Quiz 2 The Cell and Membrane. Flashcards
Under what domains do prokaryotes fall?
Under Domains Bacteria and Archaea
Characteristics of prokaryotes
- small in size
- no nucleus just nucleoid region
- most have no membrane bound organelles
- DNA in nucleiod region, ribosomes (dif from eukaryotic ribosomes), and plasma membrane
- may also have a cell wall, capsule, fimbriae, and flagella (tail)
What domain and kingdoms can eukaryotes fall under?
Domain Eukarya, Kingdoms Fungi, Plantae, Animalia, and Artificial Protists
Characteristics of eukaryotes
- larger in size than prokaryotes
- surrounded by a plasma membrane and have ribosomes
- have nucleus and other membrane bound organelles
- May have cell walls (Plantae, Fungi, and many Protists)
protoplasm
living part of the cell
cytoplasm
area between nucleus and plasma membrane, or interior of prokaryotic cell
cytosol
semi-fluid matrix of cytoplasm
organelles
subcellular structures with specific functions, most are surrounded by a membrane (except ribosomes)
why are ribosomes not actually considered organelles?
lack a membrane, but still function as organelles
ribosomes
composed of rRNA and proteins
has two subunits (large and small)
two types: free ribosomes in cytoplasm and ribosomes attached to rough ER
in both prokaryotes and eukaryotes
what is a difference between proteins made by ribosomes free in the cytoplasm and ribosomes attached to rough ER
proteins made from the free ribosomes are soluble in cytoplasm and proteins made in attached ribosomes are needed for other organelles
main function of ribosomes
protein synthesis
what type of ribosomes do prokaryotes only have?
free, because don’t have an ER
main functions of nucleus
- directs metabolism, growth, development, and reproduction by directing protein synthesis
characteristics of nucleus
nuclear envelope is made of two lipid bilayers
nuclear pores are very selective
nuclear lamina
netlike array of protein filaments that mechanically supports the nuclear envelope, nuclear matrix of proteins also present throughout the nuclear interior
chromatin
DNA associated with proteins, dark stained hazy area in non-dividing cells, in dividing cells chromatin condenses into chromosomes
nucleolus
site of synthesis of ribosomal subunits, may be two or more per cell, dark oval stained area in non-dividing cells, rRNA synthesized
nucleolar organizing center
contains multiple copies of genes needed to make rRNA
vesicles
short lived sacs enclosed by a membrane, often used to transport molecules that are pinched off of golgi apparatus or ER
Rough Endoplasmic Reticulum
composed of cisternae
ribosomes are attached to the outer cisternae membrane
can be continuous with nuclear envelope
cisternae
parallel fluid filled sacs surrounded by membrane
main functions of the Rough ER
- protein synthesis
- protein packaging
- protein secretion
- phospholipid synthesis (makes membranes)
- glycoprotein synthesis (often secretory proteins)
- synthesize transport vesicles (pinched off)
Smooth ER
composed of cisternae
no ribosomes attached to membrane
Functions of smooth ER
- carbohydrate metabolism
- detoxification of drugs and poison
- calcium ion storage
- produces oils, phospholipids, and steroids including steroid hormones
Golgi apparatus
composed of cisternae
different rxns occur inside or on outside in membrane enclosed sacs
receives ER transport vesicles with molecules enclosed, membranes fuse and the molecules enter cis side and exit trans side of Golgi in vesicles
vesicles can carry molecules backwards to other side of Golgi or to ER
Functions of Golgi Apparatus
- directs macromolecule transport
- sorts, modifies, and re-labels molecules for transport
- synthesizes carbohydrates including polysaccharides
- modifies carbohydrate tags on molecules
- modifies glycoproteins
- modifies phospholipids
lysosomes
“recycling center”
membrane bounded sacs containing powerful digestive enzymes
they are first made in rough ER or Golgi, pinched off of the Golgi apparatus
Main functions of lysosomes
- involved in exocytosis
- digests old macromolecules (recycled and reused)
- digests old organelles
- programmed cell death (apoptosis)
- contain lipases (enzymes that breakdown lipids)
- contain carbohydrases
- contain proteases
- contain nucleases
- food digestion in protists
vacuoles
membrane enclosed sacs
usually larger and live longer than vesicles
present in plant cells, not as prevalent in animal cells
food vacuoles
store and break apart food in some protists
contractile vacuoles
expel excess water in some protists
central vacuole in plants
enclosed by tonoplast (membrane), helps maintain turgidity (water pressure) of cells, stores organic compounds and inorganic ions, break down organic molecules, store pigments, dumping ground for toxic waste
endomembrane system
“work together”
INCLUDES: nuclear envelope, rough ER, smooth ER, Golgi apparatus, lysosomes (if present), vacuoles (if present), and plasma membrane
peroxisomes
membrane enclosed sacs
sometimes crystalline lattice appearance
contain many enzymes
Main functions of Peroxisomes
- involved in oxidation reaction that strip hydrogen atoms from organic molecules to make double bonds and produce H2O2 (oxidases)
- contain catalase to break down hydrogen peroxide
- in some peroxisomes, fatty acids are broken down into smaller molecules
- detoxify alcohols
Main function of mitochondria
- Site of aerobic respiration
- food is broken down to make ATP
- synthesize some proteins but most are transported from cytosol into mitochondrion are moved around in cell using cytoskeleton
mitochondria
surrounded by membrane with inner membrane system
contain their own DNA
contain free ribosomes (space inside)
divide independently of cell
outer membrane of mitochondria
smooth and permeable to many small ions
inner membrane of mitochondria
convoluted, more selective, many enzymes of cellular respiration are embedded in membrane, convolution increases surface area (cristae = folds)
intermembrane space on mitochondria
area between two membranes
matrix of mitochondria
inner compartment, contains enzymes involved in cellular respiration
plastids
organelles in plants only
amyloplasts
store starch
chromoplasts
plastids with colored pigments other than chlorophyll
chloroplasts
plastids that contain chlorophyll (green pigment that absorbs light energy during photosynthesis)
contain their own DNA and ribosomes
divide independently of cell (similar to binary fission not mitosis)
double membrane surrounds internal membrane system
main functions of chloroplasts
- photosynthesis
- synthesize carbohydrates
- synthesize amino acids
thylakoids
internal membrane enclosed sacs, where light dependent rxns occur in chloroplasts
grana
term for stacks of thylakoids in chloroplasts
stroma
semi-fluid region outside of thylakoids where light independent rxns occur (ex. Calvin’s cycle)
endosymbiosis or endosymbiont theory
theory that mitochondria and chloroplasts are ancient prokaryotes that took up residence in the precursors of eukaryotic cells, survived, and started to divide independently of eukaryotic cell precursor
some of their genes have been thought to have moved into the nucleus of their host cell
evidence of endosymbiosis
- many symbiotic relationships between prokaryotes and eukaryotes are known to exist
- mitochondria and chloroplasts are similar to bacteria in size and shape
- both have their own single circular DNA not associated with histones
- mitochondria and chloroplasts both have ribosomes that are like prokaryotic ribosomes
- mitochondria and chloroplasts both divide independently of host cell and they divide like prokaryotes (binary fission)
- inner membranes of both have enzymes and transport systems that are homologous to these found in living prokaryotes
cytoskeleton
network of fibers throughout the cytoplasm that functions in support, movement, and regulation, dynamic
can transmit forces from the surface to the interior of the cell
what are the 3 types of filaments associated with the cytoskeleton
microtubules, microfilaments, and intermediate filaments
they all function as cell support and cell structure
dynein motor proteins
responsible for bending movements of cilia and flagella, shape changes using energy of ATP, one foot maintains contact while other foot releases and attaches one step further “like walking”
microtubule doublets held in place by cross linking proteins
microtubules
hollow fibers made of protein tubulin dimers
grow out of a centrosome (microtubule organizing center) in animal cells
Main functions of microtubules
- cell support (compression resisting)
- cell movement (part of cilia and flagella structure)
- involved in cell division (moves chromosomes around as spindle apparatus)
- organelle movement
- vesicle movement
centrioles
small cylindrical structures in pairs oriented at right angles in centrosomes
contain 9 triplets of microtubules
replicate before cell division
may help organize spindle apparatus that moves chromosomes during cell division
plant cells lack centrosomes with centrioles
cilia and flagella
hair like structures that move cell or move things past cell
surrounded by a membrane
anchored by basal body
flagella (few and long)
cilia (many and short)
primary cilium
nonmotile signal receiving cilium in many vertebrate animal cells,
membrane proteins transmit chemical and mechanical signals from the environment to the cell interior triggering pathways that may lead to changes in cell activity
microfilaments (actin filaments)
solid fibers made of protein actin
often interacts with myosin
main functions of microfilaments
- cell support (bear tension)
- cell division (cytokinesis or division of cytoplasm)
- cell movement (creeping movement)
- enable contents of cell to move around in order to distribute things (cytoplasmic streaming)
- organism movement (muscle contraction)(work with myosin protein)
cortical microfilaments
supportive microfilaments just inside of the plasma membrane that helps give cells shape
make up microvilli that increase surface area of membranes
intermediate mircofilaments
structure is highly variable
some are made of repeating keratin subunits
only in some animals including vertebrates
main functions of intermediate microfilaments
- cell support (bear tension)
- cell adhesion (desmosomes)
- hold organelles such as nucleus in place
- formation of nuclear lamina that supports nuclear envelope
cell wall
supportive layer outside cell membrane
can find in plants., fungi, most bacteria, and many protists
main functions of cell wall
- cell and organism structural support
- prevents excessive uptake of water
- may decrease water loss
- protection of cell and organism
cell wall in plants
mostly cellulose and other carbohydrates that support cells and organism
helps to retain water in plant
primary cell wall
thin, can stretch, laid down first (outer)
secondary cell wall
in between primary and membrane
makes wall rigid
cannot stretch
middle lamella
cements adjacent cells together
mostly made of pectins (carbohydrates)
cell walls in fungi
cell walls are mostly chitin
cell wall in bacteria
mostly peptidoglycans (polymers of modified sugars cross linked by short polypeptides)
walls of archaea lack peptidoglycans
cell wall in protists
highly variable
extracellular matrix
outside of the membrane of animals
include glycoproteins (main), collagen, proteoglycans, fibronectins
glycoproteins in extracellular matrix
main component along w other carbohydrate containing molecules
collagen
glycoprotein fibers, abundant
part of extracellular matrix
proteoglycans
form a web in extracellular matrix
fibronectins
bind to integrins (integral proteins) that are built into the membrane
integrins bind to microfilaments in the cytoskeleton
main function of extracellular matrix
- tissue support**
- provides tracks for cell movement
- cell signaling
intercellular junctions in plants
plasmodesmata (areas in cell wall where cytoplasm of one cell is directly continuous with another)
functions in cell to cell communication
plasmodesmata in plants
intercellular junction in plants in which is the areas in the cell wall where cytoplasm of one cell is directly continuous with another
lined with plasma membrane with a central desmotubule of ER
what are the types of intercellular junctions in animals?
tight junctions and gap junctions and desmosomes
tight junctions in animals
intercellular junction in which membranes of neighboring cells are fused with help of proteins
holds cell together tightly and forms a seal
FUNCTION IS: cell adhesion
gap junctions in animals
intercellular junction in which protein channels lined between cells
FUNCTION: in cell to cell communication
desmosomes in animals
intercellular junction in which a plate using intermediate filaments holds cells together
FUNCTION IS: cell adhesion
selective permeability
membranes allow some things to cross but not others
amphipathic (one side is charged the other isnt)
molecules that are hydrophobic pass easily
polar molecules and ions do not easily cross the membrane
transport proteins move things across that can’t on their own (ions and polar molecules)
active transport
requires energy
move things against concentration gradient (low to high)
ex: membrane pumps - carrier proteins
proteins use energy to move molecules or ions against their gradients
passive transport
does not require energy
can only move things along concentration gradient (high to low concentration)
types of passive transport?
diffusion and facilitated diffusion
diffusion
movement of molecules so they spread out evenly int available space
net movement of a substance from high to low concentration until equillibrium
increases randomness of molecules
due to kinetic energy of molecules
spontaneous because it decreases free energy and increases entropy
facilitated diffusion
passive transport of molecules or ions aided by proteins
two types: channel proteins, and carrier proteins
osmotic concentration
total solute concentration of a solute
concentration gradient
graded change in the concentration of a substance over some distance
the higher the osmotic (particles) concentration…..? in a solution
the lower the water concentration in a solution
osmosis
diffusion of water across a selectively permeable membrane
free water concentration difference is important
isotonic
solution has same osmotic concentration as cell (or another solution)
hypertonic
solution has greater osmotic concentration than the cell ( or another solution)
hypotonic
solution has lower osmotic concentration than cell (or another solution)
Animal cells in an isotonic solution?
no net movement of water, normal situation
Animal cells in a hypertonic solution?
water diffuses from cell to solution and cell may shrivel or crenulate
Animal cells in a hypotonic solution?
water diffuses from solution to cell and the cell can lyse or explode
Plant cells in an isotonic solution?
no net movement of water
Plant cells in a hypertonic solution?
water diffuses out of cell, plasmolysis (membrane pulls away from cell wall, cell contents shrink)
Plant cells in a hypotonic solution?
water diffuses into cell and so water pressure inside of cell increases (turgor pressure) , normal situation
Membrane structure
lipid boundary that surrounds cell
fluid and selectively permeable
phospholipids and many proteins are amphipathic molecules (hydrophobic one one side and hydrophilic on the other)
membranes have distinct inside and outside faces
phospholipids held together by weak hydrophobic interactions
cholesterol often present in animal cell membranes
Fluid Mosaic Model (Characteristics of Membrane)
membrane comprised of phospholipid bilayer
fluid mosaic (mixture) of lipids, proteins, and carbohydrates
selectively permeable
fluidity- membrane flows, phospholipids drift laterally, some proteins move
fluidity of membrane
fluidity is decreased when fatty acid tails are saturated
stays fluid at lower temperatures if many unsaturated hydrocarbon tails are present
fluidity decreased when too much cholesterol present
transport proteins functions in membranes
active transport through carrier proteins (pumps)
passive transport through channel proteins and carrier proteins
enzymatic activity functions in membranes
some enzymes catalyze reactions on membrane
signal transduction functions in membranes
process in which a cell signal is converted to a cellular response
cell to cell recognition function in membranes
oligosaccharides (carb) serve as name tags
allows cells to recognize like cells
allows cells to develop properly and organize into tissues
provides immunity
intercellular joining
EX: intermediate filaments in desmosomes
cell structure function in membranes
attachment of proteins to cytoskeleton and extracellular matrix
membrane pumps
carrier proteins that move molecules or ions against their gradient often using ATP
membrane potential
all cells have voltage across their plasma membrane
voltage is electrical potential energy
due to separation of opposite charges
usually -70 millivolts
more negative inside the cell
unequal distribution of ions across a membrane
unequal distribution of charges
electrogenic pumps
membrane pumps that generate a voltage by redistributing ions
ex: NA+/K+ pump and H+ pump (actively transports H+ ions out of cell)
electrochemical gradient
osmotic gradient plus gradient charge
helps govern diffusion
substances ALWAYS diffuse along electrochemical gradient (lot of potential energy)
substances USUALLY diffuse along osmotic gradient (when there is a electrochemical gradient and/or difference in charge)
cotransport
substance that has been pumped across membrane can carry another substance with it as it diffuses back
ex: sucrose-H+ cotransporter
What two types of bulk transport are there?
exocytosis and endocytosis
exocytosis
movement of large molecules to outside of cell
membrane enclose vesicle fuses with cell membrane and moves molecules to outside of cell
endocytosis
movement of large molecules to the inside of the cell
membrane forms a vesicle around molecules and pulls them inside the cell
three types of endocytosis
phagocytosis
pinocytosis
receptor-mediated endocytosis
phagocytosis
movement of particles into cell
ex: cell engulfs bacterium
pinocytosis
movement of fluid into cell
nonspecific
receptor-mediated endocytosis
movement of specific molecules into the cell that first binds to receptors
ex: cells use to take in cholesterol
