A&P 1 Ch 3: Cells: The living units

Ribosomal RNA

rRNA; along with proteins, forms the ribosomes, which consist of two subunits-one large and one small. The two subunit types comine to form functional ribosomes where protein synthesis occurs.

Toncity

refers to the ability of a solution to change the shape or tone of the cells by altering the cells' internal water volume

G-protein

regulatory molecule that acts as a middle man or relay to activate or inactivate a membrane bound enzyme or ion channel. Causing a second messenger to connect plama membrane events tot the internal metabolic machinery of the cells. Two important second messengers are cyclic AMP and ionic calcum. These acitvate protein kinase enzymes which transfer phosphate groups from ATP to other proteins acivating a whole series of exzymes that bring about cellular activity. 1. Ligand binds to the receptor. Receptor changes shape and activates. 2. The activated receptor binds to a G protein and activates it. The G protein changes shape causing it to release GDP and bind GTP 3. Activated G protein activates or inactivates an effector protein by causing its shape to change. 4. Activated effector enzymes catalyze reactions that produce 2nd messengers in the cell 5. Second messengers activate other enzymes or ion channels 6. Kinase enzymes activate other enzymes

cytosol

viscous semitransparent fluid in which the other cytoplasmic elements are suspended. Complex mixture with properties of both a colloid and a true solution. Water, protein, salts, sugars, and other solutes are dissolved in the cytosol.

Chromatin

--30% Dna, 60% histone proteins which package and regulate DNA, 10% RNA chains new or newly forming - functional unit is nucleosomes which consist of flattened disc shaped cores or clusters of eight histone proteins connected like beads on a string by a DNA molecule. -folds into chormosomes when cell is ready to divide

S phase

-Dna is replicated, ensuring the two feature cells being created will have identical copies of genetic material. - new histones are made and assembled into chormatin.

Interphase

-period from cell formation to cell division -resting from division or growth phase -consists of G1, S , and G2 phases

Flagella

-projections formed by centrioles but are substantially longer than cilia. -sperm -9+2 formation

Cell adhesion molecules

(cams) - molecular velcro that cells use to anchor themselves to molecules in the extracellular space and to each other -arms that migrating cells use to haul themselves past one another -SOS signals sticking out from the blood vessel lining that rally protective white blood cells to a nearby infected or injured area -mechanical sensors that respons to changes in local tension or fluid movement at the cell surgace by stimulating syntheseis or degradation of tight junctions - transmitters of intracellular signals that direct cell migration, proliferation, and specilization

gap 2 subphase

- brief -enzymes and other proteins needed for division are synthesized and moved to their proper sites. -End of g2, centriole replication is complete -cell check point

Early Prophase

- chromatin coils and condenses, forming barlike chromosomes. -each duplicated chromosome consists of two identical threads, called sister chromatids held together at the centromere -the centrosomes act as focal points for growth of a microtubule assembly called the mitotic spindle. As the microtubules lengthen, they propel the centrosomes toward opposite end of the cells. -microtubule arrays called asters extend from the centrosome matrix

golgi apparatus

- consists of stacked and flattened membranous sacs, shapped like hollow dinner plates, associated with swarms of tiny membranous vesicles. -traffic director for cellular proteins. -modify, concentrate, and package the proteins and lipids made at the rough ER and destined fro export from the cell. 1. Protein containin cesicles pinch off rough ER and migrate to fuse with membranes of golgi app 2. Proteins are modified within the golgi compartments 3. proteins are then packaged within different vesicle types depending on their ultimate destination 4. leave via exocytocis, vesical membrane to be incorporated into plasma membrane, or lysosome

Sodium-Potassium Pump

- most investigated example of a primary active transport system. - the carrier is an enzyme called NA+-K+ ATPase - this results in the concentration of potassium inside the cell being 10x the outside concentration and the reverse of sodium. -pumps almost continulously due to leakage 1. Three cytoplasmic NA+ bind to pump protein 2. Na+ bidning promotes hydrolysis of ATP. The energy released during this reaction phosphorylates the pump. 3. Phosphorylation causes the pump to change shape, expelling Na+ to the outside. 4. Two extracellular k+ bind to pump 5. K+ binding triggers release of the phosphate. The dephosphorylated pump resumes its original conformation 6. Pump protein binds ATP; relaease K+ to the inside and Na+ sites are ready to bind Na+ agian. The cycle repeats

Late Prophase

- nuclear envelope breaks up, allowing he spindle to interact with the chromosomes -some of the growin spindle microtubules attache to kinetochores (special protein strucutres at each chromosomes centromere. ) -nonkinetochore microtubules slide past each other forcing the poles apart -kinetochore microtubules pull one ach chromosome from both poles in a tug of war that ultimatley draws the chromosomes to the center of the cell

Mitochondria

- thead like or lozenge-shaped membranous organelle. -power plants of cells - providing most of its ATP supply -density of mitochondria depends on the cells energy requirements. liver= lots of mitos lymphocyte= few - enclosed by two membranes -outermembrane is smooth and feature less -innermembrane folds inward, forming cristae that protrude into the matrix, and has ribosomes attached to it -matrix is gel like substance -aerobic cellular respiration occurs here -contain their own DNA, RNA and can reproduce themselves - pinch themselves in half and regrow when they are needed more

Cilia

-Whiplike motile cellular extensions that occur, typically in large numbers, on the exposed surfaces of certain cells. - moves substance in one direction across cell surfaces. -power and recovery movements 9+2 formation

centrosome

-acts as a microtubule organizing center -granular-looking matrix that contains paried centrioles, small barrel shaped orangelles oriented at right angles to each other. -mitotic spindle during cell divison

telophase

-begins as soon as chromosomal movement stops. -final phase is prophase in reverse. -identical sets of chromosome begin to uncoil and resume chromatin status. -new nuclear envelope forms around each chromatin mass, nucleoli reapear within the nuclei and spindle breaks down and disappears

gap 1 subphase

-cell is metabolically active, synthesizing proteins rapidy and growing vigorously. -last several minutes to hours typically, but take days or years. -Cells that have stopped dividing are in G0 phase - As g1 ends, the centrioles start to replicate in preparation for cell divison.

Cytoskeleton

-cell skeleton -elaborate network of rods runnign through the cytosol and hundreds of accessory proteins that link these rods to other cell structures. Provides structure and machinary to proved various cell movement - three types: microfilaments, intermeditate, filaments, and microtubules

Glycocalyx

-consists of glycoproteins and glycolipids that form a fuzzy sticky carbohydrate rich area at the cell surgace. -cells are sugar coated -glycocalyx is enriched both by glycolipids and gylcoproteins secreted by the cell -every cell type has a different pattern of sugars in its glycocalyx, the glycocalyx provides highly specific biological markers by which approaching cells recognize each other

smooth endoplasmic reticulum

-continous with the rough ER and consists of tubules arranged in a looping network. Its enzymes play a role in metabolizing lipids, synthasizing cholesterol and phospholipids. synthesize steroid based hormones. absorbe synthesize and transport fats. detoxify drugs, peticides, and cancer causing chemicals, break down stored gylcogen to form free gluclose.

nucleus

-control center/gene containing -instructions needed to build nearly all the body's proteins -dictates the amounts and kinds of proeins to be synthesized at any one time in response to signals acting on the cell -can be multinucleate such as skeletal muscle cells, bone destruction cells, and some liver cells. - includes nuclear envelope, nucleoli, and chromatin

RNA

-decoding and messenger functions are carreid out by RNA -Single stranded and it has the sugar ribose instead of deoxyribose, and the base Uracil rather then Thymine. - three forms: messenger, ribosomal, and transfer

cytokinesis

-divison of the cytoplasm, begins during late anaphase and is completed after mitosis ends. - contractile ring made of actin filaments draws the plasma mebrane inward to form a cleavage furrow over the the center of the cell. This deepens until it pinches the cytoplasmic mass into two parts, yielding two daughter cells.

Mitosis

-divison of the nucleus - series of events that parcels out the replicated DNA of the mother ell to two daughter cells -prophase, metaphase, anaphase, and telophase -last about an hour or less.

Nuclear Envelope

-double membrane barrier separated by a fluid-filled space - outer nuclear membrane is continuous with the rough ER of the cytoplasm and is studded with tibosomes on its external face. -inner nuclear membrane is lined by the nuclear lamina (a network of lamins or rod shaped proteins that assemble to form intermediate filaments) that maintain the shape of the nucleus and acts as scaffold to orgainze DNA in the nucleus -has nuclear pores (an intricate complex of proteins called a nuclear pore complex, lines each pore, forman aqueous transport channel and regulates entry and exit of molecules and large particles into and out of the nucleus). -jelly like fluid called nucleoplasm similar to the cytoplasm

Integral Protiens

-firmly inserted into the lipid bilayer -some protrude from one membrane face only, but most are transmembrane proteins that span the entire membrane and protrude on both sides. -all integral protiens have both hydrophobic and hydrophilic regions allowing them to interact with both the nonpolar lipid tails buried in the membrane and the water inside and outside the cell. -transmembrane proteins can form channels or pores, allowing water soluble molecules to bypass the lipid barrieer -transmembrane proteins can act as carriers that bind to a substance and then move it through the membrane. -can also be enzymes or receptors for homones to relay messages to the inside of the cell also known as signal transduction

Primary Active Transport

-hydrolosis of ATP results in the phospohorylation of the transport protein. This step causes the protein to change its shape in a manner that it pumps the bound solute across the membrane.

M phase

-includes mitosis and cytokinesis

Microvilli

-minute fingerlike extensions of the plasma membrane that project from an exposed cell surface -increase cells surface area -most often found in absorptive cells like intestinal and kidney tubule cells.

Peripheral Proteins

-not embedded in the lipid bilayer -loosely attach to integral proteins and are easily removed without disrupting the membrane -network of filaments that helps suport the membrane from its cytoplasmic side. -some are enzymes - some are motor protiens and are involved in mechanical funcitons such as the changing cell shape during cell divison and muscle cell contraction -some link cells together

Microfilaments

-semiflexible stands of the protien actin -terminal web which is dense crosslinked network of theses attached to the cytoplasmic side of the plasma membrane -involved in cell motility -work with myosin to generate contactile forces in a cell - involved in endo and exo cytosis

tight junction

-series of integral protein molecules in the plasma membranes of adjacent cells fuse together, forming an impermeable junction that encircles the cell. Tight junctions help prevent molecules from passing through the extracellular space between adjacent cells. ex. stomach lining

Anaphase

-shortest phase; centromeres of the chromosomes split simutaniously. Each chromatid now becomes a chromosome in its own right -kinetochore microtubules moved along by motor proteins in the kinetochores, gradually pull each chromosome toward the pole it faces. - nonkinetochore microtubules slide past each other, lengthen, and push the two poles of the cell apart -moving chromosomes look v-shaped.

ribosomes

-small dark -staining granules composed of proteins and a variety of RNA's called robosomal RNA's. - site of protein synthesis - free and membrane bound

Nucleoli

-spherical bodies where the ribosomal subunits are assembled -not membrane bounded -one or two per nucleus

lysosomes

-spherical membranous organelles containing activated digestive enzymes. -demolition crew - digesting particles taken in by endocytosis, ingested bacteria or viruses or toxins -degrading stressed or dead cells or worn-out non functional organelles called autophagy - glycogen breakdown and release -break down bone to release calcium

rough endoplasmic reticulum

-studded with ribosomes -Proteins assembled on these ribosomes thread their way into the fluid-filled interior of the ER cisterns -ribosomes manufacture all the proteins secreted from cells - membrane factory where inegral proeins and phospholipids that form part of all cellular membranes are manufactured.

Intermediate filaments

-tough insoluble protein fibers that resemble woven ropes -made of twisted units of teramerfibrils -most stable and permanent and have high tensile strength

Metaphase

-two centrosomes are at opposite poles of the cell -chromosomes cluster at the midline of the cell, with their centromeres precisely aligned at the spindle equator. This imaginary plane midway between the poles is called the metaphase plate. -at the end of metaphase, enzymes that will act to seperate the chromatids from each other are triggered

Secondary Active Transport

-use of a atp-powered pump -moves sodium across the plasma membrane against its concentration gradient, the pump stores energy, sodium is then moved back into the cell following its gradient and this indirect energy carries along other substances.

DNA Replication

1. Enzymes unwind the DNA molecule, forming a replication bubble 2. Separation: The two DNA strands seperate as the hydrogen bonds between base pairs are broken. The point at which the strands unzip is known as the replication fork 3. Assembly: Parental starnds acting as templates, DNA polymerase positions complementary free nucleotides along the template strands, forming two new strands. Leading and lagging strands in opposite strands because it only runs in a single direction. Two daughter molecules result from one parental DNA. Since each new moelcule consists of one old and one new nucleotide stand, it is known as semiconservative replication 4. Restroration: Ligase enzyme splice short segments of DNA together, restoring the double helix structure.

Transription

1. Initiation: With the help of transcription factors, RNA polymerase binds to the promoter, pries apart the two DNA strands, and initiates mRNA synthesis at the start point on the template strand. 2. Elongation: As the RNA polymerase moves along the template strand, elongating the mRNA trancript one base at a time, it unwinds the DNA double helix before it and rewinds the double helix behind it 3. Termination: mRNA synthesis ends when the termination signal is reached. RNA polymerase and the completed mRNA transcript are released.

Translation

1. Initiation: occurs when four compnents combine at the P site: A small ribosomal subunit, an initiator tRNA carrying the amino acid mehionine, the mRNA, and a large ribosomal subunit 2. Elongation: Amino acids are added one at a time to the growing peptide chain via a process that has three repeating steps (2a,2b,2c) 2a. Codon recognition: The anticodon of an incoming tRNA binds with the complementary mRNA codon in the A site of the ribosome. 2b. Peptide bond formation: growing polypeptide bound to the tRNA at the P site is transferred to the amino acid carried by the tRNA the A site. 2c. Translocation: The entire ribosome translocates, shifting its position one codon along the mRNA. 3. Termination: When a stop codon arrives at the A site elongation ends.

endocytosis

1. coated pit ingests substance 2. protein coated vesicle detaches 3. coat proteins are recycled to plasma membrane 4. uncoated vesicle fuses with a sorting vesicle called and endosome. 5. transport vesicle containing membrane components moves to the palsma membrane for recycling. 6. fused vesicle may....(a) fuse with the lysosome for digestion of its contents or (b) deliver its contnets to the plasma membrane on the opposite side of the cell. aka tanscytosis

Cell theory

1.) A cell is the basic structural and functional unit of living orgnaisms. When you define cell properties, you define the properties of life. 2.) The activity of an organism depends on both the individual and the combined activities of its cells 3.) According to the principle of complenmentarity of structure and function, the biochemical activities of cells are dicatated by their shape and form, and by the relative number of the subcellular structures they contain 4.) Cells can only arise from other cells

Extracellular Material

1.) Body fluids 2.) Cellular Secretion 3.) Extracellular Matrix

Cell Diversity

1.) Cells that connect body parts, form linings, or transport gases: Epithelial, Erthryocytes, Fibroblasts 2.) Cells that move organs or body parts: Skeletal Muscle Cell, Smooth Muscle Cell 3.) Cells that store nutrients- Fat cell 4.) Cells that fight disease- Macrophage 5.) Cells that gather information and control functions- Nerve 6.) Reproduction Cells- Sperm

3 factors that act to bind cells together

1.) glycoproteins in the glycocalyx act as an adhesive 2.) Wavy Contours of the membranes of adjacent cells fit together in a tongue and groove fashion 3.) Special Cell juncitons form

Microtubules

=hollow tubes made of spherical protein subunits called tubulin. -radiate from the centrosome -determine overall shape of cell, as well as the distribution of cellular organelles -motor proteins attached to these move and reposition organelle along the microtubule

Polypeptide Synthesis

Two major steps 1. transcription- DNA's information is encoded in mRNA 2. Translation- information carried by mRNA is decoded and used to assemble polypeptides

Carrier-mediated Faciliated Diffusion

Carriers are transmembrane integral proteins that are specific for tansporting certain polar moelcules or classes of molecules such as sugars and amino acids that are too large to pass thorugh membrane channels. Alterations in the shape of the carrier allow it to first envelop and then release the transported substance allowing it to bypass the nonpolar regions of the membrane. Essentially the carrier proten changes shape to move the binding site from one face of the memrane to the other. Substance still moves down a concentration graident.

Facilitated Diffusion

Certain Molecules, notably gluclose and other sugars, some amino acids, and ions, are transported passivley even though they are unable to pass through the lipid bilayer. Instead they use facilitated diffusion. in which the transported substance 1.) binds to protein carriers in the membrane and is ferried across or 2.) moves through water filled protein channels

Channel-mediated facilitated diffusion

Channels are transmembrane proteins that transport substances, usually ions or water, thorugh aqueous channels from one side of the membrane to the other. They are selective due to pore size and the charges of the amino acids lining the channel. Leakage channels are always open and simply allow ions or water to move according to gradients gated channels are controlled bu chemical or electrical signals.

gap junction

Communicating junctions that allow ions and small molecules to pass are particularly important for communication in heart cells and embryonic cells

Receptor Mediated Endocytosis

Extracellular substances that bind to specific receptor proteins enabling the cell to ingest and concentrate specific substances in protein coated vesicles. Ligands may simply be released inside the cell or combined with a lysososme to digest contents. Receptores are recycled to the plasma membrane in vesicles.

Pinocytosis

The cell "gulps" a drop of extracellular fluid containing solutes into tiny vesicles. No receptors are used, so the process is non specific.

phagocytosis

The cell engulfs a large particle by forming projecting pseudopods around it and enclosing it within a membrane sac called a phagosome. The phagosome is combined with a lysosome. Undigested contents remain in the vesivle or are ejected by exocytosis.

Gerneralized Cell

Three main parts: 1.) Plasma Membrane- outer boundary of the cell which acts as a selectively permeable barrier 2.) Cytoplasm- intracellular fluid packed with organelles, or small structures that perform specific cell functions 3.) Nucleus- an organelle that controls cellular activites. Typically the nucleaus lies near the cell's center

Osmolarity

Total Concentration of all solute particles in a solution

Exocytosis

Vesicular transport processes that eject substances from the cell interior into the extracellular fluid. Typically stimulated by a cell surface signal such as binding of a hormone toa membrane receptor or change in membrane voltage. Accounts for hormone secretion, neurotransmitter release, mucus secretion, and ejection of wastes. 1. Membrane bound vesicle migrates to the plasma membrane 2. There proteins at the cesicle surgace bind with plasma membrane protiens 3. The vesicle and plasma membrane fuse and a pore opens up 4. Vesicle contents are released to the cell exterior.

Endoplasmic Recticulum

an extensive system of interconnected tubes and parallel membranes enclosing fluid-dilled cavities or cisterns. Smooth or rough.

desmosomes

anchoring junctions that bind adjacent cells together act like moelcular "velcro" and also help form an internal tension-reducing network of fibers

hypotonic solutions

are more dilute than cells. cells palced in a hypotonic solution plump up rapidly as water rushes into them.

cytoplasm

cellular material betwenn the plasma membrane and the nucleus and is the site of most cellular activites. Contains cytosol, organelles, and inclusions

Basal Bodies

centrioles forming the bases of cilia and flagella

Inclusions

chemical substances that may or may not be present depending on cell type.

Ligands

chemicals that bind to specifically to plasma membrane receptors. Include neurtransmitters, horomones, and paracrines.

Cholesterol

has polar region and a non polar region. It stabilizes the membrane and decreases the mobility of the phospholipids and the membrane

Fluid Mosaic Model

depicts the plasma memrane as a exceedingly thin structure composed of a double layer, or bilayer of lipid molecules with protein moelcules plugged inot or dispersed in it. The proteins, many of which floar in the fluid lipid bilayer, form a constantly changing mosaic pattern.

Osmosis

diffuison of a solvent such as water through a selectively permeable membrane. Even though water is highly polar, it passes via osmosis thorught the lipid bilayer. This is thought because of the random movments of the membrane lipids opening small gaps between their tails allow water to slip by. Also moves through aquaporins or AQPs which allow single file diffusion of water molecules.

Passive transport

diffusion (simple diffusion, facilitated diffusion, osmosis) and filtration. diffusion is used as a means of membrane transport in every cell of the body. filtration only occurs generally across capillary walls

Vesicular transport

fluids containing large particles and macromolecules are transported across cellular membranes inside bubble like membranous sacs called vesicles.

Lipid Bilayer

forms the fabric of the plasma membrane and is constructed largly of phospholipids and smaller amounts of glycolipids and cholesterol

Phospholipids

have a polar head that is hydrophilic (loves water) and an uncharged polar tail made up of two fatty acid chains that is hydrophobic (hates water). The polar heads are attracted to water- main constituent of both intracellular and extracellular fluids- so they lie on both the inner and outer surfaces of the membrane, with the non polar tails avoiding water and lining up in the center of the membrane

Hypertonic Solutions

have higher concentration of non-penetrating solutes than seen in the cell. Cells immersed in hypertonic solutions lose water and shrink or crenate.

membrane receptors

huge and diverse group of integral proteins and glycoproteins that serve as binding sites.

Contact signaling

in which cells come together and touch, allowing them to recognize one another

exon

informational sequences often seperated by introns

endomembrane system

is a system of organelles that work together to 1. produce, degrade, store, and export biological molecules 2. degrade potentially harmful substances. includes ER, golgi, secretory vesicles, lysosomes, as well as nuclear membrane, nuclear envelope, plasma membrane

Glycolipids

lipids with an attached sugar group. account for 5 percent of total membrane lipids Its head is polar and its tale is nonpolar

Messenger RNA

mRNA; relatively long nucleotide strands resembling "half-DNA" molecules; carries the coded information to the cytoplasm where protein synthesis occurs.

Membrane Proteins

make up about half of the plansma membrane by mass and are responsible for most of the specialized membrane functions. Some membrane proteins float freely. Others are tethered to intracellular or extracellular structures and are restricted in their movement Membrane proteins are involved in transport, receptors for signal transduction, attachement to the cytoskeleton and extracellular matrix, enzymatic activity, intercellular joining, cell-cell recognition

organelles

metabolic machinery of the cell. specialized cellular compatments or structures each performing its own job to maintain the life of the cell.

transcytosis

moving substance into across and then out of the cell via vesicular transport

vesicular trafficking

moving substances from one area in the cell to another

Simple Diffusion

non-polar and lipid soluble substances diffuse directly through the lipid bilayer. Substances like oxygen, carbon dioxide, and fat soluble vitamins.

introns

noncoding, often repetitive, segments. Often referred to as "junk DNA"

Two ways substances move through the plasma membrane

passive- substances cross the membrane without any energy input from the cell active- the cell provides the metabolic energy needed to move substances across the membrane

hydrostatic pressure

pressure exerted by water against the membrane

Active Transport

requires carrier protiens that combine specifically and reversibly with transported substances. This uses Solute pumps that move solutes most importantly ions, uphill against a concentration gradient causing the cell to expend energy. These processes are distinguished according to their source of energy primary active transport, the energy to do work comes directly from the hydrolysis of ATP secondary active transport, transport is driven indirectly by energy stored in concentraion gradients o fions created by primary active tranport pumps. these are coupled systems: moving more than one substance at a time. In symport they move the same direction. in antiport they are opposite.

Plasma Membrane

separates two of the body's major fluid compartments, the intracellular fluid within cells and the extracellular fluid outside of cells. Functions include: 1.) Mechanical Barrier 2.) Selective Permeability 3.) Electrochemical gradient 4.) communication 5.) cell signaling

cell cycle

series of changes a cell goes through from the time it is formed until it reproduces two major periods: interphase and mitotic phase

peroxisomes

spherical membranous savs containing a variety of powerful enzymes the most important of which are oxidases and catalases. -detox via oxidases and free radicals by oxidases and then stabilized by catalases. -prevelant in the kidney and liver

Transfer RNA

tRNA; small roughly L shaped molecules that ferry amino acids to the ribosomes. This where they decode mRNA's message for amino acid sequence in the the polypeptide to be built.

osmotic pressure

tendency of water to move into the cell by osmosis

Isotonic Solution

the same concentrations of non penetrarting solutes as those found in cells. Cells exposed to isotonic solutions retain their normal shape , and exhibit no net loss or gain of water.

Cells

the structural units of all living things

Diffusion

the tendancy of molecules or ions to move from an area where they are in high concentration to an area where they are in lower concentration, that is down or along their concentration gradient. This constant random and high-speed motion of the molecules and ions results in collsions. The higher the difference in concentration o fthe diffusing moelcules and ions causes the particles to diffuse faster. Driving force is the kincetic energy and the speed of diffusion is influenced by molecular size (smaller faster) and temp ( warmer faster). Membrane is selectively permeable and will allow only what the cell needs to enter the cell and will keep out undesirable substances. Substance can pass if they are lipid soluble, small enough to pass through a channel, or assisted by a carrier molecule.