear envelope
plasma membrane
cytoplasm
mitochondria
vesicles
Golgi apparatus
ribosomes
smooth ER
rough ER
structure of plant cell
chloroplast
plasma membrane
cell wall (made of cellulose)
everything else similar to animal cell
structure of nucleus
Phospholipid nuclear envelope
nuclear pores
nucleolus
chromatin
function of nucleus
stores genetic info
site of ribosome assembly
RNA production
ribosomes (definition)
enzyme complexes that are considered organelles (not membrane-bound)
largely made up of rRNA
assembled in nucleolus
ribosome structure
large enzyme complex made of ribosomal proteins and ribosomal RNA (rRNA)
ribosome function
protein synthesis factories
endomembrane system components
network of internal (lipid bilayer) membranes that include:
ER
- smooth (SER): no ribosomes
- rough (RER): has ribosomes on its surface
Golgi apparatus
vesicles
endoplasmic reticulum structure & characteristics
network of interconnected tubules
wall of tubules composed of lipid bilayer
space inside the tubes is called the lumen
smooth and rough ER are interconnected w/ each other & the outer lipid bilayer of the nuclear envelope
distinct functions of SER
site of lipid synthesis
site of fatty acid desaturation
site of cholesterol and steroid synthesis
various carbohydrates are synthesized there
distinct functions of RER
makes proteins that are bound for export from cell or for use in the endomembrane system
golgi apparatus structure
series of flattened tubes (sacs)
wall of tubes are a lipid bilayer
cis face - receives transport vesicles from ER
trans face - transport vesicles exit from the Golgi
golgi apparatus function
proteins and other molecules may be modified
molecules sorted by eventual destination
molecules are released in vesicles
endomembrane system summary
rough (RER) - has ribosomes on its surface, primarily manufactures proteins
smooth (SER) - no ribosomes, manufactures other macromolecules
vesicles - transport of molecules to and from Golgi complex
Golgi apparatus - modifies, sorts, packages, and distributes macromolecules
journey through endomembrane system
proteins made in RER
transport vesicle - contains products
cis face
chemical modifications
trans face
secretory vesicle
exocytosis
exocytosis
process by which material is exported out of cell
secretory vesicle fuse w/ plasma membrane to release their contents to the outside of cell
- ex. insulin secretion
endocytosis
material taken into cell
- plasma membrane surrounds material from outside cell, trapping it in an endocytic vesicle
- can be a specific process (using receptors) or passive (taking up water and nutrients)
- endocytic vesicle will then fuse w/ a digestive vesicle: a lysosome
lysosome structure
membrane-bound vesicles that contain digestive enzymes
lysosome function
to digest material from outside and inside the cell
primary lysosome
new lysosomes that bud off from trans face of Golgi
secondary lysosome
formed from fusion b/n primary lysosomes & an endocytic vesicle or a cellular organelle
tuberculosis bacterium
kills ~2 million ppl annually
able to prevent endocytic vesicle/lysosome fusion
avoids digestion and lives in cell
multiplies inside macrophage –> kills and devours it –> spreads to infect more cells
mitochondria structure
double-lipid bilayer
- outer membrane covers entire organelle
- inner membrane is extensively infolded
- folds are called cristae
- intermembrane space
mitochondria reproduce themselves –> supports endosymbiotic theory
divide by binary fission
have their own circular chromosomes
mitochondria function
energy metabolism (ATP production)
cristae
folds of mitochondria inner membrane
matrix
liquid center of mitochondria
endosymbiotic theory
evolutionary theory that eukaryotic cells came from prokaryotic cells
chloroplast structure
double lipid bilayer
- outer and inner membranes cover entire organelle
- intermembrane space is b/n outer and inner bilayers
internal membranes inside chloroplast, organized into stacked disks.
- thylakoid
- granum
- stroma
divides by binary fission
- has own circular chromosomes
- also supports endosymbiotic theory
chloroplast function
site of photosynthesis in plant cells
- light energy converted into usable energy (glucose)
cytoskeleton structure
network of multiple types of protein fibers inside cells
cytoskeleton function
provides structural support w/in cells
has a role in transport w/in cells
helps motile cells move
extracellular matrix structure
network of multiple types of protein fibers outside of cell
extracellular matrix function
provides structural support outside of cells
“glues” cells into higher order structures (organs)
has a role in cell-cell communication
extracellular matrix/cytoskeleton diagram
extracellular matrix: outside cells
cytoskeleton: inside cells
plasma membrane
barrier that defines inside and outside of cell
selective barrier - regulates transport into and out of cell
dynamic; cells can adjust chemistry of PM & molecules associated w/ PM
in 1924, Dr. Gorter discovered…
that PM is made of phospholipid bilayer
used RBCs to show phospholipid membrane was 2 layers thick
why did Dr. Gorter use RBCs?
easy to obtain
easy to count
they are of uniform size
Dr. Gorter’s experimental method:
1) counted # of RBC’s after obtaining
2) calculated total SA of RBC’s
3) destroyed cells and collected the membrane phospholipids (chemical separation)
4) placed phospholipids into chamber of buffer where they would form a floating monolayer.
5) measured total SA of the phospholipids in the chamber, and compared it to he total SA of the RBCs.
if phospholipid was monolayer….
SA of monolayer = SA of cells (1:1 ratio)
if phospholipid was bilayer….
SA of bilayer is double the SA of cells (2:1 ratio)
conclusion of Dr. Gorter’s experiment:
SA of phospholipids = 2X the calculated SA of the cells
–> cell membranes are a phospholipid bilayer
plasma membranes are much more than just phospholipid bilayer
also contains:
- membrane proteins
(peripheral, integral/transmembrane) - cholesterol
- polysaccharides
fluid mosaic model of membranes
plasma membranes are fluid structures/fluid mosaic
phospholipid bilayer like “lake”, molecules “floating”
evidence for membrane fluidity
cell fusion experiment:
- membrane proteins of 2 cells were stained w/ fluorescent dyes
- human cell membrane proteins w/ red dye
- mouse cell membrane proteins w/ green dye
- over time, colors mixed –> proteins diffused around membrane –> membrane is fluid
photo-bleaching experiments
photo-bleaching experiments
membrane proteins labeled w/ fluorescent dye –> laser beam bleaches an area of cell’s surface –> fluorescent-labeled molecules diffuse into bleached areas.
results support Fluid Mosaic Model of plasma membrane.
if membrane too fluid….
won’t serve as barrier and will fall apart
if membrane too solid….
won’t permit integral proteins to flex (change shape) and carry out functions
- ex. integral transport and signaling proteins
regulation of membrane fluidity (definition)
constantly making new phospholipids & adjusting fluidity to surroundings
2 ways of changing FA chains of phospholipids:
cell can generate phospholipids that have more or fewer unsaturations in the FA chains.
cell can generate phospholipids that have much longer or shorter FA chains.
thylakoid
single membrane disk in chloroplast
site of photosynthesis in plant cell
granum
stack of thylakoids in chloroplasts
stroma
aqueous material surrounding grana in chloroplasts
control of membrane fluidity (% of sat/unsat. FA chains)
cells can change the % of phospholipids that have sat. or unsat. FA chains
higher [ ] of phospholipids w/ unsat. FAs
effect on membrane fluidity
pack less tightly
unsat. hydrocarbon tails w/ kinks
more fluid
higher [ ] of phospholipids w/ sat. FAs
effect on PM fluidity
pack more tightly
sat. hydrocarbon tails have no kinks
less fluid
control of membrane fluidity (short/long FA chains)
cells can change % of phospholipids w/ long or short FA chains
higher [ ] of phospholipids w/ short FA chains
effect on PM fluidity
pack less tightly
more fluid
higher [ ] of phospholipids w/ long FA chains
effect on PM fluidity
pack more tightly
less fluid
lower external temps
effect on PM fluidity
PM becomes less fluid (more solid)
how cell maintains PM fluidity during lower external temps
make phospholipids w/ FA chains that are:
shorter
more unsaturated
higher external temps
effect on PM fluidity
PM becomes more fluid (less solid)
how cell maintains PM fluidity during higher external temps
makes phospholipids w/ FA chains that are:
- longer
- more saturated
membrane permeability –> hydrophobic interior
major barrier for molecules crossing a plasma membrane
PM is permeable to…
non polar molecules
PM is less permeable to…
small polar molecules
PM is not permeable to…
large polar molecules
ions
types of membrane transport
diffusion
active transport
diffusion
movement of molecules across the membrane from high [ ] to low [ ]
does not require use of cellular energy
active transport (anti-diffusion)
movement of molecules across the membrane from low [ ] to high [ ]
does require use of cellular energy
2 subtypes of diffusion
simple diffusion
facilitated diffusion
simple diffusion occurs if…
1) PM is permeable to a particular molecule
and
2) there is difference in [ ] of that molecule across the membrane
then
molecule will diffuse across membrane by simple diffusion
simple diffusion (mechanism)
no energy input is required
no transport proteins are required
facilitated diffusion (definition)
diffusion of molecules that can’t cross the membrane on their own must be facilitated
facilitated diffusion (mechanism)
occurs thru transport proteins (integral membrane proteins):
channel proteins and carrier proteins
driven by diffusion, no energy input required
transport proteins are…
selective and only transport certain molecules
cells regulate FD by:
1) regulating presence or absence of particular transport proteins
2) regulating the activity of particular transport proteins
channel proteins in FD
like tunnels
don’t bind to the molecules they transport
can always be open or gated – open or closed
direction of movement depends on [ ]
movement does not require energy input from cell
carrier proteins in FD
must bind to the molecules that they transport
direction of movement depends on [ ]
movement does not require energy input from cell
3 basic types of carrier proteins
uniporters
type of carrier protein
only transports 1 type of molecule
symporters
type of carrier protein
transports 2 types of molecules, in same direction, at same time
antiporters
type of carrier protein
transports 2 types of molecules, in opposite directions, at same time
channel & carrier protein kinetics
each displays different kinetics (rates) of transport
channel protein kinetics
display linear kinetics
carrier protein kinetics
display saturation kinetics
active transport (anti-diffusion) (definition)
used by cells to build up a [ ] gradient of a molecule across a plasma membrane
active transport (anti-diffusion) (mechanism)
moving molecules against a [ ] gradient requires:
1) carrier proteins
2) energy input from cell
nuclear envelope
double lipid bilayer membrane that surrounds the nucleus
inner & outer bilayer
outer bilayer of nuclear envelope
connected to endomembrane system
nuclear pores
passages thru the nuclear envelope that regulate nuclear transport
chromatin
chromosomal DNA bound to proteins (histones)
nucleolus
area inside nucleus
where ribosome complexes are assembled
