Class Five Flashcards
function of the nucleus (3)
contact + protect DNA
transcription
partial assembly of ribosomes
function of the mitochondria (2)
produce ATP via the Krebs cycle & oxidative phosphorylation
function of ribosomes
synthesize proteins
function of rough ER
location of synthesis/modification of secretory, membrane-bound & organelle proteins
function of smooth ER (2)
detoxification and glycogen breakdown in liver
steroid synthesis in gonads
function of Golgi apparatus
modification and sorting of protein, some synthesis
function of lysosomes
contain acid hydrolases that digest various substances
function of peroxisomes
metabolize lipids and toxins using H2O2
what 2 organelles have 2 membranes surrounding them
nucleus and mitochondria
what 2 organelles have no membranes surrounding them
ribosomes and rough ER
purpose of nuclear envelope
separates the contents of the nucleus from the cytoplasm and other organelles
how many human chromosomes
23
which chromosomes do we not have 2 copies of
sex chromosomes
inactivity of telomerase
implicated in cell aging and death
regions of a chromosomes where genes are inaccessible
heterochromatin
loosely packed regions of chromosomes - more accessible
euchromatin
nucleolus
region within the nucleus that functions as a ribosome factory
function of nuclear pores
allow the passage of material into and out of the nucleus
nuclear localization sequence
proteins with this are translated on cytoplasmic ribosomes and then imported into the nucleus by specific transport mechanisms
site of oxidative phosphorylation
mitochondria
inner membrane of the mitochondria
location of the electron transport chain
impermeable to polar substances
folded into cristae
endosymbiotic theory of mitochondrial evolution
mitochondria has a second system of inheritance → theory that mitochondria originated as independent unicellular organisms
mitochondrial maternal inheritance
mitochondria are inherited only from the mother (cytoplasm of egg becomes cytoplasm of the zygote)
why is rough ER rough
lots of ribosomes bound to its surface
two sites of protein synthesis
on free ribosomes in cytoplasm
or ribosomes bound to the rough ER
where do proteins translated on free ribosomes go
peroxisomes, mitochondria, nucleus or stay in cytoplasm
where do proteins synthesized on the rough ER go
secreted into extracellular environment
plasma membrane proteins
or in the membrane of the ER, Golgi apparatus or lysosomes
what happens if a protein has a signal sequence
recognized by signal recognition particles (found on the rough ER)
gets translated on the rough ER
how are signal sequences removed
removed by a signal peptidase in the ER lumen
where are signal sequences found
N terminus
what has transmembrane domains
integral membrane proteins
purpose of transmembrane domains
they are hydrophobic amino acid residues that allow to pass through lipid bilayer membranes
signal sequences found in the interior of proteins
not removed after translation
glycosylation
addition of saccharides - post translational modification
occurs in the lumen of the ER and Golgi apparatus
functions of the Golgi (3)
modification of proteins made in RER
sorting + sending proteins to their destinations
synthesize macromolecules (polysaccharides etc)
direction of flow in Golgi
vesicles from ER fuse with cis stack
they are then transferred to the medial stack for more modification
proteins leave the Golgi at the trans stack
constitutive secretory pathway
proteins are sent in vesicles from the Golgi immediately to the cell surface
regulate secretory pathway
some secretory proteins are stored but vesicles and only released at certain times (signal from extracellular environment)
what do lysosomes do
degrade macromolecules via hydrolysis
where are lysosome proteins made
RER
autophagy
lysosomes eating damaged organelles
phagocytosis
degradation of large matters by lysosomes
crinophagy
lysosomal digestion of excess secretory products
enzymes responsible for lysosomal degradation
acid hydrolases
safety mechanism - lysosomes
acid hydrolases only hydrolyze substances in acidic environments
if a lysosome is ruptured, the enzymes cannot act in the cytoplasm (higher pH)
what does catalase do
converts H2O2 into H2O + O2 to protect the rest of the peroxisomes
three lipids of eukaryotic membranes
phospholipids
glycolipids
cholesterol
where are there a higher number of proteins than lipids in membranes
mitochondrial inner membrane
peripheral vs integral membrane proteins
integrated: embedded in the membrane, held by hydrophobic interactions
peripheral: stuck to an integral protein, held by H bonding
unsaturated fatty acids effect In membrane fluidity
more kinks = higher fluidity
what do colligative properties depend on
the number of solute particles in solution rather than the type of particle
4 colligative properties
vapour pressure depression
boiling point elevation
freezing point depression
osmotic pressure
boiling point elevation
delta Tb = kbiim
freezing point depression formula
delta Tf = -kfim
diffusion
solutes move towards equilibrium
osmosis
solvent moves towards equilibrium
isotonic environment
solute conc is the same inside and outside the cell
hypotonic solution
less solute
hypertonic solution
more solute
osmotic pressure
the pressure it would take to stop osmosis from occurring
osmotic pressure formula
MiRT
passive transport
thermodynamically favourable movement of solute across a membrane
aka diffusion
types of passive transport
simple and facilitated diffusion
simple diffusion
diffusion of a solute through a membrane without help from a protein
facilitated diffusion
movement of a solute across a membrane down a gradient with the use of proteins
types of proteins for facilitated diffusion
channel proteins and carrier proteins
symporters vs antiporters
symporters: 2 molecules in the same direction
antiporters: 2 molecules in opposite directions
active transport
movement of molecules through a membrane against a gradient
requires energy input
primary active transport
transport of a molecule is coupled to ATP hydrolysis
secondary active transport
transport process is driven by an ATP gradient
sodium potassium pump molecules
3 sodium out of the cell
2 potassium into the cell
hydrolysis of one ATP
3 main functions of sodium potassium pump
maintains osmotic balance between inside/outside of cell
establishes RMP
provides conc gradient to drive secondary active transport
exocytosis
vesicle in cytoplasm fuses with plasma membrane → expelled into extracellular space
endocytosis
materials taken into the cell by invagination of cell membrane
3 types of endocytosis
phagocytosis
pinocytosis
receptor mediated endocytosis
phagocytosis
nonspecific uptake of material into phagocytic vesicle (later merges with lysosome)
e.g. macrophages
pinocytosis
nonspecific uptake of small molecules and extracellular fluid via invagination
receptor mediated endocytosis
very specific
sites of endocytosis is marked by pits coated with clathrin & receptors
e.g. cholesterol
3 types of signal transducing cell surface receptors
ligand gated ion channels
catalytic receptors
G protein linked receptors
ligand gated ion channels
opening of an ion channel upon binding a ligand
catalytic receptors
initiates enzyme activity by ligand binding
G protein linked receptors
don’t directly transduce a signal → transmits it onto the cell with the aid of a second messenger
most important second messenger
cyclic AMP
universal hunger signal → second messenger for epinephrin and glucagon
allows for greater signal
3 proteins that make up the cytoskeleton
microtubules
intermediate filaments
microfilaments
proteins that finish translation at the rough ER
secreted proteins
transmembrane proteins
lysosomal proteins
who has signal sequences (3)
secreted proteins
lysosomal proteins
membrane bound proteins
where is signal sequence found for membrane bound proteins
anywhere in amino acid sequence
what is a microtubule
hollow rod with 2 proteins: alpha and beta tubulins
why can’t one end of a microtubule elongate
it is anchored to the microtubule organizing center (MTOC)
aster
microtubules that come out from centrioles during mitosis
polar fibers
microtubules that connect the chromosomes to aster
centromere of each chromosome contains..
kinetochore
what is essential for mitosis and what is not
MTOC = essential
centrioles = not (plant cells don’t have them, but still undergo mitosis)
what has a 9 +2 arrangement
cilia and flagellum
dynein
connects microtubules, allows for movement of filaments
what is cilium/flagellum anchored to the plasma membrane by
basal body
microfilaments are formed from..
the polymerization of actin
amoeboid movement
changes in cytoplasmic structure which causes cytoplasm and the rest of the cell to flow in one direction
what causes amoeboid movement
microfilaments
differences with intermediate filaments
heterogenous - wide range of polypeptides
more permanent than microfilaments/tubules
tight junctions
form a seal between membranes of cells - blocks flow of molecules
desmosomes
just holds cells together
anchored to plasma membrane by keratin plaque
intermediate filaments from cytoplasm attach here
gap junctions
connections between cells so their cytoplasm can mix
exchange of small soulutes
e.g. cardiac muscle, action potentials
what happens in S (synthesis) phase
cell actively replicates its genome
what happens in mitosis
partitioning of cellular components into halves
what happens in cytokinesis
physical process of cell division
the cell spends most of its time in..
interphase
4 phases of mitosis
prophase
metaphase
anaphase
telophase
first sign of prophase
genome becomes visible → densely packed chromosomes
two copies of a chromosome =
sister chromatids
key points of prophase
nucleolus disappears
spindle & kinetochore fibers appear
centriole pairs begin to move to opposite sides
2 MTOCs aka asters
key points of metaphase
chromosomes lined up at center of cell → metaphase plate
kinetochore of each sister chromatid attached to spindle fibers that attach to MTOC on opposite ends of cell
key points of anaphase
spindle fibers shorten → centromeres pulled apart
cell elongates
formation of cleavage by microfilaments
key points of telophase
nuclear membrane forms around the end of each cell
chromosomes decondense
nucleolus becomes visible for each cell
each daughter chromosome has 2n chromosomes
karyotype
display of organism’s genome
photograph is taken during metaphase
mutated genes that induce cancer
oncogenes
protooncogenes
normal versions of the genes that allow for regular growth pattern → can be converted into oncogenes in the right circumstances
tumour suppressor genes
produce proteins that are the inherent defence system to prevent conversion of cells into cancer cells
apoptosis
allows a cell to shrink + dose without damaging neighbouring cells
internal cause of apoptosis
p53 (tumor suppressor proteins)
caspases
family of proteases that carry out event of apoptosis
cleave target proteins at aspartic acid sites
initiator caspases
respond to extra/intracellular death signals by clustering together (activating each other)
effector caspases
cleave a variety of cellular proteins to trigger apoptosis
oxidative stress
level of reactive oxygen species builds up
oxidative stress - cancer
can damage DNA, proteins & lipid bilayers
allows oncogenes to be activated
senescence
biological aging that occurs at the cellular and organismal levels
length of the telomeres is indicative
___ and ___ decrease with addition of solutes to solution
freezing point and vapour pressure
___ and ___ increase with increased number of particles
boiling point and osmotic pressure
where in the cell cycle is it highly regulated
between G1 and S
