Chapter 6 - A Tour of the Cell Flashcards
what is found in all cells?
ribosomes
what is found in eukaryotic but not prokaryotic cells?
endomembrane system
what is a structure is found only in prokaryotic cells?
nucleoid
what are the 3 domains of life?
1) bacteria
2) archaea
3) eukarya
what falls under the domain of prokaryotes?
domain of bacteria and archaea
what falls under the domain of eukarya?
literally everything else
plants, animals, fungi, protists
what features do ALL cells share?
1) plasma membrane (selective barrier)
2) cytosol (fluid in plasma membrane)
3) chromosomes (carry genes in form of DNA)
4) ribosomes (make proteins)
where is the DNA in a eukaryotic cell?
the nucleus - bound by a double membrane called the nuclear envelope
where is the DNA in a prokaryotic cell?
nucleoid - a region that is not membrane-enclosed
what are the components of a prokaryotic cell?
1) fimbriae (attachment structures on the surface)
2) nucleoid
3) ribosomes
4) ribosomes)
5) plasma membrane (encloses cytoplasm)
6) capsule (outer coating)
7) flagella
what is the cytoplasm?
refers to the interior of either type of cell
what is the cytoplasm in a eukaryotic cell?
the region between the nucleus and the plasma membrane - does not include the nucleus!
what is the cytosol?
a component of eukaryotic cells inside the cytoplasm that suspends organelles
do prokaryotic cells have membrane bound organelles?
no
what is the plasma membrane?
a selective membrane that function as a selective barrier that allows passage of enough oxygen, nutrients, and wastes
surface area and volume relationship?
for each square micrometer of plasma membrane, only a limited amount of a particular substance can cross per second so the ratio of surface area to volume is critical
as a cell increases in size its SA grow proportionately less than its volume –> smaller objects have a greater ratio of SA:volume
microvilli increase SA without really increasing volume
what is the cytoplasm in a prokaryotic cell?
cytoplasm is everything found inside the plasma membrane (including nucleoid)
are prokaryotic or eukaryotic cells bigger?
eukaryotic cells are generally much larger than prokaryotic cells
eukaryotic cells: 10-100 micrometers
prokaryotic: 1-5 micrometers/.1-1
how do we study cells?
light microscopy, electron microscopy, unaided eye
what is magnification?
size relative to actual specimen
what is resolution?
measure of the clarity, minimum distance of two distinguishable points
what is cell fractionation?
it takes apart and separates major organelles and other sub cellular structure from one another
does this by size and density with a centrifuge
enables scientists to determine the functions of organelles through further biochemistry and cytology
you can correlate cell function with structure - by separating one organelle from another, you can do biochemical analysis to test what these components of the cell are doing and allows you to correlate cell function with structure
what is the plasma membrane of a eukaryotic cell made of?
made of double layer of phospholipids and proteins
proteins are embedded in the lipid bilayer - proteins are important because they help with membrane transport (channel protein needed so hydrophilic molecules can cross hydrophobic lipid bilayer)
which organelle functions in cellular respiration?
mitochondria
structure of animal vs. plan cells?
check out pg. 100 in the book, it’s awesome
what is the nuclear envelope?
it encloses the nucleus and separates its contents from the cytoplasm = it’s a double membrane of two lipid bilayers
perforated by pore structure
nucleus | nuclear envelope | cytoplasm
what is the nuclear pore complex?
a protein* structure called a pore complex lines each pore and regulates the entry and exit of proteins and RNA
at the lip of each pore in the nuclear envelope, the inner and outer membranes of the nuclear envelope are continuous
what is the nuclear lamina?
the inner side of the envelope is lined by the nuclear lamina which is an array of protein* filaments that maintains the shape of the nucleus by supporting the nuclear envelope - supports cytoskeleton
the nuclear lamina is thought to help organize the DNA within the nucleus
what are chromosomes
structures that carry genetic information of DNA
structure consisting of one, tightly coiled DNA molecule and associated proteins. Formed when cell is ready to divide
what is chromatin?
The complex of DNA and proteins that makes up chromosomes
how many chromosomes does a human cell have?
46
what are the components of a eukaryotic cell? what do they do?
1) plasma membrane
2) cytoskeleton: the structural frame work of the cell and tracks for transporting cargo
3) mitochondria: makes ATP molecules
4) nucleus and ribosomes: DNA is structurally arranged in nucleus
what is used to make mRNA?
DNA
what is the nucleolus? (nucleoli)
distinct structure where rRNA (ribosomal RNA) is transcribed and ribosomes are assembled
ribosomal proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes –> subunits exit nucleus through nuclear pores into the cytoplasm where a large and small subunit can assemble into a ribosome
what is rRNA?
ribosomal RNA
what is the nucleus?
contains most of the cell’s genes
mitochondria and chloroplast also house genes
where else can DNA be found in the cell?
mitochondria and chloroplasts
what is a nucleosome
1 unit of chromatin consisting of histones and coiled DNA
what are ribosomes?
complexes made of rRNA and ribosomal proteins than carry out the synthesis of proteins
not membrane bound = not organelles
they are free in the cytosol or bound to the rough ER/nuclear envelope
are ribosomes organelles?
no! because they are not membrane bound
general structure of a cell
nucleus | cytoplasm (cytosol) | plasma membrane
what is in the nucleus?
chromatin, nucleuolus, nuclear lamina
nuclear pores, nuclear envelope envelope the nucleus
ribosomes build proteins in two cytoplasmic locales. what are they?
free ribosomes are suspended in the cytosol, nucleus, mitochondria
membrane bound ribosomes are attached to the rough ER or nuclear envelope
bound and free ribosomes are structurally identical and cal alternate between the two roles
what kinds of proteins do free ribosomes usually make?
the proteins usually function within the cytosol
ex. like the enzymes that catalyze sugar break down
ex. nuclear histome
what kind of proteins do membrane bound ribosomes usually make?
1) proteins that are destined for insertion into membranes
2) proteins for packing within certain organelles such as lysosomes
3) secretion (insulin)
ex. digestive enzymes released into the gut, insulin receptor protein (on membrane), antibodies in the blood, collagen (found in extra-cellular matrix)
what are the parts of the endomembrane system?
1) nuclear envelope
2) endoplasmic reticulum
3) golgi apparatus
4) lysosomes
5) vesicles/vacuoles
6) plasma membrane
Please Never Eat Gross Lettuce Vallory
what does endomembrane system do?
- synthesis, modification, and transport of proteins going to the membranes, organelles, or out of the cell
- metabolism and movement of lipids
- detoxification of poisons
what are vesicles?
sacs made of membrane
the membranes of the endomembrane system are related either through direct continuity or by the transfer of the membrane segments as tiny vesicles
the various membranes are not identical in structure and function!
characteristics of a given membrane can be modified during the membrane’s life (thickness, compositions, types of chemical rxn)
What is the ER?
extensive network of membranes that counts for more than half the total membrane in many eukaryotic cells
consists of a network of membranous tables/sacs called cisternae
ER membrane is continuous with the nuclear envelope so the space between the two membranes of the envelope is continuous with the lumen of the ER
what are the function of the smooth ER?
- synthesis of lipids (steroids)
- metabolism of carbohydrates
- detoxification of drugs and poisons
- storage of calcium ions (in ER lumen)
not studded with ribosomes, translation doesn’t occur here
what is the ER lumen?
the internal compartment of the ER - a cavity/space
what are glycoproteins?
most secretory proteins from the rough ER are glycoproteins: proteins with carbohydrates covalently bonded to them
the carbohydrates are attached to the proteins in the ER lumen by enzymes built into the ER membrane
what are transport vesicles?
vesicles in transit from one part of the cell to another
secretory proteins depart from the rough ER in the membranes of vesicles from the transitional ER
what are the functions of the rough ER?
- makes secretory proteins
- helps with protein folding
- glycosylation
- source of new membrane
it’s a membrane factory: grows in place by adding membrane proteins and phospholipids to its own membrane then it expands are portions of it are transferred in the form of transport vesicles to other components of the endomembrane system
- makes membrane phospholipids
what is the golgi apparatus?
a warehouse for receiving, sorting, shipping, and manufacturing
products of the ER (like proteins) are modified and stored then sent to other destinations
located close to ER but not connected membrane wise
what are the two distinct sides of the golgi apparatus?
cis: receiving side
trans: shipping side
cis is usually located near the ER so transport vesicles move material from the ER to the golgi membrane
what does the golgi modify?
products of the ER are usually modified during their transit from cis to trans region of golgi
modifies: carbohydrates by changing sugar substitutes, membrane phospholipids
how does the golgi sort it’s products before sending from the trans side?
1) molecular identification tags such as phosphate groups are kind of like zip codes
2) transport vesicles budded from the golgi may have external molecules on their membrane that recognize “docking sites” on the surface of specific organelles or on the plasma membrane
what are the function of the golgi?
1) modification of proteins (further glycosylation)
2) modification of phospholipids by carbohydrates
3) polysaccharide synthesis
4) sorting and release of products into vesicles
golgi pinches off transport vesicles that give rise to lysosomes, other types of specialized vesicles, and vacuoles
What is a likely function of a cell with an extensive Golgi apparatus?
High levels of protein secretion
what is a lysosome? what does it do?
vesicles that have digestive enzymes in them - enzymes used to break down macromolecules
when do lysosomal enzymes work best?
in the acidic environment - which just so happens to be found in lysozomes
where are hydrolytic enzymes and the lysosomal membrane made?
made by the rough ER and are then transferred to the golgi for more processing
what is phagocytosis?
the engulfing of smaller organism/food particles
the food vacuole is formed then fuses with the lysosome whose enzymes digest the food
what are some of the products that are digested by the lysosome? what happens to them?
simple sugars, amino acids, other monomers
they pass into the cytosol and become nutrients for the cell
what are macrophages?
a type of white blood cell that helps defend the body by engulfing and destroying bacteria through phagocytosis and lysosomes
what is autophagy?
when lysosomes use their hydrolytic enzymes to recycle the cell’s own organic material
damaged organelle or small amounts of cytosol become surrounded by a double membrane and a lysosome fuses with the outer membrane of this vesicle while the inner membrane is degraded along with the damaged organelles –> resulting compound releasing into cytosol
cell renews itself!
what are vacuoles?
large vesicles formed from the ER and golgi
vacuole membrane is selective so the solution inside a vacuole differs in composition from the cytosol
what are contractile vacuoles?
pump excess water out of the cell = maintain suitable concentration of ions and molecules inside the cell
what is the function of vacuoles?
1) cell growth
2) protection (by storing compounds that are poisonous) 3) storage (proteins in seeds)
what is a central vacuole?
plant cells have a central vacuole which helps with cell growth and allows cell to be bigger without having to use up a lot of expensive nutrients
what is the pathway of proteins that are going to be secreted?
rough ER —> golgi apparatus —> plasma membrane (fuses and secretes)
what are the two structure in eukaryotic cells that convert energy to forms that a cell can use for work?
1) mitochondria
2) chloroplasts (plants/algae)
what are mitochondria?
sites of cellular respiration
the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, etc
what is cellular respiration?
the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, etc
what are cholorplasts?
sites of photosynthesis:
process that converts solar energy into chemical energy
mitochondria then uses this energy to make ATP
what is the endosymbiont theory?
the theory that an early eukaryotic cell engulfed an Roxy-gen using non-photsynthetic cell –> they formed a relationship and eventually merged into a single organism = a eukaryotic cell with a mitochondrion –> then this cell also took up a photosynthetic prokaryote = has chloroplasts
makes sense because it explains many structural features of mitochondria and chloroplasts:
- double membranes (organelles of endomembrane system have single membrane)
- contain ribosomes and circular DNA associated w/ their inner membrane
- autonomous organelles (able to grow in size and reproduce within cell)
how many mitochondria does a cell have?
based on activity
more active = 100’s, 1000’s (muscles)
less active = 1, 2 etc
how many layers enclose the mitochondria and what are they?
2 phospholipid bilayers w/ embedded proteins
outer membrane is smooth
inner membrane is convoluted with infolding called cristae = gives inner membrane large SA
what does the inner membrane of the mitochondria do?
it divides the mitochondrion into two internal compartments
1) inter membrane space (region between inner and outer membranes)
2) mitochondrial matrix (it’s enclosed by the inner membrane)
why are cristae important?
extensive foldings = it increases surface area which is important because electron transport chains (carries out production of ATP) –> high surface to volume ratio means lots of oxidative phosphorylation can happen
what happens in the mitochondrial matrix? where is it located?
inside/enclosed by the inner membrane
where Krebb’s cycle occurs
contains ribosomes
contains mtDNA
what is the thylakoid?
flat, interconnected sacs. membrane contains chlorophyll in the chloroplast
what are plastids?
family of specialized organelles. includes chloroplasts, amyloplasts (starch storage), elaioplasts (lipid storage) - not all sites have different kinds of plastids
the membranes of the chloroplast dive the chloroplast space into 3 compartments. what are they?
1) inter membrane space
2) storma
3) thylakoid
what is a geranum?
stack of thylakoid
what is the stroma?
fluid outside of thylakoids, contains DNA, ribosomes, enzymes; (Calvin cycle: ATP —> sugars)
what is a peroxisome?
a specialized metabolic compartment bound by a single membrane
contain enzymes that remove hydrogen atoms from various substrates and transfer them to O2 producing H2O2
what is the cytoskeleton?
a network of fibers extending through the cytoplasm
plays a major role in organizing the structures and activities of the cell
what are the three molecular structures in the cytoskeleton?
1) microtubules
2) microfilaments
3) intermediate filaments
what are the functions of the cytoskeleton?
1) give support to the cell and maintain its shape
(important for plants that lack cell walls)
very dynamic - can be dismantled in one part of the
cell and reassembled in a new location = changes
shape of cell
2)cell motility
requires interaction of the cytoskeleton with motor
proteins
3) manipulated plasma membrane
bends it inward to form food vacuoles
what are the thickest and thinest components of the cytoskeleton?
microtubules are the thickest
microfilaments are the thinnest (aka actin filaments)
intermediate filaments are middle range
what are microtubules?
components of the cytoskeleton - hollow rods constructed from a globular protein called tubulin*
tubulin
forms microtubules
each tubulin protein is a dimer: a molecule made up of two subunits - each dimer consists of two slightly different polypeptides: alpha and beta tubulin
what is the function of microtubules?
- shape and support the cell
- serve as tracks along which organelles w/ motor proteins can move
- guide vesicles from the ER to the golgi and from the golgi to the plasma membrane
- involved in separation of chromosomes during cell division
- cell motility: cilia and flagella
what is a centrosome?
in animal cells, microtubules grow out from a centrosome - often located near nucleus
what are centrioles?
within the centrosome is a pair of centrioles, each composed to nine sets of triplet microtubules arranged in a ring
centrome is like the pack of straws
centriole is a set of triplet straw in a star ring
the microtubule is the straw
what are flagella and cilia?
in eukaryokes, a specialized arrangement of microtubules is responsible for flagella and cilia
cilia: rowing movement, large numbers
flagella: swimming movement, 1 or a few/cell
what are microfilaments?
thin solid rods that are part of the cytoskeleton
built from molecules of actin (globular polymer protein)
twisted double chain of actin* subunits
structural role is to bear tension (pulling forces)
well known for their role in cell motility: actin and myosin cause contractions of muscle cells
which parts of the cytoskeleton are found in all eukaryotic cells?
microtubles and microfilaments
intermediate filaments are only found in the cells of some animals including vertebrates
what are intermediate filaments?
fibrous proteins coiled into cables
diverse in shape and size
keratin*
inside of nuclear envelope is made of intermediate filaments
what are the function is microfilaments?
- maintenance of cell shape (tension bearing)
- changes in cell shape
- muscle contraction (actin/myosin)
- cytoplasmic streaming in plant cells
what are the functions of intermediate filaments?
- maintenance of cell shape
- anchorage of nucleus/other organelles
- formation of nuclear lamina
what is the cell wall?
- component of cell that only exists in some cells
ex. plants, fungi, unicellular eukaryotes, most bacteria
what is the cell wall made of in plants?
cellulose fibers and other polysaccharides and proteins
what is the cell wall made of in bacteria?
peptidoglycan (polymers of sugars and amino acids)
what are plasmodesmata?
channels that exists between adjacent plant cells that let water and small solutes (proteins, RNA) pass from cell to cell
what is the extra cellular matrix?
matrix outside and between animal cells
made up of glycoprotein (protein modified with sugar/carbohydrate)
ex. most abundant glycoprotein: collagen
what does the extra cellular matrix do?
ECM is important for cell adhesion and communication: anything that happens on the outside of the cell will be transmitted to change gene expression
cell differentiation, proliferation, are determined by cell communication through ECM
changes in the ECM affect the cytoskeleton and thus affect signaling inside and eventually genes in the nucleus
what are the three types of cell junctions in animals?
1) tight junctions: membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid
2) desmosomes: anchoring junctions, fasten cells together into strong sheets
3) gap junctions: communicating junctions, provide cytoplasmic channels between adjacent cells
