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BI 5103 FISIOLOGI TERINTEGRASI (Integrative Physiology) Core Principle 4 : The Cell (Konsep Inti 4 : Sel) Sem I 2013/2014 tjandraanggraeni 1 Why the Cell ? The cell is the basic unit of life. Sem I 2013/2014 tjandraanggraeni 2 The cell is the smallest, selfreplicating unit of integrated function. A multicellular organism is an organized structure made up of different cells, with each cell having some properties in common with other cells in the organism and each cell having some specialized structures and functions. Sem I 2013/2014 tjandraanggraeni 3 An animal cell Smooth endoplasmic reticulum Nucleus Rough endoplasmic reticulum Flagellum Not in most plant cells Lysosome Centriole Ribosomes Peroxisome Golgi apparatus Microtubule Cytoskeleton Plasma membrane Intermediate filament Microfilament Mitochondrion Sem I 2013/2014 tjandraanggraeni 4 Nucleus Rough endoplasmic reticulum Ribosomes Smooth endoplasmic reticulum Golgi apparatus Microtubule Not in animal cells Central vacuole Intermediate filament Cytoskeleton Chloroplast Microfilament Cell wall Mitochondrion Peroxisome Plasma membrane Sem I 2013/2014 tjandraanggraeni 5 Sub Topic A.The cell membrane contains the contents of the cell and determines what can enter and leave the cell. B.The internal constituents and state of the cell are different than the extracellular environment. C. Although all cells have the same DNA, not all genes are expressed in every cell. D. As a consequence, cells have many common functions but also many specialized functions. E.The organism is a collection of cooperating cells, with each cell type contributing its special functions to the “economy” of the organism. Sem I 2013/2014 tjandraanggraeni 6 A.The cell membrane contains the contents of the cell and determines what can enter and leave the cell. Sem I 2013/2014 tjandraanggraeni 7 Figure 5.1 CYTOPLASM Enzymatic activity Fibers of extracellular matrix (ECM) Phospholipid Cholesterol Cell-cell recognition Receptor Signaling molecule Transport Attachment to the cytoskeleton and extracellular matrix (ECM) Signal transduction ATP Intercellular junctions Glycoprotein Microfilaments of cytoskeleton CYTOPLASM Membranes are fluid mosaics of lipids and proteins with many functions Membrane proteins perform many functions. 1. Some proteins help maintain cell shape and coordinate changes inside and outside the cell through their attachment to the cytoskeleton and extracellular matrix. 2. Some proteins function as receptors for chemical messengers from other cells. 3. Some membrane proteins function as enzymes. © 2012 Pearson Education, Inc. Membranes are fluid mosaics of lipids and proteins with many functions 4. Some membrane glycoproteins are involved in cellcell recognition. 5. Membrane proteins may participate in the intercellular junctions that attach adjacent cells to each other. 6. Membranes may exhibit selective permeability, allowing some substances to cross more easily than others. © 2012 Pearson Education, Inc. Many cell organelles are related through the endomembrane system The endomembrane system is a collection of membranous organelles ◦ These organelles manufacture and distribute cell products ◦ The endomembrane system divides the cell into compartments ◦ Endoplasmic reticulum (ER) is part of the endomembrane system ◦ (nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane) Sem I 2013/2014 tjandraanggraeni 11 Rough endoplasmic reticulum makes membrane and proteins The rough ER manufactures membranes Ribosomes on its surface produce proteins Transport vesicle buds off 4 Ribosome Sugar chain 1 3 Secretory (glyco-) protein inside transport vesicle Glycoprotein 2 ROUGH ER Polypeptide Sem I 2013/2014 tjandraanggraeni 12 Smooth endoplasmic reticulum has a variety of functions Smooth ER synthesizes lipids In some cells, it regulates carbohydrate metabolism and breaks down toxins and drugs Sem I 2013/2014 tjandraanggraeni 13 SMOOTH ER ROUGH ER Nuclear envelope Ribosomes SMOOTH ER ROUGH ER Sem I 2013/2014 tjandraanggraeni 14 The Golgi apparatus finishes, sorts, and ships cell products The Golgi apparatus consists of stacks of membranous sacs ◦ These receive and modify ER products, then send them on to other organelles or to the cell membrane Sem I 2013/2014 tjandraanggraeni 15 The Golgi apparatus Golgi apparatus Golgi apparatus “Receiving” side of Golgi apparatus Transport vesicle from ER New vesicle forming “Shipping” side of Golgi apparatus Transport vesicle from the Golgi Sem I 2013/2014 tjandraanggraeni 16 Lysosomes digest the cell’s food and wastes Lysosomes are sacs of digestive enzymes budded off the Golgi LYSOSOME Nucleus Sem I 2013/2014 tjandraanggraeni 17 Lysosomal enzymes – digest food – destroy bacteria – recycle damaged organelles – function in embryonic development in animals Sem I 2013/2014 tjandraanggraeni 18 Rough ER Transport vesicle (containing inactive hydrolytic enzymes) Plasma membrane Golgi apparatus Engulfment of particle Lysosome engulfing damaged organelle “Food” LYSOSOMES Food vacuole Sem I 2013/2014 Digestion tjandraanggraeni 19 B.The internal constituents and state of the cell are different than the extracellular environment. Sem I 2013/2014 tjandraanggraeni 20 Passive transport is diffusion across a membrane with no energy investment Diffusion is the tendency of particles to spread out evenly in an available space. ◦ Particles move from an area of more concentrated particles to an area where they are less concentrated. ◦ This means that particles diffuse down their concentration gradient. ◦ Eventually, the particles reach equilibrium where the concentration of particles is the same throughout. © 2012 Pearson Education, Inc. Passive transport is diffusion across a membrane with no energy investment Diffusion across a cell membrane does not require energy, so it is called passive transport. The concentration gradient itself represents potential energy for diffusion. © 2012 Pearson Education, Inc. Molecules of dye Membrane Pores Net diffusion Net diffusion Equilibrium Net diffusion Net diffusion Equilibrium Net diffusion Net diffusion Equilibrium Osmosis is the diffusion of water across a membrane One of the most important substances that crosses membranes is water. The diffusion of water across a selectively permeable membrane is called osmosis. © 2012 Pearson Education, Inc. Osmosis is the diffusion of water across a membrane If a membrane permeable to water but not a solute separates two solutions with different concentrations of solute, ◦ water will cross the membrane, ◦ moving down its own concentration gradient, ◦ until the solute concentration on both sides is equal. © 2012 Pearson Education, Inc. Lower Higher concentration concentration of solute of solute Equal concentrations of solute H2O Solute molecule Selectively permeable membrane Water molecule Solute molecule with cluster of water molecules Osmosis Water balance between cells and their surroundings is crucial to organisms Tonicity is a term that describes the ability of a solution to cause a cell to gain or lose water. Tonicity mostly depends on the concentration of a solute on both sides of the membrane. © 2012 Pearson Education, Inc. Water balance between cells and their surroundings is crucial to organisms How will animal cells be affected when placed into solutions of various tonicities? When an animal cell is placed into ◦ an isotonic solution, the concentration of solute is the same on both sides of a membrane, and the cell volume will not change, ◦ a hypotonic solution, the solute concentration is lower outside the cell, water molecules move into the cell, and the cell will expand and may burst, or ◦ a hypertonic solution, the solute concentration is higher outside the cell, water molecules move out of the cell, and the cell will shrink. © 2012 Pearson Education, Inc. Water balance between cells and their surroundings is crucial to organisms For an animal cell to survive in a hypotonic or hypertonic environment, it must engage in osmoregulation, the control of water balance. © 2012 Pearson Education, Inc. Water balance between cells and their surroundings is crucial to organisms The cell walls of plant cells, prokaryotes, and fungi make water balance issues somewhat different. ◦ The cell wall of a plant cell exerts pressure that prevents the cell from taking in too much water and bursting when placed in a hypotonic environment. ◦ But in a hypertonic environment, plant and animal cells both shrivel. © 2012 Pearson Education, Inc. Hypotonic solution H2O Isotonic solution Hypertonic solution H2O H2O H2O Animal cell Normal Lysed Plasma membrane H2O H2O Shriveled H2O Plant cell Turgid (normal) Flaccid Shriveled (plasmolyzed) Transport proteins can facilitate diffusion across membranes Hydrophobic substances easily diffuse across a cell membrane. However, polar or charged substances do not easily cross cell membranes and, instead, move across membranes with the help of specific transport proteins in a process called facilitated diffusion, which ◦ does not require energy and ◦ relies on the concentration gradient. © 2012 Pearson Education, Inc. Transport proteins can facilitate diffusion across membranes Some proteins function by becoming a hydrophilic tunnel for passage of ions or other molecules. Other proteins bind their passenger, change shape, and release their passenger on the other side. In both of these situations, the protein is specific for the substrate, which can be sugars, amino acids, ions, and even water. © 2012 Pearson Education, Inc. Transport proteins can facilitate diffusion across membranes Because water is polar, its diffusion through a membrane’s hydrophobic interior is relatively slow. The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an aquaporin. © 2012 Pearson Education, Inc. Solute molecule Transport protein Cells expend energy in the active transport of a solute In active transport, a cell ◦ must expend energy to ◦ move a solute against its concentration gradient. The following figures show the four main stages of active transport. © 2012 Pearson Education, Inc. Transport protein Solute 1 Solute binding Transport protein P ADP Phosphate attaching ATP Solute 1 Solute binding 2 Transport protein Solute 1 Solute binding 2 P ATP ADP Phosphate attaching P Protein changes shape. 3 Transport Transport protein Solute 1 Solute binding 2 P ATP ADP Phosphate attaching P Protein changes shape. 3 Transport Phosphate P detaches. 4 Protein reversion Exocytosis and endocytosis transport large molecules across membranes A cell uses two mechanisms to move large molecules across membranes. ◦ Exocytosis is used to export bulky molecules, such as proteins or polysaccharides. ◦ Endocytosis is used to import substances useful to the livelihood of the cell. In both cases, material to be transported is packaged within a vesicle that fuses with the membrane. © 2012 Pearson Education, Inc. Exocytosis and endocytosis transport large molecules across membranes There are three kinds of endocytosis. 1. Phagocytosis is the engulfment of a particle by wrapping cell membrane around it, forming a vacuole. 2. Pinocytosis is the same thing except that fluids are taken into small vesicles. 3. Receptor-mediated endocytosis uses receptors in a receptor-coated pit to interact with a specific protein, initiating the formation of a vesicle. © 2012 Pearson Education, Inc. Phagocytosis EXTRACELLULAR FLUID Pseudopodium CYTOPLASM Food being ingested “Food” or other particle Food vacuole Pinocytosis Plasma membrane Vesicle Receptor-mediated endocytosis Coat protein Receptor Plasma membrane Coated vesicle Coated pit Specific molecule Coated pit Material bound to receptor proteins Phagocytosis EXTRACELLULAR FLUID Pseudopodium CYTOPLASM “Food” or other particle Food vacuole Food being ingested Pinocytosis Plasma membrane Vesicle Plasma membrane Receptor-mediated endocytosis Coat protein Plasma membrane Coated vesicle Receptor Coated pit Specific molecule Coated pit Material bound to receptor proteins Cells transform energy as they perform work Cells are small units, a chemical factory, housing thousands of chemical reactions. Cells use these chemical reactions for ◦ cell maintenance, ◦ manufacture of cellular parts, and ◦ cell replication. © 2012 Pearson Education, Inc. C. Although all cells have the same DNA, not all genes are expressed in every cell. Sem I 2013/2014 tjandraanggraeni 49 Multiple mechanisms regulate gene expression in eukaryotes ◦ Many possible control points exist; a given gene may be subject to only a few of these – Chromosome changes (1) – DNA unpacking – Control of transcription (2) – Regulatory proteins and control sequences – Control of RNA processing – Addition of 5’ cap and 3’ poly-A tail (3) – Splicing (4) – Flow through nuclear envelope (5) Copyright © 2009 Pearson Education, Inc. Multiple mechanisms regulate gene expression in eukaryotes ◦ Many possible control points exist; a given gene may be subject to only a few of these – Breakdown of mRNA (6) – Control of translation (7) – Control after translation – Cleavage/modification/activation of proteins (8) – Breakdown of protein (9) Copyright © 2009 Pearson Education, Inc. NUCLEUS Chromosome DNA unpacking Other changes to DNA Gene Gene Transcription Exon RNA transcript Intron Addition of cap and tail Splicing Tail mRNA in nucleus Cap Flow through nuclear envelope mRNA in cytoplasm CYTOPLASM Breakdown of mRNA Translation Brokendown mRNA Polypeptide Cleavage / modification / activation Active protein Breakdown of protein Brokendown protein D. As a consequence, cells have many common functions but also many specialized functions. Sem I 2013/2014 tjandraanggraeni 54 Differentiation results from the expression of different combinations of genes ◦ Differentiation involves cell specialization, in both structure and function ◦ Differentiation is controlled by turning specific sets of genes on or off Copyright © 2009 Pearson Education, Inc. Muscle cell Pancreas cells Blood cells White blood cells help defend the body White blood cells function both inside and outside the circulatory system ◦ They fight infections and cancer Basophil Eosinophil Monocyte Neutrophil Lymphocyte Sem I 2013/2014 tjandraanggraeni 57 Five major classes of antibodies in human and other mammals (differs in where it found and how it works) IgA IgD IgE IgG IgM Sem I 2013/2014 tjandraanggraeni 58 E.The organism is a collection of cooperating cells, with each cell type contributing its special functions to the “economy” of the organism. Sem I 2013/2014 tjandraanggraeni 59 EXAMPLE The islet of Langerhans in the pancreas is composed of five different types of cells, each of which has the common feature of a membrane across which glucose can be transported. However, each of these different cells releases a different hormone involved, in one way or another, in the integrated regulation of glucose metabolism. Sem I 2013/2014 tjandraanggraeni 60 Hormones produced in the islets of Langerhans are secreted directly into the blood flow by (at least) five different types of cells. In rat islets, endocrine cell subsets are distributed as follows:[3] Alpha cells producing glucagon (15–20% of total islet cells) Beta cells producing insulin and amylin (65–80%) Delta cells producing somatostatin (3–10%) PP cells producing pancreatic polypeptide (3–5%) Epsilon cells producing ghrelin (<1%) Sem I 2013/2014 tjandraanggraeni 61 It has been recognized that the cytoarchitecture of pancreatic islets differs between species. In particular, while rodent islets are characterized by a predominant proportion of insulin-producing beta cells in the core of the cluster and by scarce alpha, delta and PP cells in the periphery, human islets display alpha and beta cells in close relationship with each other throughout the cluster. Islets can influence each other through paracrine and autocrine communication, and beta cells are coupled electrically to other beta cells (but not to other cell types). Sem I 2013/2014 tjandraanggraeni 62 Paracrine feedback The paracrine feedback system of the islets of Langerhans has the following structure : Insulin: activates beta cells and inhibits alpha cells Glucagon: activates alpha cells which activates beta cells and delta cells Somatostatin: inhibits alpha cells and beta cells Sem I 2013/2014 tjandraanggraeni 63 Another example ? Sem I 2013/2014 tjandraanggraeni 64