Cell Structure (Exam 2) Flashcards
Basic cell structure of prokaryotes/bacteria
genetic material: single, circular (not in nucleus, in a nuclear region), double stranded DNA
cytoplasm
cell membrane
some may also have a cell wall which provides additional protection
List the cell structures that prokaryotes/bacteria MAY have
plasmids pili fimbriae flagella capsule endospore
how are most bacteria classified?
by their cell wall type
how can cell wall type be determined?
by gram staining
how can cell wall type be determined?
by gram staining
Different cell types are susceptible to different _____
antibiotics
gram positive
stains purple thick peptidoglycan layer rigid stronger thin LPS
Gram negative
stains pink
thin peptidoglycan layer
thick lipopolysaccharide layer
List the strategies an antibiotic uses to affect bacterial cells
- interference with cell wall: lose integrity
- Blocking of ribosome activity: if ribosomes don’t work, they can’t make the cell wall, produce well, etc
- Blocking of DNA synthesis
Cephalosporins + an example
Keflex
affect peptidoglycan synthesis
Penicillins
affect peptidoglycan synthesis
Tetracyclines
bind ribosomes
Macrolides + example
zithromax
bind ribosomes
Lipopolysaccharide
- LPS
- major component of the outer membrane of gram negative bacteria
- induce inflammation in animals.
Peptidoglycan
- has polysaccharide and protein chains
- found in bacterial cell walls
- maintains cell shape
Explain the significance of the eukaryotic cell size and complexity
It allows them to contain internal compartmentalization/organelles.
This allows it to have specific regions to adjust the pH based off of the enzymes present.
*Nuclear envelope w/ pores
double membrane
*Nucleoplasm
only exists in interphase
composition of nucleus in eukaryotic cells
nuclear envelope w/ pores
nucleoplasm
nucleolus
chromatin
Function of nucleus in eukaryotic cells
protects DNA
initiates replication
carries out transcription
function of rough ER in eukaryotic cells
carries out translation
modifies proteins
(attached to nucleus and contains ribosomes)
composition of golgi apparatus
incoming vesicle Cis surface Cistern Trans surface outgoing vesicle
Function of golgi apparatus
modifies, activates, and packages proteins
Nuclear envelope w/ pores
- bilipid membrane (double membrane)
- in eukaryotes, not prokaryotes
- nuclear pores control the movement of molecules between the nucleoplasm and cytoplasm
Nucleoplasm
only exists in interphase
- contained by nuclear envelope
- has nuclear bodies, chromosomes, and nuclear matrix
*Nucleolus
- within the nucleus
- has proteins, DNA, and RNA
- creation of ribosomes
list the components of a mitochondria
DNA, ribosomes, matrix, outer membrane, inner membrane, F0 and F1 complexes, cristae junction, intermembrane space
Intermembrane space of mitochondria
has a lower pH than the matrix because it’s pumping in H+ ions
Mitochondria
- double membraned structure
- has specialized pHs and within the mitochondria itself, has 2 regions with different pHs
- site of aerobic respiration
DNA in mitochondria
the mother’s DNA. Can link you to your mother (Grandma, etc) based off of a mitochondrial DNA analysis
mitochondrial ribosomes
more similar to prokaryotic ribosomes than eukaryotic ribosomes
functions of lysosome
- breakdown/digestion of macromolecules
- cell membrane repairs
- responses against foreign substances such as bacteria, viruses, and other antigens
explain what happens when food is eaten or absorbed by the cell (lysosomes)
- releases its enzymes to break down complex molecules including sugars and proteins into usable energy needed by the cell to surface
explain what happens if no food is provided (lysosomes)
- enzymes digest other organelles within the cell in order to obtain the necessary nutrients
composition of lysosomes
- lipids which make up the membrane
- proteins which make up the enzymes within the membrane
where are lysosomes found
- found in all animal cells
- rarely found within plant cells due to the tough cell wall surrounding a plant cell
functions of peroxisomes
- catalyze fatty acids
- detoxifies hydrogen peroxide (an oxygen radical that can be dangerous to the cell)
- detoxifies alcohol
definition of peroxisomes
vesicles containing degradative enzymes
definition of lysosomes
vesicles containing digestive enzymes
where are lysosomes produced
produced by the golgi apparatus
functions of peroxisomes
- catalyze (breakdown) fatty acids
- detoxifies hydrogen peroxide (an oxygen radical that can be dangerous to the cell)
- detoxifies alcohol
how are peroxisomes produced
by the growth and subdivision of existing peroxisomes
what the most abundant enzyme within the peroxisome and what does it do?
catalase. it breaks down the hydrogen peroxide that’s produced by the enzyme, into oxygen and water.
where are peroxisomes found?
they’re present in all cells but their numbers are highest in metabolically active cells such as liver cells
list the components of a peroxisome
peroxisome membrane
enzyme core
peroxisome lumen
hydrogen peroxide
an oxygen radical that can be dangerous to the cell
Peroxisomes have a more _______ than lysosomes
neutral pH
microvilli
extensions of the plasma membrane containing microfilaments
proteasomes
- made of proteins
- a protein degradation “machine” in the cell that can digest a variety of proteins into short polypeptides and AAs
- requires ATP
major functions of microfilaments
- anchor the cytoskeleton to integral proteins of the plasma membrane (more strength)
- Determines the consistency of the cytoplasm (if they’re dense, cytoplasm is gelatinous. if they’re dispersed, more fluid)
- actin can produce movement of a portion of a cell or change the shape of the entire cell by interacting with the protein myosin
function of gap junctions?
allow for direct communication between adjacent cell
where are gap junctions located?
below the adhesion belt
how are gap junctions formed
by connexin proteins
where can you find gap junctions?
- called intercalated discs in cardiac muscle
- electrical synapse in the nervous system
electrical synapse
don’t use NTs to go across a space. They can’t be modified and happen very rapidly
Integral proteins
- firmly attached in the plasma membrane, with its hydrophobic component interacting with the phospholipids.
- enter the hydrophobic space within the cell membrane
Peripheral proteins
- interact with the surface of the lipid bilayer of cell membranes
- don’t enter the hydrophobic space within cell membrane
Carrier proteins
- proteins that carry substances from one side of a biological membrane to the other
- type of membrane transport protein.
free ribosomes
present in the cytosol. not attached to any structure
membrane bound ribosomes
attached to the rough ER
channel proteins
- type of membrane transport protein
- embeds in the cell membrane
- makes a hydrophilic passageway for water and small, polar ions to go through.
definition of cell junctions
- fusion point between 2 cells
- protein complexes that connect cells
functions of cell junctions
- stabilize tissue structure
- form impenetrable barriers between cells
- allow for communication between cells
list the cell junctions
tight
what do tight junctions form
- a selective barrier
the junction region in tight junctions is called the…
zona occludins
where does the tight junction attach to? what’s the significance of this
microfilaments (actin). This is a signal to the cell that it has to connect with another cell
where are tight junctions located
- closer to the apical surface (near the top of the cell)
what carries out the process of fusion in tight junctions?
claudin and occludin proteins
what regulates the degree of fusion (tightness) in tight junctions?
phosphorylation
phosphorylation of tyrosine in tight junctions does what
loosens the junction
phosphorylation of threonine does what to the tight junction
tightens it
phosphorylation of threonine does what to the tight junction
tightens it
plasma membrane definition + functions
- a selectively permeable barrier which maintains the intracellular environment
- regulation of nutrients into the cell
- removal of wastes
what characteristics impact the degree of permeability to a specific molecule and method of transport?
- solubility/charge
- molecular size (can it diffuse easily? can it go through a channel)
- gradient (with a concentration gradient is easier than against a gradient)
what characteristics impact the degree of permeability to a specific molecule and method of transport?
- solubility/charge
- molecular size (can it diffuse easily? can it go through a channel)
- gradient (with a concentration gradient is easier than against a gradient)
where are desmosomes found?
closer to the basal surface and attach to intermediate filaments
where are adherens (adhesion belts) found?
inferior to the tight junctions and attached to microfilaments
How is adheren junction and desmosome fusion carried out?
by various cadherin proteins.
what forms adherin belts and desmosomes
cadherin
what does adheren do?
adds strength to the tissue
Where do hemisdesmosomes connect to?
ECM
Cadherin proteins
include desmocollin and desmoglein
desmocollin and desmogelin
- thick fibers that reinforce
- attached to intermediate filaments
Hemidesmosomes
- when you use the same structure ot attach to the basement membrane
- there’s no desmosome formation from another cell
- 1/2 desmosomes
- found locking into the basement membranes
are desmosomes larger or smaller than adherens
larger
tight junctions form ____, while adherens/desmosomes _________
barriers. strengthen
They bring the cell close enough together so that it’s almost fused: what kind of junction
tight junction
what’s the purpose of a cell junction?
to connect one cell to the next for communication so there can be a direct pore between 2 cells.
what are the functions of intermediate filaments in the cytoskeleton?
- movement
- support (Ex: keratin)
- communication (link from cytoskeleton to exoskeleton)
- adhesion (Ex: desmosomes)
Myosin
- intermediate filament fiber
- for movement
Keratin
- inside the cell
- protection
- intermediate filament
“catch all group”
intermediate filament
Intermediate filaments are a diverse population of _____
proteins
Intermediate filaments are a diverse population of _____
proteins
what are microfilaments composed of?
actin. F actin and G actin
functions of microfilaments
- maintains shape/tension of cell
- contraction/movement
- communication with ECM
- organizes cytosol contents
what happens if a cell loses shape?
it becomes spherical
where does glycolysis take place?
in the cytosol
where are all glycolytic enzymes stuck to?
microfilaments
actin
exists in 2 forms. G actin and F actin
G actin
- globular actin
- monomer of F actin
- soluble
F actin
- fibrous actin
- insoluble
- double stranded
where is there a reservoir of G actin?
in the cytoplasm
what happens when G actin binds with other G actins?
it becomes F actin which is insoluble
cytoskeleton
fibers that run through the cell
what are the categories of cytoskeletal fibers?
- microfilaments (smallest diameter)
- microtubules
- intermediate filaments
what are the categories of cytoskeletal fibers?
- microfilaments (smallest diameter)
- microtubules
- intermediate filaments
what are microtubules composed of?
tubulin dimers
function of microtubules
- transport highways for (transport) vesicles (they’re directional, on one side you go one direction, if you want to go opposite direction have to go on opposite side)
- directs movement of chromosomes (spindle fiber is made of tubulin)
- flagella and cilia (tubulin gives us this)
what do microtubulins require?
MAPS
MAPs
- microtubule associated proteins
- require ATP to do the movement
- tubulin itself can’t move so it needs this protein
sometimes called motor proteins
facilitated diffusion
- diffusion of solutes through proteins in the plasma membrane
what kind of transport is facilitated transport?
passive because the solute is moving down the concentration gradient
what are the types of transport proteins that are involved in facilitated diffusion?
channel proteins
gated channel proteins
carrier proteins
channel proteins
- act like a pore in the membrane
- lets water or small ions through quickly
- ex: aquaporins
- ex: voltage gated ion channels
gated channel protein
- transport protein that opens a gate, allowing a molecule to pass through the membrane
- binding site is specific to a molecule/ion
example of gated channel protein
the sodium gated channels of a nerve cell are stimulated by a chemical signal which causes them to open and allow sodium ions into the cell
carrier protein
- transport protein that is specific for an ion, molecule, or group of substances
- carry the ion or molecule across the membrane by CHANGING SHAPE after binding of the ion or molecule
what kind of transport are carrier proteins
involved in passive and active transport
what do gated channels respond to?
specific stimuli like - charge differential ligand binding (hormone or signals) - mechanical stress (when membrane is distorted)
