CH 6/7 STRUCTURES AND FUNCTIONS OF THE CELL (NUCLEUS (RIBOSOMES ( Protein…
CH 6/7 STRUCTURES AND FUNCTIONS OF THE CELL
enabled scientists to see and study cells
Cytology with biochemistry have intergrated to understand relations between cellular structures/functions.
Super-resolution microscopy- provide extremely high-resolution images
(EM) Electron Microscope:
First revealed structures specimens in 1950's
Focuses a beam of electrons through a specimen or onto its surface.
Resolution of about 2um ; 100 times more than the LM.
(SEM) Scanning Electron Microscope:
Electron beam scans the surface of a specimen that is usually coated with a thin gold film.
Beam excites electrons from the surface; gives translated image that is 3-D.
Electromagnets act as lenses focus image onto a monitor.
(TEM) Transmission Electron Microscope:
Beam of electrons is passsed through a thin section of a specimen
Stained with atoms of heavy metals.
Electromagnets act as lenses focus image onto a monitor.
(LM) Light Microscope:
Refract the visible light passing through a specimen; causing it be magnified
Magnification: ratio of the size of an image to the real size object.
Resolution: measure of the clarity of an image & determined by minimum distance 2 points
Resolving power: limited; anything finer than 0.2 um cannot be distinguished.
Not all membrane enclosed organelles can be resolved by the light microscope.
Cells broken apart and the homogenate is separated into components fractions by Centrifugation at increasing speeds.
Technique that separates subcellular structures; to be identified and functions be studied.
PROKAR. VS EUKAR. CELLS
P: only members of the domains Bacteria and Archaea
P: cells with no nucleus or membrane-enclosed organelles.
P: DNA concentrated in a region called the NUCLEOID.
P: Range from 1 to 5 um in diameter
E: members of domains Protists/ Fungi/ Animals/ Plants.
E: true NUCLEUS enclosed in a double membrane.
E: numerous membrane-bounded organelles suspended in the Cytosol.
E: Range from 10 to 100 um in diameter.
E: internal membranes that comparmentalize their funtions
provides local environments for specific metabolic funtions.
participates in metabolism through membrane-bound enzymes
all types of E. Cells share commen structures but have differences between them.
BOTH TYPES OF CELLS
All: contain chromosomes (with genes composed of DNA) and ribosomes (which make proteins)
All: CYTOPLASM: region between the nucleus and the plasma membrane
All: CYTOPLASM: interior of the prokaryotic cell.
All: are bounded by a plasma membrane; encloses a semifluid called CYTOSOL.
SURFACE VS VOLUME RATIO
All: Small size is influenced by Geometry:
Area is proportional to the square of linear dimension; whereas Volume is proportional to its cubes.
Plasme membrane: surrounding every cell must provide sufficient area for exchange of oxygen, nutrients, and wastes relative to the volume of the cell.
Surrounded by a Nuclear Envelope: a double membrane perforated by pores.
Protein Pore Complex: lining each pore regulate movement of materials between nucleus and cytoplasm.
Inner membrane lined by the Nuclear Lumina: layer of protein filaments; helps maintain shape of the nucleus.
Nuclear Matrix: of fibers appears to extend throughout.
Most of cells DNA is in the nucleus.
DNA organized into units called CHROMOSOMES.
Chromosomes consists of one DNA molecule complexed with protein to form; CHROMATIN.
Chromosomes are visible under microscope when condensed in a dividing cell.
a dense structure visible in the nondivind nucleus, synthesizes ribosomal RNA (rRNA)
Combines synthesized rRNA with proteins (imported from the cytoplasm) to ribosomal subunits, pass through nuclear pores to the cytoplasm
Protein Factories: ribosomes are composed of proteins and ribosomal RNA.
Free ribosomes: most proteins produced are used within the cytosol.
Bound ribosomes: attached to the endoplasmic reticulum or nuclear envelope; makes proteins included within membranes, packaged into organelles, or exported from the cell.
regulates protein traffic and performs metabolic functions in the cell.
many of the organelles in a cell are components of this system.
the nuclear envelope/ endoplasmic reticulum/ Golgi apparatus/ lysosomes/ vesicles/ vacuoles/ and the plasma membrane.
Related either through direct contact or by the transfer of membrane segments by membrane sacs called Vesicles.
membranes move from the ER to the GOLGI APPARATUS and to other organelles.
their compositions/functions/contents are modified along the way.
(ER) Endoplasmic Reticulum
a membranous system continous with the nuclear envelope; encloses a network of interconnected tubules/sacs called cisternae.
internal compartment called the ER lumen or cisternal space.
Ribosomes are attached to the cytoplasmic surface of rough ER; smooth ER lacks ribosomes.
enzymes are involved in a phospholipid and steriod (including sex hormone) synthesis.
carbohydrate metabolism and detoxification of drugs/poisons; enzymes involved.
Barbiturates/ alcohols/ other drugs increase a livers cell's production of smooth ER; increased tolerance and reduced effectiveness.
Functions in storage and release of calcium ions during muscle contraction.
Transport vesicles: help secretory proteins transport from the rough ER.
Glycoproteins: a protein with one or more covalently attached carbohydrates
Enzymes built into the membrane assemble phospholipids; membrane proteins formed by bound ribosomes inserted into ER membrane.
Transport vesicles transfer the ER membrane to other parts of the endomembrane system.
shipping and receiving center; like a post office.
consists of stacks of flattened sacs; PANCAKE STACK.
Vesicles that bud from the ER join to the cis face of a Golgi stack; adds to their content and membrane.
cisternal maturation model: Golgi products are processed/ tagged as the cisternae progress themselves from the cis to trans face.
Glycoproteins have their attached carbohydrates modified.
PLANT CELLS: manufactures some polysaccharides; pectins.
products are sorted into vesicles; pinch off from the trans face.
Vesicles may have surface molecules to help direct them to the plasma membrane or other organlles.
digestive compartments; e.cells- membrane-enclosed sacs containing hydrolytic enzymes that digest macromolecules.
provide an acidic pH for these enzymes.
unicellular eukaryotes: lysosomes fuse w/ food vacuoles to digest material ingested by phagocytosis.
Macrophages; a types of white blood cell, uses to destroy ingested bacteria.
Recycle a cell's own macromolecules by fusing with vesicles enclosing damaged organelles or small bits of cytosol; autophagy.
large vesicles; diverse maintenance compartments.
Food vacuoles: formed as a result of phagocytosis.
Contractile vacuoles: pump excess water out of freshwater unicellular eukaryotes.
Plant cells: carry out hydrolysis, store organic compounds for the cell, contain poisonous or unpalatable compounds that may protect the plant from predators
Central Vacuoles: large vacuole found in mature plants cells and encloses a solution called CELL SAP.
Plant increases in size with a minimal addition of new cytoplasm as its vacuole absorbs water and expands.
MITOCHONDRIA & CHLOROPLASTS
ENDOSYMBIONT THEORY: both Mitochondria and Chloroplast originated as free living prokaryotic cells engulfed by an ancestral eukaryotic cell.
the double membranes surrounding both appear to have been part of the prokaryotic endosymbiont.
grow and reproduce independently within the cell
contain small amount of DNA and ribosomes, synthesis some of their proteins.
2 membranes, each a phospholipid bilayer with unique embedded proteins, enclose a mitochondrion.
narrow intermembrane space exist between the smooth outer membrane and the convoluted inner membrane.
cristae: the folds of the inner membrane; create a large surface area & encloses mitochondrial matrix.
Matrix consists of: respiratory enzymes, mitochondrial DNA, and ribosomes.
other respiratory enzymes and proteins are built into the inner membrane.
form a dynamic network within the cell; although appear static in TEM.
M: cellular respiration, metabolic processing of fuels to produce ATP happens within.
2 membranes separated by a thin intermembrane space enclose a chloroplast.
inside the inner membrane; thylakoids: a membranous system of connected flattened sacs
inside would be the thylakoid space.
Grana: photosynthetic enzymes are embedded in the thylakoids, may be stacked together to form this structure.
Stroma: the fluid surrounding the thylakoids, which has chloroplast DNA, ribosomes, many enzymes.
Plastids: family of plant organelles; chloroplast + amyloplasts (store starch, and chromoplast (contain pigments))
CH: photosynthesis occurs within plants and algae which produces sugars from carbon dioxide and water by absorbing solar energy.
oxidative organelles filled with enzymes that function in a variety of metabolic pathways by removing hydrogen atoms and combining them with oxygen to produce hydrogen peroxide
in plant seeds, contain enzymes thast convert fattys acids to sugars for emerging seedlings.
eukaryotic cells: dynamic network consisting of 3 types of protein structures: microtubules, microfilaments, & intermediate filaments.
provides mechanical support to the cell
provides anchorage for organelles
maintains cells shape
cell motility: (both internal structures and the cell as a whole) - interacts with special proteins called motor proteins.
are hollow rods constructed of columns of globular proteins called tubulins.
change length through the addition/subtraction of tubulin Dimers.
provides the support framework of cell; separate chromosomes during cell division and serve as tracks along which organelles move with the aid of motor proteins.
they grow out from a CENTROSOME; region closest to nucleus.
pair of CENTRIOLES, each composed of 9 sets of triplet microtubules arranged in a ring; locared withing CENTROSOME.
Some e.cells lack centrosomes with centrioles; organize their microtubules by other means.
-CILIA & FLAGELLA: locomotor extensions.
Cilia: numerous and short
Flagella: occur one or two to a cell and are longer
Unicellular eukaryotes use both to move through aqueous media
Once attached to the stationary cells of a tissues move fluis past the cell.
Nonmotile: signal-receiving cilium, primary cilium on vertebrate animals; transmits environmental signal to cells interior.
-MOTILE CILIA & FLAGELLA
composed of two single microtubules surrounded by a ring of 9 doublets of microtubules.
enclosed in an extension of the plasma membrane.
Basal body: (9+0 arrangement) microtubules triplets, anchors a cilium or flagellum in the cell.
ATP drives the sliding of the microtubule doublets past each other
The two 'feet' of large motor proteins called DYNEINS alternately attach to adjacent doublets, pull down, release, and reattach.
Bending of the flagellum or cilium caused in conjunctoin with anchoring cross-linking proteins and radial spokes.
are thin solid rods consisting of a twisted double chain of globular proteins called ACTIN.
also known as ACTIN FILAMENTS
cortical microfilaments: form a network just inside the plasma membrane that creates a semi-solid or gel consistency inside the cortex.
CORTEX: cytoplasmic layer.
animal cells: microfilaments form a supportive core of small cytoplasmic extensions called microvilli.
muscle cells: thousandsof actin filaments interact with thicker filaments made of motor proteins (myosin) produce muscle contraction.
during amoeboid movement: actin and myosin interact in the formation of cellular extensions called pseuadopodia.
cytoplasmic streaming: in plant cells involes actin-myosin interactions.
intermediate in size between microtubles and microfilaments and are more diverse in their protein composition.
found in some animal cells, are less dynamic than other cytoskeletal elements.
important in maintaining cell shape
nucleus is securely held in a web of intermediate filaments.
nuclear lamina lining the inside of the nuclear envelope is composed of intermediate filaments
CELL WALLS OF PLANTS
cells walls are composed of microfibrils of cellulose embedded in a matric of polysaccharides and protein.
primary cell wall: secretd by a young plant cell is relatively thing and flexible.
adjacent cells are glued together by the Middle Lamella, a thin layer of polysaccharides (pectins)
secondary cell wall: between the plasma membrane and the primary call wall, after plant stops growing some cells secrete a thicker stronger cell wall.
(ECM) Extracellular Matix Animal Cells.
composed primarily of glocyproteins and other carbohydrate-containing molecules.
Collagen: forms strong fibers that are embedded in a network of proteoglycan complexes.
Larger complexes form when multiple Proteoglycans, each consisting of a small core protein with many carbohydrate chains, attach to a long polysaccharide.
Cell attach to ECM by FIBRONECTINS & other glycoproteins that bind to INTEGRINS
Intergrins- proteins that span the plasma membrane and bind to microfilaments of the cytoskeleton.
Info about change in/outside of the cell can be communicated through a mechanical signaling pathways
Pathway involves: Fibronectins/ Integrins/ Microfilaments of the Cytoskeleton.
Plasmodesmata: channels in plant cell walls that link most cells of a plant into a living continuum.
water, small solutes, and even some proteins and RNA molecules may flow through adjacent cells.
ANIMALS: three types of junctions
Tight junctions: proteins hold adjacent cell membranes tighty together; creating an impermeable seal across a layer of epithelial cells.
Desmosomes: (anchoring junctions):reinforced by intermediate filaments and rivet cells into strong sheets.
Gap junctions: (communicatin junctions): cytoplasmic connections that allow for the exchange of ions and small molecules between cells throguh protein-lined pores.
BOUNDARY OF LIFE
selective permeability- allowing some materials to cross it more easily than others.
Fluid mosaic model- consists of various proteins attached to or embedded in a bilayer of amphipathic phospholipids.
Amphipathic PhospholipidsL having both hydrophilic and hydrophobic regions.
lipid rafts- the existence of stable regions of specialized lipids
DIFFIUSION OF FREE WATER
MOVES INTO A CELL
IN WHICH ANIMAL CELL WILL LYSE
PLANT CELL IS TURGID
HAS LOWER SOLUTE CONCENTRATION
MORE FREE WATER AVAILABLE TO MOVE
IN HYPOTONIC SOLUTION
MOVES OUT OF A CELL
HAS HIGHER SOLUTE CONCENTRATION
LESS FREE WATER AVAILABLE TO MOVE
IN WHICH ANIMAL CELL WAS SHRIVEL
PLANT CELL WILL PLASMOLYZE
IN HYPERTONIC SOLUTION
NO NET MOVE NET MOVEMENT
ANIMAL CELL IS NORMAL
IF CELL IS IN AN ISOTONIC SOLUTION
PLANT CELLS IS FLACCID
THROUGH A SELECTIVELY PERMEABLE MEMBRANE