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CHAP 6-7 (6.4 Endomembrane systemregulates protein traffic and performs…
CHAP 6-7
6.4 Endomembrane systemregulates protein traffic and performs metabolic functions
endomembrane system- includes the nuclear envelope, the endoplasmic reticulum, the golgi apparatus, lysosomes, various kinds of vesicles and vacuoles, and the plasma membrane.
Vesicles- sacs made of membrane
Endoplasmic reticulum: Biosynthetic factory
Endoplasmic reticulum (ER)- such an extensive network of membrane in many eukaryotic cells.
Smooth ER- because the outer surface lacks ribosomes
Rough ER- studded with ribsomes on the outer surface
Functions of Rough ER
Glycoproteins- proteins with carbohydrate covalently bonded to them.
Transport vesicles- vesicles in transit from one part of the cell to another.
Golgi apparatus- a wharehouse for receiving, sorting, shipping, and even some manufacturing.
Lysosomes: Digestive Compartments
Lysosome- membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest macromolecules.
Phagocytosis- amoebas and many other unicellular eukaryotes eat by engulfing smaller organisms or food particles.
Vacuoles: diverse maintenance compartments
Vacuoles- large vesicles derived from the endoplasmic reticulum and golgi apparatus.
Food vacuoles- formed by phagocytosis, have already been mentioned
Contractile vacuoles- pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell.
Central vacuole- develops by the coalesence of smaller vacuoles.
6.6 Cytoskeleton is a network of fibers that organizes structures and activities in the cell
cytoskeleton- network of fibers extending throughout the cytoplasm (figure 6.20).
motor proteins- work together with plasma membrane molecules to allow whole cells to move along fibers outside the cell.
Microtubules- hollow rods constructed from globular proteins called tubulins.
centrosomes and centrioles
centrosome- region that is often located near the nucleus
centrioles- composed of nine sets of triplet microtubles arranged in a ring.
Cilia and Flagella- microtubule-containing extensions that project from some cells.
basal body- which structurally very similar to a centriole, with microtubule triplets in a "9+0" pattern (figure 6.24c).
dyneins- that are attached along each outer microtubule doublet.
Microfilaments (actin filaments)
Microfilaments- thin solid rods
Actin- globular protein
Cortex- the semisolid consistency of a gel, in contrast with the more fluid state of the interior cytoplasm.
myosin- interaction to cause contraction of muscle cells.
Pseudopodia- cellular extensions.
cytoplasmic streaming- circular flow of cytoplasm within cells.
intermediate filaments- named for their diameter, which is larger than the diameter of microfilaments but smaller than that of microtubules.
6.5 Mitochondria and chloroplasts change energy from one form to another
mitochondria- are the sites of cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels.
Chloroplasts- found in plants and algae, are the sites of photosynthesis.
Endosymbiont theory- illustrated in (Figure 6.16), states that an early ancestor of eukaryotic cells engulfed oxygen-using nonphotosynthetic prokaryotic cell.
Mitochondria: chemical energy conversion
Cristae- outer membrane is smooth, but the inner membrane is convoluted, with infoldings
mitochondrial matrix- enclosed by the inner membrane, contains many enzymes as well as the mitochondrial DNA and ribosomes.
Chloroplasts: capture of light energy
thylakoids- inside the chloroplast another membranous system in the form of flattened, interconnected sacs, stacked like poker chips.
granum- each stack
stroma- fluid outside the thylakoids, which contains the chloroplast DNA and ribosomes as well as many enzymes.
plastids- plant organelles.
Peroxisome- a specialized metabolic compartment bounded by a single membrane (figure 6.19).
6.7 Extracellular components and connections between cells help coordinate cellular activities
Cell walls of plants
Cell wall- is an extracellular structure of plant cells.
Primary cell wall- relatively thin and flexible cell wall that a young plant excretes.
middle lamella- thin layer rich in sticky polysaccharides called pectins.
Secondary cell wall- between the plasma membrane and the primary wall.
The extracellular Matrix (ECM) of animal cells
Extracellular matrix (ECM)- animal cells that lack akin
Collagen- most abundant glycoproteins in the ECM of most animal cells.
proteoglycans- consists of a small core protein with many carbohydrate chains covalently attached.
fibronectin- bind cell-surface receptor proteins.
integrins- that are built into the plasma membrane.
plasmodesmata in plant cells
plasmodesmata- channels that connect cells.
6.1 Biologists use microscopes and biochemistry to study cells
Microscopy
Light microscopy (LM)- visible light is passed through the specimen and then through glass lenses.
Organelles- membrane-enclosed structures within eukaryaotic cells.
Electron microscope (EM)- focuses beam of electron through the specimen or onto its surface.
Scanning electron microscope (SEM)- especially useful for detailed study of the topography of a specimen (Figure 6.3)
Transmission electron microscope (TEM)- used to study the internal structure of cells. ( Figure 6.3 )
Cell fractionation- Which takes cells apart and seperates major organelles and other subcellular structures from one another.
CHAP 7 Life at the edge
Selective permeability- allows some substances to cross it more easily than others
7.1 Cellular members are fluid mosaics of lipids and proteins
amphipathic- "water-loving"
fluid mosaic model- the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.
membrane proteins and their functions
integral proteins- penetrate the hydrophobic interior of the lipid bilayer.
Peripheral proteins- not embedded in lipid bilayer at all, loosely bound to the surface of the membrane, often to exposed parts of integral proteins.
The role of membrane carbohydrates in cell-cell recognition
glycolipids- membrane carbohydrates covalentyl bonded to lipids.
glycproteins- however most bond to proteins.
6.2 Eukaryotic cells have internal membranes that compartmentalize their functions
Comparing Prokaryotic and eukaryotic cells
Cytosol- inside the cells is semifluid, jelly like substance, in which subcellular components are suspended.
eukaryotic cell- most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane (firgure 6.8)
prokaryotic cell- DNA is concentrated in a region that is not membrane-enclosed, called the nucleoid
Cytoplasm- in eukaryotic, the region between the nucleus and the plasma membrane.
Plasma membrane- functionsas a selective barrier that allows passage of enough oxygen, nutrients, and wastes tom service the entire cell (Figure 6.6)
Eukaryotic cells's genetic instructions are housed in the nucleus and carried out by the ribosomes
The Nucleus: information center
Nucleus- contains most of the genes in eukaryotic cell.
nuclear envelope- encloses the nucleus (figure 6.9), separating its contents from the cytoplasm.
Nuclear lamina- netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope.
Chromosomes- structures that carry the genetic information.
Chromatin- complex of DNA and proteins making up chromosomes.
Nucleolus- which appears through the electron microscope as a mass of density stained granules and fibers adjoining part of the Chromatin.
Ribosomes: protein factories
ribosomes- which are complex made of ribosomal RNAs and proteins, are the cellular components that carry out protein synthesis (figure 6.10)
CHAP 7
7.2 Transport Proteins
Transport proteins- span the membrane
aquaporins- channel proteins.
CHAP 7
7.3 Passive transport is diffusion of a substance across a membrane with no energy investment
diffusion- movement of particles of any substance so that they spread out into the available space.
concentration gradient- region along which the density of a chemical substance increases or decreases.
passive transport- the diffusion of a substance across a biological membrane.
osmosis- diffusion of free water across a selectively permeable membrane, whether artificial or cellular.
Water balance of cells without cell walls
Tonicity- the ability of a surrounding solution to cause a cell to gain or lose water.
isotonic- no water movement across the plasma membrane.
Hypertonic- lose water.
hypotonic- cell will gain water
osmoregulation- control of solute concetraations wand water balance.
water balance of cells with cell walls
turgid-(very firm) healthy state of most plant cells.
Flaccid- the plant wilts.
plasmolysis- causes the plant to wilt and can lead to plant death.
Facilitated diffusion: passive transport aided by proteins
Facilitated diffusion- the help of transport proteins that span the membrane.
Ion channels- channel proteins that transport ions.
gated channels- which open or close in response to a stimulus.
CHAP 7
7.4 Active transport uses energy to move solutes against their gradients
The need for active transport
Active transport- type of membrane traffic.
Sodium-potassium pump- which exchanges Na+ for K+ across the plasma membrane of animal cells.
How ion pumps maintain membrane potential
membrane potential- voltage across a membrane.
electrochemical gradient- combination of forces acting on an ion.
Electrogenic pump- transport protein that generates voltage across a membrane.
Proton pump- main electrogenic pump of plants, fungi, and bacteria
Cotransport- transport protein can couple the "downhill" diffusion of the solute to the "uphill" transport of a second substance against its own concentration gradient.
CHAP 7
Bulk transport across the plasma membrane occurs by exocytosis and endocytosis
Exocytosis- cell secrets certain molecules by the fussion of vesicles with the plasma membrane.
endocytosis- cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane.