Lecture 3 Cellular level of organization 1.pdf

Cellular Level of Organization 1 Dr. Elita Partosoedarso Kaltura Recordings: Part A, Part B, Part C YouTube Recording 1  Cellular level of organization 1 overview...

Cellular Level of Organization 1 Dr. Elita Partosoedarso Kaltura Recordings: Part A, Part B, Part C YouTube Recording 1  Cellular level of organization 1 overview Basics of the cell Main components Cell (plasma) Phospholipid bilayer membrane Other components Cellular level of Compartments organization Fluid in the body Semi-permeable membrane and Tonicity Active transport Movement between compartments Passive Transport Organelles involved in synthesis Organelles Other organelles Fibers Cytoskeleton Extension 2 Overview of the anatomy of a cell Main components 1 1 1. Plasma, or cell, membrane: separates cell from its surrounding environment 2.2 Cytoplasm: thick gel-like substance inside cell 3 composed of organelles suspended in watery cytosol 3.3 Nucleus: large membranous structure near the center 2 3 3  The cell (plasma) membrane is a pliable or fluid structure composed mainly of 2 adjacent layers of phospholipids (phospholipid bilayer). This structure is also found in membranes around some organelles and Main component of cell (plasma) the nucleus Phospholipids are long amphipathic compounds, containing one negatively charged end and one neutral (uncharged) end. Arrangements of phospholipids in a bilayer allows the separation of intracellular fluid (and its solutes) from extracellular fluid (and its membranes solutes) Charged end of phospholipids is formed by negatively charged phosphate group ○ These hydrophilic (phosphate) heads are soluble in water: the heads of each layer face outwards: polar regions which are attracted to the water of the ICF and the ECF Neutral (uncharged) end is formed by 2 neutral fatty acids chains (saturated or unsaturated) ○ The hydrophobic (fatty acid) tails are insoluble in water: the tails of the two layers face each other to create a hydrophobic environment in the middle. This middle zone stops water moving across the bilayer: separates water inside the cell (intracellular fluid or ICF) from the water outside the cell (extracellular fluid or ECF) 4  Components of a cell membrane 2 3 The cell membrane is fluid; that is, its components can move around, increase or decrease in quantity 3 2 1 3 3 1. 1 Phospholipid bilayer: main component 2 Lipids 2. Cholesterol Glycolipids: contains carbohydrate and lipid components 3.3 Proteins Glycoproteins: contains both protein and carbohydrate components, eg cell identity markers to distinguish self-cells from nonself cells (spike proteins) Integral membrane proteins: protein which spans the entire width of the membrane, eg receptors and ion channels Peripheral membrane proteins: protein attached to a single side of the membrane with a specific function, eg enzymes on intestinal cells 5  1 Fluid in the body Fluid environments around a cell 1.1 Intracellular fluid (ICF): fluid environment _______________ 2.2 Extracellular fluid (ECF): fluid environment _______________ 3.3 Interstitial fluid (IF): ___________________________________ 3 Substances (and water) in the ICF are kept separate from the ECF by the plasma membrane. The plasma membrane is selectively permeable, 2 controlling the movement of substances across the bilayer Water moves across the membrane through protein channels or by slipping between phospholipid tails Relatively small, nonpolar materials (eg lipids, gases (CO2, O2), alcohol) can penetrate the main portion of the phospholipid bilayer Water-soluble materials (eg nutrients like glucose, amino acids, and electrolytes like Ca++, Na+, K+, and Cl–) are stopped by the main portion of the phospholipid bilayer So…. How do water soluble materials move across the plasma 6 membrane?  The semi-permeable membrane and concentration gradient A semi-permeable membrane controls the movement of substances across it ○ Allows some substances to move across freely ○ Prevents other substances to move across freely: these substances require help to move across A B A concentration gradient is a difference in concentration of a substance across a space or semi-permeable membrane The beaker is divided into two sides by a semi-permeable membrane. Each side contains water and a solute. This semi-permeable membrane allows water, but not solutes, to move across it. Side _____ has a higher concentration of solutes than side ____. Side _____ has a higher concentration of water than side ____ 7  Tonicity of a solution (relative to the ICF of a cell) Tonicity refers to the concentration of solutes in a solution A B Isotonic solution: Contains the same concentration of solutes (and water) as another solution 1 Hypotonic solution: Contains a lower concentration of solutes (and a higher concentration of water) as another solution Hypertonic solution: Contains a higher concentration of solutes (and a lower concentration of water) as another solution In Beaker 1,1 water, but not solutes, can move across the semi-permeable membrane. the solution in Side A is ___________ to the solution in Side B the solution in Side B is ___________ to the solution in Side A Osmosis (diffusion of water) ____________________ A B In Beaker 2,2 water, but not solutes, can move across the semi-permeable membrane the solution in Side A is ___________ to the solution in Side B 2 the solution in Side B is ___________ to the solution in Side A Osmosis (diffusion of water) ____________________ 8  What happens if red blood cells (RBCs) are placed in solutions with different tonicities? How would you determine the tonicity of the solution that the RBCs were placed 1 in? (Remember that the cell membrane of a RBC is semi-permeable) 1.1 The same amount of water is entering and leaving the RBC- these RBCs are in a(n) ____________ solution. The effect of this is ______________. 2. 2 More water is leaving the RBC - these RBCs are in a(n) ____________ solution. The effect of this is ______________. 3. More water is entering the RBC - these RBCs are in a(n) ____________ 2 3 solution. The effect of this is ______________. 3 9 General Types Of Movement Across a Passive transport Energy _____________________________________________ Substances move __________ the concentration gradient: from area of Semi-permeable Membrane __________ concentration to one of __________ concentration ○ Solutes in the beaker move from Side ___ to Side ___ ○ Water in the beaker move from Side ___ to Side ___ A B Active transport Energy _____________________________________________ Substances move __________ the concentration gradient: from area of low concentration to one of higher concentration ○ Solutes in the beaker move from Side ___ to Side ___ Substances are transported across the membrane in bulk, either into the cell or out of the cell 10  Types of Passive transport 5 1. Diffusion: movement of substances (gases, nutrients, electrolytes, fluid) from an area of higher concentration to one of lower concentration 2.2 Osmosis: “diffusion” of water through a semi-permeable membrane 3.3 Simple Diffusion: requires no additional help for diffusion to occur across a 2 semi-permeable membrane 4.4 Facilitated Diffusion of larger solute: larger solute diffuses across a semi-permeable membrane through an integral membrane protein (carrier protein) 5.5 Facilitated Diffusion of charged solute: charged solute diffuses across a semi-permeable membrane through an integral membrane protein (ion 4 channel/pore) 6. Filtration: movement of fluid and solutes from a higher hydrostatic pressure area to a lower hydrostatic pressure area. 3 11  Active transport: Transport AGAINST their concentration gradient Primary active transporter: uses ATP as its energy source + + 1. 1 Sodium-potassium (Na /K ATPase) pump uses energy from ATP to move sodium out of a cell and potassium into the cell, both 1 against their concentration gradient. Maintains electrical gradient across membrane Secondary active transporter: uses the energy released when one substance diffuses across the membrane to move a 2nd substance Na+ Glucose against its gradient either in the same direction (symporter) or in the Extracellular opposite direction (antiporter) 2 Sodium-glucose symporter: sodium diffusing into the cell releases 2. 2 enough energy to move glucose against its concentration gradient in the same direction. Glucose is needed by the cell to produce Intracellular energy 3.3 Sodium-hydrogen ion antiporter: sodium diffusing into the cell releases enough energy to move hydrogen ions (H+) against its Na+ Extracellular concentration gradient in the opposite direction. To maintain the 3 pH of the cell's interior An electrical gradient is a difference in electrical charge across a semi-permeable membrane Intracellular Nerve cells have an electrical gradient of -70 mV relative to its extracellular environment 12 H+  Active transport for bulk movement 1 Transport of substances in bulk using vesicles (independent, intracellular sac/organelle bounded by a lipid bilayer membrane) across the membrane Endocytosis: transports material into the cell by surrounding it in a portion of its cell 2 membrane, and then pinching off that portion of membrane to form a vesicle 1 Phagocytosis: endocytosis of large particles (eg pathogens) to be digested 1. 2.2 Pinocytosis: endocytosis of fluid together with its dissolved substances 3.3 Receptor-mediated endocytosis: endocytosis of a specific substance due to that substance binding to a specific receptor on the cell surface, eg the iron-transferrin 3 complex binds to specific transferrin receptors on RBC surfaces 4.4 Exocytosis: export of material (hormones, neurotransmitters) from a cell using vesicles 4 13  3 Cytoplasm and organelles of a Cell 3 3 4 3 3 3 3 3 1 1.1 Cytoplasm: internal environment of a cell which consists of the cytosol and organelles 2. Cytosol: jelly-like substance within the cell containing water as a medium for biochemical reactions 3.3 Organelle: functional components within a cell, each with a unique function. Some organelles are kept within lipid bilayer members while others are not. All organelles within a cell work together to keep the cell healthy 4.4 Nucleus: central organelle of the cell, contains DNA of cell 14  Organelles involved in synthesis 3 2 1. Endoplasmic reticulum (ER) ○ Continuous with nuclear membrane, made of lipid bilayer, winding system of channels with a large surface area 5 ○ Support synthesis, transport, and storage of synthesized materials 4 2.2 Rough ER (RER) ○ contains ribosomes which gives it a rough appearance. ○ Site of protein synthesis 3.3 Ribosome 3 ○ contains 2 subunits that wrap around mRNA produced by the nucleus ○ Connects amino acids together to form a polypeptide → functional protein 4.4 Smooth ER (SER) ○ does not contain ribosomes so appearance is smooth 2 4 ○ Synthesizes lipids and carbohydrates, detoxifies, stores calcium (Ca++) 5 5. Golgi apparatus 3 ○ membranous stacked flattened discs, with cis and trans sides ○ Synthesizes and modifies proteins, packages protein in vesicles ○ vesicles from rough ER enter into cis side, is sorted, modified, repackaged into secretory vesicles, and released from trans side 15  Process of protein synthesis 1 Instructions for protein synthesis is produced by nucleus 1 2 Protein is assembled by ribosomes in the rough ER 2 3 Assembled proteins are folded in the ER and placed in transport vesicles 3 4 Transport vesicles from ER move to the Golgi apparatus for 4 processing and packaging Processed proteins are packaged into secretory vesicles and 5 released from trans side Secretory vesicles move towards the plasma membrane 6 5 Secretory vesicles binds with the plasma membrane and 7 releases proteins for export (or insertion into the membrane) 7 6 16 16  Other organelles 1 1.1 Mitochondria Anatomy: membrane-bound organelle with highly folded inner lipid bilayer membrane (cristae) to increase surface area Physiology: contains enzymes involved in cellular respiration (conversion of stored energy into cellular energy, ATP) 2 2.2 Lysosome Anatomy: membrane-bound organelle that contains enzymes Physiology: enzymes break down and digest foreign material and unneeded/damaged This Photo by Unknown Author is licensed under CC BY cellular components 3.3 Peroxisome Anatomy: membrane-bound organelle that contains enzymes Physiology: enzymes are involved in lipid metabolism and chemical detoxification 3 4.4 Proteasome Anatomy: Hollow cylinders that allow proteins to go through Physiology: Break down of abnormal or misfolded proteins, or of normal proteins that are no longer needed: proteins are unfolded and disassembled into shorter peptides and amino acids as it travels inside the cylinder 4 17 This Photo by Unknown Author is licensed under CC BY  The Nucleus 1 2 Overview: largest and most prominent of organelle in a cell, muscle cells have 4 multiple nuclei while red blood cells (RBC) have none Purpose: control center, contains DNA which provide genetic instructions used to build and maintain an organism 1.1 Nuclear envelope: Lipid bilayer membrane surrounding the nucleus 2.2 Nuclear pore: tiny passageway between nucleus and cytoplasm for proteins, RNA, and solutes to go between nucleus and cytoplasm 3. Nucleoplasm: gel-like substances containing solutes and building blocks of nucleic acids 4.4 Nucleolus: manufactures RNA necessary to construct ribosomes RBC ejecting its nucleus 18 Multinucleated muscle cells  2 Structure: composed of group of fibrous proteins that form a complex network throughout the cell 3 Purpose: maintain their structural integrity of cell, involved in cell motility, cell reproduction, and transportation of substances within the cell. The Cytoskeleton 1 Types of fibers 1.1 Microfilament Thinnest one containing actin chains creates furrow during cell division and is involved in muscle contraction 2.2 Intermediate filament Intermediate thickness containing keratin chains 1 2 3 helps resist tension of cell, forms cell-to-cell junctions and help anchor organelles together within cell 3.3 Microtubule Thickest one containing tubulin subunits helps resist compression of cell, maintain cell shape and structure and helps position organelles within cell 19  Cell extensions of the Cytoskeleton 1. 1 Cilia 1 ○ Location: epithelial cells in respiratory tract and Fallopian tube ○ Structure: consists of microtubules ○ Function: move dust, mucus, bacteria towards mouth/nose or eggs towards uterus 2.2 Microvilli ○ Location: epithelial cells in small intestine 2 ○ Structure: Outward projections of plasma membrane which form tiny, fingerlike processes, similar to hairbrush bristles ○ Function: increase surface area to help with nutrient absorption 3 3.Flagellum ○ Location: one end of a sperm cell 3 ○ Structure: consists of microtubules ○ Function: propels sperm cell towards female egg cell 4 4.Centriole ○ Location: nucleus of a dividing cell ○ Structure: consists of microtubules 4 ○ Function: assist with the separation of DNA during cell division 20