Chapter 3: Cell Biology AP1 Chapter 3 1
Cell I. Fxns of a cell the basic unit of all living things (the smallest part of a living organism in our case humans) Shared Characteristics Plasma Membrane Outer boundary of the cell though which the cell interacts with its external environment Nucleus Directs activities of the cell Cytoplasm Most cell activities occur here Organelles Perform specific fxns in cell AP1 Chapter 3 2
I. Fxns of a cell 4 major fxns of cells A. Cell metabolism & e+ use: Metabolic rxns in the cell e+ is released to accomplish cell activities & maintain Body Temp. B. Synthesis of Molecules Can prod proteins, nucleic acids, lipids Cell s fxn & characteristics are determined by the molecules they prod C. Communication Cells prod & respond to chemical & e+ signals wh/ allows them to communicate w/each other * Neuron to a muscle = contraction or relaxation D. Reproduction & inheritance Cell holds the genome. It determines structure & fxnl characteristics of that cell. Cells can prod new cells AP1 Chapter 3 Gametes transmit genetic info. 3
III. Plasma Membrane AP1 Chapter 3 4
III. Plasma Membrane Outer most component of the cell Fxns as a boundary to separate inside from outside of the cell (intra vs extra cellular) Encloses and supports the cell s contents Attaches the cell to the extracellular environment or to other cells Cell s ability to recognize & communicate with each other occurs via the plasma membrane Determines what moves into ot out of the cell (therefore the contents inside the cell can be different from what is outside). Make-up: 45-50% Lipids 45-50% Proteins 4-8% Carbohydrates Membrane potential: electrical charge difference across the PM resulting from the cell s regulation of movement into and out of the cell AP1 Chapter 3 5
III. Plasma Membrane Terminology Intracellular: (Intra- Inside) inside the cell Extracellular: (Extra- Outside) outside of the cell Intercellular: (Inter- Between) from 1 cell to another Glycoproteins: carb s + proteins Glycolipids: Carb s + Lipids Membrane Potential: result of uneven distribution of ions on the inside verses the outside of the cell Glycocalyx: Collection of glycoproteins, glycolipids, and carb s that lies on the outer surface of the plasma membrane 6
IV. Membrane Lipids AP1 Chapter 3 7
IV. Membrane Lipids Phospholipids (PL s): Predominant lipid in membrane Bipolar: Hydrophilic head is water loving and polar and faces both surfaces (inner & outer) Hydrophobic tail is water hating and non-polar and crowd together between the heads Cholesterol Makes up 1/3 of the membrane and lie btwn PL s Helps to limit PL s mvmt providing stability for the PM It is also bipolar and the tail is embedded in head while the ring is embedded in the tails AP1 Chapter 3 8
IV. Membrane Lipids *Fluid Mosaic Model* The lipid bilayer is mobile with things floating w/in it Consequences of this: a) Important for molecule distribution in the membrane b) Slight damage can be repaired because the PL s will move to cover it c) It enables two different membranes to fuse with each other AP1 Chapter 3 9
V. Membrane Proteins A. Marker Molecules B. Attachment Proteins C. Transport Proteins D. Receptor Proteins E. Enzymes AP1 Chapter 3 10
V. Membrane Proteins (MP) Many fxns of the plasma membrane are determined by the combination of membrane proteins present. The ability of these proteins to fxn properly is determined by their 3-D shape There are 2 major types: 1. Integral/Intrinsic (Transmembrane) contain hydrophobic and hydrophilic regions to match the phospholipids characteristics & location 2. Peripheral/Extrinsic Surface proteins on inner or outer surface. Can be bound to an integral protein or the phospholipids head There are 5 major classes of MP s AP1 Chapter 3 11
5 major classes of Membrane proteins I. Marker molecules II. Attachment Proteins III. Transport Proteins IV. Receptor Proteins V. Enzymes A B C A B a Non-gated Channel Channel Proteins b Gated Channel Carrier Proteins a b c Uniporter Symporter Antiporter ATP powered pump Receptors linked to channel proteins Receptors linked to G-proteins i ii Ligand-gated channel Voltage-gated channel AP1 Chapter 3 12
Membrane Proteins: I. Marker Molecules Glycoproteins or glycolipids that allow for cells to identify other cells or other molecules Important because cells aren t isolated and must function as a whole for normal body function. May be integral or peripheral proteins Ex/ immune cells AP1 Chapter 3 13
Membrane Proteins: II. Attachment Proteins Integral proteins that may attach to intracellular molecules. Integrins can also function in cellular communication. AP1 Chapter 3 14
Membrane Proteins: III. Transport Proteins AP1 Chapter 3 All exhibit 3 characteristics 1. Specificity Each binds to & transports only 1 types of molecule/ion 2. Competition Closely related substances may bind to the same binding site & the one w/ greater [ ] or higher affinity is more readily moved across the PM 3. Saturation Movement is limited by the # of transport proteins rate will eventually plateau because the # of proteins are going at their maximum rate 15
Membrane Proteins: III. Transport Proteins A. Channel Proteins Form passageways through the plasma membranes that have both hydrophobic and hydrophilic regions. B. Carrier Proteins Move larger ions or molecules across the membrane, when bound it changes shape to allow it to move from one side of the membrane to the other then return to its original shape to work again. C. ATP-powered pumps Moves ions or molecules across the membrane using ATP. AP1 Chapter 3 16
Membrane Proteins: III. Transport Proteins A. Channel Proteins a. Non-gated Channels Always open responsible for the permeability of the plasma membrane when the cell membrane at rest. b. Gated Channels Can be opened or closed i. Ligand Gated ii. Small molecules must bind in order to open or close the channel Voltage Gated Change in voltage across the plasma membrane causes the gate to open AP1 Chapter 3 17
Membrane Proteins: III. Transport Proteins B. Carrier Proteins a. Uniporter Movement of 1 ion or molecule across the plasma membrane. b. Symporter Movement of 2 ions or molecules in the same direction (into the cell or out of the cell). c. Antiporter Movement of 2 ions or molecules in opposite directions (one in and one out or vise versa). AP1 Chapter 3 18
Membrane Proteins: III. Transport Proteins C. Sodium-Potassium Pump These have 2 binding sites. One is for the molecule to be moved the other is for ATP Breakdown of ATP releases e+ ing shape of the pump protein which moves the molecule across the membrane AP1 Chapter 3 19
Membrane Proteins: IV. Receptor Proteins Proteins or glycoproteins in the plasma membrane that have an exposed receptor site on the outer cell surface which can attach to specific chemical signals. Many are part of an intercellular communication system that coordinates cell activities. AP1 Chapter 3 20
Membrane Proteins: IV. Receptor Proteins A. Receptor linked to channel proteins These help form ligandgated channels & when bound it changes the channels shape to move ions B. Receptors linked to G- protein complexes Uses a second messenger system, binding of the receptor externally causes to the cell internally 3 ways α can stimulate a cellular response 1. Intracellular chemical signals 2. Opening channels in the plasma membrane 3. Activation of enzymes AP1 Chapter 3 associated with the plasma membrane 21
Membrane Proteins: V. Enzymes These may work on the inner or outer surface of the plasma membrane. Some are always active but others are activated by things like GPCR s AP1 Chapter 3 22
VI. Movement through the plasma membrane AP1 Chapter 3 23
V. Mvmt thru the PM Inside of the cell: Enzymes other proteins, glycogen, high potassium concentration Outside of the cell: High concentration of sodium, calcium, & chloride The cell has to be able to bring in nutrients inside and get waste products out without changing the cell s volume, because too much can cause the cell the rupture (causing cell death) or to shrivel (also causing cell death). Movement 1. Molecules that are lipid soluble or very small water soluble molecules will freely go across the plasma membrane. 2. Large lipid soluble molecules and water soluble molecules can t pass through the plasma membrane and may need to use transport proteins. 3. Larger water soluble molecules or whole cells may be moved by vesicles. AP1 Chapter 3 24
Membrane transport mechanisms A. Passive Transport Mechanisms No energy required to move molecules from one side of the membrane to another B. Active Transport Mechanisms Energy required to move molecules from one side of the membrane to another AP1 Chapter 3 25
Membrane transport mechanisms Passive Transport Mechanisms A. Diffusion B. Osmosis C. Facilitated Diffusion Active Transport Mechanisms A. Active Transport B. Secondary Active Transport C. Vesicular Transport a. Endocytosis b. Exocytosis AP1 Chapter 3 26
Passive Transport Mechanisms A. Diffusion: Movement of solutes from an area of high concentration to an area of low concentration Concentration gradient: concentration difference between 2 points divided by the distance between the 2 points, Rate of Diffusion 1. Magnitude of the concentration gradient 2. Temperature of the solution 3. Size of the diffusion molecules 4. Viscosity of the solvent AP1 Chapter 3 27
Passive Transport Mechanisms B. Osmosis Diffusion of water across a selectively permeable membrane Will allow water but not all solutes with in the water Important because it can influence a cell s function when water moves. Osmotic Pressure: Force required to prevent water movement across a selectively permeable barrier via osmosis 1) Isosmotic 2) Hyperosmotic 3) Hyposmotic Concentration of solutions AP1 Chapter 3 28
Passive Transport Mechanisms B. Osmosis Tonicity: refers to the cell s shape remaining constant b/c it maintains it s internal pressure 1. Isotonic sol n: no net mvmt of H2O, cell doesn t shape 2. Hypertonic sol n: mvmt out of cell b/c sol n has a greater [ ] of solute thus a higher osmotic pressure (crenation) 3. Hypotonic sol n: mvmt into cell b/c sol n has a lower [ ] of solute thus a lower osmotic pressure (Lysis) AP1 Chapter 3 29
Passive Transport Mechanisms C. Facilitated Diffusion Amino acids & glucose go into the cell and area going out of the cell can t occur via direct diffusion because they are too big. Thus there is Mediated transport (facilitated diffusion): Process by which transport proteins assist the movement of water soluble molecules or electrically charged molecules or ions across the plasma membrane. AP1 Chapter 3 30
AP1 Chapter 3 31 Active Transport Mechanisms A. Active Transport also a type of mediated transport. Requires energy provided by ATP movement dependent on the number of pumps and availability of ATP. Important because it can move things against their concentration gradients.
Active Transport Mechanisms B. Secondary Active Transport Passive transport of 1 molecule with its concentration gradient helps to energize the carrier so that it can transport the second molecule against its concentration gradient. AP1 Chapter 3 32
AP1 Chapter 3 33 Active Transport Mechanisms C. Vesicular Transport Movement of larger volumes of substances across the plasma membrane through the formation and release of vesicles requiring ATP. BUT the specificity seen in others doesn t occur in this process. a. Endocytosis i. Pinocytosis ii. Phagocytosis iii. Receptor mediated endocytosis b. Exocytosis
ctive transport mechanisms a) Endocytosis: uptake of material into the cell. 3 types: i. Pinocytosis ii. iii. Molecules dissolved in liquid Phagocytosis Cells and solid particles Receptor mediated endocytosis Specificity for substances Receptor-mediated Pinocytosis Phagocytosis AP1 Chapter 3 34
Active Transport Mechanisms b. Exocytosis Materials manufactured by the cell are packaged in secretory vesicles that fuse w/the PM & release their contents outside of the cell ATP req d Proteins & other water soluble substances AP1 Chapter 3 35
AP1 Chapter 3 36 http://www.animalcute.net/wp-content/uploads/2012/01/animal-cell-cytoplasm5.jpg VII. Cytoplasm The material outside the nucleus and inside of the plasma membrane
VII. Cytoplasm (1/2 cytosol/1/2 organelles) 3 parts to cytoplasm 1. Fluid Portion Anatomy: H 2 O w/dissolved ions & molecules; colloid w/many suspended molecules espicially proteins Physiology: Contains enz s that catalyze decomposition & synthesis rxns, ATP is also prod d in glycolysis rxns 2. Cytoskeleton Supports cell & holds nucleus & organelles in place Responsible for mvmt in & of the cell Made up of 3 groups of proteins: a) Microtubules b) Microfilaments c) Intermediate filaments 3. Cytoplasmic Inclusions Anatomy: Collections of molecules manufactured or ingested by cell and may be membrane bound Physiology Fxn is dependent on the molecules Ex: energy storage lipids&glycogen AP1 Chapter 3 37
VII. Cytoplasm 2. Cytoskeleton Made up of 3 groups of proteins: a) Microtubules Provide support & structure to cytoplasm Involved in cell division & transport of intracellular materials Form essential components of organelles (centrioles, spindle fibers, cilia, & flagellum) b) Actin Filaments Provide structure to cytoplasm & mechanical support for microvilli Responsible for cell mvmts c) Intermediate filaments Protein Fibers Provide strength to cells 38
VIII. The Nucleus & Cytoplasmic A. Nucleus B. Cytoplasmic Organelles: A. Ribosomes B. Endoplasmic Reticulum C. Golgi Apparatus D. Secretory Vesicles E. Lysosome Organelles G. Peroxisomes H. Proteosomes I. Mitochondria J. Centrioles & Spindle Fibers K. Cilia & Flagella L. Microvilli Organelles: structures w/in cells that are specialized for a particular fxn. Number & types within each cell are related to the specific structure & function of the cell Largest organelle Nucleus (all others are considered cytoplasmic organelles) AP1 Chapter 3 39
VIII. The Nucleus & Cytoplasmic Organelles A. Nucleus Large membrane bound structure usually centrally located Shape & # of lobules vary dependent on cell type (may be multiple or spit out of cell) 3 Major structures of the nucleus: AP1 Chapter 3 40
3 Major structures of the nucleus 1. Nuclear Envelope Double membrane enclosing the nucleus that separates the nucleus from the cytoplasm, also uses nuclear pores to regulate mvmt in/out of the nucleus 2. Chromatin Thin strands of DNA wound around histones (proteins) that regulate protein synthesis thus also regulating the chemical rxns in the cell 3. Nucleolus 1 or more dense bodies consisting of ribosomal RNA, 10 stretches of DNA called nuclear organizer regions that contain the rrna templates, & proteins that serve as the assembly site for ribosomal subunits 41 IX. The Nucleus & Cytoplasmic Organelles A. Nucleus
IX. The Nucleus & Cytoplasmic Organelles B. Ribosomes rrna & proteins make-up both the large & small subunits of ribosomes Site of protein synthesis 2 categories: 1. Free: mainly prod proteins that will be used inside the cell 2. Bound: mainly prod proteins that will be excreted from the cell C. Endoplasmic Reticulum Series of membranes continuous w/ the nuclear envelope distributed throughout the cell 2 major types: Rough ER: ribosomes attached fxns in protein synthesis & transport of those to the golgi Smooth: no ribosomes fxns in manufacture of lipids & carb s; detoxifies harmful chemicals; can store Ca 2+ AP1 Chapter 3 42
IX. The Nucleus & Cytoplasmic Organelles D. Transport Vesicle membrane bound sack from the ER that goes to the GA for processing E. Golgi Apparatus (GA) F. Secretory Vesicle Membrane bound sac that pinches off of the GA that carries the finalized proteins & lipids to the cell surface for secretion These can accumulate in the cell until proper signal is received to initiate its release Flattened membrane sacs stacked on each other modifies, packages, & distributes proteins & lipids prod d by RER & SER for secretion or internal use Can concentrate, or chemically modifies by adding carbs or lipids making glycoproteins or glycolipids AP1 Chapter 3 43
IX. The Nucleus & Cytoplasmic Organelles F. Lysosome Membrane bound sac pinched off of GA carries digestive enz s that can break down NA, polysaccharides, lipids, thus old cell parts & phagocytized bacteria G. Peroxisome Membrane bound vesicle 1 site of fatty acid & AA degradation byproduct is H 2 O 2 using catalase brksdwn to H 2 O + O 2 High # in liver & kidney cells AP1 Chapter 3 44
IX. The Nucleus & Cytoplasmic Organelles H. Proteasome Tube-like protein in the cytoplasm as proteins enter the cell they are enzymatically degraded in the cytoplasm I. Mitochondria Dynamic structure enclosed by a double membrane. Inner projections are called cristae. Major site of ATP-synthesis when O 2 is available. #/cell based on cell fxn AP1 Chapter 3 45
IX. The Nucleus & Cytoplasmic Organelles J. Centrioles Pair of cylindrical organelles in centrosome made-up of microtubules Center for microtubule formation Determine polarity of the cell during division For basal bodies of cilia & flagellum K. Cilia Short hair-like Extensions of the PM using microtubules to hold their shape Fxnally in humans it moves materials over cell surface Basal Body: located at base of cilia AP1 Chapter 3 46
IX. The Nucleus & Cytoplasmic Organelles L. Flagellum Long Hair-like extensions of the PM using microtubules to hold their shape. Responsible for the mvmt of sperm M. Microvilli Short extension of the PM containing microfilaments Increase surface area of the PM for absorption or secretion. May fxn as a modified sensory receptor (hair cells in ear) AP1 Chapter 3 47