Cell Physiology.pptx

Cell Physiology OUTLINES  Introduction  Definition  Cell functions  Organization of the cell  Membraneus & non membraneus organelles  Plasma membrane & Transport mechanisms  Cytoplasm  Nucleus  An Introduction to Cells  Cell Theory  Developed from Robert Hooke’s research  Cells...

Cell Physiology OUTLINES  Introduction  Definition  Cell functions  Organization of the cell  Membraneus & non membraneus organelles  Plasma membrane & Transport mechanisms  Cytoplasm  Nucleus  An Introduction to Cells  Cell Theory  Developed from Robert Hooke’s research  Cells are the building blocks of all plants and animals  All cells come from the division of preexisting cells  Cells are the smallest units that perform all vital physiological functions  Each cell maintains homeostasis at the cellular Definition  Cell is defined as structural and functional unit of the living body  Somatic cells (soma = body)  All body cells except sex cells  Sex cells (germ cells)  Reproductive cells  Male sperm  Female oocyte (a cell that develops into an egg) Cell Functions  Metabolism  Use molecules for cellular functions, to make ATP and heat  Molecule synthesis  Different cells synthesize different molecules. Structural and functional characteristics are based on molecules they produce.  Communication  Cells produce and respond to chemical and electrical signals  Reproduction and inheritance  A cell is surrounded by a watery medium known as the extracellular fluid  Extracellular fluid is interstitial fluid + plasma + cerebrospinal fluid + synovial fluid  The plasma membrane separates cytoplasm (intracellular fluid) from the extracellular fluid (ECF)  Cytoplasm= cytosol + organelles  Cytosol = liquid  Organelles are intracellular structures  Organization of the Cell  The different substances that make up the cell are  collectively called protoplasm. Protoplasm is composed  mainly of five basic substances:  Water...70-85%  electrolytes…(potassium, magnesium, phosphate, sulfate, bicarbonate, and smaller quantities of sodium, chloride, and calcium).  proteins (structural &functional proteins)…10-20%  Lipids Plasma Membrane  Cytoplasm  Cytosol (watery matrix)  Dissolved materials:  nutrients, ions, proteins, and waste products  High potassium/low sodium levels compared to ECF  High protein content compared to ECF  High carbohydrate/low amino acid and fat inside cell  Fluids  Organelles=“little organs”  Structures with specific functions  Inclusions  stored nutrients (e.g., glycogen) in plasma membrane Non membranous Organelles  The Cytoskeleton — structural proteins for shape and strength  Microfilaments  Intermediate filaments  Microtubules  Organelles  Non membranous organelles  No membrane  Direct contact with cytosol  Includes the cytoskeleton, microvilli, centrioles, cilia, ribosomes, and proteasomes  Membranous organelles  Covered with plasma membrane  Isolated from cytosol  Includes the nucleus, endoplasmic reticulum (ER), the Golgi apparatus, lysosomes, peroxisomes, and mitochondria  Plasma Membrane  Comprised of a phospholipid bilayer-double layer of phospholipid molecules  Hydrophilic heads—toward watery environment, both sides  Hydrophobic fatty-acid tails—inside membrane, some are kinked to enhance fluidity of membrane.  Cholesterol (amphipathic) stabilizes membrane.  It is selectively permeable (semi-permeable). It is a barrier to large molecules, ions and water soluble compounds.  Plasma Membrane  Functions of the Plasma Membrane  Physical isolation  Barrier  Regulates exchange with environment  Ions and nutrients enter  Wastes eliminated and cellular products released  Monitors the environment  Extracellular fluid composition  Chemical signals  Structural support  Anchors cells and tissues  Fluid Mosaic Model-describes the plasma membrane as fluid, not static.  Movement of plasma membrane due to:  Unsaturated hydrophobic fatty acid tails- kink Membrane Fluidity Demonstrated Plasma Membrane  Membrane Proteins  Integral proteins  Span the membrane  They are amphipathic-polar and nonpolar  Peripheral proteins  Bound to inner or outer surface of the membrane  Plasma Membrane  Several Types of Membrane Proteins  Anchoring proteins (stabilizers)  Attach to inside or outside structures  Recognition proteins (identifiers)  Label cells as normal or abnormal  Enzymes  Catalyze reactions  Receptor proteins  Bind and respond to ligands (ions, hormones)  Carrier proteins  Transport specific solutes through membrane  Channels  Regulate water flow and solutes through membrane  Plasma Membrane  Membrane Carbohydrates  Proteoglycans, glycoproteins, and glycolipids  Extend outside cell membrane  Form sticky protection “sugar coat” (glycocalyx)  Functions of the glycocalyx  Lubrication and protection  Anchoring and locomotion  Specificity in binding (receptors)  Recognition (immune response & tissue growth)  Transport Mechanisms  The plasma (cell) membrane is a barrier, but  Nutrients must get in  Products and wastes must get out  Permeability determines what moves in and out of a cell, and a membrane that  Lets nothing in or out is impermeable  Lets anything pass is freely permeable  Restricts movement is selectively permeable  Plasma membrane is selectively permeable/semipermeable  Allows some materials to move freely  Restricts other materials from crossing over (they may need a transport protein of some type, or ATP)  Selective permeability restricts materials based on  Lipid solubility (lipophilic/ hydrophilic)  Size/ shape (small/ large)  Electrical charge (nonpolar/ polar & charged)  Transport Mechanisms  Passive transport-doesn’t require ATP  Diffusion  Osmosis  Facilitated Diffusion  Active transport and secondary active transport  requires ATP  Endocytosis/Exocytosis  Filtration  Passive Transport  Passive transport – diffusion OR osmosis across the plasma membrane in living organisms  Energy from the cell is not required.  Diffusion involves only very small hydrophobic molecules, small polar molecules, or gasses.  Osmosis is the movement of water.  Both move down their concentration gradient  Rate of movement depends on difference of gradient  What about large molecules or ions????  [high] [low] Osmosis  Osmosis is the passive movement of water across a semipermeable membrane from an area of high water concentration to an area of low concentration of water [high] [low]  OR mvt. of water to the side with more particles.  water wants to dilute the side with excess particles  Osmotic pressure  Osmotic pressure: pressure derived from particles in a solution. These particles influence movement of water. The side with more particles wins.  osmotic pressure activity  The greater the difference in concentration the greater the osmotic pressure will be the greater the pull will be on water  Why is this important for our bodies???  Tonicity  Tonicity –relative term that describes how a cell will behave in a solution. It indicates the conc. of the soln.  Isotonic – body fluids are isotonic to cells; there is an equal concentration of solutes and water on both sides of the cell membrane.  No net movement of water occurs  Hypertonic solution – the solution contains a higher concentration of dissolved solutes than the cell.  Net movement of water is out of the cell by osmosis  Cell shrivels/ crenates  Hypotonic solution – the solution contains a lower concentration of dissolved solutes than the cell.  Net movement of water is into the cell  Cell swells OR hemolyzes.  Facilitated Diffusion  Passive transport –facilitated diffusion  Facilitated diffusion involves moving ions and large polar molecules down their concentration gradient.  They cannot diffuse through the membrane due to size or charge so they need transportation.  There are two categories of transport proteins  Channel proteins  Non-gated channel proteins and gated channel proteins (ligand + voltage)  Carrier proteins Channel Proteins Channel proteins are like pores in the membrane to let small polar molecules OR ions through the membrane. 1. Nongated channels Always open in normal cells. Responsible for the permeability of the plasma membrane to ions when the plasma membrane is at rest 2. Gated channels= open or close by certain stimuli Ligand gated channels open in response to small molecules that bind to integral proteins or glycoproteins Voltage-gated channels open when there is a change in charge across an area of the plasma membrane Carrier Proteins  Carrier proteins are integral proteins that carry large nonpolar, polar, or ionic molecules across the plasma membrane down the molc. conc. gradient.  Tranport amino acids, glucose, and proteins  Have specific binding sites  Protein changes shape to transport ions or molecules  Resumes original shape after transport  Carrier proteins exhibit the following characteristics similar to enzymes:  Specificity for a single type of molecule  Competition among molecules of similar shape  Saturation: rate of transport limited to number of available carrier proteins Active transport Active transport: pumping substances across the membrane against their concentration gradients; this requires ATP. Usually these are referred to as pumps. [low]  [high] Primary Active Transport  1o active transport requires ATP. ATP allows the cell to accumulate substances against its conc. gradient  Rate of transport depends on [substrate] and [ATP]  Example: Na+/K+ exchange pump creates an electrical potential across membranes  Secondary Active Transport  Use the concentration gradient derived from a primary active transport pump to drive another pump.  Example: Na/K ATPase sets up a Na gradient for Na/Glucose pump to pump glucose AGAINST it’s concentration gradient. Transport Mechanism How do we get large molecules into the cell?  Exocytosis and endocytosis – movement of large molecules across the membrane  Exocytosis occurs when a membrane-bound vesicle carrying a substance fuses with the plasma membrane and secretes its contents to the cell’s exterior.  Endocytosis occurs when a substance is brought into the cell and the plasma membrane buds inward. Exocytosis=accumulated vesicle secretions expelled from cell Examples  Secretion of digestive enzymes by pancreas  Secretion of mucous by salivary glands  Secretion of milk by mammary glands  Endocytosis  Internalization of substances by formation of a vesicle  Types  Phagocytosis (shown)  Pinocytosis  Receptor-mediated endocytosis Pinocytosis  Process by which cells ingest minute molecules  Through the formation of coated pits  And invirgination ……. Cell drinking Filtration  Works like a sieve  Depends on pressure difference on either side of a partition  Moves from side of greater pressure to lower  Example: blood pressure causes fluid movement out of capillary  interstitium  Water and small molecules move through the membrane while large molecules remain in the blood  Other Mechanisms  Secondary messenger systems  cAMP and G-protein coupled mechanisms Non membraneous organelles  The Cytoskeleton — structural proteins for shape and strength  Microfilaments  Intermediate filaments  Microtubules  Microfilaments—thin filaments composed of the protein actin  Provide additional mechanical strength  Interact with proteins for consistency  Pair with thick filaments of myosin for muscle movement  Intermediate filaments—mid-sized between microfilaments and thick filaments  Durable (collagen)  Strengthen cell and maintain shape  Stabilize organelles  Stabilize cell position  Microtubules—large, hollow tubes of tubulin protein  Strengthen cell and anchor organelles  Change cell shape  Move vesicles within cell (kinesin and dynein)  During cellular division they form the spindle apparatus that attaches to chromosomes to pull them to opposite ends of the dividing cell centrioles  Centrioles  Two only and housed in the centromere  Barrel-shaped, composed of nine microtubule triplets  Forms spindle apparatus during cellular division and used in cilia and sperm flagella for movement  Cellular Extensions  Microvilli  Extension of the cell to increase surface area of the cell  Found in brush border of small intestine, stereocilia of ear, WBC, and oocyte.  Cilia  Small, whip-like, motile extensions of the cell surface  Ciliary movement move fluids across the cell surface  Found in bronchioles and fallopian tubes  Flagella  Tail of sperm that consists of microtubules Microvilli Cilia Ribosomes  Ribosomes  Composed of two subunits containing protein + RNA  Made in nucleus and shipped to cytoplasm  Build polypeptides in protein synthesis  Two types  Free ribosomes in cytoplasm: – manufacture proteins for cell  Fixed ribosomes attached to ER: – manufacture proteins for cell membrane, lysosomes, or secretion Membranous Organelles  Membranous Organelles  Nucleus (double membrane)  Endoplasmic reticulum (ER)-Rough and Smooth ER  Golgi apparatus  Lysosomes  Peroxisomes Nucleus  Nucleus  Houses the DNA  Serves as the cell’s control center  Surrounded by two membranes, together called the nuclear envelope  The nuclear envelope is studded with nuclear pores.  Nuclear pores regulate traffic into and out of the nucleus.  Inside the nucleus:  Chromatin – composed of DNA + proteins  Nucleolus – site of ribosome manufacture  Nucleoplasm – fluid inside the nucleus  ER  Endoplasmic reticulum (ER)  Continuous with outer nuclear envelope  Has cisternae are storage chambers within membranes  Functions  Synthesis of proteins, carbohydrates, cholesterol and lipids  Storage of synthesized molecules and materials  Transport of materials within the ER, to Golgi Apparatus, and extracellularly  Detoxification of drugs or toxins  Smooth endoplasmic reticulum (SER)  No ribosomes attached  Synthesizes lipids and carbohydrates: – phospholipids and cholesterol (membranes) – steroid hormones (reproductive system) – glycerides (storage in liver and fat cells)  Metabolizes lipids ad breaks down glycogenglucose  Absorbs, synthesizes and transports lipids  Detoxifies drugs, pesticides and carcinogens (liver/ kidney)  Modified SER in skeletal muscle and cardiac muscle for storage of Ca+2  Rough endoplasmic reticulum (RER)  Surface covered with ribosomes: –active in protein and glycoprotein synthesis –folds polypeptides protein structures –encloses products in vesicles that go to Golgi apparatus  Golgi Apparatus  A stack of membranous sacs  Vesicles pinch off from the ER to fuse with the Golgi apparatus and empty their digestive enzyme, protein or lipid contents.  The lipids and proteins are then modified, sorted, and sent to their appropriate destination in new vesicles that bud off from the Golgi apparatus.  The digestive enzyme contents remain in the cell as lysosomes  Lysosomes=powerful, acidic, enzyme containing vesicles Clean up inside cells  Break down large molecules  Digest ingested bacteria, viruses and toxins  Recycle damaged organelles  Eject wastes by exocytosis Autolysis  Auto- = self, lysis = break  Self-destruction of damaged cells: –lysosome membranes break down –digestive enzymes released –cell decomposes –cellular materials recycle  Peroxisomes  Enzyme containing vesicles (oxidases + catalases)  Oxidases use O2 to detoxify harmful substances and neutralize byproducts of metabolism  free radicals (unpaired e-) + hydrogen peroxide  H2O  Breakdown and synthesize fatty acids Mitochondria  Mitochondria  Uses carbs, lipids, and proteins to synthesize ATP  Has outer and inner membranes separated by the intermembrane space  Inner membrane carries proteins involved in ATP production  Matrix is site of reactions that release energy from nutrients THANK YOU  QUESTIONS & COMMENTS